Brett Buck-LA 25

So what is the hot setup for the LA/FP 25?

I have one on my P-Force...

'zilla,

Well, I'm not Brett, so my opinion probably isn't the best, but I've watched Bob Smiley run one on a P-force all last year. The hot setup seemed to be leave it mostly alone. It's a one speed engine. He set his at a ground rpm of about 11,500 or 11,800. Used a 9-4 APC prop, thought it wasn't bad at all with a 10x4 APC cut down to 9.5. 10% nitro with 22% oil (your basic Powermaster). Just hummed along at about 5.2 second laps with lots of power.

tank?

Big Bad Brad...

I have ran everything on the LA 25 all kinds of wood props and APCs. The APC 9X4 seems to be the one at about 11500-11700 on the ground. I fly on 60' lines. I dont really keep laptimes with this plane. I pay more attention to how it handles the maneuvers and set speed accordingly.

Tank??? Come on, there is no other tank...Sullivan! I have run GRW uniflow, ran like crap it hates to draw against uniflow. The needle is tough to set on uniflow. It either runs way fat or lean. Maybe something to do with the venturi size(too large, but green filters and balsa in the venturi didnt make a difference). I ran it on suction and on pressure not uniflow, ran so so but not very consistant. I ran it on a Smith's Tank. Same results as above. Then I went to a Hays blowmolded pattern tank. Ran it on pressure and off of pressure it ran better than the metal ones but it had a funny inconsistant run. Finally went to old faithful Sullivan, setup the way we always do and have been for many years. The same way you have in your Shear Panic. It runs pretty darn good and I can get consistant run to run performance.

Mufflers, I have run it on the Stock muffler. Runs OK. I have run it open and it had the most power but it was more inconsistant. I once had the back half the muffler rattle lose and fly off after I had gotten in there and removed he stock baffle. It actually runs real good on the half stock muffler(back half missing) Makes lots of power. I found it and bolted it back on. Then I opened up the exit hole to 1/4" and it ran better much better. I hunted for a tongue muffler for a while but couldnt locate one. Does anyone have one? I thought Brodak had one but I got a look at it at Mike's it was for the 40. I think it will work best on a tongue, power wise. I want a tongue muffler so maybe I can get a little bit longer prop on it and see if I can get the plane to trim out a little better. Especially above 45.

Fuel, I have run Sig 15 and 10 and YS 20/20. It doesnt care what you feed it it pretty much eats it right up with nothing bad to say. For the most part testing out my 25 was alot of fun. It just needs a tiny bit more punch. I am the process, long process, of making a muffler for it out of the front neck of a Randy pipe. Should have much less back pressure. And weight about 1/4 of the stock one...

Len, you got a tongue for it?

By the way get a real light weight handle for it. I flew mine on the Bone for a while and it didnt seem to have very good tension. Then I got a Brodak small handle. A wood copy of the E-Z Just and it was like night and day on the amount tension. It doesnt like dragging that big heavier full size handle. Oh yeah, you have some Ted Handles they are light weight. It is fun to fly. I think you will like it once you get used to how small it is.

Brad,

3oz (if you can find one - Hayes is good) clunk tank. Doug is right, they don't seem to like uniflows much. Personally, I like the tube muffler best, but a tongue muffler or even the stock muffler with the baffles pulled works pretty well.

I started with an APC 10 X 4 on my P-Force/LA25 combo. I could not get the lap time slow enough. I was flying under a 5 sec lap.

Finally put an APC 10 X 3 with a Mac Muffler. Still has lots of power.

What are you putting the engine on?
What do you want the engine to do?

I have 8 of these OS Max 25 engines. I have one on a Sterling Ringmaster and a Flite Streak. The engine has no problem turning a 10x6 prop on 15% nitro with 20% oil. The engine will fly 75 mph with a 8x6 or 9x5 prop on an F2D combat airplane. It will fly 95 mph with a 8x8 prop.

It will fly 60 with a 9x4, 10x4 prop on the Rimgmaster or Flite Streak. It will fly 50 mph with a 10x3 or 11x3 prop. I bought a 12x3 prop but have not tried it yet.

Its interesting there is no change in speed between a 9x5 pitch and 8x6 pitch prop both are 75 mph.

Yes, I have an LA-25 on a Primary Force. Weighs now at 37 oz. using the stock muffler with the baffle removed from the inside an APC 9x4 running free off the ground around 11,400- 11,600 10% nitro 22 blend oil runs about 4.8 second laps. Flies a little faster than Mike Pratt's force because his is a little lighter at 35 oz. Even so, it is a fabulous flyer for an elevator only plane, has made a 502 flight.

Fuel tank is a 3 oz Hayes clunk tank that has a tongue on the front. Used as a uniflow with the uniflow input at the front of the tank. Makes no difference on the runs. Gives you a two lap warning before quitting.

