Stuka Stunt Main Forum · 38 of 38 known posts recovered
Mr. Mike Scott is being a super pal and has loned me his RO Jett 65 and Werwage pipe.
I am still intent on running the Eather red prop wit hthe Ro Jett. I understand that Brett runs this combination. Is there any advice or setup that would help using this smaller prop (small for a RO Jett).
What chart do you use for pipe length for the RO Jett?
Actually. I am using a 12.5-3.75 "green" flatback prop, straight out of the pizza box it came in, literally no changes and no cleanup, etc. . #5 spigot venturi (long), stocking diffuser, Thunderbolt 4-cycle plug, 10% Powermaster R/C fuel, stock engine (no idea about button or head clearance, never took it apart to see), 17 7/16" pipe length on regular Smith/Werewage 60 pipe, largest available "stinger" (important), ground launch RPM of 10,100 or so. Nothing at all tricky, clever, etc, just remove parts from box and bolt in place.
I would use Randy's pipe chart, if you want a pipe chart, and add maybe 1/4" to the number it comes up with. But the right answer will very likely be in the range between 17 1/4 and 17 5/8. I would set it on the short side and move it out if necessary. The engine is not sensitive to changes and if you get it anywhere close it will work. The one thing not to do is stack up a bunch of head shims to get more clearance - I think it messes up the plug depth. Steve Millet's engine was like that and it started flaming out. Put it back to stock and no problem.
There is no danger with getting too much compression, as far as I can tell. I've had the head so tight (on the previous, crashed, motor) you almost couldn't turn it over without it hitting and it still ran fine. Ran it that way at the team trials, as a matter of fact. It was really hard to start, because one pico-liter of excess fuel and it was flooded.
I strongly urge you, however, to simply use the guts exactly as they come aside from the venturi, don't take it apart in any way or "adjust" it until you know for certain it won't work. Actually, that's good advice in general, and I'm sure Richard, Randy, Mr. Ogawa, Mr. Garofali, Mr. Saito, etc, would appreciate it greatly. It will probably work OK with the stock venturi, too, but I have a lot of experience with the spigot venturi and just prefer it as a known entity.
I've switched back and forth with the red prop, and it works with the same setup. It works somewhat better in good air, but the airplane tends to "float" a little coming around into the wind. It's a subtle effect but detectable.
RO tells me I am using too much castor and varnishing up the engine, so I will probably try all synthetic helicopter fuel next. Ted used YS 20/20 for a few flights at the W/C, with generally good response.
Brett
Things change over time. I was running a #6, but I moved to a #5 and have a #4 and #2 ready to try. Going from a #6 to #5 made a noticable but not grossly excessive difference. Nothing you do seems to be a gross change on this engine.
I couldn't say if it's optimized at 17 7/16" vice 18", but bear in mind I am running a Randy/Billy pipe instead of RO/Windy pipe. I have been everywhere from about 17 to about 17 3/4. Ted had his Eather set to 18 at the W/C but I can't recall what it ended up at. I'm running a 61 vice 65, too.
It's just a core dump of the current configuration. It works pretty well but no guarantee that its as good as it can get.
Brett
How much fuel do you burn with those venturis?
Mine has a #12.
Right around 6 3/4.
Brett
Pretty neat guesswork. No way am I going back to ST 51s, even though I had a couple I liked quite a lot and that were really nice engines for my particular application and skill level.
I'll be going with a RO-Jett, the only issue is 61 or 65. Rear exhaust, piped of course. Had my new 72-powered Impact--the one with a mere 10-12 flights--on the bench again last night seeing what it would take to convert it. Not much, it turns out, although I am leaning toward simply building another model.
As to PW, I know what's going on, and there has been no final decision. I expect to soon run across him up at Arlington site; further, I expect him to have an Impact or two with him, at least one fitted with a RO-Jett 61.
While some don't want to hear it, Len certainly not, all the time spent flying those unmentionable engines earlier this year served to focus my attention quite nicely. I'd fly some piece of crap profile, yet the powerplant was so good it all came together nicely.
