Re: [Paddlewise] Group Paddling - folders stability

In a message dated 4/12/99 2:28:26 AM Pacific Daylight Time, 
rdiaz_at_ix.netcom.com writes:

<< 
 Will folding kayaks flip?  Of course they can and do.  But it takes a
 lot, and my observation tells me that the bouyancy aids inside are
 kicking in at some point to some degree enough to say that the
 phenomenon does exist.
  >>
 Sounds fun, Ralph. :-)

I respect the depth and breadth of your experience, but nothing *inside* a 
dry  boat will right you from a sharp heel (well, maybe a coupla hundred 
pounds of lead along the gunnels:-)).  Not the sponsons (sorry -- a buoyancy 
aid is a British PFD / life jacket) or your tackle box or the PFD you're not 
wearing.  The external shape of the chine area of the boat is responsible for 
that function.  The sponsoned side of some folders looks much more like a 
liferaft than any hard-shell kayak I've ever seen, having a short-radius 
convex shape.  Perhaps that "P" shape on the side does the trick, but I still 
think it is, in the case of the Klepper, also due to lots of beam.  I don't 
dispute that sponsoned boats have more secondary stability.  My Khats-S does, 
but as I stated before, I have still seen no evidence or convincing argument 
that it is not due solely to the hull shape.  I don't mean to down-talk 
folders, but I think accuracy in making claims is important.  Folders are not 
super stable because they're folders or because they're skin boats.  The 
original non-spononed Khatsalano is very tender, as are the other 
non-folding, Greenland and Aleutian skin boats that I have paddled.  In fact, 
I've paddled both the plywood and skin Greenland yaks built from Christopher 
Cunningham's _Sea Kayaker_ plans, and the skin boat was *way* more tender 
than the hard-shell.  Does that prove anything?  No, because the widths and 
shapes of the two kayaks are not quite the same.

I appreciate all the input on this subject, especially from the boat 
designers.  I need to go back and reread the posts about the flooding 
question, because I always assumed that the sponson would increase edge 
buoyancy and thus righting moment, beyond that contributed by hull shape, 
when flooded.  I reasoned that, since there was water surrounding the bottom 
and sides of the chamber, the chamber is displacing water toward the center 
and ends of the craft.  Should this not add buoyancy and righting moment to 
the edge of the craft, or does the entrapped air know its inside the boat and 
refuse to do its duty?  I would love to see a clear analysis of this.  Matt, 
John, guys?  Inquiring minds of limited reasoning (mine) need to know.

Thanks

Harold
So. Cal.
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