OK, this is how to do it - 20FP

Alright, enough. I've been setting these things up for the last 10 years, and I have flown it many, many times.

This is a well-tested in competition and extensive experimentation, and repeatable with at least a dozen engines actually tested in flight on a variety of small 35-sized planes (Skyray 35, Flite Streak, Medic, very fast Ringmaster):

Stock 20FP ABC
Stock Muffler
Stock Venturi
Stock Spraybar
APC 9-4 or MK-Custom 8.5-4.5
Low-profile Uniflow hard tan, no pressure
or Sullivan SS-4 clunk tank, set up per instructions (except third tube for overflow, convenience only), suction with muffler pressure
Thunderbolt 4-cycle or R/C plug
Sullivan "Crap Trap" 2-stage filter
Sig 10% Champion fuel
Skyray/Flite Streak-size model
60-62 foot .015 stranded lines
lap time will be between 4.6-5.0. Can be slower or much faster if desired

Ringmaster will be flying about 3.8-4.0 -second laps on 60' lines at proper setting with 9-4.

No break-in required, two-three tanks on ground desirable. to stabilize fuel consumption

Set at about 11,300 on the ground, or peak out and then back off about 5-6 clicks until its noticably off-peak. First flight may sag on hard outsides, will fix itself in a few flights. Fuel consumption will be close to 3.5 oz on first run, will decrease to about 2.4-2.5 oz after about 15 flights, then stabilize.

In-flight setting in level flight should be a rich-medium 2-stroke. If airplane is too fast, reduce venturi with Bru-Line "fine" air filter. If too slow (very unlikely), lean out, or move to 15% nitro. Can be run near peak with little chance of damage. Speed can be tweaked slightly with needle, but running a 4-stroke in level flight will likely result in excessive speed variation in flight. In extreme cases (Ringmaster), speed can be reduced with ST needle, but this is not necessary for run stability, just power reduction. Use 15FP on Ringmaster instead.

The engine will spin much more prop. But don't. When in doubt, add less prop.

Things NOT TO DO:
modify muffler
replace muffler
modify venturi
run more load than APC 9-4 prop
run hard tank with pressure
run excessively wide hard tank
add head gaskets
modify timing
plug up boost port

This will work, there is NO DEBATE that it works, it's not an experiment. If for some reason it does not work, look for some reason aside from engine setup -like all the usual suspects, fuel lines, crud, tank leaks, etc.

If you want to experiment, by all means go ahead, but this is good enough to win any advanced contest and most expert contests, and is a completely turn-key operation that repeats from engine to engine. AND IT DOES IN FACT PUNCH THROUGH THE WIND BETTER THAN MOST OTHER SETUPS ON SIMILAR AIRPLANES.

Note that this will more-or-less work on the 25FP, but not as reliably, in my experience. The 25 occasionally runs away unless you use a filter or reduced venturi, which is fine since a properly-running 25FP will GROSSLY OVERPOWER many of these type of airplanes and you will need to slow it down anyway.

Brett

p.s. Here is the hard tank I used before I switched to the clunk. It works well with open vents on uniflow, but sometimes went lean just after the square 8 with muffler pressure.

Template with tank "Unfolded" for construction purposes:

and a 2-view with the tubing configuration crudely shown:

> This will work, there is NO DEBATE that it works, it's not
>an experiment. If for some reason it does not work, look
>for some reason aside from engine setup -like all the usual
>suspects, fuel lines, crud, tank leaks, etc.
>

No debate that it will work. However, since stock CL FP 20s are getting a little tough to find, the only recourse for many is to convert an RC version. Might be a good idea to list the stock venturi ID so that if they need to order one, they spec the correct opening with the .135" NVA.

I don't want to get into a debate with this. Brett is happy with his set-up and it works for him. Brett has a set up on his pipe engine that he is happy with. Paul has his. David has his. Ted has his. Oh, and Randy has his, and Matt has his and Doug has his, and...

What I am saying is, they work for them and they are happy with them. But they are all different. The stock venturi on the 20 FP is a .257. By any logic it is too big. It works with the restrictive stock muffler the way Brett has it set up, but I attribute the too large venturi size to the fact that they cannot seem to get it to run properly on other lighter and less restrictive mufflers. With a smaller venturi they could. And this would also have probably solved Dan's problem in finding he needed to use muffler pressure when he changed the tank.

I find it ironic that a .257 venturi (with a .017 choke area) was put on the 20 FP by OS when they used a .265 venturi (with a .019 choke area) on the 35 FP, 40 FP, and even 46 LA when it first came out. Now they were close to correct on the 40 FP, and maybe, with the restrictive muffler that they supplied, OK on the 20 in that it can be made to work. (After all, it works for Brett.) But if you are starting from scratch or wishing to use a lighter, less restrictive muffler, then certainly go to a smaller venturi (like a .228).

Not all roads lead to Rome and, although I appreciate Brett's efforts to share his set-up (and a lot of other things that he has shared, all of which have helped the CL community immensely) I just don't want to leave the impression that there is no other way to go. If you have a stock engine with a stock venturi and stock muffler, then try it Brett's way. But I would run mine differently. There is nothing wrong with choice.

>What I am saying is, they work for them and they are happy
>with them. But they are all different. The stock venturi
>on the 20 FP is a .257. By any logic it is too big.

When you flew it, stock, in an airplane, what suggested that it was too big instead of just right?

>
>When you flew it, stock, in an airplane, what suggested that
>it was too big instead of just right?
>
> Brett

You are an evil man, Brett Buck.

Not trying to cause a ruckus but I think Len has a point.. Only because we had a club member that was not able to get a decent (consistent) engine run out of a stock LA 20. I am pretty sure he wasn't using the stock muffler, either no muffler or a tongue, can't remember. Anyway the fix was something like a .228 venturi.

I have no doubts your FP-20 setup works as outlined, In fact I am using your recommended set up on two FP 25's, stock muffler with Bru-Line airfilter and both run great.

>Not trying to cause a ruckus but I think Len has a point..
>Only because we had a club member that was not able to get a
>decent (consistent) engine run out of a stock LA 20. I am
>pretty sure he wasn't using the stock muffler, either no
>muffler or a tongue, can't remember. Anyway the fix was
>something like a .228 venturi.

I don't have any experience with the LA20 (didn't even know there was such a thing). But if you don't run the supplied tuned pipe, er, muffler, then all bets are off, as Dan found. Open exhaust turns it into a classic schneurle "runaway special" just like all those 40FPs with "improved" exhaust systems.

The reason you can run the stock very large venturi is that the pipe, er, muffler, regulates the speed - not because a pure restriction like a muffler, but a *frequency-dependent* restriction/enhancement characteristic of a tuned pipe.

Do the math - for an engine with similar exhaust timing, at about 12000 rpm, you want a pipe length of about 16" (single wave travels to tail cone and back in one open period), 8" (bounces back twice), or 4" (bounces back 4 times). Then measure along the centerline of the path from the exhaust port, along the center of the "stack", then fr0m there along the center of the "chamber part" to the 1/3 point on the tapered tail cone. Hey, what about that- ~4"! Almost as if it were tailor-made for our application. It's not as "sharp" cutting as a full-wave pipe, but it's far better than venting it into the air, or a randomly-chosen length of some other resonant chamber.

THATs why running a 9-5 doesn't work (too fast. since it tuned for ~12000). that's why running a 10-4 doesn't really work (too fast because although the pitch is about right, it's still too fast, because the advance ratio is better). A 9-4, particularly the APC, puts the in-flight rpm, at a decent speed on Skyray 35-size models because the advance per rev is low enough to allow the in-flight revs to be "over the cliff" and thus stable and nicely responsive in the air. And of course running faster improves the fuel draw.

Note this is also why the 25FP, with the same muffler, frequently goes just slightly too fast - because everybody figures you can run a 10-4 or 11-4 (and it will swing it, and more, with no strain) on the same airplane to get more "power". Tuned to the same frequency, you can't just back it off with the needle since it will just pop up to the tuned RPM and stay there first chance it gets. And the tuned RPM and a 10-4 flies the airpalen too fast because of the better advance ratio.

Ted and I spent an afternoon one time tweaking on the Coyote/25FP and just couldn't get it to do anything but fly just a hair too fast. It would start out OK, but as some point it would "jump" to about 4.7 second laps no matter how rich it was. Note that this was not "running away" in the classic sense - it could have gone FAR FASTER. We didn't have any APC 9-4's, which when I tried it later on a different airplane, fixed the problem.

It's a system, not a random collection of parts. Change one piece and you have to reoptimize all the other pieces, as well. I've gone down these roads, most all of them, and came to the conclusion based on 10+ years of on-and-off development and competition flying, that it's close to optimal for small 35 planes, and provided the best overall performance, straight as it comes out of the box, in totality.

I figure when you can get a $52 pre-tuned bulletproof pipe system that runs perfectly on a typical profile trainer, provides expert-level performance with a $2 prop and hobby-shop fuel, you might just want to try it that way - instead tossing a key ingredient to save 10 grams, and then complaining it doesn't work without further mods.

But what the heck to I know?

Oops I meant FP 20 instead of LA 20..

Brett, once again I am not arguing that your system works or doesn't work. You say it works. That is good enough for me. However, I am not so sure it is working as a tuned pipe. Even with a tuned pipe we adjust the venturi for the set-up. We change two or three thousandths with Matt's .61 set up when the temperature gets too cool (or too warm). Why does this system work as a pipe ignoring the venturi size.

But, yes, there are people who were having problems that I have set up with smaller venturis and it solved their problems. It greatly improves suction, too.

I am having the same problem with my LA25 on my P-Force. No matter what prop I put, the model seems to be happy at a high RPM. I've tried everything from 9 X 4, 10 X 3, 10 X 4 to 10.5 X 4.5. All of my lap times were in the 4.5 range. The 10.5 X 4.5 worked the best with a lap time of 5.0 but lack power in critical manuevers.

Several people in our club have the LA25 and, I notice that on lighter models, like Flite Streak. the engine stay wear you set the needle. It does not seem to run alway like on larger model.

It this, run away caused by the amount of load on the engine?

Also, the LA25 seem to be more forgiving on the tank setup. Many of the sport flyer in our club just fly them on standard vented tanks with no problem. I've experimented use uniflow only, muffler presure to the overflow and muffler presure to the uniflow. The engine seems to run about the same.

SNIP>>IT Ted and I spent an afternoon one time tweaking on the Coyote/25FP and just couldn't get it to do anything but fly just a hair too fast. It would start out OK, but as some point it would "jump" to about 4.7 second laps no matter how rich it was. Note that this was not "running away" in the classic sense - it could have gone FAR FASTER. We didn't have any APC 9-4's, which when I tried it later on a different airplane, fixed the problem.

Wow a WHOLE afternoon! Good minds make things short. Like Trimming and Engine runs.

Scott(my FP-20 likes the .236 venturi.)Riese

>SNIP>>IT Ted and I spent an afternoon one time tweaking on
>the Coyote/25FP and just couldn't get it to do anything but
>fly just a hair too fast. It would start out OK, but as some
>point it would "jump" to about 4.7 second laps no matter how
>rich it was. Note that this was not "running away" in the
>classic sense - it could have gone FAR FASTER. We didn't
>have any APC 9-4's, which when I tried it later on a
>different airplane, fixed the problem.
>
>
>Wow a WHOLE afternoon! Good minds make things short. Like
>Trimming and Engine runs.
>

Well, a whole afternoon, then giving up, followed by 4 years of not trying any more and then later replacing it with an OS26 Surpass.

Might be a good idea to
>list the stock venturi ID so that if they need to order one,
>they spec the correct opening with the .135" NVA.
>
>
>Bob Kruger

Just about gone cross-eyed reading this lot - intresting though. This question still seems unanswered though, - what is the size of the 'stock' venturi supplied by OS and is it the same for 20 & 25? I have both 20 and 25 but with iron pistons not ABC will these work just as well? Muffler supplied is the OS842 is that the same as the ABC version. I was retrofitting the 25 to a 38 inch wingspan EZ (was Frog 3.49cc diesel, but not enough power) but could just as easily fit the 20 if that is the prefered option.
Thanks.

>
>Just about gone cross-eyed reading this lot - intresting
>though. This question still seems unanswered though, - what
>is the size of the 'stock' venturi supplied by OS and is it
>the same for 20 & 25? (snip)

I answered on my first response which set everybody off in every direction without really reading what I said. But the stock venturi for the most part has been a .257 with a .135 needle. And it is the same for both the .20 and the .25. OS had been all over the place with the .35 and .40 in the early years, and then finally settled on the .265 for both engines. Then they started with the .265 for both the 40 and 46 LA. They have been gradually making it bigger until, at last count, it was over .300. I sometimes think they plop an operator down at the machine, he punches in a "nice" number, makes the things for an hour, and then they change operators and let him pick a number he likes.

Brett,

Thanks for the great information. Couldn't be more clear, except for one thing in my case. When you say don't use "too wide" a tank, what dimension of the tank are you referring to (front to back, or distance from the fuselage to the outboard edge)? Which of the commonly available stock hard tanks would you recommend?

Thanks,
Mike Wisnieski

Mike,

Brett is referring to the width of tank as it relates to distance between fuel outlet and needle valve assembly. You may remember Ted's Medic and Doctor designs both having the tank recessed into the fuselage. That's one way to deal with the problem, another is to run a skinnier tank, such as a 4-ounce clunker with what is normally the bottom of the tank flat against profile fuselage.

As for myself I have come up against some interesting problems in my allegiance to hard tanks, this being made worse by space limitations on the Flite Streak.

All is not lost, I've got some idea to fiddle around with. Until then, y'all probably need to ignore my past advice on suitable tanks. Yep, I have made several versions work, both with Stunt-normal (substandard) tune-ups on both 20FPs and 25FPs and with the relatively-new-to-me tune-up detailed in this thread by Brett. But they were lacking in that they are not easily repeatable and/or introduced compromises into a *known superior* setup which should not be compromised in any way.

Len,

You say how much you respect Brett's skills and input, yet cannot seem to wrap your mind around all of the concepts being discussed. To tell the truth, I don't mind that very much, especially as neither Brett nor myself have any ego involvement in what is known to be happening, the pleasant results.