I'd get the 56-powered Impact out. Nice, really nice, especially now that I have gotten more serious about it, am now much more "adventurous" when it comes to trim.
But "not there" in some relatively hard-to-define ways. And I'm not talking just about entry into four-leaf clover where the already-pinned, constant-speed setup is so annoying. As stated already, hard to define.
And then I'd go back to a rather silly assemblage of non-Stunt parts, only to quickly be back in a really comfortable groove, doing actual Stunt tricks at a fairly high level.
I wish to make it clear that I have no serious issue with Saito 56 or 72 four-strokes in a CL Stunt application, especially former as it's the better of the two in many cases, for many flyers. A long-time friend is looking for his next-step project--just finished a quite nice 25LA-powered Oriental--and I am strongly in favor of him build a 56-powered Impact.
In fact, before getting out implements of destruction I will be taking a serious shot at getting my 72-powered model whipped into some decent trim. But one way or another, I fully intend to be flying a piped, big-bore two-stroke next year, and the RO-Jett package just looks too good to ignore.
Dan
I can define it. I can define it fine.
The modern pattern was WRITTEN around a 4-2 break. It is just that simple. Some of the manuevers require a subtle BOOST to be performed correctly. The 4 stroke has none. The hourglass for example, to be performed CORRECTLY (in a way that will make Nats judges OOH and AHH) requires a subbstantial boost at the top corners. The 4 stroke (normall) produces an hourglass that is somehat akin to a vertical eight (especially in the forward CG configuration). Al Rabe is the ONLY HUMAN BEING ON THE PLANET that I have witness flying a a sharp cornered hourglass top UNDER 90 DEGREES. On the PLANET mind you. How he does it, I do not know.
If you use the boost afforded by running the engine over rich, it will be unpredictable and will have no wall of peak to hit when the wind starts blowing, it is simply like a standard 2 cycle with no pipe effect and it has no where to go but faster.
running the engine "over the top" like Paul is wayyyyy better in the wind but has no boost for vertical manuevers.
Well.........then WHY DON'T you tell us your findings!
I know I am all ears. Have been for some time. All I hear is crickets...
Well. I would say the conclusion is - it's really not too hard to be a stunt flier these days.
Brett
And I thought I was the only crazy person here. My poor Time Machine has gone from an OS 52 four stroke, to an ST .51 (bad move), to a RO-Jett .61, to a Saito .56 (one more try), and finally back to the RO-Jett. My Legacy was simpler: it went from the Saito .56 to a RO-Jett .65 after I slit open its belly and built a pipe tunnel.
Please fill us in on the details of this major paradigm shift. Inquiring minds want to know. 
Well, no not really.
I see no real advantage to an unknown pilot running a 4 stroke if you want to get into the Top 5 at the US Nats. The standard is a very small, tight, sharp corner pattern that is flown in open wind conditions. In my mind the 4 stroke, without further development is not as suited to this style of flight (at least in the "non Berringer" style plane) as the 2 stroke planes. The 2 stroke planes are THE STANDARD BY WHICH THE PATTERNS ARE DEFINED. In other words, no matter how the 4 stroke presents, it is kind of like saying "I shoot good three point shots" when all the judges are looking for is slam dunks.
Oh, sure some great pilot will prove me wrong... hopefully.
I have yet to see small, tight, hard corner pattern from anyone in the world using a 4 stroke except Al Rabe and Remi Berringer. Al does it simply on pure talent I guess (he hates it when I say he is still GREAT AND SHOULD COMPETE FOR IF NO OTHER REASON TO SHOW EVERYONE IT CAN BE DONE) but I do not possess this level of flying talent. Remi flies an airplane which I have no intention of building (Remi flies very small with tight corners----don't let anyone tell you different!!!).
>Please fill us in on the details of this major paradigm
>shift. Inquiring minds want to know.
Mainly it is the vibes. I simply see no advantage to working my ##### off to build pretty planes just to see them be shaken apart in a matter of months by the Saito 72. It really burns me to see Bob G. and Doug Moon build planes that last for YEARS of flying the low vibe pipe engines even with nose construction that is almost non existant.
