We're almost all in agreement. Just a few more details ;-) John says: > Nick says: > > As long as you move the paddle parallel to the direction of motion > > > desired all the force applied will go directly to propelling the > > > boat. > > Nick is right although I doubt if anyone actually accomplishes this > regularly. I suspect Nick mentioned this elsewhere as I recall him > discussing it some time back. > There's still an error here. You can't assume all force applied goes into forward movement of the boat. No paddle or propellor is 100% efficient at turning effort into forward motion, and indeed, John in the following paragraph quotes a study stating that racing paddles are 87% efficient which contradicts the prior claim. As for the discussion of Popper and falsifiability: John said: > Karl Popper has shown that a scientific theory must be presented in such a > way as to provide a test for the theory's falsity. If you cannot test for > falsity then the theory is not a scientific theory. > I think that's a little off base. Popper "proved" no such thing. Popper developed a theory of falsifiability in an attempt to rescue the sort of program the positivists were attempting in constructing a theory of truth. But Popper's falsifiability is a philosophical stance, not a proof of anything. And it's getting a little far afield. Still, it's an interesting diversion from our usual topics ;-) -- ------------------------- Michael Edelman mje_at_spamcop.net http://www.foldingkayaks.org http://www.findascope.com *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
Comments on the exchange below. Michael Edelman wrote: > We're almost all in agreement. Just a few more details ;-) > > John says: > > > Nick says: > > As long as you move the paddle parallel to the direction of motion > > > > desired all the force applied will go directly to propelling the > > > > boat. > > > > Nick is right although I doubt if anyone actually accomplishes this > > regularly. I suspect Nick mentioned this elsewhere as I recall him > > discussing it some time back. > > > > There's still an error here. You can't assume all force applied goes > into forward movement of the boat. No paddle or propellor is 100% > efficient at turning effort into forward motion, and indeed, John in > the following paragraph quotes a study stating that racing paddles are > 87% efficient which contradicts the prior claim. Nick would have been perfectly correct, and I think he meant to say that "all the force that is in the direction of the motion desired will go directly to propelling the boat." This is required to satisfy Newton's "theories" of motion. Of course, force is not the same thing as power. While the force will go into propelling the boat, some of the power used to generate that force will be lost. This is where the inefficiencies come in. Regards, Dave Carlson *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
At 9:45 PM -0400 5/17/01, Michael Edelman wrote: >We're almost all in agreement. Just a few more details ;-) > >John says: > >> Nick says: > > As long as you move the paddle parallel to the >>direction of motion >> > > desired all the force applied will go directly to propelling the >> > > boat. >> >> Nick is right although I doubt if anyone actually accomplishes this >> regularly. I suspect Nick mentioned this elsewhere as I recall him >> discussing it some time back. >> > >There's still an error here. You can't assume all force applied goes >into forward movement of the boat. No paddle or propellor is 100% >efficient at turning effort into forward motion, and indeed, John in >the following paragraph quotes a study stating that racing paddles are >87% efficient which contradicts the prior claim. > There is a difference between the force applied and the amount of energy required to generate that force. Effort and force aren't really the same thing. Any propulsion force will create an acceleration in the direction of the force. (F=ma). 100% of the force is used to accelerating the mass. However, you may end up applying more energy into creating the force than you receive out of it. So even though the force applied to the paddle exactly equals the force applied to the boat, you can not say that the energy applied to the paddle is equal to the energy received by the boat. Instead the Energy received by the boat is equal to the energy applied to the paddle minus the energy received by the water. Efficiency is (Energy to Kayak)/(Energy to Paddle) and not (Force to Kayak/Force to Paddle). This is why when someone says: "I can push my favorite paddle just as hard or harder than any other paddle." you can not assume that the favored paddle is more efficient. And why subjective evaluations of paddles can be inaccurate. The amount of force you feel is not directly related to efficiency. -- Nick Schade Guillemot Kayaks 824 Thompson St Glastonbury, CT 06033 (860) 659-8847 *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
Shawn Baker wrote: } Subject: Re: [Paddlewise] Paddle efficiency > > I would agree that biomechanically, a high aspect ratio paddle is more > efficient for paddling long distances. It is not a fact of fluid > mechanics though--once you're talking about calorie usage and human > efficiency, you have ceased to discuss pure fluid mechanics. I find this a little hard to believe - how does your body feel the shape of the blade to know that it is a high aspect ratio blade? More to the point, what is it about a high aspect ratio paddle that makes it more "biomechanically efficient", as you say? Are you talking about stroke rate? If so, why would not a smaller, shorter low aspect ratio blade be equivalent? The aspect ratio influence comes in via fluid mechanics or not at all, IMHO. I just can't see a biomechanical effect that can't be reduced to something else like stroke rate or the force you use to move the paddle (usually related anyway). It's also not terribly clear what biomechanical efficiency is. I would tend to define it her as calories burned / power delivered to the paddle (since we're clearly excluding fluid mechanics), but I'm wondering if you mean instead least long-term stress on your body over a long paddle, or else least energy expended to travel a long distance, both of which would probably be at a very different cadence than best efficiency. -- Bob Myers Verado Email: bob.myers_at_verado.com 18101 Von Karman Avenue, Suite 550 Phone: 949-851-8250 x227 Irvine, CA 92612 http://www.verado.com/ *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
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