Subject: RE: [baidarka] baidarka speeds
From: Alexander Leon (asleon@comcast.net)
Date: Tue Oct 05 2004 - 22:12:26 EDT
FWIW, I have paddled with my own Inuit-style paddle, and been impressed
at how it changes its resistance in the water, depending on the angle at
which it slips through the water. It is a little like using a wing
blade, when I hit that sweet-spot angle. It doesn't stop the way a wing
paddle does, but it does resist more, and I feel the boat move faster
through the water. My paddle has no special shapes to it; its just a
narrow blade with convex surfaces, like a very narrow canoe paddle. I
believe in lift.
Alec Leon
> -----Original Message-----
> From: owner-baidarka@paddlewise.net
> [mailto:owner-baidarka@paddlewise.net] On Behalf Of Peter Chopelas
> Sent: Tuesday, October 05, 2004 8:57 PM
> To: baidarka@paddlewise.net
> Subject: Re: [baidarka] baidarka speeds
>
>
> > I found an article at by John Winters at:
> > http://www.swiftcanoe.com/kayak/article_results.asp?ID=9
> >
> > In it he says "both the thrust we produce with each stroke
> and the wind
> > resistance we feel are due largely to drag." "The words
> drag, thrust, and
> > resistance can be used interchangeably" ..."the only
> variable between two
> > paddles is the coefficient of drag" If the traditional
> paddle has less air
> > drag, then it also must produce less thrust. "Traditional blades ...
> > generates more ...lift for rolling"
>
>
> I am very disappointed to read this from John Winters, some
> years ago I had
> a long email exchange with him on this very toppic, I did my
> best to explain
> to him the priciples, I thought I made some headway, but
> appearently he was
> not convinced. He too seemed to think he knew what was
> correct for paddles
> despite proof to the contrary (he explained that the non-steady state
> condition on the paddle negated everything we know about fluid
> mechanics-which is nonsence, many studies of non-steady state
> fluid mechnics
> have been done because so many things in nature occure this
> way, like fish
> fins, birds and insect wings). He even presented me with raw data of
> "proof" of this notion, and I pointed out to him that the data did not
> support his claim.
>
> This is the same kind of incorrect thinking that a parachute
> acts by drag,
> yet it is pretty clear [by both analysis and testing] that it
> can be shown
> that if drag alone is what slows a paracute, even the old
> round type, it
> would have to be some seven times bigger to fall at the speed
> they do. This
> means that most of the force generated to slow the parachute
> must be from
> lift, not drag. while it is true that the drag is in a
> useful direction for
> slowing a parachute, but without lift the jumper would be
> killed. On the
> modern para-sails, drag is only about one tenth or so of the
> slowing force.
>
> The same thing with some types of paddles, the drag is in a useful
> direction, but a few simple caclutions and tests will show
> that it is not
> the majority of the thrust genterated by a paddle. Try this,
> take your
> favorite smooth native style paddle, and put a drag
> generateding device on
> one blade (say wrap it with a rope or cord in a criss cross
> pattern), and go
> paddle with it. the "draggy" blade will generate less thrust
> because the
> flow over the surface is "spoiled" and it can not genterate
> the thrust.
>
> If you consider Mr. Winters a expert in this area, then I will simply
> disagree with him here. My education, professional and
> personel testing and
> experiance says that most of the forward thrust on a paddle
> is generated by
> fluid dynamic lift off the blade. He says otherwise. Take
> your pick, or go
> find out for your self. As one of my professors used to say,
> one simple
> experiment is worth more than a thousand expert opinions.
>
> Peter
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