But you have quite a number of people who pay serious attention to what you say, leading me to conclude that some of them will be sorely tempted to take part of Brett's instructions but then, for example, when it comes time to bolt on that admittedly heavy muffler will opt for a "better" piece. Promptly, and with a single stroke, completely negating any chance of seeing the performance being discussed.

This is especially distressing as I do not believe you have any experience whatsoever when it comes to the precise combination, the amazing results Brett and I are talking about.

Let me put a finer point on it: The models being discussed here, Cool Thing Profiles, are exceedingly rare. Of course you haven't seen one in action! So until you can bring some real-world experience to the discussion, how about we defer to Brett's experience and input, see how it goes from there?

>Len,
>
>You say how much you respect Brett's skills and input, yet
>cannot seem to wrap your mind around all of the concepts
>being discussed. To tell the truth, I don't mind that very
>much, especially as neither Brett nor myself have any ego
>involvement in what is known to be happening, the pleasant
>results.
>
>But you have quite a number of people who pay serious
>attention to what you say, leading me to conclude that some
>of them will be sorely tempted to take part of Brett's
>instructions but then, for example, when it comes time to
>bolt on that admittedly heavy muffler will opt for a
>"better" piece. Promptly, and with a single stroke,
>completely negating any chance of seeing the performance
>being discussed. (Dan)
>
>Dan

OK, Dan, I was trying to be nice and I will continue to do so. I never said Brett's method does not work nor do I have any intention to do so. If you want to run Brett's system, fine. But he sure lists a lot of "don'ts". So, if you want to use his heavy, restrictive muffler, fine. But it is not a pipe. And it is not acting like a pipe. And I don't think it can act like a pipe. We don't have a header here with a straight back path. We have an inlet to a chamber. I don't think the sound wave will reflect properly. We don't measure to the back of the pipe or muffler, we measure to the first baffle. But, use a restrictive muffler and a too large venturi to compensate, and have a blast.

But I have fixed people up with smaller venturis and lighter mufflers that work.

Now, since you are on the subject, how many flights have you had using a .228 venturi and a non-restrictive muffler? I didn't knock Brett's set-up. Why do you knock mine?

>OK, Dan, I was trying to be nice and I will continue to do
>so. I never said Brett's method does not work nor do I have
>any intention to do so. If you want to run Brett's system,
>fine. But he sure lists a lot of "don'ts".
Len,

I don't think Brett is listing a lot of "Don'ts". I think the basic philosophy of Brett's setup os "Box Stock" - "If it aid broke, don't fix-it"

In fact, I think the "Box Stock" setup of Brett is a lot more forgiving than what is stated regarding, running muffler pressure, no muffler presure, etc.

We have a lot of "Sport" and "Beginners" in our club that don't know anything about adjusting tank height,venturi opening, uniflow venting etc, etc.

Sometime they feel overwelmed when I try to convey all of these concepts to them. But, with the new Modern engines like LA 25, OS 20, Magnum 25. I don't have to explain much. I just say "Just go buy one and slap it on". I've seen many "Newbies" just slap this engine on a new Skyray, put in a tank at what ever height with no unflow or anything and it just runs fine. At least good enough for them to get a full flight and do some simple manuevers.

Yes Dan,
I will be an the NW Regional this year. I not sure what to bring.
Maybe I'll fly Advance with my new Cox Hyper Viper.

Or better yet, lets have a FP20 fly-off. Get Brett to bring is Skyray.

> But it is
>not a pipe. And it is not acting like a pipe. And I don't
>think it can act like a pipe.
>We don't have a header here
>with a straight back path.
> We have an inlet to a chamber.
>I don't think the sound wave will reflect properly.

Well, after having spent the better part of 3 years professionally analysing, measuring, and mitigating the effects of acoustic waves propogating through tangled masses of pipes. chambers, etc, and receiving both a Air Force commendation and a significant bonus doing so. I would have to disagree with you. Maybe when my AIAA papers:
"Results of In-Flight Testing of MILSTAR Propulsion System Acoustic Dynamics",

"Independent Readiness Review of Mars Polar Lander Descent Propulsion System Water-Hammer Effects"

and
"Mitigating the Effects of Acoustic Resonance in the MILSTAR Communcation Satellite Auxiliary Propulsion System Using Variable Pulse Delays",

get cleared by the government for public presentation, I'll send you copies.

But until then, I guess it's time for "Remedial Wave Propagation 099" class....

I'll try to put something together for the group. I would appreciate, until then, that you at least give me SOME credit for knowing something about the topic, and given that you haven't tried it nor do your comments suggest you have a good foundation on the underlying principles, that you refrain from effectively calling me a moron.

It's sound analysis, it matches flight experience perfectly, is proven in competition, and makes the "excessively big venturi" magically OK.

> We
>don't measure to the back of the pipe or muffler, we measure
>to the first baffle.

One, who is "we"? What if you don't have a baffle? What do you measure to then? The centroid of a tapered cone. Multiple reflective surfaces result in multiple tuning peaks. In fact, you can tune the pipe to either the first baffle, the second baffle, or the tail cone, and probably the end of the megaphone section, for that matter. On a baffled pipe, with two baffles, there are 3 reflected waves from the two baffles, and the tail cones.

Read Frank's article and data that documents this fact. Might also want to read the 2-stroke tuner's handbook, where a layman's explanation is provided. It also explains why Paul runs a 18.5" pipe length, I run a 16.75, and Gieseke and Doug run 15-somthing on the similar engines at the same revs.

In the FP muffler, there are also at least 3 strong return waves - directly off the far side of the muffler opposite the "Stack", one very weak one off the front of the muffler, and a relatively strong, but "soft", one off the tail cone.

>I'll try to put something together for the group. I would
>appreciate, until then, that you at least give me SOME
>credit for knowing something about the topic, and given that
>you haven't tried it nor do your comments suggest you have a
>good foundation on the underlying principles, that you
>refrain from effectively calling me a moron.
>

Wow, where did that come from? I never said that. Woah. I called you a friend, and a learned one at that. OK, you are a rocket scientist. Happy? Now let's try to see what I was trying to say.

Basically what I was trying to say is don't try to be so specific in saying there is only one way to run the engine. The problem that I see people having with the engine comes from the fact that the stock venturi is too large. Your solution: Keep the stock muffler. My solution: Put in a smaller venturi and it solves the problem. You can now use a much lighter, less restrictive muffler. If weight in the nose is no concern, keep it stock if you want. If you want to get the lead out of the nose, there is another solution.

You say potato, I say potato (It doesn't work in print. You have to have seen the play). What is wrong with saying someone else may have discovered an answer for running these things, too?

Brett, I will say it again. I thank you for posting your set up. If it works for you and you like it, that's what counts. And people can copy it if they wish. And if others want to post a set up that they have found that works, they should be welcome to do so, also.

And on the pipe...aw, forget the pipe.

Len,
It isnt necessary to have baffles to work as a pipe - quite the contary in fact - "power" pipes have no baffles - the wave reflection/inversion comes from the convergent cone. Baffles are used to broaden the response for stunt applications. Also, it isn't necessary to have a straight run from the exhaust port to the pipe, plenty of SE engines run very well on a pipe, in far more critical applications than a stunt/sport model. For really high power applications, a RE layout works best, sure.

I haven't had time, but I'd be confident that you could plug the numbers for the OS muffler into Gordon Blair's ( 2 stroke tuning expert) formulae & get close to a resonant frequency of about 12K - as Brett said.

FWIW, my setup for the LA25/Flitestreak (ARF & home brewed), is pretty much what Brett suggests. After trying many,many props, there is one standout - guess what? APC 9/4. In fact the only difference is my (homemade) tank is parallel, not wedged, I shim the rear of the tank out to get the same effect. Yep that heavy muffler works just fine & keeps the noise police happy too. To really kill the power of a LA, and make it run hotter, use a restrictive (but light) tongue muffler.

I appreciate that other approaches may work, but that suggested by Brett works very well, with the minimum of changes (like none) to the box-stock engine - that appeals to me, I'd rather fly than fiddle, or wait for special parts to arrive in the post.

Dan,

Thanks a lot for the clarification.

Hi Mike,
Didn't you fly at Bil Osborne a few years ago. What happened to you? Did you move the Oregon or something?

I am having the same problem with my LA25 on my P-Force. No matter what prop I put, the model seems to be happy at a high RPM. I've tried everything from 9 X 4, 10 X 3, 10 X 4 to 10.5 X 4.5. All of my lap times were in the 4.5 range. The 10.5 X 4.5 worked the best with a lap time of 5.0 but lack power in critical manuevers.

Heman Lee

Heman,

I could well be wrong, but it appears to me as if you are paying way too much attention to your stopwatch, along with a supposedly ideal lap time, versus what the model wants. I do not wish to be harsh, but you did state the 10.5 x 4.5 "worked best at 5.0 laps," but lacked power.
How could that possibly be so?

I once had to learn, in my early days with four-strokes, that lap times simply were not a concern, that there was no set lap-time goal to achieve. I have since been learning this lesson again--it's a lot easier second time through the process--with my O.S. 20FP/Flite Streak combinations.

For what it's worth, virtually every person who comes by the circle says the models are too fast. Mostly, methinks, having made a judgment based upon the sound of the engine. No one who has actually flown the models in question thinks they are too fast.

As I have virtually no hands-on experience with the 25LA, my only suggestion is that you throw your stopwatch through a running prop and start paying a lot more attention to the model. It's talking, you're just not listening!

See you at the 2004 NW Regionals?

What I mean when it lack power, it that when I go vertical like on hourglass or triangle the engine will slow down. With the lower pitch props, like 10 X 3 or 10 X 4, its the opposite. I can not seem to control the model. It feels fast and can't seem to hit 5 or ever 8 feet bottoms.

I put an OS FS26 Surpass, on it this morning. (More on another tread)
But is feels slow, like I have all the time in the world, even though my buddy said my lap was about 4.8 to 4.9.

>OK, Dan, I was trying to be nice and I will continue to do so. I never said Brett's method does not work nor do I have any intention to do so. If you want to run Brett's system, fine. But he sure lists a lot of "don'ts". So, if you want to use his heavy, restrictive muffler, fine.

Len,

And I will continue to be nice, although you are making this needlessly difficult, simply due to your lack of experience with the exact combination being put forth by Brett and myself. I don't *want* to use a heavy muffler, but have found that packing around the extra weight is much more than compensated by the superior performance.

>But it is not a pipe. And it is not acting like a pipe. And I don't think it can act like a pipe. We don't have a header here with a straight back path. We have an inlet to a chamber. I don't think the sound wave will reflect properly. We don't measure to the back of the pipe or muffler, we measure to the first baffle. But, use a restrictive muffler and a too large venturi to compensate, and have a blast.

I strenuously disagree. Let's see, convergent cone here, divergent cone there, the length is correct for 1/4-wave operation, what's not to understand? And then I supply test data which gives every indication the engine is really happy with stock muffler, shuns both open exhaust and a couple mufflers I have on hand. Further, at the field, in the air, the 20FPs readily demonstrate a strong tendency to run in a certain rpm range, are decidedly unhappy outside this range. Sure, they run and all, might even be acceptable to fly, in fact they are. But they simply *do not* deliver the sort of performance being described by Brett and myself.

>But I have fixed people up with smaller venturis and lighter mufflers that work.

Please see above. I think the real question is our individual definitions of what works. For purposes of this discussion, a combination which truly works is capable of winning any Advanced PA contest in the U.S., as Brett has correctly stated. I do not believe that is the standard to which you are comparing your small venturi/lighter muffler package.

>Now, since you are on the subject, how many flights have you had using a .228 venturi and a non-restrictive muffler? I didn't knock Brett's set-up. Why do you knock mine?

First, I don't recall knocking your specific setup, and while I accept your version of events, you have called into very serious question some of Brett's statements, a few of mine as well.

But to answer your question, and I thought this was already fairly clear, last year I was in fact using a tune-up much like you suggest. And I got some pretty good performance out of it, certainly slightly above the performance of your average profile, considerably better than anyone has a right to expect from a lowly ARF and a rather pedestrian power plant.

That model/engine combination, while enjoyable, would get whacked off the podium at a great many Advanced PA contests.

Len, in essence I have tried your combination, in addition to understanding the logic behind it. And I have seen a great many succumb to conventional wisdom when it comes to rooting around inside an RC-market two-stroke with a hand-held grinder, adding head shims, chucking stock muffler, etc.

It's time for you to try Brett's setup. After all, he was good enough to post the whole thing from one end to the other, so it's not like you have to do any research at all. Plug 'n play indeed.

I anxiously await the results of your tests.

Best regards,

Dan, I will also supply the set-up that Matt is using on his PA/pipe engine if you wish to try to copy it. But since you have a set-up that you are currently happy with, I have a feeling you really don't care.

By the same token, I have no desire to fly a 20 size engine at the moment. And I certainly have no desire to compete with it. I don't have time to fly what I want to fly right now. But if I did, I would have no problem setting it up with a lighter muffler and a larger prop. But, that's choice. And that's why when you look at the top 5 at the Nats or the top 20, you will find very few people flying the very same set up, even with the same engine. Why even Brett and Ted and David each set up their PA 61 engines differently. And I wouldn't want to argue a bit with any of them.

But if they wish to post what they are running, they are welcome to do so. And you can post what you are running. And when whoever wins the Walker Cup, I am happy for them. But I really doubt that any of them did it because their set up was the best, or the only way to go.

Dan, et al;

I think we are missing a critical perspective that we have talked about earlier with the FP series.

As it comes from the factory, the OS FP series is optimized for a run characteristic that is not always conducive to a good stunt run. All of these engines want to "wind up" or "run away". Their total power potential can not be utilized by the props available and the kind of flying we do.

To get past that, we do a number of things to reduce the power potential and possibly change the power curve for the engine. Some focus on the intake size and reduce the venturi cross section. Some focus on the combustion side and reduce compression or change the timing. Some focus on the exhaust side and restrict the exhaust flow. Regardless, limiting or modifying the intake, compression/ignition, or exhaust will limit the engine's raw potential and make the engine run in a manner that is conducive to stunt.

Brett's method involves the least obtrusive way to get there - pull the engine out of the box, make sure the venturi diameter is correct, and run it like it is with a 9x4 APC at an acceptable RPM. The "limiter" is the stock muffler. Leonard's (if running a stock timed engine) is to reduce the venturi cross section. That is his "limiter". Others decompress the engine so that it won't run away - that is their "limiter."

