Kim and Bill-
'sorry I'm late in replying. I'd forgotten this thread and was just taking time off from Newsletter editing to see what's going on. Fortunately, I just flew the P-Force yesterday for one of my few tries this summer and think I made some progress...
>Serge, Would you describe your 40+ oz PF as overpowered with the FP-.35?
If the engine runs away, then yes, but it's fine when it stays at the transition to wet 2-cycle. That goes for both the FP .35 and the LA-.40, although the LA-.40 seems slightly "friendlier". I ran the FP-.35 in club specialty events requiring extremes (slowest flight, fastest, longest lines, etc.) a couple seasons ago and it had the best overall scores. But it didn't balance on the "edge" well. I switched back to the LA-.40 and tried a lot of "stuff", some of which worked at certain temperatures, but problems persisted, even on the usual uniflow set-ups; it would lean out suddenly and not return. Yesterday morning I put on a Zinger 11" x 3" and wound it out a bit more, but still at that edge of 2-cycle. Ambient temperature was probably 80+ degrees F. I didn't however fill the tank, so results on uniflow are not conclusive. I got the 5-5.2 -second laps and just slightly leaner/faster inverted. The plane was consistent for the entire flight and handled well before running out of fuel suddenly inverted for a soft, slow landing inverted in grass - no damage. So, I liked what I saw with this less efficient, lighter, lower-pitch prop. Tension was nice. Tomorrow, if I'm far enough along on the club newsletter, I'll try it in the evening again adding 1/4 oz weight back to the other 1/2-oz on the tail.
I would say that the power available, if harnised correctly is just fine, but when it leans out, the lap times on an APC 10" x 4" prop go down to 4.0 - 4.4 seconds per lap. I'm a bit old now to do many tricks at that vertical speed. If it were a 36-oz plane, I think the LA-.25 would be a fine match.
>How's it going? As to the laps times around 5.0, traditionally that seems to be the area that most profiles like to fly. I think some of the newer designs with newer powerplants,
>can be slowed down a bit (*maybe 5-2-5.3*), but it isn't by much it seems, and it is a model to model situation. What cha think?
Things are pretty interesting and hectic as usual in this retirement thing, Bill. I'm enjoying designing and trying to mathematically analyze my very unconventional model design and have neglected my conventional, by-the-numbers stunter that's about 2/3 complete (has been for months!). This has been sandwiched among Gusti's LaCave reunion committee musical events leading up a big concert weekend that took place over three days a couple weeks ago. Super event! Now I'm back on airplanes for a couple weeks.
Anyway, I agree, it seems that the planes themselves seem to make a big difference. I first had the LA-.40 (which I bought from Richrd Oliver at VSC-14) in a heavier, flapped, hodge-podge profile made by Mike Alimov from his crashed Tucker Spl. wings and tail. That engine would not perform at all on the same clunk tank that had been used for his ST .51. Even Mike couldn't get it to work. So I put a GRW (?) metal uniflow tank on it and coaxed it into working really well. Some leadout adjustment made that plane fly just great with that engine on 60' lines. Then of course it went in inverted, when I got too comfortable near the ground and forgot which way I was flying. After flying Foxes on SkyRays for a while, I built the P-Force and never, got any consistency other than a handful of flights or separate days on a variety of tanks. So the LA-.40 liked the Tucker derivative, but has never liked the P-Force. The nose of the P-Force is a bit flexible, and I really should put a cheek on it; so maybe I just have myself to blame. Still, the plane does seem to make a difference. Possibly also the engine worked harder on the draggier Tucker than on this relatively clean 500 in^2 flapless profile. Of course, the model weight makes a significant line-tension difference, perhaps affecting line length as well. 'lots of "stuff" to coordinate in any plane and change.
SK