I'm building the GP 60 size J3 Cub. They want me to build in 3/8" of right thrust by slanting the firewall. I have never put that much thrust on any of the many kits I've built. I made it straight and am going to see how it flies. Then if it needs more thrust I'll add it by putting washers behind the left ends of the engine mount bolts. Does this sound like it will work and have you ever put that much thrust on a kit.

Thanks,

Gibbs

I'd be inclined to go with the kit manufacturer on the thrust angle, and adjust as you see fit from that starting point. They didn’t get the instructions from an Ouija board.

I'm sure it's there to overcome the 'P'Factor. I would start with 3 degrees right thrust or be prepared to add lots of right rudder on take off.
Most tail dragers need some right thrust built in.



Happy Flying


Tom

I am building a little House of Balsa Super Decathlon which has an astounding 3/16" offset in the firewall. After some internal debate I went with the design.

Newc,

I'd agree with you on this issue but so far the instructions have been terribly wrong on several major areas. I have had to improvise many things to get this kit together. Also many of the parts are not cut anywhere near right. This is the worst kit and instructions I've ever built. It will be my last Great Planes kit. If I didn't know what I was doing I would be totally lost and probably just trash it. A beginner couldn't build this kit. Thanks for your reply, I appreciate it.

Gibbs

I know the feeling-when instructions are wrong and/or parts do not fit correctly, one tends to lose faith in the mfg. However 3 degrees is not overstated-on my Stafford Bird dog it calls for 3 degrees down and 3 degrees right. You could use some Trig and maybe put 2 degrees and add washers from there. I do not like to add more than 2 washers to correct thrust-just my way of thinking.

First I'll say "Don't give up on GP Kits" I think they are some of the best, although I've never built their Cub. Maybe that's a lemon. I Prefer the Goldberg Cub)

In any case, check out how it lines up with the cowl. The cowl just may have been buitl for the 3/8" offset

With split mounts how does every 1 line up bolt holes with that much thrust ? What goes behind the right hand mount if 1 mount needs 3 washers?
ty Td

You could always mix rudder with throttle if your radio is capable. My old Sig Kadet had beau coup right thrust also, though.

It's going to bank left a lot better than it banks right. I would have reduced it some but not all. 3/8" does seem a lot, but not knowing the width it's hard to say. 2ΒΊ or 3ΒΊ in a Cub style is by no means excessive. A 4" wide firewall with 3/8" tip is 5.379ΒΊ if I remember my trig. I would have put 4ΒΊ, or 9/32" +/- before I just eliminated it.

3/8" is a lot different than 3 degrees. I think I would question that figure as a possible missprint.