I have been very satisfied witht he setup for a full contest season.

Bob Smiley
A Lancair 360 builder/pilot trying to be a modeler.

What do you mean by 'Uniflow input', are you using muffler presure or just air presure into the uniflow vent?

I have not had sucess using Uniflow to air stream on my LA 25. I think the venturi is a little too big.

What is your tank height?

Question: What do you mean by "uniflow input"?

Answer: The Hayes 3 oz plastic clunk tank has three possible openings on the front end of the tank. one for the pickup with a small rubber plug. Two others on horizontally placed at the half way height of the tank. The outboard one I use for uniflow input but the inlet is at the front of the tank, not the back end. The second opening is the filling vent which is plugged for flight. The uniflow tubing is about 2 inches long and has a 1/8 in brass tubing and a smaller tubing with about a .050 diameter inlet. That brass assembly is pushed into the pushrod hole of a 1/2 A nylon elevator horn Which is mounted to the top rear motor mount bolt and the brass tube is looking forward into the breeze. While this is not a strict uniflow setup (internal outlet near the pickup in the tank), it neverthe less behaves like a uniflow setup.

Bob Smiley
A Lancair 360 builder/pilot trying to be a modeler

Bob,

It's slower on the longer lines.

>So what is the hot setup for the LA/FP 25?
>
>I have one on my P-Force...

I don't think the LA and FP are the same animal - the FP is more powerful, and I really only have a lot of experience with the FP. And, I prefer the way the 20FP runs over the 25. So, having addressed that caveat...

Straight out of box, stock muffler, stock .256 venturi, stock OS needle. I use SIG 10% fuel, but 15 is OK, too. Prop of choice is either the 9-4 APC, or a 10-4 Rev-Up. With the Rev-up. you will probably need either 15%, and ST needle, or an air filter to get sufficient fuel draw and reliable runs. I don't think it cares what fuel you use withing reason. Try some YS 20/20 - I'd be interested in how that works.

With the 9-4 it should be able to rev high enough, but if not, fine air filter. If in doubt, use less prop. A 9-4 or 10-4 Tornado will work, but it's much more load than the APC, and less load the better.

I have used either 3 oz tapered uniflow tank, or, after you led the way, a Sullivan SS-4 clunk tank on suction with muffler pressure. It didn't like the uniflow with muffler pressure. I think it ran better with the uniflow, since you didn't have to set it too rich at the beginning, but either way is fine.

It doesn't really need a lot of break-in, but it will tend to cut out on outsides on the first few runs. And it will take heroic amounts of fuel - maybe 3.5 oz on the first flight, and then go down drastically to maybe 2.25 in maybe 10 flights.

Happy motoring.

LAST EDITED ON Dec-24-03 AT 01:20 AM (CDT)
 
I saved this post awhile ago from Mr. Mikey.

(the transference from forum to Apple Works word processing program and back here has created some
quirky symbols)

Paul H.
p.s. personally I have used Brett Buck's sugestion on the OS MAX .20 FP and found the
engine run very good.

"OS .25 LA & FP Setup"
 
   After receiving a number of phone call and e-mails about how I was setting up the OS .25 FP & LA for the Primary Force I thought it would be a good idea to post it here on SSW. Please donít think I know all there is to no about these engines but I have found a few things that worked really well.

OS .25LA: I used the engine in stock form and was quite surprised how well it ran right out of the box after a short break-in. There were a few things about the engine I didnít like but the biggest thing was its lack of consistency (I am really fussy when it comes to engine runs but I believe that most sport flyers would be more than happy with the way the engine runs out of the box). I had to reset the needle before every flight and it was almost impossible get the same setting flight after flight. During some flights it would drop out of the rich 2-cycle and into a doggie 4-cycle for a few laps and then jump back to rich 2-cycle. In addition, the engine would go lean and almost quit in the second loop of the four-leaf clover (with plenty of fuel still in the tank).

I thought the rear mounted remote needle was the culprit and replaced the remote needle with a ST needle valve assembly (through the venturi). This was a little better but still far from what I wanted. I used different combinations of fuels, glow plugs, head shims, air filters, and muffler pressure with little or no change to the run. Completely frustrated, I switched to a tongue muffler and instantly most of the problems went away. The run was much smoother and more consistent cruising along at a rich 2-cycle but it still had a tendency to lean out in the four-leaf. Using a Bru-Line green air filter helped and almost stopped the leaning out at the end of the flight, but switching to a .250 dia. venturi (from Leonard at SSW) cured the problem completely. One other little change that I made was making a plug for the uni-flow vent that had a .050 hole drilled in the end to keep the engine from running a little fat (rich) at the end of the pattern.