The issue with the FP series and its clones is how to turn its raw potential into usable power.

V/r

Heman,

Yes, that's me. What happened was the startup company I was working for went under, and I wound up moving up to Salem to live and work. If I can work it in around Little League and Cub Scouts and what not, I hope to make it to the NW Regionals this year, and if so I'll see you there.

Randy, Jim and I have been at the NW Regional since 2001. Randy and Jim are the number one team to beat in NW Sport Race.

I think I saw you name come on at a local contest result on the back pages of Stunt News. I guess it lucky that you move to an area that is the MECA of Control Line.

Out club is doing very well, we are getting tons of the on Saturday and Sunday. Today was about 80 degrees and there was about a dozen people flying. Some weekends we have a better turn out that a WAM contest.

>>>Do the math - for an engine with similar exhaust timing, at about 12000 rpm, you want a pipe length of about 16" (single wave travels to tail cone and back in one open period), 8" (bounces back twice), or 4" (bounces back 4 times).<<<

Brett, nice theory, but it opens more questions than it answers

I am not sure how does that muffler look, but isn’t it that type with relatively long cone at outlet? It makes back wave flatter than just vertical end of muffler (or baffle). How do you think it works after 4 times reflecting? Or do you think the shock wave forms back to stronger head until it reaches opposite wall? Isn’t it too short distance to form the shock wave?

And what is the opposite reflecting area? Front of muffler or area at engine exhaust? Or wall of sleeve opposite to exhaust port? Or intake ports? Or end of crank case? Did you find any dominating areas & dimensions, which can really form dominating resonance, which can force the engine to tune up?

It is closed, means half wave resonator. It is typically easy to force to higher harmonic resonation, but this is example of “lower???” harmonic resonation. The muffler is empty, so it should not make too much damping, but anyway half wave resonators have typically good damping at such condition, especially if its internal shape is so complex.

Do not you think there are other effects like exhaust went to volume of muffler is and 1/4 wave resonator which is short enough to be tuned at first harmonic to blowdown of engine?

FP 20's arn't being mande anymore. Right???
New FP 20's can't be had or can they?

I might note, at the expense of major fire hazard, that I've watched Bob Smiley fly his P-Force with LA25 and largely the same setup that Brett has outlined. Stock muffler, venturi, NVA with 9x4 APC prop and 10/22 fuel. This has been a very effective setup for Bob. Good laps time, good power without runaway. Whatever the reason, the setup works.

Wow what an argument!

That was awesome!

I took a brand new out of the box FP 25 and bolted it on the plane and ran it per BB to the T on clunk tank. Its very first flight was an official in a P-40 on a P-force. It was OK a bit fast. The second flight was better got a decent needle. That was between rounds. The third flight landed me in Second place in Expert. Got a good needle and the motor seemed to make max power and just stomp on through. It was AWESOME! Not to mention SIMPLE as heck!

2s engines rely heavily on the chambered exhaust to make max power. That is common knowledge throughout the industry. Restircting the intake and removing the chambered exhaust robs power. That doesnt mean it wont work but it will NOT be as strong. The motor will have an excellent run stock out of the box and use its power in the RPM range it was designed to run so I still dont see why you would change it away from that rpm range or restrict it in any way.

Mufflers as tuned pipes. Yes they are. A chambered exhaust on a 2s motor will always act a "tuned pipe". Trick is getting it the right length. Stock mufflers cant be changed so we have to hope OS got it right? We can rely on the OS company to figure that out for us. Remember the 40s on pipes. They had that tremendous rattle that you could hear anywhere. You thought rods were coming out of the nose of the plane. The OPS was loudest I ever heard. Well when I was running the FP 40s and getting killer results. I was running a long, 2.5" long, tube muffler with a pretty small exit. When I finaly got the pitch low enough to really let the motor run in its designed RPM range that pipe rattle sound would just start jumping right out of the motor. On the ground you thought is was on a pipe! I kid you not. The curve of the setup has nothing to do with hurting the ability for the sound wave to charge the cylinder. Just look at a 2s motor cycle, especially one with 4 cylinders. Curves everywhere. You here of a powerband? That is when the soundwaves and the pressure and the rpm jump up and you are gone. Some thing happens when you prop it right and get the RPM in the DESIGNED range and pow the motor is on. After getting the pipe rattle on my FP 40 I checked the instructions and yes my ground RPM were right in the neighborhood of where they say to operate the motor. It was even neelded just like they said to needle it when the carb that, wasnt there, was at full throttle. Pretty cool if you ask me.

In closing to argue BB's points on this subject would be futile.

Doug, look at Igor's take on the muffler as a "pipe". It just ain't so. The muffler on the FP 20 is a restrictive muffler and nothing more.

A while back you argued with me when I said another modeler had too small of a venturi on his engine. (It turned out he did.) Now you are ready to say a too big one is OK.

You talked about restricting power by going to the smaller venturi. Well, that is what I argued on that above mentioned engine when the modeler went to a venturi that was smaller than the formula. There is a range that works, that is very consistent from engine to engine. The choke area is directly proportional to the cubic inch displacement of the engine. Double the size of the engine, double the size of the choke area. Cut the displacement to a third, cut the choke area to a third. It is very consistent. Matt is running a .189 to .193 true venturi (no restriction) on his PA 61 on a pipe. That is a choke area of .028 to .029. But the pipe is a non-restrictive (well, not much anyway) muffler. OS got ir right (for once) when they put a .265 restrictor tyupe venturi on the FP 40. That is a choke area of .019 (same ratio, approximately). But they put a .257 restrictor with a choke area of .017 on the 20, when it should have been a choke area of about .010. That is my argument and my only argument.

Now, I have never said that what Brett is doing will not work. I want to make that clear. But just as you set up your PA engine on a pipe in one way and Brett does it in another way and I will chose to do it in a third way, and we will all be happy with what we have because it suits our needs--and it works, can't we also acknowledge that there might be (just might be?) another way to do this as well?

Now, why would I want to do that? Well, maybe I would want to change props. Or maybe I would want to get an ounce and three quarters of dead weight out of the nose by changing mufflers. Or maybe I would want to use a different tank (I don't like plastic. However, if you want to use one, I don't care. I really don't.) or maybe I want to change fuel. Or...just remember, there is choice in the world. There is very little in this hobby that only works one way.

Brett, thanks for putting up your setup for the FP20. Just for the record as other have pointed out, the same things seem to work very well on the LA 25, and just as easily.

As to whether or not the stock muffler is a "tuned pipe" get over it. The man knows what he is talking about. The only exhaust system on a model engine that doesn't have "tuned" modes is the open exhaust. ANY conglomeration of pipes and chambers you hang on WILL have resonant frequencies. Whether or not they are the right ones to make the engine run better is a subject of testing. But Brett is right on that the stock OS muffler tunes the exhaust to some degree in the 12K range. Take a look at the OS line over the last few years. Several of their motors have mufflers that were modified with extension tubes. Obviously an add-on to tune the muffler and make the engine run better instead of retooling the casting.

This has been a very interesting discussion, too bad it has gotten to be a little personal in nature, but with the severe disagreements seen, the high resistance to a "new" way of thinking, such seems to have been avoidable.

At least we got Brett fired up to the point where he listed the *entire* setup he has found to work. I'm not whining, but you guys got a whole lot more information out of him than I ever did when it comes to the 20FP. But then I didn't need much, having years ago just decided to take the man at his word no matter the topic.

Someplace there was a comment that "The List" sure has a lot of Don't-do-This to it.

That is a direct result of what I have experienced in minor degrees, Brett to a major degree. The conversation starts out, "I'm not getting good results and I'm doing what you told me to do." It *always* turns out that some seemingly minor thing has in fact been changed.

When this happens enough times, you tell them what to do and then reinforce it by telling them what not to do.

I think a major point here has already been alluded to, and that is that the tune-up Brett has outlined and Len's preferred tune-up **do not** deliver equal-but-different levels of performance.

Of course Len's suggestion will result in a nice Stunt motor which, when bolted to any number of competent profile models, will do nicely in Beginner and Intermediate, may even come up to the mid-pack level in some Advanced competitions. And if that's what you want, basically Fox 35-type running characteristics without all the vibes, you can achieve this with Len's tune-up or something similar. It will be fairly tolerant to fuel, props, NVAs, tanks and so on.

And you'll have a good time with it. I know, because that is the basic tune-up I used last year on my new-at-the-time ARF Flite Streak, fitted with a Stunt-normal, de-tuned 25FP.

On the other hand, following Brett's suggestions *exactly* as laid down will result in absolutely sparkling performance. While I was a little surprised to see Brett say it, what we're talking about here is a combination which truly can win every single Advanced PA contest in 2004, along with most of the Expert PA contests. And of the Expert contests it would not win--2004 NW Regionals, for example--the pit chatter would be all about how the R&D, building effort, piped 65s, deep-breather four-strokes and so on resulted in so few extra points over the lowly Skyray/O.S. 20FP which looks like a reject from a shop class for 8-year-old children.

If you're on the fence over this, haven't quite decided to take the same leap as Doug Moon, that's no problem. Nor is it a problem if you apply this thinking to the 25LA, even though neither Brett nor myself are ready to suggest it is a direct replacement for the 20FP, or even that all the tips for that motor apply to the newer 25LA.

I do, however, sincerely hope you are ready to be open-minded about this, along with recognizing the potential for a higher level of performance, not merely a Fox 35 run wrapped in Japanese packaging.

>This has been a very interesting discussion, too bad it has
>gotten to be a little personal in nature, but with the
>severe disagreements seen, the high resistance to a "new"
>way of thinking, such seems to have been avoidable.
>
>At least we got Brett fired up to the point where he listed
>the *entire* setup he has found to work. I'm not whining,
>but you guys got a whole lot more information out of him
>than I ever did when it comes to the 20FP. But then I didn't
>need much, having years ago just decided to take the man at
>his word no matter the topic.

I took and it kicked butt all the way to the bank!!! Even thought the fuse on my plane was broken and the tail was about to come off it still dominated!

>
>Someplace there was a comment that "The List" sure has a lot
>of Don't-do-This to it.
>
>That is a direct result of what I have experienced in minor
>degrees, Brett to a major degree. The conversation starts
>out, "I'm not getting good results and I'm doing what you
>told me to do." It *always* turns out that some seemingly
>minor thing has in fact been changed.

When listing a setup the DONTS are just as big as the DOs and should be asked for if they are not posted and they should be followed to the T just as the DOs. Not doing so will only add to frustration. Seen it many times.

>
>When this happens enough times, you tell them what to do and
>then reinforce it by telling them what not to do.

VERY GOOD WAY TO GET THE POINT ACROSS AND HELP PEOPLE GET IT RIGT THE FIRST TIME!

>
>I think a major point here has already been alluded to, and
>that is that the tune-up Brett has outlined and Len's
>preferred tune-up **do not** deliver equal-but-different
>levels of performance.
>
>Of course Len's suggestion will result in a nice Stunt motor
>which, when bolted to any number of competent profile
>models, will do nicely in Beginner and Intermediate, may
>even come up to the mid-pack level in some Advanced
>competitions. And if that's what you want, basically Fox
>35-type running characteristics without all the vibes, you
>can achieve this with Len's tune-up or something similar. It
>will be fairly tolerant to fuel, props, NVAs, tanks and so
>on.
>
>And you'll have a good time with it. I know, because that is
>the basic tune-up I used last year on my new-at-the-time ARF
>Flite Streak, fitted with a Stunt-normal, de-tuned 25FP.

Yep. Been there done that. Fought it for over 100 flights. Tried BB's setup and got it nailed down on just the third flight. It is just to easy. I am going to find a Skyray and put a killer finish on it and knock em dead!

>
>On the other hand, following Brett's suggestions *exactly*
>as laid down will result in absolutely sparkling
>performance. While I was a little surprised to see Brett say
>it, what we're talking about here is a combination which
>truly can win every single Advanced PA contest in 2004,
>along with most of the Expert PA contests. And of the Expert
>contests it would not win--2004 NW Regionals, for
>example--the pit chatter would be all about how the R&D,
>building effort, piped 65s, deep-breather four-strokes and
>so on resulted in so few extra points over the lowly
>Skyray/O.S. 20FP which looks like a reject from a shop class
>for 8-year-old children.

Yes and it is so much fun when the warped multicolored monokote(leftovers) winged plane with a busted fuse lays in a salty pattern that makes em say "What the heck was that?"

>
>If you're on the fence over this, haven't quite decided to
>take the same leap as Doug Moon, that's no problem. Nor is
>it a problem if you apply this thinking to the 25LA, even
>though neither Brett nor myself are ready to suggest it is a
>direct replacement for the 20FP, or even that all the tips
>for that motor apply to the newer 25LA.
>
>I do, however, sincerely hope you are ready to be
>open-minded about this, along with recognizing the potential
>for a higher level of performance, not merely a Fox 35 run
>wrapped in Japanese packaging.
>
>
>Dan
>
>
>

Isn't this fun?

>Doug, look at Igor's take on the muffler as a "pipe". It
>just ain't so. The muffler on the FP 20 is a restrictive
>muffler and nothing more.

You should Igor's post again. He starts out by saying that he doesnt know what the muffler looks like. So how is he going to make a statement on it that has any merit.

Anyway it is very obvious in your posting that you dont know that ALL combustion engines use soundwaves to positively charge the cylinder. Yep that includes the one in your car. However the less the performance or effeciancy that you are after in a 4s(it is critical in 2s engines to have a chambered exhaust to get max power) engine the less the soundwaves have an effect. For instance in your car the effeciancy is probabloy about 80%. Pretty normal for most every day cars. But cars that are for straight out drag racing have what is called step headers. They are header tubes with small wedges on the inner walls placed strategically in the right spots to reflect the proper sound waves at the right time to keep the cylinders charged and ready for the next fire. They are so small the amount of back pressure is not noticable to the valve but the soundwave it sends back is critical to getting the most power available. Also look up flowmaster mufflers and read up on thier muffler design. They use soundwave technology to actually quiet the exhaust and make power at the same time. Their mufflers never wear out. There is nothing in them but a few baffles. They cancel the loud tones with reflective technology and fuel the cylinders with the proper soundwaves to keep the max effeciancy up. I know about this stuff because I used to build high effeciancy race motors and research goes along way when you need a little leg up on the comp. Now about the little 20. The chamber is restrictive yes but it uses the soundwaves to charge the cylinder not the back pressure. The muffler while heavy will give more usable power than a tongue will. I ordered a tongue from you a while back. It helped the LA 25 "stunt run" a little better but the power was down and it stunk. For me all the LA 25 setups stunk. So, yes it is a tuned system. The only difference being you cant change the length, or tune of the muffler. You get what you get.

