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> Hello Rick:
> There is one aspect of the primary/secondary stability discussion I did
> not see mentioned. I read about it in Nick's book. It has to do with the
> desirability of high primary stability.
> Consider two boats, one high primary stability, the second one lower. When
> sitting in the boats, either underway or stopped and the water is
> relatively flat, the high primary stability boat will naturally feel more
> solid, and the second boat will feel less so, twitchy perhaps. The
> "solidity" that you perceive is from the hull's design that
> keeps your torso perpendicular to the water's surface. You tilt a little
> and the water and the boat "push back"--it feels stable. The
> second boat doesn't resist your initial movements as much, it's shape
> displaces the same amount of water when you're vertical as when you're a
> few degrees to one side or the other. Without the boat "holding"
> you upright as strongly, you could feel less stable. Flat water, remember?
> Now, if the water has some chop or some waves to it, the percections will
> quickly be reversed. Here's why: The same forces that you perceive as
> making the boat feel stable, that is, keeping your torso perpendicular to
> the water, still act on the boat. But now, the surface of the water is no
> longer parallel to the horizon and what you'll sense is that the boat is
> pitching around, being tossed about by the waves. Definitely not a stable
> feeling! But the second boat, the one that felt looser, the one that
> didn't seem to mind whether your torso was vertical or tilted some to one
> side or the other, will now feel more comfortable. This is because it's
> hull shape will not resist the movement of the water underneath and around
> it.
> This may give the impression that the first boat is easier to remain
> upright in. Perhaps, but often the water is not very flat and in those
> stiuations, the boat with the less well defined primary stability will ...
> "roll" with the motion of the water, and fling you about far
> less.
> The secondary stability becomes more prominent in moving water for this
> reason.
> Ed Valley *****************************
Ed; Best explanation I've heard yet! I'll get a chance to compare the Walden Vision(soft chine) with a Walrus(hard chine) if I ever get the Walrus finished. There is something in my mind that tells me I personally seek hard chine hulls. My canoe is a 17' Browning with molded (in the aluminum hull) sponsons that resist rolling. Now I understand that they could resist stability(feeling of well-being) in rough water. TNX much, Scotty
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Guillemot Kayak - High
Performance Wooden Sea Kayak Designs
