Why ? of day Elevator and Rudder horns.

Why are the Elevator and Rudder horns Squared off and not Rounded off for less drag?


Just wondering...............

Mine are rounded - RV4 (elevator only, no horns on the rudder). What are you flying? Of course mine are pointed directly into the slipstream. Other RV?s (7, 8, 9) as far as I know are not pointed into the slipstream, but are nested behind a streamlined leading edge of the control surface. Unless it?s deflected into the slipstream (usually a non cruise trim condition, generally) it shouldn?t matter. If you decided to make that horn streamlined when deflected from normal cruise condition, you are only reducing drag during a non-cruise flight phase. This would effectively make the horn area smaller, and in the case of the elevator would limit the necessary room for the lead counterweight. You would have to add more weight further aft in the horn area, which would require more weight than would be necessary if placed in the nose of the horn, as designed. I don?t think there would be anything gained by rounding the leading edge of the horn, but if you try it, let us know. Who knows, if your horn is constantly deflected so it?s exposed to the slipstream, it might make a difference, but I think the lowest drag cure would be to alter rigging to eliminate this deflection during normal cruise flight.
Just my opinion.

Not flying anything yet

First picture in this thread :

http://www.vansairforce.com/community/showthread.php?t=181985

got me (re)thinking about this, as that little bump looks draggy.


I really don't think you'd lose any counterbalance, as it wouldn't have to be rounded much.

Just a little bit rounded, for a slightly different CG/speed situation and no bump in airflow.

Ah, I think you meant the elevator and rudder counterbalances. When you said horns, I thought you were referencing the control horns of these surfaces.

Being squared off makes for a minimal gap between back of the fixed surface and the front of horns. Minimizing that gap reduces drag always. Rounding the front of the horn reduces drag only when control surfaces are deflected greater than a nominal trim range.