Gene,

I've read the other posts and believe that talking about hulls without
mentioning the kayaker may not really be the point. While the physics of the
posters may be right or wrong (I can't definitively state that a moving hull
is more stable than one that is stationary, though I believe this to be so).
I can state, however, that if you are moving forward in your kayak, you are
also moving your body as you paddle (or even if you cruise between strokes).
These small muscle adjustments may not seem to be much at first, but they
add up to a significant amount of righting force (note that the boat has
little tendency to be tippy until you add a paddler in the frist place,
hench changing the center-of-gravity by a significant amount). As one
individual said to me, "there are no tippy boats, just tippy paddlers,"
(meaning, of course, that any boat can be paddled by the properly skilled
person).

When stationary, just like on a bicycle, kayaks tend to be less stable.
Stand on one foot and you are less stable than you are on two. Close your
eyes, and you tend to become unstable very quickly. Hop on one foot, eyes
closed, and you can do that for quite a while. It isn't the bike that is
unstable, it's the human. In the absence of eyes, the dynamic changes the
body makes during motion are very effective at keeping balance, so hopping
is easy, standing is less so.

I remember in the film, "Baidarka," the boat was uncomfortably unstable to
the paddlers when they were launching, but once under way, they found it to
be a real joy. While part of this was definitely hull design (the bifurcated
hull improved stability while moving, something the boat designers hadn't
considered), the dynamic motions of the paddler as they autonomously
adjusted for balance were probably more significant.

Rick

"Gene Cosloy" wrote in message
m...
Does the final stability of a kayak depend on how much forward
propulsion the boat is undergoing, all things being equal. In other
words if edging a boat dead still on flat water gets me to the edge of
the combing before the boat wants to capsize, will the same boat
permit further edging when it's underway? A bicycle heeled over at
speed is stable and unstable heeled at rest. While a kayak does not
experience centrifugal forces, does the hydrolic surge force of
propulsion provide a similar effect?

Gene