The Mr. Hyde (that is spelled Hyde not Hide) was simply not going to survive much longer running the 4 stroke. It will probably last for years with a RO Jett. So the decision to modify the airplane was simply made to keep it around for a while longer.
Thanks to Brett and Brian Eather I simply feel there is no need to run huge props. The small Eather props that Brett recommended pull the 67 ounce Mr Hyde with all the authority it needs. I do not need a Saito to pull a 12" 3 blade. The prop ultimately pulls the plane not the engine.
Also, I have started to believe I am working in a vaccuuum. The only tips I have gotten are from Gordy, Paul, and Joe Parisi in Aussieland (Joe is way ahead of the game). Maybe it is time to hitch my wagon to someone else's caravan while I practice my pattern.
Keep in mind the Dr. J will still have a 4 stroke of undisclosed origin. I simply want to see how the other half lives!
Great thread. This is the sort and manner of discussion for which the forum is intended.
I'll be curious to see your response to the RoJett. It is truly a fine engine and I expect you'll be pleased with it. Having said that, after reading your discussion about the four bangers and the hourglass (where we are in agreement, by the way)it'll be interesting to see what you think of the RJ in that same maneuver. One of the things I really like about it is the "similarity" to the four stroke run (in much the same way as the .20FP or the .40VF)in that it and they are largely one speed engines. Even when the RJ breaks aurally it is hard to discern a significant surge in the airplane as a result.
In the top of the hourglass and the four leaf entry in a breeze it can leave you wishing for just that tiny touch more ...
Of the two engines I think the PA probably will prove superior in the verticals and hourglasses simply because it is more amenable to "coming" on a bit. As Brett mentioned, the RJ pretty much shrugs off tuning changes that can have a significant effect on the way a PA runs. As I've stated, this can be both great and disappointing in the same flight.
By the way, I've not personally run Richard's .65 (or Randy's, for that matter). It is entirely possible that that touch more displacement will make it better in this regard.
See, all we need is a tiny little guy to sit in the cockpit and when we shout "NOW" he could whack the supercharger button for a second or so ... about two or three times a flight!
Randy was nice enough to call and chat about engine stuff the other night and our conversation was very instructive to me. He's got me thinking about a muffled rear exhaust .65 for the Hughes Racer project rather than a four stroke. For a lot of the reaons discussed in this thread, that appeals to me.
Isn't it wonderful to be in a position to argue about such relatively tiny differences in excellence? Many thanks to Randy, Richard, Mr Saito and Mr. OS for making our decision making so difficult!
Ted
p.s. by the way, many of the top European fliers were doing some outstanding stuff with some engines for which we'd have a hard time reading the owner's manuals. The Retro and Belko engines did some pretty amazing things while appearing to be loafing. If I was twenty years younger and still fired up I would have brought a couple home to "fiddle" with. Hint, hint.
It will take these subtle difference to compete with guys such as yourself. Especially for me.
I doubt I will ever win anything, but I will be darned if I plan on not trying...
I have donated enough of my development time for now. I will let someone else crack that egg. I would like nothing more than just using a good ol' made in USA stunt motor.
Point of fact, the engines are good enough now that really it is just a matter ofinding the right prop and hooking a suitable power plant to that said prop. I think this approach is more fruitful.
I remember when flying a 6 second lap and doing a suitable pattern was considered near impossible. The guy I fly with does it all the time. I think we have enough power...
Wait till the RO Jett 77 hits the market. Bolts into the same holes, runs the same props, just better.
yes yes yes
Beside uphill/downhill, those variations are triggered also against and down the wind (means exactly opposite than we need) and on our turbulent European fields it really makes troubles. I solved it by large volume aluminium pipe with only one baffle with relatively small holes. That large volume with one baffle does not allow too much variation of RPM and rich / lean run makes soft variation in sound instead of strong rpm changes. Brett told me that he means also ventury with thin hypodermic needle also helps that way of run. I do not know I did not test usual pipe with that ventury, but that pipe works that way for sure also with original PA black ventury without filter.
Alexander and many others here around does it different way, they use (almost) steady 2 cycling run with large loady prop on constant rpm. That also kills too much variation, but it needs shorter lap times to have enough power overhead as it slows down little on rpm as it goes uphill.