>
>A while back you argued with me when I said another modeler
>had too small of a venturi on his engine. (It turned out he
>did.) Now you are ready to say a too big one is OK.

Yes your larger venturi on that particular setup did work. But in THIS ONE PARTICULAR SETUP THE LARGER ONE DOES WORK AND MAKES MORE POWER THAN YOUR SMALLER ONE! I KNOW FROM EXPERIENCE!!!! THE BIG ONE WORKS WHEN YOU USE IT JUST LIKE BB SAYS TO!!!!

>
>You talked about restricting power by going to the smaller
>venturi. Well, that is what I argued on that above
>mentioned engine when the modeler went to a venturi that was
>smaller than the formula. There is a range that works, that
>is very consistent from engine to engine. The choke area is
>directly proportional to the cubic inch displacement of the
>engine. Double the size of the engine, double the size of
>the choke area. Cut the displacement to a third, cut the
>choke area to a third. It is very consistent. Matt is
>running a .189 to .193 true venturi (no restriction) on his
>PA 61 on a pipe. That is a choke area of .028 to .029. But
>the pipe is a non-restrictive (well, not much anyway)
>muffler. OS got ir right (for once) when they put a .265
>restrictor tyupe venturi on the FP 40. That is a choke area
>of .019 (same ratio, approximately). But they put a .257
>restrictor with a choke area of .017 on the 20, when it
>should have been a choke area of about .010. That is my
>argument and my only argument.

You are missing the point there on your last sentence. OS through research and development is able to get a 20 to run good and make good usable power on a very large venturi for that size motor with the stock chambered muffler. Why on earth would they make the venturi smaller when they can use a larger one? You are not making any sense now. The larger venturi moves more air and fuel through the motor. That means it makes more power and on motors that small you need as much power as possible. They only deal with motors using chambered exhaust systems not tongues so if the motor will run good and fly models well with the large venturi why choke off power with a small one? I dont get that thinking at all.

Going smaller on the venturi on a small engine is a major power killer through and through. Power on engines goes up exponentially with the increase in displacement and down the decrease. Randy Smith will tell you this all day long. So when you start getting down to the size we are talking about it is an actual advantage to keep the heavy muffler you are so worried about because of the power you will have to fly your model. When seriously stunting with smaller engines power is the main thing you are after. If you have to hang onto some extra weight to get all there is then do it.

>
>Now, I have never said that what Brett is doing will not
>work.

I know that. But there were many people wanting to know BB's setup so he placed it up here for them to get. And he placed up the DONTS and rightly so. He has been down the road so if you(general flier) want the run he talks about you will do what he says to do and dont do minor changes and then say it wont work. That drives people nuts. DO what he says and follow the donts also. Then you come on and say there is other ways of doing it. And you are correct but he was responding to those who were wanting his well known on the WC setup that will pretty much kick butt!

I want to make that clear. But just as you set up
>your PA engine on a pipe in one way and Brett does it in
>another way and I will chose to do it in a third way, and we
>will all be happy with what we have because it suits our
>needs--and it works, can't we also acknowledge that there
>might be (just might be?) another way to do this as well?

In this instance BB's is the BEST way for someone who has no idea what is up to setup the motor and go fly their ARF Flightstreak. Think of it from the point of view from a new flier who has very few if any flights. First thing you tell him is to drop the muffler and make mods and this and that. BB says to use all the stuff in the box and this prop and a tank that are available right there when he purchases his new ARF FS. Seems like a no brainer to me.

>
>Now, why would I want to do that? Well, maybe I would want
>to change props. Or maybe I would want to get an ounce and
>three quarters of dead weight out of the nose by changing
>mufflers. Or maybe I would want to use a different tank (I
>don't like plastic. However, if you want to use one, I
>don't care. I really don't.) or maybe I want to change
>fuel. Or...just remember, there is choice in the world.
>There is very little in this hobby that only works one way.

You are right it all works in many ways but this wasnt about saying it work this way the best.(which it is the best by the way) It was about getting his setup and the donts out to the masses who have been wanting it for sometime now. That's all.

Len's point concerning varying setups on PA 61s and so on borders on simple bickering, as there is very little relationship between Brett's optimized setup for a 20FP and the admittedly wide variety of setups for big-bore piped motors.

For one thing, the motor tune is a constant, as in *leave it stock*. When it comes to the muffler, everybody has *exactly* the same piece of equipment as opposed to various pipes from all over the world. The prop is another constant, and this is hardly a minor point, there being to my knowledge--and I believe this applies to Brett as well--only one specific size, and only one from one specific manufacturer, which is also *readily available* from most any hobby shop. Brett does list another prop, an 8.5 x 4.5, but I have no idea where to get one, and it doesn't appear as if there is any advantage to this prop.

Acknowledging all these givens going on, why is it so hard to understand there may very well be only one workable combination, specifying that a garden-variety pukey profile that flops all over the sky is not the goal, kick-tail performance as seen by Doug is what we're after.

Dan, I think a lot of what I was trying to say just got missed. I wish people would just look at the first post I put up. I was making a comment on a stock engine. I realize there are a lot of ways to "detune" or "retune" these engines, some of which make them worse. And there are also ways to make them better. But some people want to leave it stock. So, acknowledging the intent of the post, I was not suggesting any changes to the engine itself or the way that Brett was suggesting to run the stock engine. The only suggestion I was making was that if you went to a lighter, less restrictive muffler, you could do so by then going to a smaller venturi. You would still have the same rpm, same power, same prop, same type of run. You exchange one restriction (muffler) with another (venturi).

If you are happy with the weight of the muffler, or don't want to buy different parts, then Brett offered his set-up for stock parts all the way, and that is fine. And I offered my suggestion only because you had earlier posted some results of using different mufflers (on the bench) which you were not happy with. Some of these I know nothing about so I may not be happy with them either. But I was suggesting that if you were using a less restrictive muffler, then you would probably need to go to a smaller venturi to get the same type of run you were expecting with the stock parts.

Interestingly, I don't get upset when people want to change my engines the way I set them up. I give them a three or four page instruction sheet saying this is how I have set it up, this is what we have used, this is what I know works. If you change it and find something that works better, let me know. Several people have reported back on different props, different fuel, and I appreciate that.

I thought people might appreciate this. I guess not.

Len,

You're a stubborn man. And in many cases I admire that, especially if both parties to the debate are fully informed.

There is the problem: I have used something quite like your setup for the O.S. 20FP and 25FP, and I have used the setup Brett suggests. You have yet to experience the latter.

As mentioned before, we are not talking about equal-but-different styles of engine run; instead, we are looking at nominally okay (actually, "marginally okay" is better), versus performance which is only slightly less than Galaxy-class. Yes, I embellish the truth. Apologies.

Ah, but now we've had input from a hard-core competitor, Doug Moon, a flier who has still been flying on Top Five day at the Nationals, who as far as I know has taken Brett's information off this site and applied it to his own engine/model combination. Improving it hugely from what previously was the typical CL Stunt setup.

I do not believe Doug agrees with your statements as to same power, same type of run and so on.

Brett is suggesting stock parts simply because this is the way the 20FP runs the best, delivers the best results. There is nothing in the way of expedient compromise going on here. If it's a fluke or anomaly, fine. But we are most definitely not taking the easy way out to avoid the very minor amount of effort required to Stunt-normalize these engines.

Again, I don't "like," or even "like-like" the stock muffler. Yes, it is heavy. No, I do not like bolting lead to the tails of my models. No, I am not trying to avoid after-market parts; in fact, I already have them.

But I am willing to do nearly whatever it takes to get a run which is so good even an ARF Flite Streak or a SIG Skyray will be made to look nearly the equivalent to any number of PA models littering the landscape.

Dan,

Well said.

I am not in any way saying that Brett's system doesn't work. So I don't need thousands and thousands of (or even one or two) people testifying to the fact. Just Brett telling me, fine, that's enough.

OK, and I am not saying changing the muffler and venturi is going to improve it or make it run different. That is not my goal (yet). I am just trying to supply the answer to get a less restrictive muffler to act the same way. If we could get a lighter weight muffler to run on this engine the way you want it to, we would have improved it for you because we improved the weight. There are others who may not want to mess with an aftermarket muffler. They don't want to go to the additonal expense. Or maybe they need the additional weight. OK, keep it.

But let's say you would be happy taking some weight off the nose. Help me out here. You have tried a tongue muffler. Which one did you try? And which venturi did you try it with? You have a base set-up. Stock muffler, stock venturi, suggested prop. What happened when you changed to your tongue muffler while keeping everything else the same?

I saw your report in an earlier thread, but you didn't tell me which tongue muffler you tried. You did say you used an ST needle, however, so you already brought the venturi size down 20 thousandths at the same time. Would you be willing to try one of mine? I would love to see the comparison of the power difference between the stock muffler and this one. If this muffler doesn't give as much power as the stock muffler, then we don't need to go any further. If, however, the engine takes off and runs away, then maybe we try going to a smaller venturi to bring the power back to what you had. Are you game?

Len,

I guess we're both pretty stubborn people.

You like to claim that you are not saying Brett's setup doesn't work while immediately claiming the pipe is not a muffler. Or the muffler is not a pipe. Whatever. I won't let you have it both ways. The stock muffler is an integral component in Brett's setup and until you get over that hurdle you will continue to have great difficulty.

The tongue muffler to which you refer, and which was used in tests posted on another thread, is an RSM unit which had originally been used on a Fox 35. Thus my standard modification of very slightly oversizing the outlet holes to .078. When first beginning to fly my ARF Flite Streak--25FP for power--I modified this muffler such that it would bolt up to the 25.

Going by memory alone, the 25 was detuned with ST NVA, although I also used a similar unit from J&J Sales.

While I did not know it at the time--the 25FP had a couple years earlier been installed in my Super Combat Streak--the motor also had three (3) extra .005 head shims in addition to single stock shim.

Other details are a bit sketchy, although I can refer to my notes this evening. Several different props were used and I liked the APC 9-4 even if was not Killer with that tune-up.

I guess the real point is, and I hang my head now, admitting that I wrote about it in Stunt News, I got to a traditional type of 4-2-4 run which was more than adequate for the ARF FS. GRW 3.25-ounce chicken hopper, which did in fact work well in this application, straight uni-flo, no muffler pressure. SIG 10/25 all-castor fuel, although a fair amount of 10% Champion fuel as well. Modded RSM tongue muffler.

It was nice. Probably as nice as what you suggest. But the combination was still a pukey profile, made remarkable only due to the price of the ARF, the ease with which it all went together, that I had never owned a profile Streak, that it was the most competitive piece I owned when a contest came up with P-40 on the menu.

For back-up, the only person active on this site who has actually flown the model in question, with above 4-2-4 break characteristics in the motor, is Preston. While I set the model off too fat, needle settings being an ongoing problem when not using stock muffler, I believe he will confirm what I am saying and that model was always "there," even if giving a light feel at the handle. (Plus he had been flying an AMA Combat model, had not erased the muscle memory.)

Then I switched to Brett's tune-up, albeit still with the 25. Whoa! Major improvement and my motor did not exhibit any sort of run-away problems.

Over the winter I landed a couple used 20FPs. Again using Brett's tune-up the model went up in status to a Cool Thing Profile.

The answer to your query of what happened when I went from tongue muffler to stock muffler may be answered by reading my posted test results in reverse order. The revs were solid, both at peak and throughout normal rpm range with stock muffler. They jumped around with tongue muffler. These results, obtained on test stand, exactly mirror the results seen while out flying.

While game for a great many things, let's modify the challenge a bit.

First, **you try Brett's tune-up.**

There are a few of us on this site who have, most notably Doug Moon because he in not on the left coast, certainly has not seen Brett's model fly, had made some effort at getting a 25FP/Primary Force to work in the traditional way. And you saw his enthusiasm, the result obtained in Expert PA.

Then, and only then, you may certainly send me any and all components which you feel will improve the 20FP or the 25FP. Better yet, develop a complete package of venturi, motor, muffler, prop, fuel and so on. You assemble and verify as working to specification. Loan me the hardware for a month, I will supply model, fuel, plugs, etc.

It will be easy to swap all this stuff back and forth over a couple flying sessions, after which I will return all of it to you.

As to a lighter muffler, of course I would prefer such a unit, especially as my FS is packing an extra 14 grams at the tail.

However, wing loading is not an issue for the model in question, nor is it for the Skyray, certainly not for the Primary Force. But power loading, and the correct power delivery, is a huge issue, the single factor in elevating what are otherwise pukey profiles to a package fully capable of winning more than a few Expert PA contests in 2004.

For what it's worth, my first attempts at a lighter muffler will be to test a MACS muffler on the 20FPs. You are of course welcome to send one of yours to me, but package approach suggested above is preferred.

Well, Dan, the challenge won't work in reverse because you have the model and the engine. I don't have a model at present, nor the time, nor the desire to fly a 20 size plane. Since you had one, and had is set up the way you like it, I was offering the opportunity to try the tongue muffler on it.

But, since we are both stubborn... Hmm.

What does the RSM muffler have, ten holes, or twelve? The ones I have use fifteen holes of .078 diameter. Art's tongue mufflers use ten holes of .089 for reference. I have those, too.

Anyway, you used an unknown engine with a choked down venturi, and added head shims and our test was supposed to be stock.

How about just running the tests again with a stock set-up of a 20 FP with the preferred prop, muffler and fuel. Check it on the test stand and then give us the results of open exhaust, tongue muffler (use yours for now) and stock muffler. I would be interested to see who tese compare. What are the peak readings each way, and then bring it down a couple of hundred rpm with each and see how it holds. That should be simple enough.

