This may be a better question than you first imagined. I didn't reply yesterday because I didn't have a good answer. I still really don't. I've thought about it for a day now, and I can only come up with "Yes"

I think that the hull's dihedral (Vee) will play some part in contributing to the righting action at speed. As the boat rolls, one side of the boat is deeper in the water, so it will have more wetted surface. The are two distinctly different possibilities.

The side with more surface could generate more lift due to the angle of attack of the hull relative to the incoming flow of water (picture the boat not moving and the water flowing past it)

Now, according to Bernoulli Principle, that side should get sucked downward a little bit more. This suction could grip the boat in a given position and keep it from rotating as fast.

The fact that the boat is moving has nothing to do with the stability. It is the fact that the water is flowing over the hull. A bicycle moving 2 mph is not less stable than a bicycle moving 55 mph. If you don't belive it, try to balance a bicycle in the bed of a moving truck. What keeps the bicycle up is the wheels moving over the ground causing geometry changes when the bicycle leans. The wheels have a tendency to sort of pull themselves back under you. If you have a treadmill, and can ride at exactly the speed of the treadmill, you can ride while standing still. It is the flow of the ground beneath the bicycle that matters, much as the flow around a boat changes how it behaves. It doesn't matter if you're standing still (relative to shore) in a flowing river, or going downstream at twice the speed (same speed on the water), until you hit a rock.

> While paddling home into a confused and foamy kind of 3 foot
> chop yesterday . . . I noticed that I was not really having to brace
> very much for stability (at least consciously) despite the waves coming
> from various different directions. Stability seemed to increase the
> faster the boat went, at least when I wasnt slapping down the backsides
> of the waves.

> All this in a boat (Guillemot Coastal) that dumped me on the
> back side of a one foot wave within 45 seconds of first launch!

> So, my question for the lurking design gurus . . . does a kayak's
> forward movement add to its initial or final stability in any way?
> I assume most stability curves are based on a static model -- i.e.,
> assuming a boat lying still in the water. But does the movement of
> the kayak through the water create any kind of lift as the kayak begins
> to heel?

> Or is it just an illusion, based on the natural, subconscious
> bracing you get with each paddle stroke it takes to keep the boat
> moving in those kinds of conditions?