Not exactly a hypdermic needle. It's just like Lonestar told us - 1/16" OD or ~1.6 mm for you metric fans. It might make a good hypo for Secretariat.
Brett
This is what I have seen. When Doug was testing the RO Jett, the thing I liked was you could shoot some pitch to the sucker and it would behave. The corner exits were much more "4 stroke like" and yet the bursts commonly associated with the PA when it allowed to break were non existant.
Absolutely no kidding here after my infamous hourglass in the wind gusts Thrusday afternoon at the Nats (The infamous circle 4 you know).
Quite unfortunately I didn't have time to experiment with propellors before the Nats. I ran the Werwage/Phelps prop for a whole two flights before the Nats and didn't have time to tweak it where it needed to be. Therefore I was just curisng along with an Eather 13" 3 blade cut to 12.5" With 3.75 pitch which was tweaked to 4.0 at the tips. Still didn't help. Might have had something to do with the plane (Intrepid X/L) weighing 67 ounces maybe?
Question for Randy: Since the RO Jett doesn't break much could it be used in a slightly heavey Staris? Just curious...
Jim Pollock 
I was raised on Noblers with Fox 35s. I expect a boost when I pull the nose up and the four stroke just stays the same. The four stroke engines are great, but I plan to leave them under the bench until I feel more comfortable with their behaviour.
Even though I have tons of four stroke experience from the RC days, it's a whole different ball game in the control line circle. I could not simply take the setups and info from my RC Pattern engines and become an instant expert in contol line engines. Having said that, I feel with the right airframe the Saito 56 will be a great engine. It is the smoothest running four stroke I ever owned. I applaud and admire Brad for his efforts and his willingness to share the info - good, bad, and ugly.
As a retread coming back to this sport after thirty years away, I decided I didn't need to be a pioneer. I had enough on my plate already. I'll reconsider after I feel better about my flying abilities.
Now Brad can fly the 72 on one day in the new plane and the 65 the next day in his old plane. This will be very fun.
I have had 2s and 4s planes for some time now. Intermixing them as you go is always a real eye opener. For the most part it has really helped my flying.
What Brad mentioned was exactly what I ran into years ago when I first tried the 4-strokes. It has been my experience that they worked really good most of the time but there were times when it just wasn't there in places like the hourglass and the fourleaf. There was also a serious drop off in power on hot and humid days. You could (and I did) up the Nitro on days like that and although it helped, it still didn't give you that feeling of powering through the pattern with authority.
The newer 4-strokes are far better than when I was seriously campaigning them and I have had the pleasure of flying properly trimmed models powered with the Saito 56 and the 72. They fly very well but the same problems are still present in the same manner as before. In calm to light wind conditions they are just great but in high winds they start lacking the punch needed and they still have the drop off in power when it is hot. I know that all engines drop off in power when it is hot and humid but I think it is more apparent with the 4-strokes than the 2-strokes.
My flying style may be a little different than most of you but I dislike a models that pull too hard. It gives me the feeling of trying to driving a truck through a road course instead of finessing a sports car through the turns. This is the reason that I never liked the ST 60 as much as the ST 46 or ST 51.
Now we are talking about engines as large as 90's. OK bigger is better most of the time and it should be interesting to say the least. But larger engines will (more than likely) mean larger models that can hold up to that kind of power (as Brad has found out). I am always willing to try different engines and set ups and try to keep an open mind about such things. That is why I own so many different stunt engines LOL.
The pipe setups have worked very well for me and I find them to be very easy to set up and maintain. For the most part they are trouble free, dependable, and have a very long life. Having said that, I am currently working with some of the Russian engines to see if they offer any advantages or fit my flying style. The Retro, Double Star, and the Union 60's seem to have a very smooth 4-2-4 run that is appealing to me along with being very quite. But I also think it takes a combination of the airframe design along with the chosen engine to ensure a winning model that is capable of performing at the highest level.
Mikey
P.S. Where can I get a Belko engine?
I feel a Vinny Barbarino moment coming on here... "I'm soooo Confuuused"!
