Aerodymaics question - spades

[RogerT]

I've been working on an experimental for the last year and have been
flying it for the last few weeks. It has aileron spades. I've been tweeking
them and the plane flies pretty straight. Can someone explain to me
the theory for the spades, and what the proper way to adjust them
is. I have zero experience with spades. They just came with the plane
kit.

The ones I have are about 8 x 10 or so and have angled sides on
both sides (Up) at about a 45 deg angle. It seems to me if spades
are angled up on one side only there would be some inter relation with
rudder movement.

The instructions in the plans said to adjust them parallel to the
bottom of the aileron. Is there any merit to them being parallel
to the oncoming air? In other words if you're straight and level they're
parallel to the horizon?

Thanks

RT

 

[Steve]

I'd think you'd want to adjust the spades to give the desired "feel" in roll at whatever angle that requires. The more angle the more "boost", so to speak. I'd be suprised if they were intended to be used to compensate for an out of rig wing, which would affect the tendency of the aircraft to fly straight.

A quick Google indicates:

Design and installation of an aileron spade.
SPORT AVIATION Oct 1987 (v.36#10) pg. 66

You might be able to locate someone with a collection of back issues or contact EAA for a reprint.

 

[Henning]

Sure, if they aren't, they will be exerting force in straight and level flight. What they are is basically an aerodynamic balancing tab to reduce the force required on the stick to make large deflections with large control surfaces. There are other ways to achieve this balance, but the spades are simple and effective.