Date: Fri, 19 Feb 1999 09:11:17 -0800 (PST)
Message-Id: <199902191711.JAA06310@ns.intelenet.net>
To: baidarka@lists.intelenet.net
From: redcanoe@pangea.ca (Douglas Ingram)
Subject: Re: baidarka carving in s
>> The shape of the vessle is also very important: how the kayak parts the
>> water, and especially, how it RETURNS the water behind it. The drag created
>> by the water filling in the vacumn behind the passing kayak is greater that
>> the resistance of the water having to part at the bow. A clean gentle flow
>> al along the length is critical.
>
>Are you suggesting that a fish-form hull has greater speed potential than a
>swede-form? Most fish would agree, I am sure. But most Olympic flatwater
designers
>favor the swede-form. I wonder if there is a difference between operating
on top of
>the water and immersed in it that would relate to this. Airfoils are all
>"fishform," with the widest point typically about one third back from the
leading
>edge, depending on how far back you want laminar flow to prevail.
I'm not really advocating either position. I am only pointing out that a
clean flow is important. You are correct that the hydrodynamic priciples at
work when a vessle is overating at the interface between two media, in this
case air and water, is indeed different than that when operating entirely
within that medium. The advantage of the Swede for hull is not in how the
water moves around the hull, but rather in how the boat deals with the bow
wave that is generated as the canoe or kayak apporaches its maximum hull
speed. that speed, incidently, is acheived when the wavelength of the bow
waves is equal to the length of the vessel. Once this speed potential is
acheived, then the canoe/kayak must then climb up the bow wave to go any
faster. This requires enormous amounts of energy to sustain, and the gain
is very small for the expenditure. What the swede form hull does is allow
the bow of the boat to punch THROUGH that bow wave, rather than have to
climb it, allowing for a greater speed potential. Mind you, this is only an
issue if you expect to be travelling at the maximum speed potential for
extended periods of time, such as Olympic Flatwater racing. Most of us will
usually be travelling a somewhat lower speeds in favour of travelling for
longer periods if time. In this case, maximum efficiency of passage is
more important that maximum speed potential.
>Also, can anyone remember the name of the freestyle canoe designer who
built some
>fish-form boats several years ago? The Proem, I think was one of his
designs. He
>also held to the idea that the way you replace the water is more important
than how
>you get it out of the way in the first place.
That would most likely be either Pat Moore or Mike Galt. Assymetrical hulls
for Freestyle have lost favour. All of th ebest Freestyle canoes today are
unabashedly SYMETRICAL. This has nothing to do with efficiencies of
hydrodynamics, and everything to do with the paddler requireing absolute
predictability if forwards and reverse manouvers, of which there are a lot.
I have designed both symetrical and asymeetrical solo canoe hulls. I can
tell you that the symetrical ones are far more predictable,a nd perform nicer.
If anyone is interested in learning more about Freestyle, I have a Frestyle
Symposium lined up to take place during the first weekend of July. I have
two fo the best Instructor/paddlers lined up to teach. Its going to be
great, better than last year!
OK, my ad is finished.
Sorry, I can't help with kayak skins. I will defer to kayakers in this regard.
Douglas Ingram
Red River Canoe & Paddle
P.O. Box 78, GRP 4, RR 2
Lorette, Manitoba
Canada
ROA OYO
(204)878-2524
URL: www.wilds.mb.ca/redriver
e-mail: redcanoe@pangea.ca