OK, you feel a power kick, like we get from the 4-2 break is a good thing for Hourglass and Clover. OK, I got it. No problem or disagreement.
I am some how missing something (go easy on me) probably obvious to everyone else.
Basically you state that the 4-stroke will kick up power reserve similar to the 4-2 when run with high pitch props, BUT will also wind up in the wind, and conversely if run with flat pitch props Ala Walker, no wind up in wind, but no joy on power kick on hourglass and clover? Have I got it so far?
I am curious how this phenom is any different from current 2 strokes? Isn't it just a matter of finding the right compromise of prop/fuel/intake ratio to "dial it in" to where you balance kick with not enough kick? I mean, it's not binary On or Off, there must be some middle ground.
I get the feeling the 72 would be overkill for most of my intended situations, with the vibrations you mention and added weight, being more negatives for me.
As I understand it, to not slow down as much in the corners and conserve energy (flat prop scenario?)less flap and a light weight ship could be one way to go. Where as if we have enough power / constant air speed to hang it out there, a LOT of flap could visibly enhance the "stop, pivot & continue" kind of turn (higher pitch power kick in reserve scenario).
All that sounds logically right to me, so what is the missing setup modification that can be done simply at the field for a high winds day in this scenario? Back off the nitro, smaller venturi, more restrictive muffler etc? There should be a way to stop the motor from unloading on those days without sacrificing all the power needed for penetration. Maybe go the opposite direction? More power? More Nitro etc, but switch to flatter prop on the high winds day?
How far did your tests go in this regard?
I know you are sick of experimenting, but I am invested at this point, my new Legacy w/ Saito 56 is about ready to debut this month, and I will be continuing the process to some extent.
Please, if you want to pass on a little more knowledge of what you tried, didn't try yet, what worked and didn't work for you, so we can share the burden and pick up and continue running with it for you, we'll gladly take it.
For what it's worth, in my limited experience so far, I like the power delivery of the 4strokes I have run to date, compared to their non-piped 2 stroke counter parts. They have been mostly the smaller engines OS26, OS40, Saito45, Saito56, but no full boogie 72's yet.
Eric V.
Wait till you try the 72!! 
>Basically you state that the 4-stroke will kick up power
>reserve similar to the 4-2 when run with high pitch props,
>BUT will also wind up in the wind, and conversely if run
>with flat pitch props Ala Walker, no wind up in wind, but no
>joy on power kick on hourglass and clover? Have I got it so
>far?
Well, no not really. The problem is not pitch. The 4 stroke will run easily from 8500 to 11000 RPMs and have the same types of behaviors.
The best setup for consistence in my mind was the original setup that i use, which was the loaded condition. In the loaded condition the engine ran just fine, with all of the power that you would need. The fuel consumption was high so the fade in the heat was tolerbable. This was the setup I ran at the 2002 NAts. If anyone saw the airplane fly there, I think you could say the setup was smooth, consistent and powerful. The problem was the the airplane would not tolerate the 14" propellor and still have a corner that would make the airplane easy to fly in the wind and make everybody say "OK". The engine ran fine. I had no complaints about power at all.
The setup that I flew in the 2003 Nats was nearly identical, except I had gone to the Eather 14" UCT 2 blade. I had plently of power, my overheads never slowed in the high winds when many of the pipes did. Once again the problem was the stick loads and the lack of a corner. This is an airplane problem not an engine problem. One of the Japanese fliers at the Worlds was running the same prop as my original setup and his plane HAD A WICKED CORNER. In fact, his airplane appeared to be an Impact deravation, the same as mine, but the nose was about 7.5" to 8" long.
Everyone was enamoroed with gordy's engine and airplane at that Nats, but I only feel that it was due to the fact that his airplane handled the engine much betterthan mine (Mr. Hyde was a complete basket case). There were several comments after the Nats, so I decided to pursue a different setup. I have gone that route now, that being said, with the right airplane the old setup was way better.
Doug and I have agreed to go back to the loaded big prop run and change the airplanes.
Mr. Hyde would never perform the way I wanted with the 9.25" nose. The tail weight to balance caused too much barbell effect. So, I decided to put a lighter motor in the nose.
