I have a GP Ultimate. It is fast becoming my fav plane but it has a few traits that I would like to figure out.
Firstly It does not do positive snaps very well. While doing one It kinda looks like it is not full stalled and is doing some kind of wierd roll with aileron and rudder. However it does wicked negative snaps. Its cool to hear the gasps from people watching when I do these. It will even do an inverted flat spin power off with just rudder and elevator input.
Why the difference between positive and negative? I have a bit more throw than the max throw suggested in the manual. I also have about 5% more up elevator than down. The CG is set so that I need almost no down elevator when inverted.
Also it has bad yaw / pitch coupling. In knife edge it wants to continue rolling into the turn and badly tuck to the belly.
Also it does not stall turn good, I believe due to the coupling.
Any suggestions? Does others do this? Should I mix the knife edge problem out?

Yes, mix out the pitch/yaw and roll/yaw coupling. That will help all around and present a much better flying airplane. It will help your stall turn a bit, but this airplane needs a little lead too and sometimes a good shot of elevator to keep the nose from tucking or lifting on the rotation.

For positive snap it needs very little elvator. Negative snap is normal. On positive barely blip the elevator and it'll snap quickly and cleanly. OR, the other way. Flying a medium speed, not fast, input a good dose of elevator and just as it pitches hard rudder, NO aileron, and it will truly autorotate. Remember, accelerated stall then rudder gives the real autorotation. Too high a speed and the airplane simply will not stall cleanly for a real autorotation snap. Don't see many real snaps today. Not like the Pitts where you see the nose come up sharply for about a quarter second and then the wings corkscrew around. Watch some full size airplanes snap roll. Nose up, then rotate. That's all this one needs too.

Spins are different because of the incidences and wing offsets relative to each other and the center of mass on the airplane that change the way the wings work together. Its normal. Some bipes like it inverted, other positive, some are OK both ways (very liberal, huh).

Mark

Thanks MarK!

I have the same types of problems that Ed has. I haven't done any inverted snaps yet, and I haven't been able to get it to spin at all. I have only been flying the model 1 season, though. I have noticed a lot of coupling in stall turns and generally as the plane stalls and pivots I have fed in full opposite aileron to keep it level. Mine flys hands-off inverted. Knife-edge is terrible because of coupling. I roll in and add rudder and it tries to pull to the top. I push in down elevator and it tries to roll upside-down. That's usually when I give up!

I just got a new Futaba 7 CAP and am planning to try mixing some of the rudder-aileron coupling out. The manual does make some suggestions about this although I can't recall the exact numbers. I'm hoping it works.

I currently have the mixing that the manual suggests but it is far from enough. I think I'll experiment a bit more next time I'm at the field.

I've got a GP Ultimate on the building board right now. Just got my cowl from Stan's and should start sanding this weekend. So from what I can tell from all your posts is that I should set up the mixing called for in the manual, just more of it?? how much more?

Thanks in advance

I can't remember what the mixing is in the manual but I do know it is not very much. I will try to mix out my knife edge / stall turn problem and I will post my results. I also added some right rudder to throttle mix to counter act the torque but then again I have a biggish engine (TT 61 pro).

Ed:

Nice! I was starting to think I was the only freak here. I have an FX .61 in mine. It'll go straight up forever. Lots of fun!

Ken:
You can start with the manual's mixing or with none. Originally, I had a Flash 5 on mine so I couldn't do the mixes. It flew fine. In fact it flies better than fine, but now that I have a programmable radio I'm going to try to mix some of the bad habits mentioned above out.