I have an OS .40 FP on my high wing trainer and I swing a 10x6 prop with no real issues. I just built a low wing trainer (plastic over foam) and have an extra OS.40FP and a 10x6 prop. The planes are about the same weight and size but the OS papers state that an 11x6 prop is best.. Should I give the 11x6 a go versus the 10x6 or do you think that it works on the high wing so it should be good for a slow, low wing? Any suggestions would be helpful.

hey the 11 inch will give you a bit more torque and that slow controllable flight.. but a 10 inch will fly it just fine... If I were you I'd go ahead and fly it with the 10 inch until I could get my hands on the 11

The best prop in my opinion for any given plane is one that will fly it the way that you like. The 10 x 6 might not be quite right, then again you might not like the 11 x 6 either, but it should fly fine with the 10 x 6 until you try the other.

Try a number of different props. Even different props of the same size by the same manufacturer will not always fly the plane the same way. Give a few different ones a go as you have the ability and decide what works best for you. That's what is important, but more so, have fun doing it!

I have a number of OS 40 FP engines and 10 X 6 prop has been the one that I have always used with great success for sport planes. Good Luck, Dave

An 11X6 is a relativly heavy load for an old 40FP. The FP's were the low priced predasessor to the LA's with deliberately detuned port timing and and smaller venturi for better fuel draw and user friendliness.

My recommendation personally if you want a to try an eleven inch would be to start with a 11x4 maybe and 11/5 but that to may be a bit of a stretch.

Also yes of course do experiment, its good to start acquiring a small selection of props for this and future projects anyway.

John

Over time you will discover that for non-competition models, any prop within an inch of the "best" diameter will work as good as you can fly. Best thing is that many, many props work well for just boring holes in the sky.

On the other hand, if you know what to look for, the same prop (a 10x6 for example) by different mfg will perform just a bit different. So there will almost always be differences, just not always much.

Matter of fact, just today, one of the guys broke his favorite 14x6. He pulled out a brand new one by the same mfg. Perfectly identical, right? Well, his needle setting had changed and that identical prop seemed a bit slower as well. Same diameter. Same pitch. Same mfg. Same everything...... different performance.

Try whatever you think might work, because it most probably will. And any you try might be better than the last. They ain't magic, and they're not perfectly predictable.

UPDATE:

All happy that I had finally built a plane myself and got it airworthy was short lived when I got to the field and found that the engine would not even get my plane airborne.. The 40 was the low end of the recommended engines for the model but it just went up and then turned to the ground. I don't think that it even got 5 ft off the ground.

I determined from reading other posts that the engine just does not have it to lift the plastic over foam model. I have purchased a 90 Super Tigre and plan to install that.


I will let you know how it goes.