The new plane has a 8" nose and 18.5" tail. I hope this will be enough to go back to the big prop. We will see.
>I am curious how this phenom is any different from current 2
>strokes? Isn't it just a matter of finding the right
>compromise of prop/fuel/intake ratio to "dial it in" to
>where you balance kick with not enough kick? I mean, it's
>not binary On or Off, there must be some middle ground.
The "kick in" is really a matter of plumbing not prop. The prop is nearly immaterial. The last time I flew I was using uniflow and running the engine rich in level flight and letting it "come on" as it entered the manuever. This basically approximates a 4-2 break. I did all this at 10,400 RPM and 3.75 pitch. Al does the same thing at 9500 RPM. The poor Mr. Hyde will simply not handle the vibes anymore to my satisfaction.
The way I used to run the engine was semi-flat. It was smooth and constant but not excessive. It simply required too much prop for a Nats corner. This may not effect your local contest scores ONE SINGLE BIT!!!!!
On the other hand if you went to a smaller engine, say a 56 and put the max prop on it it would not be as excessive. Then, the heat problem starts to be exaggerated.
BE SURE WE WILL CONTINUE TO RUN THE 4 STROKE AND I ENCOURAGE EVERYONE ELSE TO CONTINUE ALSO!!!!
I simply decided to take my older plane and convert it to 2 stroke to compare. Also, I think the weight of the engine will make the airplane much better. That's all.
There was a bad time in CL Stunt where there seemed to be plenty of decent models, few good engines. I still remember reading Mikey's instructions for the SIG Magnum. About the best he could come up with for a good powerplant was the hope purchaser of kit would be able to find an ST 46, by then long out of production.
I'll bet they could have sold a lot more kits had it not been for lack of suitable engines.
Still with Mikey, I had forgotten that he and Ted had fiddled with four-strokes many years ago, reminded of this nearly a year ago when flipping through old Model Aviation magazines on the AMA site.
Jeeez, that developmental program must have appeared hopeless right from the beginning; yet somebody had to do something, they tried pond scum. Among a lot of other approaches.
More to current theme, still with paradigm shifts, a lot more people have given up on conventional wisdom that states: "Of course it sucks; it's an RC motor. Toss the muffler. Add a stack of head shims more easily measured with a ruler than a micrometer. Root around inside with a hand-held grinder. Prop it like it's a Fox 35."
No, not everybody has learned this lesson. And it is not expected to apply in all cases. But I have certainly been taught well, seen the results, a good bit of same argued about here, written in Stunt News.
And I have been blabbing locally about learning this "new" lesson. To something less than complete effectiveness. Long-time friend Rick, same guy I am converting from RC Pattern to CL Stunt, shows up at Helmick-promoted trim fest in Arlington with a new Oriental. Stock 25LA for power. With stock muffler. Somewhat nose-heavy.
Second thing he said when I showed up fashionably late was "the guys" had told him to junk stock muffler and install a tongue muffler. Far as I know, not one of these little helpers even owns a 25LA, let alone is able to predict with all certainty muffler is useless.
I told him, "One mentor is probably all you need for the time being, until further notice I'm it; and those guys don't have a clue as to what they're talking about. Even when I show 'em with the demo ARF FS most of them still don't get it."
So here we are, an increasing number of us are actually taking seriously design skills behind lowly entry-level O.S. engines right up to the RO-Jett 65. That certainly qualifies as a paradigm shift, even if one that is hardly universal.
Another shift is that with so many good engines out there, one can, among other options, first ask if he wants to fly two-strokes or four-strokes. In either case, small-bore engines are readily available off the shelf or as used pieces. Cheap, easy-to-build profiles work, especially as we have learned how important the engine is to the engine/airplane combination, this probably being yet another paradigm shift.
(I no longer look for a pretty airplane to build, powering it with something which seems appropriate. I first look to what I want in power and power delivery, determine which engine meets specs. And then look for a suitable model.)
I suppose Brett said it best, "Well. I would say the conclusion is - it's really not too hard to be a stunt flier these days." Indeed. And truly a paradigm shift, one to positive side of the scale this time.
