Re: [Paddlewise] Racing and paddles with hydrofoil shape

On Fri, 24 Jul 1998, John Winters wrote:

> Julio wrote;

SNIP

> >
> >The lift of the wing has a vertical and a horizontal component.
> >The vertical component is upward in wing paddles, and downward in
> >Greenland paddles, unless they are use for sculling or bracing.
> 
> How do you know this? If the lift is downward how
> does it pull the boat forward?  Maybe using Cartesian co-ordinates would
> clarify what you are saying.

Julio did use cartesian coordinates! He said the vertical component of
lift is in the downward direction. This would necessarily imply that the
horizontal component of the lift (i.e. the one that does the work) is in
the horizontal direction... at least on this planet.

> I was just asking what your response would be not suggesting that such a
> test had been done (it may have been) . The reason I ask is that a lot of
> the Greenland paddle
> stuff has the appearance (to me anyway) of a lot of subjective opinion
> masquerading as fact. What I am seeking are quantifiable facts. If there
> are none it is not a sin but at least one knows what kind of credibility to
> attach to the opinions.

Oh is it facts that you seek? In whose opinion are facts actually facts?
Yours? Maybe we should add a disclaimer to the bottom of the
Paddlewise trailer which says that all facts are provisional until
approved by Mr J. Winters. :)

That last bit definitely touches a sore spot for me. There are very few
quantitative data in kayaking, except in the simplest possible
situations, and when there are quatifiable data, there is not much of a
peer review process so one must be cautious of calling anything "fact".
But even without little gauges and dials measuring things, it is quite
possible for someone to give a purely subjective opinion which closely
approximates physical truth. Indeed, I think that kayaking is such a
complex combination of static and dynamic processes, that quantitative
modeling is rather pointless. A red flag goes up for me whenever I see too
much importance placed on so-called quantitative facts. 

I think too little importance is placed on trial and error in kayak and
paddle design. Eskimos spent generation after generation of trial and
error in kayak and paddle design, and for them it was more than a hobby,
it was their livelihood. As far as I know, no current designer can
accurately predict all handling characteristics of a kayak with computer
programs alone. Current designers spend plenty of time testing their boats
on the water too. Not too many quantifiable facts there...

Having said that, I am currently in the market for a nice kayak design
program that will make a model of boat from cross sections, and then
calculate static righting moments from varying degrees of heel or pitch.
Is there any freeware of this sort? Knowing when to apply a computer is as
important as know how to apply one. Cheers,
Kevin

> 
> This, of course is not to say that you would respond that way since I
> suspect that you would prefer facts as well.
> 
> In the meantime Fluid Dynamic Drag by Hoerner and Theory of Wing Sections
> by Abbott and Doenhoef might be a good place to start.
> 
> Cheers,
> John Winters
> Redwing Designs
> Specialists in Human Powered Watercraft
> http://home.ican.net/~735769/
> 
> 
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