It's that certain distance of seperation that I'm suspicious about as it relates to kayaks, their slow speed and the type of rudders normally installed. If the rudder is within the envelope (don't know the proper term btw) of the lift generating air flow, then certainly it can be physically removed from the wing. One sees this regularly on commercial airliners where the flaps are seperated by several inches from the surface of the wing when deployed. However in looking at the water flow patterns behind many kayaks, it seems pretty clear to me that the rudders are well abaft of this, working in the turbulance instead. His design is inherently avoiding this problem.

> The torque about the wing does occur, but it's cancelled out to some
> extent by the torque on the opposite wing. When you apply flaps, both
> wings deflect part of the trailing edge downward, and a negative pitching
> moment (nose downward) occurs, which has to be compensated for by the
> elevator. It isn't really all that different from a separated rudder
> surface. Some early biplanes had the ailerons separate from the wing (away
> from the trailing edge), which acts like a slotted airfoil up to a certain
> distance of separation. I believe the Fieseler Storch (STOL) had separate
> ailerons. The principles are a bit different because the aileron, rudder,
> or other control surface at some point becomes an autonomous lift
> generating surface.

Is that drag symetrical above and below the surfaces of the wing? I tend to suspect not, but I don't know. If not, that effect could be significant in the case of his kayak. Since a kayak is very light, and is presenting a large aerofoil to the water. Which could result in some very quick turning if this is a significant force.

> BTW, as one wing increases its lift, it also gains more drag, while the
> wing with reduced lift has reduced drag, which results in what's referred
> to as adverse yaw effect. (the airplane leans one way, but tries to point
> the other way). In flying wings (incl hanggliders and parasails) there is
> no rudder to counter this yaw, which becomes somewhat of a design issue
> (though usually small).