Enough. I feel a Bad Boy Stunt column coming on, a subject to just beat to death via the printed word. But having had a bad experience loosing such commentary--again, my fault--on the Stunt World via this medium, I'll take a real big pass...
As for mention that "something" must have happened at W/Cs, Nationals which escaped the notice of many, I was not there, don't have an inside track. But I will tell you that PW and I spoke (briefly) about things, and while I will let him share his feelings, my sense of the conversation was that he felt his equipment let him down and is fixin' to do something as to exploring alternatives.
Still with rememberances, catastrophic failure of number one model not regarded as a big problem; instead, engines are the focal point of his current thinking. My personal view is that knowing Paul and his drive to excell, loss of primary model was likely overcome within a day or so and was not a factor of significance in his performance at either event.
Dan
Thanks for the info. Sorry, I didn't mean to infer that it was ALL prop, when I tried to put a brief description on the 2 scenarios, I put them into 2 categories, the loaded up higher pitch, and all that went with it, nitro, intake, tank, etc. and then the low pitch high RPM scenario, and all that it takes to run it. The piece I did miss early on was that your basic dissatisfaction is with the airframe/powerplant combo, not the power plant itself.
BTW, your clunk tank solution does make an obvious improvement in my overheads with the stroker, for instance, regardless of the prop. Good bye overhead over lean sag.
I'm a little concerned with your 8" neighborhood front end estimates. My concerned is not for you, but for me! I'm glad I chopped 1/2" off the front of my Legacy in the 4stroke design/build phase for my 56, but what you just said makes me wish I lopped off another 1/2". Well, maybe you were mostly talking about the 72, which is a bit heavier and swings a larger prop...
As to heat issues, man, you could roast peanuts on mine early on, especially the muffler! I solved most of that by getting the engine to consume more fuel. I drilled out the DS spray bar*, shortened and opened up the intake and opened up the exhaust baffle. Runs pretty cool now and a big power gain. No sags, not even at the end of the last corner of the second square 8.
*(I know some people don't believe in this, and some have even said "That's what the needle thingie sticking out is for, just open the needle more"**, the spray bar exit hole size makes no difference". I'm going to ask them to give me the benefit of the doubt on this one, since I have done the tests, and there is a HUGE difference. FYI SOME spray bars exit holes are so small, they self meter***, as in; the engine can't draw the fuel fast enough under load.
IE; if you are trying to launch a little leaner (within reason of coarse), but not have it go over lean (not talking 4-2 break harshness, I'm talking power sag) in the maneuvers, and can't figure out why your high zoot engine won't haul the mail as expected, you may have one of those spraybars that needs to be drilled out. Don't get me wrong, this is only a small link in the fuel chain, there is still tank, intake size, nitro, compression etc. But one weak link in the chain can cause a problem.
**I think just opening the needle more might work if the system was under pressure, <fuel pump?> but we deal with suction.) Also, I've never tried a spigot with the 4-stroke, but I have wondered if an advantage might be there somewhere for fuel draw issues.
*** Self metering - Have you ever had trash clogged in your spray bar, and no matter how much you open the needle, it's still screaming lean with no rpm change? Hence my use of the term Self metering. At some point backing out the needle stops being the limiter and the trash in the spraybar has the more predominant effect.
Eric Viglione
I've not experimented with enlarging the holes on any particular set up so don't know if that might be a factor in some set ups. But I do clean out these burrs. On rare occasions I have found so much trash in the hole that it was virtually shut off. Simple thing to check, easy to fix. Much like taking the backplate off of 50-60's era engines and taking out all the metal garbage that was usually left in the crankcase back then. I'm sure that a lot of us older guys do many things like this that we don't even think about but the new guy or someone getting back in after many years absence may not know or may have forgotten.
The old saying "He's forgotten more about (insert subject) than you will ever know" takes on a little different context when one gets older. Because the shame is, I have forgotten a lot of things and I do the "DUH!" (while hitting forehead with heal of hand thing) a lot more often at 60+ than I did when I was 30.
