improvement mods for KF 3?

[NotSoAmish]

What are the mods that can be done to the KF 3 to improve performance? I'm hoping that Vne can be improved also somehow. My brother and I are intending to put the Viking HF-110 in it. We think the flaperons have received the re-enforcement mod. We just finished adding some 9/16" tubing in front of the rudder for a smoother entry angle and slightly larger total rudder area. I was also wondering if the aileron differential modification kit is worth the price.
Just one more thing. has anyone added side thrust on engine mounting to compensate for adverse yaw? If so, how much angle should be added?

[jtpitkin06]

Let’s see if we can help.

The Model 3 wing airfoil differs from the 4 and later models. The 3 has an airfoil that is great for low speed but has increasingly high drag as speed increases. The Model 3 flaperons also have a different airfoil. Even with more power, it is doubtful you will gain much cruise speed to warrant any change to the Never Exceed Speed. (Vne). The low speed wing may create some control flutter at higher speeds. The model 3 also uses different flaperon attach methods, A change to the all metal flaperon brackets is advisable. I don’t know about the inside of the Model 3 wing, but you may want to look at the drag and anti-drag bracing as well. Off hand, I would say pushing the Vne on this wing to a higher never exceed speed may not be advisable.

You mention side thrust to counteract “adverse yaw”. Perhaps you mean “p-factor.”

P-factor is asymmetrical thrust from a propeller caused by blade angle of attack variance as it rotates about the crankshaft.. The greater the angle between the relative wind and the thrust line: the greater the p-factor. You can adjust thrust angle to aid in balancing controls with power changes.

The easy fix for p-factor is to install a ground adjustable trim tab on the rudder. Adjust it so you get the minimum rudder required in cruise. You’ll still need some rudder input in climbs and descents. If you want to balance the rudder inputs with power on and off you can start with 1 or 2 degrees side thrust (to the right if you have a right hand prop) and 1 or 2 degrees down thrust.

Adverse yaw occurs when you deflect the ailerons. The induced drag of the ascending wing causes a yaw in the direction opposite the roll. Changing the engine thrust line will not help adverse yaw.If you are really trying to lessen the adverse yaw, then the differential flaperon kit will make a big difference.

Regards,
John

[NotSoAmish]

Thanks for such a complete answer John. Guess the only way we are going faster than 100 mph is to change over to a KF 4 wing, if thats possible.