Re: [Paddlewise] Paddling in Space

From: "Matt Broze" <mkayaks_at_oz.net>

> I'm pretty sure that there is something wrong with Peters getting 5%
> efficiency for a  paddle.

When Peter posted this stuff on Baidarka last year, I asked him to show
his work.  For example, he calculates 0.4 hp for a Euro paddle.  I 
pointed out that this was quite high and a lower value (based on a 
discussion I had with John W at the time) was more appropriate.  Peter 
then told me _my_ estimate was too high!  However, he has yet to correct 
for his newer value (which was lower than mine) nor is he willing to 
reveal that (or any other) part of his calculations.  If you pull enough 
numbers out of your hat, you can prove* anything.

Mike

*For those not inclined toward math or physics, just be aware that 
one can use math concepts to prove another math concept but one 
cannot use math concepts to prove a physical concept.  Peter's
equations do not represent a proof of anything, just a hypothesis.
They require experimental evidence to back them up.  When John asked
for evidence, he was given a list of textbooks.  Fluid mechanics 
textbooks are filled with theories based on basic concepts derived
from studies of flat plates, spheres, cylinders and other simple 
shapes.  Occasionally, a standard NACA foil is used.  Kayak and
canoe paddles are not representative of these basic shapes and 
to ensure the appropriateness of the mathmatical models, tests
of real paddles must be performed.  John and others have done these
tests, Peter has not.  When I worked on towing tank tests of ice
interactions with icebreakers and offshore structures, my boss
always told me that if theory agrees with practice by a factor of 
two, you're doing pretty good.  Consider Peter's model in that
light.

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