RSM's Don Still Stuka (Engine Recomendat

Hello,

I will soon be building a New Don Still Stuka Kit produced by RSM. Eric at RSM recomends that I use a OS-LA .25 engine because of weight and balancing considerations. It appears to me that a plane of this size would be underpowered by that engine, can I get some recomendations and feedback on your experiences with this plane and your engine combinations. I am also located in the Midwest where altitude plays a roll in engine performance. Please email me at [email protected] or post your feedback on the forum.

Thank You,
John Matenko:o

The original was flown with a Fox 29, so it doesn't need a great deal of power. I don't have much running time on my LA 25, but I'm convinced that with the proper propeller it has more power than a Fox 29 (or 35)

The kit prototype flew at the last VSC with a 25 and seemed to have plenty of power.

That said, the LA25 is heavier than a Fox 35. So if you wanted to use a 35 that would not have an impact on overall weight or balance, there is another solution. I haven't seen the kit yet, so don't know how much tank space there is. I would expect the Fox to burn a little more fuel than a LA25. Eric sells the L&J Foxes with either an iron piston or ABC. Foxes have always run better inverted than side mounted, to this could be a good application
Steve

>>The kit prototype flew at the last VSC with a 25 and seemed
>to have plenty of power.

According to Dee Rice he was using an FP25 reworked by Leonard. His plane weighed in the low 30's.

None of the Stuka versions have ever been "large" models, REALLY. Don Still started from the Lou Andrews Barnstormer wing airfoil and size, adding coupled flaps, which the Guillow kit of the Barnstormer I lacked. He preferred the Fox 29 over the 35 at first, and later changed the engine choice to the Fox 25's from the 1957/ 1965 production. The Ambroid kit was based on the 25-powered Stuka.

Most of the modern Schneurle-Ported 25's have PLENTY of power for a small plane like a Stuka. I would expect that a Series 200 Veco 19 would do the job. Anything bigger/heavier than those I've named, and the plane's balance will be way off.

.
Kiwi

Back in 1966 I built the Ambroid version of the Stuka Stunt and powered it with a Fox .25. It had more than enough power. The LA .25 is plenty powerful for the Stuka Stunt.

I built one of the Ambroid kits in 1965 and used a Fox 29. It had plenty of power. However, we didn't run mufflers back then, so that could make a small difference.

I have one of the RSM kits and I am considering the LA 25 with a tongue muffler or the Fox 35. I have flown both engines on the same Skyray and they seem to produce equal power. The LA 25 runs much better in a side mount than the Fox. Either should be fine in the Stuka.

My LA 25 has been converted to a front needle valve and I use the same 50-50 mix of Fox Superfuel and Duke's fuel for both engines. Too bad the engine mounts aren't the same. Then we could swap the engines back and forth and see for sure. Oh well.... I'll build the wing first and make up my mind at the last possible moment.

Ron

Hi John, I tell you what, it really is hard to teach us old timers new stuff! However...I must say that one of my all time favorite fun planes is the Sterling Mustang P-51D. I scratched one together starting in 1985 and finished it in 1992! I flew it hundreds of times with a Fox 35 and deluded myself into thinking it was great! For my mind perhaps but not really as a stuntable craft. For the past two years I've been sucking all the oil soak out of it and finally called it a job this spring. I mounted the LA .25 with FP NVA up front and flew it in June when the Pennsylvania monsoons let up. Wow what an improvement! I have been flying it on my OTS lines of 58' eyelet to eyelet and have a 9X4 old style Top Flite wide blade prop on it. The tach says 10,200 at relaese and it just powers through the entire PA pattern then I can fly the entire OTS pattern on 3.5ozs of fuel! Have no fear this little engine will out work any Fox .29 or .35!

>I will soon be building a New Don Still Stuka Kit produced
>by RSM. Eric at RSM recomends that I use a OS-LA .25 engine
>because of weight and balancing considerations.

I am curently building a Don Still's Stuka from scratch plans. Talking to Don Stills by phone the original model was 3/4 inches shorter in the nose, hence vintage legal. I will install the OSLA25 as per Dee Rice, He recommended a shorter nose also. I have done that. Further, I fly an OSLA25 on a primary force using 2 1/4 oz fuel for a full pattern in 4:50 - 5:20 minute patterns There is plenty of juice in the OSLA 5/8th hp. Fox 35 uses 4 oz fuel, 1/2 oz lighter. The OSLA should be preferred for power. Send it off the ground at 11,400-12,000 rpm with an apc 9x4. That is a rich 2 cycle or just a little faster. No wind up problems in the wind.

Use a Hayes 3 oz clunk tank. Weight .8 oz vs 1.4 oz for a 3 oz metal tank with cg about 1/2 inch further aft than the metal tank. Install the tank immediately in front of F2 in front of the wing. Use a tongue muffler and ST needle valve. The larger needle valve assy will choke down the venturi suffiently for stable runs and still have plenty of power. Remove the remote needle valve for weight and cleaner installation. Weight savings are .6 for tank and about 1 to 1.5 for fuel or 2+ oz. Subtract motor weight and overall the LA configuration should be lighter about 2 oz and more powerful by 1/8th hp. Not to mention the cleaner bird with less oil on the plane.

Use 10/22 Powermaster fuel. The motor starts well after one prime flip and several flips to mix fuel and air throughout the motor, attach battery and then gentle backflips usually starts the motor right away.

Don McClave suggests that we need to build these models no heavier than 32 oz for a competetive stunt plane.

Good Luck

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

Additional comments.

Forgot the following.

TO provide flexibility on powerplants I suggest that you install a 1/8 inch 6061-T6 aluminum mounting inset plate on the motor mounts. That way you can install multiple engine configurations in the plane. You might find that a Fox 25 which is lighter might be a preferred motor and/or multiple engine options can give you more flexibility in certain situations. I plan to do just that. Weight penalty? yes, some however, if you plan to keep your plane for a couple or few hundred flights; this construction addition may just add some additional life to the airframe.

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