Onex107 wrote:I agree with the aileron yaw canceling, but, on my Onex I have installed a rudder gap seal and it definetly made a difference in taming the tail, which could be construed as yaw.
The tail is a bit different than the wing, and feels the effect of adverse yaw a bit differently. The drag created by deflecting the rudder shows itself as a slight decrease in control power. Essentially, the rudder deflects causing lift to be generated by the tail to the side (i.e. yawing the airplane). Deflecting the rudder also has the negative effect of increasing the drag (i.e. increasing induced drag), which pulls the surface backward. This backward pull serves to cancel a small amount of the yawing motion created by the rudder. Effectively, the drag reduces the effectiveness of the yaw.
This effect is not symmetrical. Deflecting the surface in such a way as to open the hinge gap will increase the drag of that gap, and closing the gap decreases it. Although this is the exact effect you want on the ailerons to cancel the unwanted (adverse) yawing motion caused by rolling, it doesn't really work the same on the rudder. Rudder one way (say left rudder that opens the hinge gap) vs the other (e.g. right rudder that closes the hinge gap) simply creates a bit more drag one way than the other. You'll notice this as a more effective rudder in one direction (in this case, right rudder is slightly more effective than left rudder).
Sealing the hinge gap eliminates the drag-creating asymmetry caused by increasing or decreasing the hinge gap, and perhaps reduces the overall drag of the tail itself. These are not bad things for the tail, and would almost certainly provide a better tail. Why doesn't Sonex do this in the first place? Well, my opinion is that the beneficial changes from adding the gap seals are not all that significant, and they feel it doesn't really justify the effort/weight/complexity of gap seals. Plus, using the triangular hinge is just so darn convenient!
So I guess the bottom line is that the Sonex hinge design works amazingly well on the ailerons, and is simple and effective (enough) for the tail surfaces. Is there room for improvement, probably. Is it worth it, perhaps...
Jeff