>Well, Dan, the challenge won't work in reverse because you
>have the model and the engine. I don't have a model at
>present, nor the time, nor the desire to fly a 20 size
>plane. Since you had one, and had is set up the way you
>like it, I was offering the opportunity to try the tongue
>muffler on it.
>
>
Len,

But I offered an alternative, one you have chosen to ignore. Don't send just a tongue muffler which I will either keep to myself or give away after a few runs, send along your version of an optimized power plant, muffler of your choice, and I will swap it back and forth between my own 20FP, will probably let a friend or two try it as well. I might even find the time to slip this unit's muffler on my own motors, we'll kill two birds with one stone. When finished, probably a month or so, all will be returned.

>But, since we are both stubborn... Hmm.
>
I will address this in another posting.

>What does the RSM muffler have, ten holes, or twelve? The
>ones I have use fifteen holes of .078 diameter. Art's
>tongue mufflers use ten holes of .089 for reference. I have
>those, too.
>

The RSM tongue mufflers I am using have twelve holes, as mentioned all of them opened slightly to .078. This is what I prefer for my Fox 35s, muffler tested on 20 and 25FPs having been robbed from a Fox.

>Anyway, you used an unknown engine with a choked down
>venturi, and added head shims and our test was supposed to
>be stock.
>
Above comment borders on bizarre, but I did dig out my notes from 4.13.99 when both my Soup Combat Streaker and 25FP were new. It was run in, a rather pointless exercise I have since discovered, completely stock, including muffler, the exception being standard ST NVA. (Motor had been converted to CL.) Run-in was for a total of 24 minutes using 10/29/61 fuel, a standard Fox 35 mixture. APC 9-4 prop as I had by then been talking to Brett, although he neglected to furnish Don't Do This! listing, as seen below.

When flying I switched to ST NVA which had been remachined to .125 diameter. Typical too-big venturi problems.

Went to ST NVA turned to .140 diameter. This helped, but added Bru-Line "green" fine air filter, which helped even more.

Flew model about 20 times over the next couple weeks.

During that time, insertions of comments about the break being better, adding head shims began to show up. And demonstrate that already I was going off the res.

Over a series of about 30 flights I added .005 head shims one at a time until I got to one (1) stock shim which I believe to be .015 thick, plus three (3) .005 head shims for a total, and monstrous, stack of .030.

Forgive me, Brett. I hang my head in shame. Especially as I then succumbed to the siren song of a really light muffler (RSM tongue) which required only minor modification to bolt directly to case of 25FP.

During the next bunch of trials I tried APC 10-3, 10-4 and 10-5 props, APC 10-4 and 10-5 cut to 9.5, a Real-Deal (Clarence Bull-produced) B-Y&O 10-5 cut to 9.375, full-blade R-D B-Y&0 in 10-5. Went back to the APC 9-4.

Lost interest in model, it had only been built for fun, not contest work, all gathered dust.

Until my first ARF Flite Streak. Without checking my notes I bolted the 25FP in place, complete with tongue muffler. Went through a series of fuel tanks, finally getting quite good results with the GRW 3.25-ounce chicken hopper.

Remember, I was much more interested in seeing if the ARF was worth a rat, substandard motor performance was fine, just as long as it kinda worked.

Noticing that the model really did fly well, I became enthused. But I was still working for a run such as we see with a really nice Fox 35.

This was quite frustrating. I'd hit it and then the magic would be gone for several flights.

About this time I had three or four lean runs in a row, and while the motor was not happy, sagging in some maneuvers, and it was a little fast, I was getting much-improved performance from the total package.

Thus it was that after the 2003 contest season wound down I started working my way from actually doing the stuff on the Don't-Do list to the side of goodness and light.

This approach worked well enough to find a couple used 20FPs.

True, I've had some problems with fuel feed, especially when going back to stock muffler and .140-diameter spray bar. However, it turns out some of this was related to motor problems with the weak sister of the two 20FPs, lack of decent space on the ARF, no workable tank which would fit available space, and so on. These problems appear to have been effectively dealt with, although I want one more flying session before blabbing the news.

>How about just running the tests again with a stock set-up
>of a 20 FP with the preferred prop, muffler and fuel. Check
>it on the test stand and then give us the results of open
>exhaust, tongue muffler (use yours for now) and stock
>muffler. I would be interested to see who tese compare.
>What are the peak readings each way, and then bring it down
>a couple of hundred rpm with each and see how it holds.
>That should be simple enough.

C'mon, Len! I've done that already. Including backing the motors down in revs, even though that exact information was not published. On the other hand, doing so only left me open to more of this exact sort of nit-picking, and I regarded the information as redundant as the same wandering revs versus locked-in revs deal was seen in every test.

You have worn me down, I grow ever more tired of this. Len, the ball is in your court. Send whatever you want to furnish, I have given you my preferred assemblage of hardware. As one who has--unlike yourself--experienced the differences between a 25FP tuned to run in the traditional manner and a 20FP to Brett's specs, be glad to spend an afternoon swapping motors back and forth, noting results.

>But, since we are both stubborn... Hmm.

>Leonard Neumann

To All,

I wish to address this in a separate post, to explain myself more fully as to actions taken, things said.

This has nothing to do with ego, or being stubborn, or even being "right," however one defines the term.

It has to do with long-time friends Mike Hazel and John Thompson, and all others like them, although surely Mike and John will be stunned to see themselves mentioned here.

Mike and John are the two guys behind Flying Lines newsletter, and without giving them the equivalent to a big wet kiss, their efforts over many years have proven vital to my current enjoyment of CL Stunt, that there was even significant CL activity when I decided to come back to it.

Mike is currently dabbling in CL Stunt. I have little to tell him when it comes to his favorite events, Speed and Racing. But I can help him enjoy Stunt more fully. Even tried to once, suggesting he build a Brett Special, Skyray with O.S. 20FP. And he did. But I failed to follow through to any extent, even when seeing the thing roaring around like an 80-mph Combat model.

Mike can benefit greatly from this discussion, as the tune-up suggested by Brett will result in a hugely improved package, his enjoyment of the event will increase substantially, as will the scores he posts in 2004. However, he cannot expect the super results I predict if the effort is watered down with well-meaning input from those without the appropriate background.

John is a different case in that his Combat background stands him in very good stead when it comes time to do the maneuvers. His problem is two-fold in that his equipment, while good, is sometimes lacking; and for some reason he tends to wilt when judges are on the scene. John is currently stuck in 440-range in Advanced PA, no matter what he does, and he in fact makes the effort.

Another factor here--and it applies to a lot of people--is that John has quite likely never experienced the sort of power delivery being discussed on this thread, and if he has certainly never with his own model. So in improving his equipment the goal, or at least a goal, is not fully appreciated.

The simple substitution of a better power plant can *dramatically* improve a great many models, especially something like a Skyray or Flite Streak or even John's current model, an Oriental, even though it would not be converting it to a 20FP.

I know for a fact I could give John my ARF FS/O.S. 20FP combination just days before any local contest and in both Classic and Advanced PA he would *immediately* be working on the 500-point barrier, not his current 450-point frustrations. Yes, without appearance points.

So as this rages back and forth, I think of Mike, John and all the others in a similar situation who have been handed by Brett the equivalent to a life-time supply of Viagra when it comes to enhanced performance in the CL circle (please don't take this analogy too far), ease of practicing and competing, more pure enjoyment from CL Stunt.

But, as emphasized so many times, each time refuted by a pretty good engine guy, as far as we know at this time there is one--and only one--setup which works properly.

So use it, don't water it down, don't change it. If you don't like it, that's one thing. But try it first--which is what Len really should be doing prior to going all wonky on us--see what you think and get back to me. After all, there is always room in Expert PA for a few more fliers.

>So use it, don't water it down, don't change it. If you
>don't like it, that's one thing. But try it first--which is
>what Len really should be doing prior to going all wonky on
>us--see what you think and get back to me. After all, there
>is always room in Expert PA for a few more fliers.
>
>Dan

Dan, I get a feeling in this whole disertation that you and several others didn't read a thing I said.

First off, my choice of engine would be different. I would modify it, change it, run it slower and with a bigger prop. But that is my choice. You don't have to like it or try it. I don't care. And I am not trying to set up a "my system is better than your system." That never was my point.

I never offered it to change your system or Brett's system in any way. I never suggested for you to make any internal changes. Run the same prop. Run the same fuel. Run the same rpm. Run the same run. If that is what you want, run it.

All I suggested in the first place was, and I stand by this, that if you like this type of run and want to save weight, you can put a lighter, less restrictive muffler on and go to a smaller venturi. It shouldn't change a thing on the run. But since this has caused such a furor, why don't you just tap the tongue muffler you have for 4-40 screws, and then close up the muffler one hole at a time until you have the same amount of restriction as the stock muffler, and then you don't have to change the venturi.

Let's quit. I'm ready.

When I have time I will post on a separate thread some tests I did with mufflers with certain conclusions to be drawn. Just remember, sometimes you need back pressure. Sometimes you don't. It can be your friend and your enemy.

>Dan, I get a feeling in this whole disertation that you and
>several others didn't read a thing I said.
>
Wrong. Absolutely wrong.

>First off, my choice of engine would be different. I would
>modify it, change it, run it slower and with a bigger prop.
>But that is my choice. You don't have to like it or try it.
> I don't care. And I am not trying to set up a "my system
>is better than your system." That never was my point.
>
I have tried "it." Nothing more than marginally good performance.

>I never offered it to change your system or Brett's system
>in any way.

Substitution of any known after-market muffler for stock O.S. muffler is a huge change.

I never suggested for you to make any internal
>changes. Run the same prop. Run the same fuel. Run the
>same rpm. Run the same run. If that is what you want, run
>it.
>
>All I suggested in the first place was, and I stand by this,
>that if you like this type of run and want to save weight,
>you can put a lighter, less restrictive muffler on and go to
>a smaller venturi.

No, you can't. The problem here is that you have never experienced, or even seen, the type of run and the performance to be gained from it.

>It shouldn't change a thing on the run.

But it does. And not by any small margin.

>But since this has caused such a furor, why don't you just
>tap the tongue muffler you have for 4-40 screws, and then
>close up the muffler one hole at a time until you have the
>same amount of restriction as the stock muffler, and then
>you don't have to change the venturi.
>
Because it ruins the overall package. Please, please refer to Brett's comments concerning pipes, er, stock mufflers.

>Let's quit. I'm ready.

I'm not, refer to post N.45 as to why.
>
>When I have time I will post on a separate thread some tests
>I did with mufflers with certain conclusions to be drawn.
>Just remember, sometimes you need back pressure. Sometimes
>you don't. It can be your friend and your enemy.

Agreed. And sometimes you need, in this case cannot do without, fast-as-the-speed-of-sound pulses manipulating how the engine runs, in what rpm range it likes to perform.

The ball is still in your court. When can I expect to see this optimized power plant for my ARF Flite Streak?

Dan, Brett..

Will the FP-25 deliver the same nirvana engine run being discussed in this thread? I would like to experience it but have no desire to buy another engine. I have a Flight Streak with an FP 25 that I use to get the spring cobwebs out. It is setup per Brett's recommendations, Stock muffler, stock venturi with a Bruline air filter turning a Tornado 9-4. Should I pull the air filter? I also has the dreded GRW 3 1/4 oz Chicken Hopper tank.

It always thought the engine run was pretty darn good but am willing to see if it can be improved..

>Dan, Brett..
>
>Will the FP-25 deliver the same nirvana engine run being
>discussed in this thread? I would like to experience it but
>have no desire to buy another engine. I have a Flight Streak
>with an FP 25 that I use to get the spring cobwebs out. It
>is setup per Brett's recommendations, Stock muffler, stock
>venturi with a Bruline air filter turning a Tornado 9-4.
>Should I pull the air filter? I also has the dreded GRW 3
>1/4 oz Chicken Hopper tank.
>
>It always thought the engine run was pretty darn good but am
>willing to see if it can be improved..
>
>Bob

Bob,

You're close, but don't forget Brett's caution that a 25FP will be way too much motor, more appropriate for a Primay Force. Refer to my series of tests for ways to de-tune without screwing up power delivery, ST NVA being a big hit and so the first choice.

Hoping Bru-Line is of the "fine" (green) version, as it is more restrictive than the black number.

You're close on the prop, but we *know* the APC 9-4 works, so that's definitely what I would start with.

Don't automatically chuck the GRW tank. Improved fuel draw from fitting ST NVA will probably see this combination work fine for your purposes where lap time variations from full to empty are not a big concern.

Might consider 4-ounce Pylon (Sullivan) clunker on inboard side of fuselage. That's what I am currently using, although I want one more flying session to prove the concept. You will find the RST-4 has most convenient arragement of plumbing, but slant-front tanks will of course work as well.

Plumb per instructions, maybe add a third tube for convenience in filling. Don't bother with uni-flo clunk which follows fuel pick-up.

If I ever happened to run into ao NIB OS.20FP I'd use Brett's *recipe*.

I've learned to take whatever he says as "gospel truth", for the folowing reasons:

1- He's one of the top 10 US stunt pilots. You don't get there without really knowing A LOT about - among many subjects - engines.

Ted is a world champ, and even though he - as the gentleman he is - has kept his nose clean on this whole thread, I know he agrees 100% with Brett.

2 - All the advice Brett ever gave me has proved to be GOOD advice.

3 - His posting makes all the sense in the world to me.

4 - It's simple and folfproof.

About Len, (since this whole thread is really a personal thing between him and Brett, I must say that.

He also has - just like Brett - in many ocasions given me precious advice.

He is a man of common sense, wisdom and generosity, not to mention he's also a man of God.

I owe him a LOT!

But I must say that Len is somewhat biased in his opinions about how to set up and run engines.

This is due to the fact that as an engine reworker Len is carrying the burden (a burden that BTW he needs as much as a hole in the head) of having to be the one to say the last word.

Len has a certain pride, a certain necessity to prove himlelf - a pride that Brett is free from, not becaus he's any better on more virtous than Leonard, but because as a top flyer his ego doesn't crave for this kind of "massage".

I've seen the same thing happen among musicians. The ones that can REALLY play usually don't react like Len did if some other cat makes a statement like, for instance:

"To be a real jazz musician you gota be able to play "Cherokee" in B natural!"

I can't play Cherokee" in B natural, but I'm not in the need of proving the world that I'm a "real jazz musician". My accomplishments speak for me.

I don't get touchy.

On the other side I find it ugly to get down on Len the way you cats are doing. This isn't a case of life and death, folks! Get out of Len's case, for God's sake!!!

