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From: <rebyl_kayak_at_energysustained.com>
subject: RE: [Paddlewise] Re: Weird Shoals or Beating Dumpy
Date: Tue, 17 Jun 2008 12:38:42 +0000
Doug wrote:
>....clapotis seekers might benefit from a kayak with lots
>of bow buoyancy, including other designs for a perfect
>playboat. I'm going for low windage and a tight cockpit.
>Can't get that need for speed, need for high-wind
>performance out of my mind. 

G'day Doug and all,

100 percent agree with the tight cockpit. Hadn't thought about the helmet but that sounds like a smart thing to do. Two weeks ago we were coming out of a place called The Drum and Drumsticks on the south coast of NSW in Oz and passed through a field of 1 to 1.5 metre clapotis extending over about a half km square. I was being followed by a friend who wanted to see how I found my way through, which is generally by letting the boat do its own thing and making regular corrections to keep going in the right direction. What was interesting is that the boat was rarely thrown into the air by the clapotis waves but seemed to slide between them and I'm wondering if this is because of the very narrow 'sail like" bow of the Pittarak. My friend ET who was fairly close behind most of the way said that the boat took a zig zag course through the clapotis.

All the best, PeterO
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From: Paul Montgomery <paul_at_paddleandoar.com>
subject: Re: [Paddlewise] Re: Weird Shoals or Beating Dumpy
Date: Tue, 17 Jun 2008 06:25:58 -0700
>> ...clapotis ...

I looked in one dictionary and did not find "clapotis". Another lists  
it as a French word meaning "wash".

Paul Montgomery
paul_at_paddleandoar.com
http://paddleandoar.com
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From: Steve Holtzman <sh_at_actglobal.net>
subject: RE: [Paddlewise] Re: Weird Shoals or Beating Dumpy
Date: Tue, 17 Jun 2008 07:04:25 -0700
> I looked in one dictionary and did not find "clapotis". Another lists
> it as a French word meaning "wash".

According to Wikipedia:

Clapotis

>From Wikipedia, the free encyclopedia
In hydrodynamics, the clapotis (from French: "lapping of water") is a
non-breaking standing wave pattern, caused for example, by the reflection of
a traveling surface wave train from a near vertical shoreline like a
breakwater, seawall or steep cliff.[1][2][3][4] The resulting clapotic[5]
wave does not travel horizontally, but has a fixed pattern of nodes and
antinodes.[6] These waves promote erosion at the toe of the wall,[7] and can
cause severe damage to shore structures.[8] The term was coined in 1877 by
French mathematician and physicist Joseph Valentin Boussinesq who called
these waves 'le clapotis' meaning 'standing waves'.[9][10]

In the idealized case of "full clapotis" where a purely monotonic incoming
wave is completely reflected normal to a solid vertical wall,[11][12] the
standing wave height is twice the height of the incoming waves at a distance
of one half wavelength from the wall.[13] In this case, the circular orbits
of the water particles in the deep-water wave are converted to purely linear
motion, with vertical velocities at the antinodes, and horizontal velocities
at the nodes.[14] The standing waves alternately rise and fall in a mirror
image pattern, as kinetic energy is converted to potential energy, and vice
versa.

Steve Holtzman
 

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From: Dave Kruger <kdruger_at_pacifier.com>
subject: Re: [Paddlewise] Re: Weird Shoals or Beating Dumpy
Date: Tue, 17 Jun 2008 07:24:22 -0700
Paul Montgomery wrote:

> I looked in one dictionary and did not find "clapotis". Another lists  
> it as a French word meaning "wash".

Wikipedia to the rescue:  http://en.wikipedia.org/wiki/Clapotis

"In hydrodynamics, the clapotis (from French: "lapping of water") is a 
non-breaking standing wave pattern, caused for example, by the reflection 
of a traveling surface wave train from a near vertical shoreline ..."

Worth noting is that Wiki claims "pure" clapotis does not involve any 
horizontal motion of water particles (read the entire citation to 
understand what they mean).  The crashing waves we body surfed out from the 
cliffs in Solana Beach would not, strictly, be clapotis by this definition.

-- 
Dave Kruger
Astoria, OR
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