Later, John
But, we aren't talking about 50-60's engines anymore - we're talking about $350 semi-custom engines built the day they went in the mail. Or engine mass-produced to tolerances and under conditions that Swiss watchmakers would envy. I can see no reason at all to take them apart and "clean" them, and plenty of reasons not to. At best, its a waste of time, at worst (and I see this all the time) it'll screw something up.
I note this because I have seen many examples in recent years of people doing the ritualisic "dissassemble/clean/oil" trick completely ruin their engines. Then complain that their engine didn't run properly. I can almost guarantee that the guys you see up at the tops of the major contest scoreboards (RO and Randy excluded, of course) don't do anything to the engine aside from regular tuning tweaks.
Of course, if you have a problem, that's different, but doing it routinely is certainly a mistake.
The only engines I would take apart and check are reworked engines from a few well-known reworking sources that have very bad reputations. But of course, a far better solution is to get one from someone with a good reputation.
Do not, I repeat, do not, "disassemble, clean, and oil" every engine you get, in fact, unless its a NIB McCoy or Fox, or from a rework artist of doubtful skill, you'll almost certainly hurt it more than help.
Brett
I know what you are referring to, but I think your pet peeve let's you jump to an incorrect conclusion too quickly. I am speaking to a known issue that many of us discuss on the sideline, but don't address in public as not to tick off the distributor. We are talking simpley about a spray bar! If we are going to mount it in a profile, or upright we have to take it out and reverse it anyways!
To back you up, I'll whole heartedly agree with you on your point, if you buy a Big $$$ engine from Randy or Richard, leave it alone, you are probably in a technical sense, voiding the warranty, even though they are such nice guys, they'll most likely ignore it. It's a custom piece, and part of that customization is proper assembly. I should know, I've dealt with plenty of "crummy" engines that only needed to be reassembled properly, both in hot rods and modeling.**
Eric Viglione
PS: As long as you brought it up; Some manufacturers do supply spare parts for fine tuning an engine. How does one fine tune his engine with these supplied spare parts, for instance add a head shim, head buttons, change a venturi size etc., without going against your pet peeve????
**IE: I did a screaming rip snorting small bock V8 for a buddy once, and for some reason he decided to pull the intake manifold to take a peek at my head work, when he re-assembled it, he used stock gaskets and it ran like CR@P! I had to drag the truth out of him and when I found out, I charged him plenty to re-install the intake again with CUSTOM PORT MATCHED gaskets. (The stock gaskets had totally nullified my port work.) It then ran as intended and he was happy.
Brett:
I certainly DID NOT advocate taking apart a PA or RO-Jett engine. If you read my thread carefully, you will see that I said I "can get into trouble doing that". I was trying to address the point that Eric made about the "possibility" of "self metering" with trash in the spray bar hole. Personally, I don't think that is any more messing with the engine than cleaning out the fuel filter or taking out the needle and squirting fuel through the NVA.
What I was trying to address was the fact that over the past few years I have seen a number of Spray bars that did in fact have burrs in the hole(s)and believe these need to be removed in order for the engine to perform properly. These experiences have all been with the currently popular "affordable" Sport engines. I'm not about to name names here. Approximately 50+ engines and maybe 5 or 6 occurrences. Not a big problem unless you have one of the 5 or 6. It's an easy check and an easy fix which I think is worthwhile.
Eric: Thanks, You got my point.
Later, John
Oh, of course. What I didn't like was the "we all know this" part. There are people who still routinely "disassemble/clean/oil" every engine they get. I know of two recent examples of this (from people who probably {well, make that certainly in one case} should have known better) where they completely ruined the engine before ever running it, in both cases brand new RO-Jetts. If people who should know better do it, it's clear that many others of lesser knowledge might get the idea that it's what the bigshots do, so they should do it too.
Could you/Eric/I take an engine apart without breaking it or screwing it up? Probably - taking ST46's apart once a month during contest season (in order to replace the ring) and once a year for a liner rough-up was standard procedure. Cleaning the spraybar, sure. But the way I read it, you left the impression that disassembly could be a standard procedure, and I wanted to make sure that it was clear that that is an artifact of 30 years ago.
Brett