I did a search, but the only comments I could find regarding thrust angle on the Cub is that Cubs like a couple degrees of right thrust.

Anyway, here's the scoop...........this is the GP .40 Cub with a .48 4-stroke. I finally decided to take the gear off and bend them back into shape after all the rough landings and other "incidents" the plane has experienced over its career. Bent in some toe-in, bent the gear back out so they're not sprung looking, and tweaked the tailwheel a bit. Due to rain I only managed to get one flight in today (and won't be able to fly until next week), but it looks like this has improved ground handling (though maybe not as much as I thought it would). However, I'm very skeptical about all the right thrust the kit has built-in. The plane was built by someone else (it was a first kit for them, as well), and after the first few flights, I thought they'd built in too much right thrust, so I dropped part of a pushrod in between the mount and firewall on the right side to straighten the engine a bit. I seem to recall having somewhat better luck with the plane after that, but I was so inexperienced at the time and the gear was so bent, I couldn't really tell if the decreased right-thrust was helping things, or if I was just getting better at it.

Now that I've got the gear worked out, the plane is a little more consistent in ground handling and it's easier to observe what it's doing. Here's what I've noticed: on takeoff, I need (mostly) LEFT rudder to keep the plane tracking straight. On landing, I had to hold some RIGHT rudder to keep the plane from veering, with power at idle and the tail in the air. Also, I noticed before the gear adjustments and after, the plane turns to the right very easily on the ground, but barely turns left. It really seems like I need less right thrust, but then I read comments in various posts here that the built-in thrust is appropriate for a Cub. The left turning tendency on landing kinda threw me off. I did have very slight left rudder trim by that time, and the field is rough so I might have hit a bump with the left main, but I remember the plane veering left on landing before I adjusted the gear too, numerous times.

On my first takeoff today, the plane got away from me and ground-looped to the left. This makes me think that if I do indeed have too much right thrust, I've still got a problem with the gear somehow.........but I dunno how, as I've tried swapping the mains, and I just totally changed the angle of the wheels last night when I put in the extra toe-in.

I did have some crosswind, which might help explain the left rudder on takeoff (and perhaps the right rudder on landing, as I was landing the opposite direction.......though I noticed the same problem before adjusting the gear, which makes me wonder), but doesn't explain the consistent inability to turn left on the ground.

So, to all you GP Cub fliers out there............have you noticed any trouble with the built in right thrust? I'm thinking maybe since my model is using an engine at the low end of the power range, that maybe GP's judgement on the firewall angle is too much for this engine.

On a positive note, I seem to have finally got the 4-stroke singing! I had a lot of fun practicing approaches, sure helps when you can throttle waaaay back and not have to worry about killing the engine. Today I made a nice smooth scale-like wheel landing with the engine still running...........just a little rudder to keep it straight, ease the tail down, and taxi back to the pits. Great fun!!!!! Had to do some right-hand donuts to get turned back to the pits though, due to the aforementioned left turn problem. But I guess it did look pretty cool, come to think of it........ [8D]

-Matt Bailey