Pitch and yaw problems with kavan Fokker DR1 with ailerons - RC Groups
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Apr 18, 2003, 12:22 PM
CO of The Flying Circus
The Blue Max's Avatar

Pitch and yaw problems with kavan Fokker DR1 with ailerons

I built a Kavan Triplane that I received from my wife and kids for Christmas and added ailerons. I built it with no dihedral just like the full size triplane, the ailerons are very effective but I am experiencing problems with it in both pitch and yaw. When I apply aileron to roll it in either direction it wants to pitch nose up and yaws in the opposite direction. I have double and triple checked the CG and have modified a special batt. pack to bring the CG forward but that still hasn't solved the problem. I havn't tried offset aileron hinges yet because this would mean a major modification. If anyone out there has any experince with this kind of problem and has tried offset hinges and had any success please let me know, I don't want to start tearing the wing of my pride and joy up unless I am absolutely sure that this will solve my problem. I also have thought about adding a small vertical fin made out of clear lexan plastic so that it will add some stability in the yaw axis, I have built several larger slimer Triplanes and both of them flew good without the clear plastic vertical fin but I also increased the size of the rudder by about 15% on both of them. I have only experienced "Dutch Roll" on one other scale model ( A Corsair ) and Increasing the size of the vertical fin and rudder slightly solved the problem on it. Any Ideas? I am leaning towards the offset aileron hinges but like I said, that would mean having to cut the existing hinges and install longer ones and relocate the control horns that are epoxied in place and that will be a major pain!!!
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Apr 18, 2003, 01:04 PM
Registered User

Can you control the adverse yaw by applying rudder ?

Also can you deecribe your aileron linkage? There are alot of ways to get differential aileron movement that do not require a major surgery.

Apr 18, 2003, 01:19 PM
CO of The Flying Circus
The Blue Max's Avatar

Aileron setup

I have one servo mounted under the machine guns in the Fuse. It operates the ailerons with pull-pull cables somewhat like the full size triplane had and there is no way to get differential aileron throw out of this type of setup. I should have used two servo's but with the small size of this plane and the lack of a place to mount them ( on my other two triplanes, which were both "giant scale" there was room to mount the servo's in the top wing and therefore get differential throw ) and to save weight I only used one servo. That is why I will have to resort to offset hinges that allow the aileron that is moving up to "droop" the leading edge of that aileron down below the bottom surface of the wing and therefore create as much drag as the aileron that is down. Yes using coordinated rudder helps but does not completely alleviate the problem, it actually flies quite well it's just that it isn't as much fun to fly as if I wasn't constantly fighting the adverse yaw, Thanks TBM.