Trim tab size

What's the ideal trim tab size and location?

This is for a movable tab that isn't just tacked onto the end of the control surface.

Mainly for an add-on tab for ailerons and rudders.

Elevators are already designed, so really don't want to deal with the elevator.
(other than why 1 tab and not 2)


A small tab needs to deflect more, and I would think be draggier because of that. But it weighs less and needs less structural change (added spar section) and thus less weight.

A large tab would be the opposite.

Also with a larger tab you might be able to keep the control linkage internal (even less drag)


So what size is ideal?

Percentage of control surface chord?

Percentage of control surface width?

Does control tab aspect ratio matter?



Does location matter? inside, outside or middle ?

Although putting the rudder tab on top might help if you put the servo in the balance horn to balance some of the weight.



Just curious, can't seem to find anything on the internet...........


Thanks

My tab.

I made an aileron tab for my RV-4 that is approximately 6" in span and 1.5" deep. I mounted it in the outboard bay of the left aileron fitting it between the existing end rib and first skin stiffener. It is very effective and doesn't need to be any bigger. Pat Hatch put a rudder tab on his RV-6, and he is a member on here..perhaps he can elaborate on that. I recall it was about half way up the rudder, between stiffeners, and maybe 2-3" in chord. I cant post pictures, but I can send them via email of my aileron tab. Simple and factory looking using same technique as the elevator tab.

Search the forum or Google "Vic Syracuse rudder trim" and you will see a simple solution for an electric rudder trim. I have not found an electric rudder trim necessary on our RV-10. We have a very small fixed tab attached to the rudder via the tail light that is all we have needed. It is trimmed for cruise. We also have the stock Van's aileron spring trim and have NEVER used it regardless of the planes loading. Just a thought.