Waiex Yaw correction

[Onex107]

I don't know anything about the "V" tail but I'll throw this in. I presume your rudders are hinged the same as the Onex, on one side. I added a simple gap seal to my rudder and elevators and saw a significant difference in the hands off cruise. Just sayin.

[Zack]

I am now thinking I might have to align the engine with a few degrees of right thrust built in unless anyone else can suggest further adjustments I could try.

Please keep us posted. As you point out, it's possible it's a Rotax / mount issue, not a waiex design issue.

[Murray Parr]

I don't know anything about the "V" tail but I'll throw this in. I presume your rudders are hinged the same as the Onex, on one side. I added a simple gap seal to my rudder and elevators and saw a significant difference in the hands off cruise. Just sayin.

This could be worth a try; do you have any pictures or advice on how you achieved the gap seals?

[Murray Parr]

Have you ever seen a Ercoupe with the cowling off? Huge amounts of right and down thrust built into the motor mounts. Sounds like you might need some right thrust to counteract some minute amount of twist in your empannage.

JMHO

Yes, I am probably going to have to add right thrust, down thrust would be harder to achieve. I am thinking of making a new set of bed mounts with the right thrust built in but knowing how much will be the trick as it wouldn't be adjustable. Another builder suggested to add shims where the engine mount meets the firewall, this would be adjustable and reasonably simple to add. Has anyone else tried this?

I am not sure if any twist in the empennage would be causing the right yaw as it totally goes away if I remove power. I would like to confirm the empennage is true, but I don't see any measurements in the plans for this.

[bvolcko38]

Yes, I agree, if the yaw goes away when you reduce power, it seems to be an engine thrust problem.

[Onex107]

Yes, it was really quite simple to do. I have pictures and can describe the process. I don't know how to post on the builders site but I can email directly to you.

[Outlaw6]

I think part of the roll issue can be caused by the ruddervators when using the stub rudder for yaw trim. The rudder trim tab moves the rudder to correct yaw but also moves the ruddervators creating roll in the opposite direction. I have an Aerovee so I trimmed for left rudder to compensate for right P-factor at cruise which gives some right roll tendency from the ruddervators which then needs to be compensated by adjusting lift on one flap (typically lowering the right). I believe the condition is worse on a tri-gear, like mine, because the nose gear turns in the direction of trim also which puts a left turning force below the center line creating some right roll tendency and drag. Plowing the nose gear through air at cruise with 15-20 degrees of left turn burns my OCD.

I brought this up in this thread:
viewtopic.php?f=15&t=4954

I've basically lived with it until now. I have the engine off for rebuild so I'm going to look at adjusting the thrust line to compensate for P-factor. Or modify the ventral fin to give me left trim, although I don't think it has enough surface area to counter the p-factor at cruise.

This is a great first step:

Yes, I agree, if the yaw goes away when you reduce power, it seems to be an engine thrust problem.

Trim pitch for cruise speed and go to idle, if it flys straight and level then the issues are from prop induced turning tendencies (p-factor, torque, spiral slipstream).

[Murray Parr]

Good news!

With the help of Cris at Sonex (thanks Cris) who sent me the newer upgraded Barry mount washers and said give these a try, we believe this is the problem (Slightly larger OD than previous which now capture all of the mount rubber instead of a small outer portion of the rubber mount spilling over the edge of the old washers).

I have to admit, I was slightly skeptical that such a small change could make such a difference, however, I installed them and went for another test flight. I noticed immediately upon applying full power and rolling down the runway that the amount of pressure needed to hold right rudder in was way less and on climb out it still felt like I wasn't having to push anywhere near as hard as before. When I looked down at the rudder pedals, I could see that instead of 2/3 of the way to the floor, the 2 pedals were only about an inch or so apart.

I think it is close enough now that I can start looking at installing a trim tab to hold enough rudder in while at cruise settings.

Thanks for everyone that chimed in here :-)