Fish It wrote:
I don't understand what is meant by "primary" and "secondary" stability. STABILITY is a function of center of bouyancy, center of gravity, metacentric height and righting arm. These are related to hull shape, volume and displacement.
This is correct. But keep in mind that the actual hull shape below water line is changing while tilting the hull. That means you can find a "treshold" where the righting arm is actually getting larger and the stability increases caused by hull shape (below water line) getting wider when you tilt it.
Fish, what you describe is what would be called secondary stability or absolute stability -- the roll angle where the boat capsizes. What is commonly described as "Primary stability" is entirely different -- it is how easily the boat tilts from its upright position or how "twitchy" the boat is.
This is what I meant in my earlier post. In an Hobie Adventure there is distinct difference beetween the primary and the secondary stability. I think the same goes for all Hobie kayaks.
But if you take an kayak made for serious racing there will be no practical difference for a no-pro kayaker. He have to be very ACTIVE, and help with paddel to not capzise. Primary and secondary stability is very close and very low, if any.
There is no problem to ride a bike as long as you move and you have to have very good balance and be active to balance an bike not moving.
And I still think there is no need or even missleading to make to much theory thinking about kayak stability.
As Roadrunner said: "Experienced users usually prefer it though because in rough weather or boat wakes, the user controls the tilt of the boat against a beam swell"
My comment: This goes for normal sea kayaks. Hobie kayak hulls are to stable to actually control that way.
This is an Struer Hunter from the sixties. Nice video showing serious racing kayak and handling by a no-pro, but experienced paddler. This is nothing like a Hobie kayak!http://www.youtube.com/watch?v=CWy6Fhr83ww