OS 25-LA Props

What props are you guys using on the 25 LA?

Thanks for the help!

The ony two props I can get to work well on my LA-25 Ukey are the APC 9-4 and 10-3. Right now I use the 10-3 since I get slightly longer lap times (4.8s on 60 foot handle to center length) with fair tension. It just doesn't seem to be able to handle 10-4 size props (and I have tried the common ones -APC-Graupner, Zinger). I use only ~2oz (60cc) of fuel (7.5% Sig Champion) for the full pattern, and the engine seems reasonably happy.

I use 9x6 props on my LA25 and FP 25 motors and it works well. Pulls through the pattern really well.

I use 9-4 Tornado's on my FP 25's but understand they are hard to come by these days.. The APC 9-3 would probably be a good substitute

There is an APC 10-3 and an 11-3, but no 9-3. There is a 10-3 Graupner, also. I like both brands, but don't have a .25 LA, so can't say which would work better, but would sure try them, and would try trimming them down, too. Steve

LAST EDITED ON Jun-27-03 AT 12:32 PM (CDT)
 
I am new to the LA 25, but I do have one mounted on a BoxCar Chief which weighs 31oz. I fly it on 60' lines. I have found a Zinger 10-5 to be the best with this package.

As for the motor itself, I love it. Runs great.

Bill Hodges
OTS Rulz

apc 9x4 on a Primary Force weighing 39.5 oz let off the deck at 11,000 rpm. It unloads after the first lap and flies a strong pulling pattern on 58 foot .015 lines eyelet to eyelet. I tried an apc 10x4 and it sruggled. Needs to be thinned down. I have heard that a 10x4 zinger thinned down (.112 at the shank and .072 at the tips works quite well (Designman)will work well. Need to try that. Pat Johnston also suggests an 11x4 although that sounds like a lot for a 25. Time will tell.

Next step is to try 64 foot .010 solid lines on the plane to slow it down. I have found it is better to let these engines run and adjust other parameters to adjust the lap times.

Mike Pratt suggested all forms of 9x4 props for the Primary Force. While larger props may have more thrust, provided the engine can carry it you have increased gyroscopic precession which brings along with it other problems.

Bob Smiley

A Lancair 360 builder/pilot trying to be a modeler

Bob- No can do on the .010 lines, at least in competition. .012 solids are the legal minimum.

Interesting that the LA struggles with the 10x4, my FPs can actually swing a 10x5, and you saw how that Flite Streak screamed with the 9x5. Hmmmmmm

I have 4 OS 25LA's, three of them I converted from R/C version. These version don't seem to like a big prop, like an 10 X 4 or 10 X 5.

But another version, I purchased from Tower as a Control LIne engine, will turn an APC 10 X 5 with authority.

I suspect, it has something to do this the boost port on the older 25LA's. Othere, people in our club also experience the same thing.

Are you saying that the newer .25 LA's don't have a boost port? Steve

I am pretty sure they do not, but I have not taken mine apart to see. I think someone else mentioned something about this on an older thread.

LAST EDITED ON Jun-27-03 AT 11:17 PM (CDT)
 
>I am pretty sure they do not, but I have not taken mine
>apart to see. I think someone else mentioned something
>about this on an older thread.

The .46LA never had a boost port, the .40LA's dropped it a couple of years ago, but I'd never heard about the .25's. What about the .10 and .15? Seeing what props were run on PW's B-17 #909, not much would surprise me...9-4 and 9-5 APC's on stock .15FP's (tho with big venturis and bored out OEM mufflers). Maybe removing the conical baffle and boring the exit tube would be something to work on if your .25 won't pull a big prop, getting rid of heat better. Steve

Yes, That was my post (back near end of May I think). In my case the boostless one was a new RC version, while the older stunt did have the boost port. My impression is that the one without the boost port (the one on my Ukey 35) cannot turn as large a prop as the one with the boost port (which I ran a 10-4 prop on a Brodak Lightning Streak), but since I haven't run both on the same plane, maybe that is part of the equation to consider too.

Another one that works is, Brodak 10-5 launching @ 8800-8900 rpm.

10-4...

And Ten Four, Good Buddy. Currell

Chris Gomez was running a 10-4 Zinger on his LA .25 powered Elliott Blackhawk P-40 OTS. It pulls it with considerable zest, and the airplane flies perhaps too fast. I have launched the model, and static thrust is amazing. I think the 10-3 APC would be very worthwhile trying. Bob, I have both APC and Graupner 10-3's in stock, so let me know when you want to try them on your official flights. Steve