I believe that not only Len, but other gouys at SSF got tickled by Brett's not-so-diplomatic way of sharing the result of his experience with them OS.20FP's; don't you guys know he suffers (in a mild way) of Asperger's syndrome?

Not so severely that he can't be an acomplished "rokkit engenieer" (sorry Brett, I'll loose the friend but not the wise crack) and a superb stunt flyer, but enough to make him lack the social varnish that makes us more accepting of what people tell us, even when they're right...

SO, what's the big deal?

Let's put an end to all this nonsense and spend our time and effort on something more useful!!

God bless ya all!

In Christ,

Ion (must have been a loooong winter at the northern hemisphere) Muniz

Ion,

You too need refer to post N.45.

The last person in CL Stunt I want to beat up on is Len, no matter how difficult he is being on this issue.

And Brett responds in the way he does because he's an engineer. They're all like that. Insert stupid smiley face.

(snip)
>About Len, (since this whole thread is really a personal
>thing between him and Brett, I must say that.
>

Ion, without responding to everything, let me at least make two points. First off, this is not and never was intended as a personal thing between me and Brett. My whole intent was misread from the very beginning.

I consider Brett a dear friend. I hope it remains that way, and that everything that was misread and misconstrued doesn't change anything.

>But I must say that Len is somewhat biased in his opinions
>about how to set up and run engines.
>

In that sentence you are correct. I am biased. You are biased. Most everyone is biased. That doesn't change any thing. We all have our opinions as to what works best for us. And then we try to set things up that way. Brett and Ted run their engines differently. It doesn't mean one is right and one is wrong. Big deal!

But, I will say it again, I never intended on this thread to offer a different way in which the engine was run other than what Brett intended. Certainly I did not suggest making internal changes on it. Brett was listing his method of running it. I thank him for that and am glad that he is willing to share this. That is what this whole forum is all about. The only problems that arise are when someone says, "If you don't run it my way, you are wrong."

I made the comment that the stock venturi is too big (I stand by that) and the muffler is too restrictive (I stand by that). The way Brett is running it, however, he has found a way for them to work together. If you are happy with that type of run and are happy with the weight of the muffler, then there is no need to go any further. (Now, this is not getting personal, is it?)

I only suggested that you can go to a lighter muffler and keep the same run. If you go to a lighter muffler that has less restriction, you can go to a smaller venturi and keep the same run. That is it. End of story. There should be no animosity here at all. If you don't care to follow what I suggest, don't. It doesn't hurt my feelings what you choose to run.

I guess what I should have said was, you can go to a lighter muffler if you make sure you keep the same amount of back pressure, because then you won't have to change the venturi. But what's the big deal about changing the venturi? OS has used six different ventiris that I know of on their LA 46 to date. They, apparently, aren't afraid to change. However, if someone sayd, "Run it stok", you had better know which one you have got.

>In that sentence you are correct. I am biased. You are
>biased. Most everyone is biased. That doesn't change any
>thing. We all have our opinions as to what works best for
>us. And then we try to set things up that way. Brett and
>Ted run their engines differently. It doesn't mean one is
>right and one is wrong. Big deal!

I AM ALWAYS RIGHT!!!!!!(hee hee hee, just kidding)

>I only suggested that you can go to a lighter muffler and
>keep the same run.

That is just it Len. People(me and Dan and Brett) are telling you that we have tried this and it doesnt work.

THE RUN IS CHANGED AND NOT IN A GOOD WAY!

The run is very inconsistant and at times flat out stinky! Read Dan's post about get the magic and then it would be gone. I had the very same thing and we live thousands of miles apart. Not coincedence if you ask me. Cant get a needle, cant get the same amount of run time, cant get the same lap time, sometimes cant even get the same rpm. It just goes haywire!

If you go to a lighter muffler that has
>less restriction, you can go to a smaller venturi and keep
>the same run. That is it. End of story. There should be
>no animosity here at all. If you don't care to follow what
>I suggest, don't. It doesn't hurt my feelings what you
>choose to run.

No animosity what so ever. But I have tried it and it doesnt work. I had a bruline green on there AND A PIECE OF BLASA STUCK IN ON HALF THE VENTURI FOR RESTRICTION AND STILL NOTHING ON THE RUN CONSISTANCY, NOTHING, ZIP, ZERO, NADDA!!! This was when I was trying the tongue to keep the weight of the muffler off the plane.

>
>I guess what I should have said was, you can go to a lighter
>muffler if you make sure you keep the same amount of back
>pressure, because then you won't have to change the venturi.

It isnt that simple, period. It needs the chamber muffler not just the pressure. It needs the soundwaves. I know you dont buy this one bit but that doesnt mean it doesnt still need them. They help so much more than you or I will ever know.

Soundwave technology is a real thing and motors this small, and weak, can have real benifits from them. So much so that keeping the heavy muffler is actually a good thing.

> But what's the big deal about changing the venturi? OS has
>used six different ventiris that I know of on their LA 46 to
>date. They, apparently, aren't afraid to change. However,
>if someone sayd, "Run it stok", you had better know which
>one you have got.
>
>
>
>

Yes they do send out many different venturi sizes. And I have run many many many OS's in the so called "Stok" form. As long as you have some sort of chamber muffler on there, be it tube, stock(yuck), or pipe, you benifit from the soundwaves needed to keep the thing alive. Take away that chamber and you have to start hunting for the exact size venturi and so on and so on and so on.....

If someone made a tube for the 25 it would be AWESOME!

Bob,

I ran the FP25 per the BB. I didnt quite know it at the time. But after he posted it and I went a looked at it I knew right away I was on the right track. I knew he was getting killer runs in the stock form with the big fatty muffler and I went his route using the APC 9-4 and Sullivan 4oz clunker sig 10% champion fuel. I am setup exactly the way he suggests and it works perfectly!

Come to think of it the very first flight was on the Tongue muffler I had on my LA 25, run away. Needless to say it was fast and I couldnt fly it well and was running in 5th place after that round. Ran home and got the stok proker. Had one more between round practice flight and knew we had something there. Got it dialed in on the thrid flight!

TO EASY!

>Stock Muffler
>Things NOT TO DO:
>modify muffler
>replace muffler

I have two FP25s both with the OS 842 muffler but one came complete with the central 1.25inch 'quiet' extension the other did not. Which is the 'stock' version?
Thanks,

>>Stock Muffler
>>Things NOT TO DO:
>>modify muffler
>>replace muffler
>
>I have two FP25s both with the OS 842 muffler but one came
>complete with the central 1.25inch 'quiet' extension the
>other did not. Which is the 'stock' version?
>Thanks,

They are both stock. My 25FP and both (used) 20FPs came with this "attenuation" cone. Others have never seen a NIB 25FP with this noise-reducing device.

When referring to "stock" 20/25 mufflers, I am pretty sure all of us are referring to muffler w/o this piece.

See my series of tests for effect on power. I think it was around 300 rpm or so.

THIS IS ALL JUST "TOO" MUCH FUN!

Tell you what. I'll buy a "Leonard" FP .20 and ask that Len ship it to the Dirt. Come the end of May we'll have the great Northwest Regional up in Oregon. We can get a ton of pilots to fly Dirt's Flite Streak with both engines, a BB stocker and Len's set-up precisely as suggested by him. We can even do the equivilant of a "double blind" thing by not telling pilots what set-up they are flying and asking them to write up their feelings on the performance.

Heck, if we've got time for adding ARF stunt at contests surely we can devote a late evening to valuable developmental evaluation (in fact, I'll insist that P. W. fly it over and over and over again just to fine tune his touch for Expert the next morning )

Tell me how much, Len and the check'll be in the mail.

Ted

p.s. Only fair that we let Len test both engines, too. I'll also agree to buy him an ARF Flite Streak for the test as long as nobody tells the anti BOM/Appearance Point faction I've contributed to the bottom line of the Chinese labor pool. Nobody will tell, will they?

Ted,

We've missed you, to the point where I had almost forgotten why.

Ah, now I remember: A wit with a pointed end to it.

We're covered on my end. Lots of room in that old van for more models, especially things such as ARF Flite Streaks, of which I have two, both within .18 ounces of each other.

As long as we are daring Len, I can add to the mix. John Leidle was flying at an adjacent circle last weekend. When leaving he stopped by and said, "Ya know, that 20FP on your Flite Streak really does sound and act like a piped motor."

Incidentally, PW has already flown one of the ARFs, again last weekend, also on his way home. Easy 500-point-plus pattern. He did say it looks a little strange with 4-ounce clunker hung to left side of fuselage...

I am quite sure Paul, and you of course, will be certain to avoid flying a profile, Cool Thing or not, within mere hours of what is bound to be a knife fight in Expert PA.

Speaking of which, do be sure to ask if you can see my new handle. It's a special-purpose deal, nothing like your superb design, but it may indeed have an application at this year's NW Regionals.

(Those who have seen my newest handle, did I swear you to secrecy yet?)

(snip)
>As long as we are daring Len, I can add to the mix. John
>Leidle was flying at an adjacent circle last weekend. When
>leaving he stopped by and said, "Ya know, that 20FP on your
>Flite Streak really does sound and act like a piped motor."
>(snip)
>Dan
>

Now the interesting thing is, I don't doubt that it *sounds* like a pipe motor. When we were running the modified 35 FP with a 12.5 x 5.5 Bolly prop, the engine wound up on the ground and sunded just like a pipe motor. As soon as it was launched it broke into a lean 4-cycle, and probably sounded a little less like one at that point because we weren't running it near its maximum power. But, if you are using a stock engine on a muffler and wind it up, it probably will sound like a pipe motor. And the stock muffler isn't the factor. We can put one of Art's tube mufflers on it (which is what we used on the FP) or even one of Randy's and it will probably still sound like a pipe motor. But you all are still missing the point.

I was never challenging the stock motor set up verses my modified set up (although I think I would like the challenge.) All I was ever trying to say was the stock set-up can run with a different muffler. If the new muffler is less restrictive, then put a smaller venturi on it and run it with the same prop, same rpm, same type of run. In fact, you should be able to set it up with the right venturi in such a way that the people at the handle wouldn't be able to tell the difference except for the sound that the different muffler would produce except...(here's the difference) if we put a lighter muffler on we are going to change the balance. Now we take some tail weight out and the stock engine with the new muffler is going to fly better.

Or, we could modify it. (Remember, I have not been talking about modifying the engine up to this point.) Then we could run the engine slower with a bigger prop and you could not only hear the difference, you would feel the difference. However, that was never the point of my argument.

Brett has played with props to find the best combination in his mind for the stock set-up done his way. I haven't played with props to find the best combinaton with an FP 20 that I might modify. Matter of fact, I don't even own a 20. I have 25s, but that is not a fair comparison. I don't really have time to play with these which is why I was suggesting putting a different muffler on Dan's set up and changing the venturi. Even there we would need to change the venturi to match his prop (just like you do with the pipe engine).

What I think would be an interesting (and easy) test would be to put a tongue muffler on Dan's engine with the holes tapped for 4-40 screws. Then leave the venturi alone and add screws in the exhaust holes until the back pressure matches that of the stock engine. At that point you should be able to match its performance.

Let's see, the ARF Cardinals should be coming out shortly. Would you like to try a challenge with a stock 35 FP vs one of mine swinging a 12.5 x 5.5 Bolly? Or how about using the Magnum 53? Now we are in my territory where I have tested prop combinations and know the set-up. And I know it will blow the stock set-up away. But, again, that was never the point of my posts. I wasn't comparing my mofidied engines to the stock engine. I was only suggesting you could use a different muffler if you changed the venturi.

A couple of questions for Len. and I'm not being a smart aleck. I'm curious as to his opinions and their sources.

What's the weight difference between the stock .20 muffler and the tongue muffler?

You've commented several times re the "correct" choke area/venturi for various engines. Can you elaborate on the method and basis for determining that dimension? On the surface it seems as though you are as adamant about "correct" choke area as you accuse Brett of being regarding his preference for the stock components. What is the driving force and perfomance expectation for modifying the engines to meet your preferred specs?

And ... again not trying to be a smarty pants ... , on what emperical basis do you support your preference for modifying the engine. Have you flown (or had Matt fly) .20 powered aircraft with the engines in various configurations or is your point of view driven by a conviction to the principles you've developed regarding what is and is not "correct" regarding choke area?

Lastly, has your developmental work been restricted to larger bore engines? I know you've a well earned reputation for building good mid size engines -- .35s and .40s -- but have you done enough work on engines of this size to be confident in your assessments?

We all know that a 1/2A must pretty much be run peaked out to get any sort of performance out of a stunt airplane. We also know that big bore stuff is happy as a clam flying pretty gross large stunters in a loafing four cycle. Somewhere in between these extremes is a cross over point where the engines and the appropriate configurations for stunt metamorph from one type to another. My experience is that cross over occurs in the Class A range about which we've been debating.

In other words, I believe the .20s etc, fundamentally require a different approach to doing the work we need done than do motors almost twice as big in displacement.

I still think the "challenge" would be a great deal of fun and informative for all of the SSW crew. I'm serious about purchasing a .20 built to your configuration and I think the ARF Flite Streaks would be an ideal and inexpensive vehicle on which to make the comparisons.

How much $$$$

>A couple of questions for Len. (snip)
>What's the weight difference between the stock .20 muffler
>and the tongue muffler?

OK, without bolts the stock muffler is 62 grams or 2.18 ounces.
I have two tongue mufflers available, both of which are pretty hefty.
One os made by Art and is a little shorter and blends more with the contour of the exhaust and case finish.
The other is custom CNC made and has a larger chamber.
Both weigh 14 grams without bolts or about .49 ounces.

In addition I now have some light weight tube mufflers that are not cheap, but are CNC made and weigh in at 34 grams or 1.16 ounces.
And for ultimate lightness, there is the RSM tongue muffler that Dan was using. I don't like these as well as they are a bit flimsy, but they weigh in at about .3 ounce.

So, with a good tongue muffler we can take over an ounce and a half off the nose of the plane. If you need the weight, well, maybe it doesn't make any difference running the stock muffler. If you don't, and need tail weight to balance, then you are adding even more unneeded weight and to the extremeties, at that (bar bell effect)

>You've commented several times re the "correct" choke
>area/venturi for various engines. Can you elaborate on the
>method and basis for determining that dimension? (snip)

This is a formula that Pat Johnston had sent to me one day for my opinion. I had been developing venturi sizes that "worked" for various engines without paying too much attention to formula, but, when comparing these to the formula he sent me, I had to agree that this worked.

