Re: [Paddlewise] chine and stability

Hi Kathleen,

    Normally when a non-engineer responds to posts like yours they usually 
end-up having the hats handed to them. But since no engineering types have 
responded, I'll offer a nontechnical response to tie you over.
    The cross-section of the hull determines how the boat responds to a lean 
by displacing water this effect is further modified by volume displacement 
along the length of the hull. Flatter bottomed or harder chined boats seem to 
have a very clear righting effect as they are leaned slightly.  The force to 
lean them further rises sharply as the angle of lean increases.  All this 
boils down to the perception of stability for most novices. Also most people 
understand this as primary or initial stability.
    Softer chined hulls tend to lack this strong initial stability but 
instead offer a smoother transition as you move from an even keel to tilting 
the boat.
    Past 10°'s or so of lean takes us into the realm of secondary stability. 
This is where the major differences lie. A softer chined boat may seem to 
have less initial stability but the secondary stability will rise smoothly up 
the point of capsize. Secondary stability is usually agreed to mean stability 
between 10° of list and the point of capsize.  A hard chined boat will seem 
to have greater initial stability but reaches it's point of capsize more 
abruptly and with little notice.
    Hard chined boats have great appeal for many people. No doubt Melissa 
could be persuaded to share with you the gospel according to 'bou.  Other's 
are equally convinced that their particular boat is, by far the best design. 
I am no exception, by boat is without doubt the best designed hull in all of 
kayakdom, and by the way it has medium chines.  I do however lust after other 
softer chined craft from time to time. But then, after all is said and done, 
I'm may be a kayaker but I'm not dead so it's only natural for me to want to 
expand the harem, er I mean fleet.
    Try every boat that strikes your fancy. Let your senses and the artiste 
in you make the decision. Paddling is an experience for the soul, not an 
exercise in logical thinking. For ever point I've made someone will take 
issue with the science, but no-one will tell you that one and only one design 
is best for all people. (Except maybe Melissa, ....just kidding!)
 Good luck and have fun!

Jed

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