Now the little .25 LA runs like a Singer sewing machine from the beginning to the end of the tank with a short power burst one lap before it runs out of fuel.

Listed below are the suggested changes and/or parts needed:

.250î i.d. Venturi.
S. T. needle valve assembly.
Tongue Muffler. Modified RSM or SSW
3 ounce Uni-flow tank (1î x 2î x 3î) Brodak or GRW.
Props: APC 9î x 4î& *10î x 4î (*trimmed to 9-1/2î).
Grisch 9î x 4î Black Magnum
Bolly 9-1/2î x 4-1/2î (re-pitched to 4î).
Glow Plug: S-300 Sonictronics or Thunderbolt R/C.
Fuel: Sig Champion 10 or 15% ? synthetic & ? castor.
RPM: Set at 10,2 to 10,500 on the ground depending on your prop choice. It should be braking back and forth from a 2-cycle to a 4-cycle (more 2 than 4) and as it warms up it should be in a rich 2-cycle (by the time you reach the handle). After launch, the model should speed up during the first lap and as the engine cools a little you should hear it back off a little into a rich 2-cycle.

OS .25 FP: This was really easy to setup because the above modifications worked perfectly on the FP. There was no need to plug the boost port or angle the intake ports on the FP. It ran really sweet and I think it even has a little more power than the LA. The FP liked the Bolly 9-1/2î x 4-1/2î with the pitch set at 3.75î.

One other thing that I will point out is I live at an altitude of 5000í so some of the changes and settings maybe a little different at lower elevations. When I travel to contests (at lower elevations) about the only changes I make to the engine is adding a Bru-Line green air filter and if it is really hot I switch to 15% nitro fuel.

I hope this helps,

Mikey

The consistency in engine runs is a fuel tank problem not an engine problem.

LAST EDITED ON Dec-24-03 AT 01:07 PM (CDT)
 
>The consistency in engine runs is a fuel tank problem not an
>engine problem.

Not necessarily. There are many engine inconsistency issues that have nothing to do with the fuel tank - in fact, most people accuse the tank when in fact it's almost always something else. Fuel tanks are cans with pipes sticking out - not a complex or hard-to-understand device.

In fact, the tongue muffler vice stock muffler problem described above is a classic case. The stock muffler for the 25FP exhibits an exhaust tuning effect (oops, I forgot you do not recognize the tuning effect) that makes the 25 "home in" on a particular speed sometimes. This can cause it to run fine for a while, fast, then slow again, no matter what tank you run.

I used an FP.25 in an original design for my campaign in the Beginner class this year. With it I received 3 firsts in four contests. My set up is different enough to be worth a mention.
My plane is 480 square inches and weighs 28 ounces.
The engine is stock with an SSW .238 ID venturi, OS needle valve assy and Bru Line air filter with green foam insert. The muffler is a Macs 6340 and the plug is an OS #8; fuel is Sig 10% nitro 20%lube (50-50) with an additional 2% castor added. The prop is a Master Airscrew 9-4. The tank is a 4 ounce Tettra Bubbless vented to atmosphere; I use a RO-Jett fuel filter.
Takeoff RPM is 13,700-14,000 in a "fat" 2-stroke (my GlowBee tach is not calibrated, but it does register 60 rpm when aimed at a fluorescent lamp). After takeoff the engine unloads to a fast, steady 4-stroke which breaks momentarily into 2-stroke in high load situations. Lap time is 5.2 seconds on 64 foot(eyelet-to-eyelet) lines.
This arrangement has proved to be powerful, steady and completely reliable. Starts are one or two flips; the end of the tank is indicated by a gradual 3 lap increase in rpm followed by a clean shutoff. I haven't had to touch the needle valve since last July.
The setup is not perfect, however. In winds over 15 mph windup occurs- at 20 mph+ the windup can be ferocious.
Derek Moran

That's a cool airplane. Is it really finished with colored tissue? That's what it looks like. Good job.

Yes, that is a sharp looking ship.

Anyway, re OS FP 25s, I have one of Len's SSW FP 25s that he whispered to, a couple of years ago. I run a BY & O 10-4 on it. Fuel is 25% oil , majority castor, and about 10% nitro. It has a Delrin venturi.

Right Howard,

I have launched this plane and it is a real delight to hold, see and touch. Excellent workmanship beyond my capability at this time and a fine flyer.

Bob Smiley
A Lancair 360 builder/pilot trying to be a modeler.

LAST EDITED ON Dec-25-03 AT 06:15 PM (CDT)
 
Thanks very much guys. Your complements mean a lot to me.
Howard, the plane is covered with polyspan, the trim is Japanese and domestic tissue, Brodak clear.
Merry Christmas all.
Derek

Leonard has tongue mufflers for .25 LAs.