Now this works for stock engines, such as Brett is running. "Trick" engines will start to leave the pattern. And I guess running the draggy, choked down stock muffler already puts this engine into the "trick" category because even Brett and Dan and others agree in saying you need to put a smaller venturi on the .25 than on the .20. It seems odd, doesn't it?

Now, before going to the formula, I want to mention first those engines that go out of the range. George Aldrich would modify engines by changing the timing to reduce blow down, hogging out the head to reduce compression, and then opening up the venturi to regain part of the power that was lost. Coincidentally, the Fox 35 follows this same pattern and its venturi size falls outside the range. The larger venturi on the Fox regains some of the power lost in timing, compression, etc., and also reduces suction causing a quicker, sharper break.

Oh, and Paul Walker went the other way with the venturi on the ST 60, for instance. He used a smaller than normal venturi, but then, he was using a much smaller prop than what the ST 60 could reasonably be expected to turn. With less load, he needed less venturi.

So, what we are talking about is a venturi in a normal range that enables the engine to behave normally for what would be expected to be props that it is capable of turning. For smaller props, go to a smaller venturi. For larger props, go to a larger venturi (within reason). And, for less choke in the exhaust go to a smaller venturi. For more choke in the exhaust go to a larger venturi. This is what Brett is doing.

Now, the formula is this: Take the effective choke area (area of the venturi at its smallest point minus any restriction caused by a protruding needle) divided by the cubic inch displacement of the engine, and the "normal" result would fall into the .045 to .052 range. I want to emphasize that this is for stunt engines in stunt trim that are not "tricked" up in some way. We are not talking speed or combat, and we are not talking about every tricked up engine.

Now, if you go to more exhaust restriction you will need either to go to a larger venturi or a smaller prop. Or, if you go to more load (larger prop) you may need to go to a larger venturi. And if you go to a smaller load, you may need to go to a smaller venturi (Paul's solution on the ST 60).

When Matt went from the 61 size pipe to the 65 size pipe on the PA 61 it allowed him to put a bigger load on the engine (larger prop) while using the same size venturi. The pipe length and rpm remained the same, however. Or he could have used the same prop and gone to a smaller venturi. And with the .65 engine he can use a little larger venturi because it is a little larger engine. That's why I get confused when people say the stock venturi on the 20 is OK, but the 25 has too much power with it so you have to go to a smaller venturi. You can do the same thing with the 20 when you decrease the restriction in the muffler.

Oh, and how does the formula work? Well, the stock venturi on the 40 FP is a .265. With its .135 needle, this gives a choke area to displacement ratio of .048 (formula .045-.052) OS has been all over the place with their venturis on this engine, but here they did something close to right. Unfortunately they used the same venturi on the stock 35 and the first 46 LA. The LA is a "tricked" up engine (no boost port) and that venturi has been correctly getting progressively larger.

How about the ST .46? Nothing tricky here. Brett recommends a .173 venturi (choke/displacement = .051)

What does Matt use on his PA 61 with a pipe?
for cool weather .189 (choke/displacement = .046)
for warmer weather (most summer conditions) .193 (choke/displacement = .048)
for real hot weather (approaching 90 degrees or above) .196 (choke/displacement = .0495)

You will note he is not pushing the max even with his large pipe. But then, that pipe is very non-restrictive. And it is also possible when the weather heats up at a contest, for instance, to simply go to higher per centages of nitro from his normal 5% to compensate for the smaller venturi. So you can add nitro when the weather heats up instead of going to a larger venturi. When the weather cools, however, then you need to choke it down.

Just remember, this is a starting point and works well with stock, non "tricked out" stunt engines. If you do something to kill the power, open the venturi. If you want and can take the extra power without it running away, open the venturi. I can open it more on my modified engines simply and only because they have better crankcase compression forcing the fuel up, and are limited, with the lack of a boost port, from runing away. But they are also set up for ideal deck heights and such with that type of set up to allow them to produce more power.

However, I will emphasize this once again, the argument was never about my modified engines verses Brett's stock engine. Only a matter of putting less restriction on the muffler (with its accompanying less weight) and moving to a smaller venturi.

>On the surface it seems as though you are as adamant about
>"correct" choke area as you accuse Brett of being regarding
>his preference for the stock components.

Well, yes. If you don't have the correct size venturi, the engine is never going to run properly. This is true if it is too small or too large. If you put a less restrictive pipe on the engine you need to go to a smaller venturi or a larger prop. This works the same with a muffler. I might add we put a "rubber duckie" on the muffler on Matt's 35 ship once to try to deflect the exhaust off of the wing. It didn't work. It was too restrictive. We had to take it off. We could have tried a larger venturi, I guess, but didn't feel like messing with something we didn't have to. Besides, it added weight.

>What is the driving force and perfomance expectation
>for modifying the engines to meet your preferred specs?(snip)

I am a guy who likes to fiddle. I like to see where I can make improvements. Matt likes to fly. He doesn't like to tinker. But he does like the improvements that result.

Many years ago Art modified a 35 FP for us that we were using and it totally changed that engine and our outlook on how those things could be made to run. I had another "noted" reworker do a 40 FP for me and he destroyed it. It almost had the power of a Fox 35. (Almost, not quite) But the comparison was dramatic. We later blocked the boost port on that engine and brought it back to life. We changed out the piston/cylinder that he had butchered and made it into one fine engine. (And, no, don't ask me who it was.) I later did some experiments with the 35 and found that by going just ten thousandths too far in timing changes made a difference between turning an 11 inch or a 12 inch prop. Sometimes you have to destroy parts, but that is how you determine where to set it.

Art did a muffler for us for that engine that didn't work. He made another that was just a quarter inch longer and it did. The first worked on a stock engine, but had too much restriction once it was modified. (And, no, it wasn't a pipe, because a tongue muffler would also work.) At that time Matt and I were both flying and we could feel the dramatic difference that going to that 12 inch prop made (especially compared to the stock engine running high rpm with a 10 inch prop). We later did some comparisons with modified Fox 40s and then went into the Magnum engines. We tested engine configurations. I did some tests on mufflers. There were some interesting results. And I want to put something up about that when I get time, because I tested length for tubes and number of holes for tongues, all of which is pertinent to this discussion.

We did some testing of head shapes for Lew Woolard at one point. And just minor differences in head shape could sometimes make dramatic differences in performance. You can't just take a dremel tool, grind a little, and say "That takes care of that". Everything was measured to the thousandth of an inch. But, this is also interesting, because it is not unusual for stock engines to vary in deck height by as much as 6 or 7 thousandths, and I have had a couple that were over 15 thousandths off. So much for "stock" engine.

>And ... again not trying to be a smarty pants ... , on what
>emperical basis do you support your preference for modifying
>the engine. Have you flown (or had Matt fly) .20 powered
>aircraft with the engines in various configurations or is
>your point of view driven by a conviction to the principles
>you've developed regarding what is and is not "correct"
>regarding choke area?

Neither Matt nor I have ever flown a 20 FP. I have modified a number of 25 FP engines (and Thunder Tigers) using the same principles as on the 35. But I have not done as extensive of a program on these as I have on the others because the bigger ones were flown by Matt in competiton and we have thousands of personal flights on them. The 35 and 40 FP engines were identical except for the bore size (and larger inlet ports in the sleeve on the 40) The stroke and timing, etc., are the same. The 25 FP is kind of a scaled down "middle ground" between the 35 and 40. I always found that interesting. So I just scaled it down proportionately in what I did to it.

But again, I never said "let me modify a 20" for comparison. (I don't even have one.) Although from experience with other engines, I am confident I could improve it for stunt purposes compared even to Brett's set-up, my comments have only been directed towards going to a lighter, less restrictive muffler and accompanying smaller venturi.

>Lastly, has your developmental work been restricted to
>larger bore engines? I know you've a well earned reputation
>for building good mid size engines -- .35s and .40s -- but
>have you done enough work on engines of this size to be
>confident in your assessments?

I have already told you that I havn't done 20s, but the principles remain the same. There are no surprises in the design (like the wider inlet ports on the FP 40) to cause problems. Timing is still a matter degrees. Principles on venturis and compression remain the same. I have never found a head shape that worked better on these engines (as I modified them) than the stock one, so it is simply a matter of setting correct head height to go along with your modifications. Oh, and when we did the head tests for Lew Woolard and sent him the data, he came up with a deck height that he felt was best and we came up with a deck height that we felt was best and we were one thousandths of an inch apart. That was not enough of a difference to worry about, but it was an interesting result. Basically we came to the same conclusions. Lew continues to work on his stuff, by the way, and continues to improve it over the years. I think this is key to knowing what you are doing.

>We all know that a 1/2A must pretty much be run peaked out
>to get any sort of performance out of a stunt airplane. We
>also know that big bore stuff is happy as a clam flying
>pretty gross large stunters in a loafing four cycle.
>Somewhere in between these extremes is a cross over point
>where the engines and the appropriate configurations for
>stunt metamorph from one type to another. My experience is
>that cross over occurs in the Class A range about which
>we've been debating.
>
>In other words, I believe the .20s etc, fundamentally
>require a different approach to doing the work we need done
>than do motors almost twice as big in displacement. (snip)

I grant that 1/2 A engines are a different animal, but great gains are being made in these engines these days as well. The day that the TD engine dominated are long over, and the new Schnurle engines have become king. But I am sure that even these could be modified to make them into a better stunt engine. It may be, however, that one would need to replace the cylinder as is done when converting the Nelsons (PA) or Jetts (RO-Jett), along with the heads and venturis to make them into a truly improved stunt engine. I don't know. I have never explored this and truly have neither the time nor desire. However, I don't think the 20 or 25 FP are any different from the norm of the larger engines. I generally have stayed with the 25 simply because it is based on the same case and gives 25% more displacement for the same size/weight. Even here, cubic inches rule.

>I still think the "challenge" would be a great deal of fun
>and informative for all of the SSW crew. I'm serious about
>purchasing a .20 built to your configuration and I think the
>ARF Flite Streaks would be an ideal and inexpensive vehicle
>on which to make the comparisons.
>
>How much $$$$
>
>Ted

How about ten thousand dollars? (Might as well be dumb here.) I agree it would be fun and informative for us all. I don't even have a 20, however, stock or otherwise, and, as said, haven't worked with it enough to know what would be the best prop, etc., to use in comparison. I wold not only need to rework the engine (which would not be difficult) but would also want to make sure that I had the absolute best prop for the engine, etc. Brett's engine would not run properly on the prop I would choose, and mine would not run as efficiently on the prop he would choose.

And it is a dead engine. So, if I did put development time into it, I don't know what purpose it would serve. But, as stated, that wasn't the issue anyway. We were only supposed to be talking mufflers and venturis. (Still, you are willing to buy the plane AND the engine, and let me use this for development before sending it to you, and...)

See you in Muncie. Bring home the gold for the US.

Len,

Now the interesting thing is, do you think it *acts* like a piped motor? Granted, there are multiple ways to make a motor sound as if it is piped. But I (and John) were referring to both the way it sounds (big clue) and the way it acts in flight (huge clue).

Agreed, someone is missing the point. It's you. And this will continue to be the case until you take an intellectually honest approach toward the strong possibility that Brett might very well know exactly what he is talking about here, that both he and I, along with quite a few others, most of whom I do not know well, have proven his theoretical approach by actually flying the things.

Another related item you continue to neatly sidestep with all sorts of blah-blah-blah about Matt's stuff, 35s, 40s, 53s, etc., etc., is that Brett and Ted and myself, and others--ooops, can't leave out Doug Moon and his recent experiences--have been well on both sides of the fence in making the wee ones work in a CL Stunt application.

At one time I had my 25FP just running as hard as it's de-tuned little self would pull, I'm thinking Doug did as well, and it was no better than average in performance. Fun? Yes. Nice enough to drag along when flying the Real Deals of Stunt. Yes, again.

But it was never something to prompt that most dreaded of male phrases, "Watch this!"

The O.S. 20FP with the tune-up Brett supplied, bolted to a competent profile, ARF Flite Streaks in my case, Skyrays for Brett and others, is in fact just such a deal.

Another perspective: When flying my 25FP/ARF last year, lots of comments on the ARF and that it was nice to fly. This year, 20FP/ARF, unbidden come comments concerning the quality of the patterns being flown.

So. Some of us have seen the results of the traditional setup, been able to compare them with Brett's setup. You have experience only with the former, cannot seem to imagine the latter, pipe/muffler fitted or not.

As to potential flight tests, I am not near as locked in as you seem to think. Both of my ARFs are now running with no added tail weight. At one time one of them had 14 grams bolted to fuse; but I discovered a wad of lead had been added back when I was using a tongue muffler, when that was dug out, off came tail weight. And as mentioned yesterday, the models are within 5 grams of each other, just slightly less than 10-ounce-per-square-foot wing loading.

But it gets better. Both models have built-in anchors front and rear to which we can easily add weight. Either in retaining desired balance point or bulking up one to equal the other, again with same balance.

Hmmm, I am so confident of current tune-up on my 20FPs, I hereby offer to pack along an extra three or four ounces, *plus* give you the option of that 25% bigger motor.

It's Ted's money, and you say you don't even own a 20FP. Well, I understand that, but it is amazing that you have such strong opinions on an engine you don't even own. Still, allowing as it is Ted's money, do you have an optimized setup which will bolt on in place of my 20FPs?

As to future challenges, you mention the ARF Cardinal. If I were to buy one--not likely at this time--I would continue to follow the theme laid down by Brett and install a square-head Magnum 36. Stock. Might even use the muffler, would *certainly* try it before just tossing it in the trash and/or jumping on anyone who did use stock muffler.

Finally, Len you're skating around the real issues here. I have watched you change emphasis, couch various statements in different ways, just flat ignore pertinent questions, and have not called you on any of it in specific terms.

But at some point you're gonna have to put my friend Pat Johnston's venturi chart away, move away from the test stand and try Brett's tune-up, proving or disproving the validity of both his setup and yours in some sort of direct comparison.

Until you do that it is, I am distressed to say, getting more and more difficult to take your opinions and comments on this subject in a serious way.

