I disagree. More apparent slippage is inefficient. You must accelerate water to propel the boat, but the more you accelerate the water, the less efficient your paddling will be. Any acceleration of the water is energy imparted to the water which would more efficiently be spent moving your kayak. Your goal therefore is to maximize the mass. The force produced by doubling the mass will be the same as if you doubled the acceleration, and will make the boat go just as fast, however it will not waste as much energy in making water move. Kinetic Energy (KE)= m * v^2. Any acceleration increases the "v" or velocity of the water and that energy had to come from you and is now gone. "Slippage" is an indication that you are accelerating water and thus wasting energy. 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. It does not matter how the force is created: drag, friction, turbulence, lift, whatever. The only time there is wasted force is when there is a component of motion perpendicular to the direction of propulsion, then all the same things - drag, friction, turbulence, lift, whatever - are bad things. The only useful force is one propelling you in the direction you want to go and it doesn't matter how you create it. But, just because you can apply the same force with two different paddles does not mean that you will get the exact same thing out of them. While the force will be the same and your boat will be propelled forward at the same speed, the paddle which creates that force by accelerating the largest mass of water will be more efficient. It will require fewer strokes to maintain the same speed. It does not take any knowledge of fluid dynamics to understand this, and no amount of fluid analysis will change it. At 8:23 PM -0700 5/14/01, Peter A. Chopelas wrote: > >Remember basic physics F=Ma, you get force from the paddle by accelerating >the mass of the water. The more you accelerate the mass of the water in a >direction that is useful to generate forward motion in the boat, the more >efficient it is. You can put exactly the same "power in" with various >paddle designs, but not all will push the boat at the same hull speed. All >will put the same amount of power in the water, but not all will result in >useful forward motion, the rest is wasted in canceled effects, turbulence >(i.e. friction), etc. And each paddle will have a slightly different >motion to get the most efficiency out of it so it would take some time >before you determine the optimum stroke with each paddle you try. > >When a paddle slices (or "slips") through the water, you accelerate the >mass of the water and get thrust, hopefully most of it in a direction that >is useful to propel the boat forward. If you accelerate a lot of water in >a useful direction with a small blade that slices quickly through the >water, you will have a very efficient paddle, with large apparent >"slippage". You can also force a large poorly shaped paddle slowly through >the water and not get a lot of forward thrust for your effort, yet it would >appear to have less "slippage" that the small blade. -- 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/ ***************************************************************************Received on Tue May 15 2001 - 10:23:57 PDT
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