RE: [Paddlewise] Comparing sweeps chine and round hull - 'inertial' vs 'damped' responses

Matt wrote:
>his original post has not yet appeared in the digest at all
>so I have only a little idea of what the actual question was

Thanks Matt,

On Saturday I was comparing two sea kayaks: a 5m round hulled Pittarak
(similar to an Icefloe - http://www.pittarak.com.au/pittaraksingle.html) vs.
a 5m Tahe Greenland style kayak with a chined hull that extended either side
of the midsection along about half the length of the boat
http://www.tahemarine.com/?module=Product&id=49. Neither boat has much
rocker, they both rely on edging to make a sharp sweep turn. The links are
given to show what they look like, I don't have any commercial interest in
either. 

There were two differences in turning performance that puzzled me:

1. In conditions of low wind the Pittarak continues to turn for quite a
while after a single sweep, provided I hold the edge, whereas the Tahe
responded very precisely to the forward sweep stroke, only turning as the
paddle moved almost as if it were damped, perhaps by turbulence or some
other hydraulic resistance at the chined section of the hull?

2. The Tahe has a much shallower deck (and less knee room) with lower wind
resistance so its ability to turn using a forward sweep on one side or the
other was symmetrical i.e.. independent of orientation to the wind and there
was no need to consider reverse sweeps. On the other hand the fastest sweep
(forward or reverse) to turn a Pittarak depends on its orientation to the
wind and the direction in which the boat is being turned. I don't really
understand why this should be but am told it's commonplace with boats that
have high deck wind resistance.

I'm not suggesting that one hull is 'better' than the other, but I'm curious
to understand   the reasons for these different characteristics, their pro's
and cons, and whether the first inertial vs. damped characteristic, can be
generalised to most rounded hull vs. chined kayaks.

All the best, PeterO
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