Re: [Paddlewise] Perfect Boat is Plastic! Now Flex

ralph diaz wrote:
> 
> >From Folding Kayaker Sept/Oct 1996, pp. 1-5
> Scientific Look At Rough Water Drag
> For Folding Kayaks Vs. Hard-Shells
> 
> "Flexible Skin In Action <subhead>
> In chaotic seas, a folding kayak’s skin sections defined by its
> stringers and crossribs pump in and out like a drum head and destabilize
> laminar flow of water along the surface of the kayak (Handbook of Fluid
> Dynamics, ibid, page 11-30).  The vibrating skin of a folding kayak is
> extremely effective in pushing the critical Reynolds number of the drag
> crisis down to lower Reynolds numbers.....  
> we believe that the dynamic in-and-out motion of skin
> sections of the flexible skin kayak is the dominant one that causes the
> critical Reynolds number of the drag crisis to fall.  Such in-and-out
> motion occurs readily in rough chaotic waters and is a common phenomenon
> that many of you have often exclaimed about, i.e. the feel of the water
> as it passes along the skin.

"Dynamic in-and-out motion of skin sections."  Isn't that the same as
"oil-canning"? At least by the definition that Mark B and I use? But
maybe it doesn't work exactly the same way because ....

> For the drag crisis regime to cause a difference in drag between
> hard-shell and flexible-skin kayaks, the Reynolds number associated with
> kayak motion through water must be near the drag crisis regime.  By one
> of those quirks of nature, it is."
> 

I don't understand that paragraph. I always thought that a drag crisis
was when some queen's evening gown and size 11 pumps didn't make it back
from the cleaners in time for the 9 PM show.

Steve
***************************************************************************
PaddleWise Paddling Mailing List - All postings copyright the author and not
to be reproduced outside PaddleWise without author's permission
Submissions:     paddlewise_at_lists.intelenet.net
Subscriptions:   paddlewise-request_at_lists.intelenet.net
Website:         http://www.paddlewise.net/
***************************************************************************