Just got a nice deal on a NIB U.S. 41, but no manual. Putting it into a 1/4 scale Cub. What size prop should I be using ?

Ed

20 x 8 Iwould think to be about right

I agree.

Ed,

I had the same engine in the same aircraft. Great combination. I ran mine with an 18x10 or 18x6-10 with great results. The suggested 20x8 should work as well.

If you will send me a PM with your email address, I will send you a copy of the manual. Ok, it is for the Quadra 42, but they are the same. I have both engines.

Have fun with it!

Bedford

A 20x6 might give you a little better takeoff and vertical performance if you like that kind of thing (vs. scale performance). Will also help prevent speed buildup on your down lines and slow the landing speed a little as well. FWIW

I've been around a lot of them in years past and the standard prop everyone used on a general sport type plane was the 18 X 10.

They turned around 7200

Thank you guys, you have been very helpful, and I have one remaining question. I have one terminal protruding from the magnito coil, is this where I attach my Kill switch ? And just how important is it that I use a kill switch ? Can I fly the plane without one ? ( whoops ... that's 3 questions isn't it ? [] )

Ed

It is nice to have an alternate method of stopping the engine if necessary

That spade connector connected to the crankcase metal will prevent the ignition coil from working.

Thanks w8ye. I can now turn it off using the throttle from the transmitter, or by choking the exposed carburetor . The kill switch would be a 3rd way.

ed

Nice

Ed,

Grounding the coil to the engine case through a switch is an important safety feature. I use a good size toggle switch on the forward side of the fuselage that is easily accessible. You never know when you will need it. A remote kill switch is even better, but I have to admit I generally don't use them (part of being cheap). I wished I had one some time back when I had a runaway engine. Stuck on full throttle. Handling was not a problem, but my endurance was. That little 21cc gasser didn't suck much fuel. The problem started about 5 minutes into the flight. About 45 minutes and one relief pilot later she came down uneventfully deadsticked. In today's commonly over-powered birds, a stuck open throttle might be a much bigger challenge to handle - safely, and survivably.

Have fun,

Bedford

I would like to convert my US 41 to electronic ignition but have been having trouble finding a conversion kit for it can anyone help here. Tried CH but no luck.I need the flywheel and pickup bracket. Also what are the rules about kill switches for cdi engines and mag engines .
Thanks Ted