I'm building a model of the 1912 Sikorsky Grand. The pictures I have of it show a "stick" extending upward at the hinge point of the aileron, apparently to give a moment arm to the control wire. What I'd like to know is whether the "stick" is rigidly attached to the aileron, or whether it is attached to the wing with a guide for the control wire.

From : Don Stackhouse

That "stick" is a control horn, functionally the same as what we use today. It moves with the aileron. That's a bracing wire that runs aft from a rigid connection on the end of the control horn to the trailing edge of the aileron, to make a rigid truss out of that whole assembly.

The thin airfoils of the ailerons and other control surfaces of that day were not strong enough in bending and torsion to just dump all the moment loads from the control horn into the spar at the leading edge of the aileron, and then expect the ribs to carry it back to the rest of the control surface like cantilever beams. In fact, the typical method involved about three wires or so fanning out from the top of the control arm to the trailing edge, so that the control horn and its bracing wires became an integral part of the entire structure of the control surface. They acted much like the king posts and flying wires typically used back then to brace the wings of monoplanes. If the horn used that "fan" of multiple wires, it made an especially important contribution of torsional stiffness to the entire control surface.

If the control horn had been fastened to the wing (your other scenario), with a pulley in the end for the control wire to go through, you would see additional static bracing rigging between the control horn and the wing. That system would actually be less structurally efficient, as well as more complex, heavier, and more likely to have problems with slop and friction in the controls.

These wire-braced control horns are fairly typical of that period on planes that used built-up wooden control surface frames. You can see them on quite a few other aircraft, such as on all the control surfaces of a Curtiss JN-4D Jenny. Conversely, the airplanes that used welded steel tube control surfaces, such as the infamous Fokkers, typically did not use these bracing wires for their control horns. The torsional stiffness of the control surface's tubular steel leading edge spar, and the bending stiffness of the control surface's ribs was sufficient that they did not need the extra bracing. That meant a few less wires hanging out in the breeze, slowing down the entire airplane and waiting to get themselves shot off in a dogfight.

Don Stackhouse
DJ Aerotech