The LA 25 is a zero boost port engine.

Doug and I both think it is a POS. Whatever grunt is added to the bigger engines (LA 40 and LA 46) over the FP series, is lost in the smaller displacement.

What is sad is that, as Len said, it is a dead engine.

Someone develop something we can buy from the LHS and does not have to be "modified".

I think a few us are looking askance at the 25LA, although I'm not ready to place it in the POS category yet.

They do handle a lot differently than a 20FP or 25FP, and I see where Smiley ended up with a 9-5 on his 25LA/ARF Flite Streak combination, not having enough speed with APC 9-4.

A friend is flying this motor on a re-bodied Top Flite Tutor and using an APC 10-4. Seems to work fine, although the combination is no more than average in profile-type performance.

I don't recall if this has been mentioned, but back when Brett bolted on a 20FP for the first time, it was for a W.A.M. event called "A" Stunt. A 25FP was not legal, as top limit was for 20s, the 25s going into "B" Stunt, which I believe allowed up to 29s.

Above also explains why, over the years, we have seen so many Veco 19-powered profiles come out of this area of the country.

Were it not for an event unique to W.A.M. the 20FP/Skyray combination may quite well have never seen the light of day.

>The LA 25 is a zero boost port engine.
>
>Doug and I both think it is a POS. Whatever grunt is added
>to the bigger engines (LA 40 and LA 46) over the FP series,
>is lost in the smaller displacement.
>
>What is sad is that, as Len said, it is a dead engine.
>
>Someone develop something we can buy from the LHS and does
>not have to be "modified".

Brad, I am not an LA fan, but only because of quality. However, I think you might be short changing it as many people seem to have gotten this engine to work. I make the same caution here that I make with other stock engines, you need to watch the deck height as this will vary from engine to engine. You also need to keep track of which venturi you are getting as they seem to be all over the place on these as well. But when you are running these you also need to throw away some preconceived ideas. Think in terms of bigger props and slower rpms than with the stock FP series.

As to someone supplying an over the counter engine, There is the Brodak 40 soon to be joined by the Brodak 25. Of course, these cost more than the cheap RC type engines, but you don't have to modify them to get them to run. And they aren't the most powerful engines, but then, neither was a stock FP. They are good quality, however, and do a good job for what they were intended.

>Agreed, someone is missing the point. It's you. And this
>will continue to be the case until you take an
>intellectually honest approach toward the strong possibility
>that Brett might very well know exactly what he is talking
>about here, that both he and I, along with quite a few
>others, most of whom I do not know well, have proven his
>theoretical approach by actually flying the things.

Dan, I quit. If I could yell, I would. In fact I will yell.

I DID NOT EVER IN THIS STUPID CONTINUATION OF BLABBER EVER SAY OR INTEND TO SAY THAT BRETT DOES NOT KNOW WHAT HE IS TALKING ABOUT OR THAT THE SET UP HE IS USING DOES NOT WORK. I ONLY SUGGESTED THAT YOU COULD CHANGE THE MUFFLER BY CHANGING THE VENTURI AND RUN IT THE EXACT SAME WAY. (I did, however, say that the muffler is not a pipe and that is why the above is true.) BUT I NEVER SAID HIS METHOD DOESN'T WORK!!!

YOU AREN'T LISTENING. END OF ARGUMENT FROM MY END. KEEP YOUR OUNCE AND A HALF OF DEAD WEIGHT ON IT! I REALLY DON'T CARE WHAT YOU FLY.

>>Agreed, someone is missing the point. It's you. And this
>>will continue to be the case until you take an
>>intellectually honest approach toward the strong possibility
>>that Brett might very well know exactly what he is talking
>>about here, that both he and I, along with quite a few
>>others, most of whom I do not know well, have proven his
>>theoretical approach by actually flying the things.
>
>
>Dan, I quit. If I could yell, I would. In fact I will
>yell.
>
>I DID NOT EVER IN THIS STUPID CONTINUATION OF BLABBER
>EVER SAY OR INTEND TO SAY THAT BRETT DOES NOT KNOW WHAT HE
>IS TALKING ABOUT OR THAT THE SET UP HE IS USING DOES NOT
>WORK.

Ah, but you did most certainly, by strong implication, say Brett does not know what he is talking about when it comes to what you see as merely being a heavy and restrictive muffler we are able to use as a tuned pipe.

I ONLY SUGGESTED THAT YOU COULD CHANGE THE MUFFLER BY
>CHANGING THE VENTURI AND RUN IT THE EXACT SAME WAY.

But you cannot. Brett knew that going in. Do you really think Brett has run a whole series of 20FPs with only one setup? He convinced me, an easy thing to do, to try his proven setup, I had already tried the traditional small venturi/low-restriction muffler setup. The runs are hardly exactly the same.

Speaking of reading comprehension, as you do later in this missive, did you actually read and understand Ted's input? Some very serious clues tucked in there, worth looking at again.

(I
>did, however, say that the muffler is not a pipe and that is
>why the above is true.) BUT I NEVER SAID HIS METHOD
>DOESN'T WORK!!!

Brett has very clearly stated that his tune-up does work and also stated the muffler is a huge factor in that it operates like a pipe. There is a very serious contradiction here, when it hits you I would love to hear the face-slap you'll be giving yourself.

You cannot give a left-handed affirmation, as above, that Brett's setup does work, when it is based upon the muffler functioning as a pipe, and then turn right around and say the muffler is not a pipe.

Please reconsider your position on this.

>
>YOU AREN'T LISTENING.

True, somebody's not listening. I printed out entire thread yesterday and reviewed it yet again. You have indeed shifted around on us a bit when it comes to what are more than just details.

END OF ARGUMENT FROM MY END. KEEP
>YOUR OUNCE AND A HALF OF DEAD WEIGHT ON IT!

Now see here, this is *exactly* what I mean. Only moments ago I told you both of my models balance without any dead weight and now you're screaming about an ounce and a half.

I REALLY DON'T
>CARE WHAT YOU FLY.

Of course not. Don't expect you to. But as mentioned previously, there is something really intriguing and interesting going on here when a bottom-feeder O.S. 20FP matches up so perfectly to models which seem to be coming out of our ears, ARF Flite Streaks.

I very much want as many people as possible, everybody below Expert PA status, although I can think of many who should not be given a pass here just because they enter Expert, to whip together the *exact* combination, for *all* the reasons Brett gave and then to go fly it.

After that, they make up their own minds. No problem.

But if they use 80% of Brett's tune-up and your input--not based upon any practical experience as far as I can see--when it comes to, guess what!?, the muffler, there was no point at all in all this spreading of the word, going clear back to my Pukey Profile thread.

***I'm not hammering you, instead I am reinforcing stated views and combinations known to work and work very well, indeed that work much better than the traditional setup you defend so strenuously.***

Len, I know people, good friends, who can use the information in this thread to elevate their skills and scores substantially. I won't let them go all wobbly on me over 14 grams of tail weight.

To review for a moment, you have been given three distinct approaches to use in making all of your points as to engine tune.

1) Send me an optimized power plant, I don't care what brand, I no longer even care if it is a 20 or 25, although larger than .25c.i. displacement would be regarded as poor form. I will of course need full instructions on its use, will wring it out thoroughly, all will be returned within, say, 30-45 days.

2) Sell an engine to Ted, ship it to me, I'll drag both of the ARFs to Albany, Oregon, we'll have even more fun than usual out late Saturday evening. While being honest enough to give all the equipment objective testing, fairly easy to do as a great many people will have not yet seen my 20-powered ARFs. (NW Regionals is the first contest of the year.)

3) Another offer from Ted, this time involving your very own ARF Flite Streak.

Dan

P.S. Having my text come out in bold was not intended, seems to have migrated from Len's text. Apologies, I find all-caps, bold text, most all forms of look-at-me manipulation of text to be less than convincing in helping to make a point.

Len.

I think you should have posted your first message in this thread as a separate post.

That would have prevented folks from geting the wrong idea that you were arguing with Brett.

That was NOT wise.

Reason along with me:

If I post something like "I found out, after many years of tests, that "ACME MIX" is the best fuel for piped engines, and next thing I see some clown replies that his piped engine runs just as fine on *Wild Dog*, *Lord Byron*, *Alpha Omega, *Morgin* *Sig-Sag* and *Count's Superfuel *, a lot of people would tend to think that between the lines, the reply read;

"You spent all those years for nothing* ,"you're a moron" , etc., etc.
Of course that was not your intention, but with the years of experience you havve at SSF and knowing how some precious minds work around here, I consider a big blunder wthat you did...

>Dan, I quit. If I could yell, I would. In fact I will
>yell.

Guys, I was so frustrated by the earlier casual dismissal of what I thought was a pretty good idea, with no logical counter-argument or empirical data, that I ceased to read this thread. I am still just as frustrated by this, but the whole thread has gotten, in my opinion, out of hand. I would have recommended stopping a week ago, had I known what was going on.

I personally think that there is an awfully lot to be learned by the less-experienced, and even the moderately experienced, by flying with the engine in this configuration, both about what "good performance" means in terms of a stunt plane, and also about more modern methods of engine setup. Heck, I learned something, and I have been doing this reasonably well for a pretty long time.

At this point, I don't see any further value in continuing this. I stand behind my previous recommendation, unaltered, that this setup is not only workable, but probably results in the optimal performance in the airplanes for which I recommend it. I've tried it in many different configurations, and along with my other experience with these sorts of systems, to be fairly confident about it. This is what I base this opinion on. I think the issue and the nature of the problem/conflict is perfectly clear.

But I honestly don't care whether anybody runs it, or doesn't. I have no stake in it one way or the other, aside from the ~10 years of development, but that was enjoyable and not really a cost to me.

I will caution everone that if you change one part, you may well have to change other parts, and in that, you are on your own. It's a system with many closely-interacting parts, just like most other systems, and simply changing things willy-nilly can easily result in an unacceptable or suboptimal system. Maybe someone can do better, and if so I highly recommend that you let us all in on it. Leonard's "traditionalist", for lack of a better word, approach, will likely result in a workable system assuming you get a small enough venturi and maybe change some internals. In my opinion, based on experience, it does not provide equivalent performance, but it will likely work and be reliable.

I do care a lot about not making a issue of it, or enemies over it, and particularly not in Leonard's forum. It's his house, and while I will happily debate any point as long as there is some point of debate, I really think it's gone to the point of beating a dead horse - everybody is entrenched, and all we are doing is the equivalent of "sez you" and "oh yeah".

Aldrich said i right -nothing in modeling is worth losing a friend over.

I said my piece above, it's up to the reader to decide.

Thanks, Brett, for your efforts. And I am agreeing with you that it is time to put this thing to bed. I never once questioned that your system worked (or didn't work, however one should say that.) And I agree, this is certainly not worth losing friends over--not you, not Dan, not anybody. You have a system that works for you and you were willing to share it with others. I again thank you for that. And I agree with you that if you change one part you may indeed need to change another. Without changing internals we have the venturi, the muffler, and the prop. If you make any significant change in any one of the above, you will probably have to change another. It is usually easiest to change the prop, but that was not your intention nor was it mine. That was why I suggested changing the venturi with the muffler. And Dan was the one who was looking for a lighter muffler so it was actually for his benefit that I suggested it. Ah, well, live and learn.

I will do a separate post in the near future on the muffler experiments that I did. There is nothing earth shaking there, but it does lay down certain principles that are involved. Plus a little learning of what did and did not work.

Again, thanks to all. I guess I will have to chalk this up to another one of those topics that gets categorized with 4-strokes, builder of the model, and the question of whether if Kerry had been in office 4 years ago he would have single handedly stopped the World Trade Center attacks.

Good night all.

I read this in an earlier message in this thread:

>This has been a very interesting discussion, too bad it has gotten >to be a little personal in nature, but with the severe >disagreements seen, the high resistance to a "new" way of thinking, >such seems to have been avoidable.

Then I read this from the same author:

>
>Agreed, someone is missing the point. It's you. And this
>will continue to be the case until you take an

I have reread everyone's post here at least three times, and the only thing I see is an honest difference of opinion. That is, except from you. Your comments are laced with sarcasm and downright insults.

Just because someone disagrees with you doesn't mean they need to be the target of your sarcasm.

That's bad form, Dan, very bad form. And, you know better.

My only question is if you have the stones to make it right.

What about contacting O.S. Engines and have them come up with some information?
Instead of beating each other up?

This thread is now of 'Entertainment value" for the vultures.

>I read this in an earlier message in this thread:
>
>>This has been a very interesting discussion, too bad it has gotten >to be a little personal in nature, but with the severe >disagreements seen, the high resistance to a "new" way of thinking, >such seems to have been avoidable.
>
>Then I read this from the same author:
>
>>
>>Agreed, someone is missing the point. It's you. And this
>>will continue to be the case until you take an
>
>
>I have reread everyone's post here at least three times, and
>the only thing I see is an honest difference of opinion.
>That is, except from you. Your comments are laced with
>sarcasm and downright insults.
>
>Just because someone disagrees with you doesn't mean they
>need to be the target of your sarcasm.
>
>That's bad form, Dan, very bad form. And, you know better.
>
>My only question is if you have the stones to make it right.
>
>
>Bob

Bob,

I should probably let this go. But I won't. Talk about getting personal...

Quoting comments out of context is very disingenuous. Bad form, indeed. And you do know better. Or should.

Throughout this thread I have responded in kind--see above paragraph for an excellent example--less only the very recent instance where Len just plain lost it. And then I continued in a reasonable tone, albeit with bold text which I did not intend to have flow from Len's text into mine.

By its nature, sarcasm is tough to bring to the fore, although you are hereby welcomed to do so. I will take a look at any instances pointed out to me.

Insults are quite a different thing in that they are glaring and easy to spot.

Should you have specific examples of insults being tossed around by myself, especially any toward a very good man like Len, do please point them out to me.

I will of course consider the examples carefully, will not hesitate to do the right thing.

Dan

An edit, because Brett's latest post says a lot I agree with, including the fact this has gone on too long already, and I admit to being a catalyst to this process.

In fact, if I had standards of conduct equal to Brett and many others on this site, I would have quit this a week ago.

But I don't have high standards when it comes to interesting discussions about model airplanes, motorcycles, women, F1 racing, supercross, politics, and a whole pile of other topics.