Jerry wrote; Wow! I will do my best. >Please comment, if you have time, on the following: (SNIP) >In a kayak, the paddler is the motor. Changing the length of the paddle or >the shape of the blade will change the point on the paddler's torque-speed >curve. Every paddler has a different curve and must choose a paddle design >that gives him either optimal power or optimal efficiency. Probably, a >different design for each objective. This seems to be born out by my experience and makes sense. > >With my 57 year old body, a long narrow paddle is most efficient over long >distance. I stroke low, with relaxed shoulders and slow cadence, while >getting most power from lower torso. I try to emulate the Greenland stroke >taught by VanDoren in his video, but more slowly. On occasions (very rare) >when I try to race a short distance (less than 1 mile), a shorter paddle >with big blades and high stroke lets me get my shoulders into it and I can >reach greater speed, but at a big cost in effort. Note that you changed four things. You changed the blade size, drag coefficient, length, and paddling style. No question that paddling hard will require more effort. The question one might ask is , "Would I achieve the same speed at less efort if I used a diffrent paddle or style or whatever?" >I think that the significant energy loss in paddling is biomechanical, >rather than losses due to inefficiencies in the paddle blade/ water >interaction. (Assuming constant loss due to boat drag.) Further, the drag >coefficient always appears multiplied by the area (I think), CdA. For a >given Cd one does not necessarily want a larger A. Similarly, for a given A >one does not necessarily want a larger Cd. Both move one to a different >point on the torque-speed curve. I wish I knew what to think. So far I have not seen any data to say one way or another. For instance, does one paddle or anothe cause greater biomechancical loss. So far we have lots of opinions but nothing quantifiable. A complication arises in boat drag because it isn't constant. For example. A wide stroke causes greater turning moment and that increases ayw whihc increase resistance. If one wanted to keep the same thrust for a given power input the area woud be reduced to compensate for a higher drag coefficient. Normally what one would want is the highest drag coefficient and smallest paddle size (weight). This si one of the problems in comparing modern paddles with traditional paddles. Most of the time the modern paddle is large and has a higher drag coefficient. >It seems to me that the implication is that efficiency is not a property >that is inherent to a particular paddle, but whether that paddle and the >appropriate corresponding technique is matched to the paddler. Yes and no. I know this will seem like quibbling but a paddle is more efficient if it can produce more power with less power loss. However, we are dealing with a system. In a system, the overall efficiency can be affected by a particular part of the system. So, yes, the efficiency of the system depends upon the proper match of paddle and paddler but the most efficient paddle may not be part of that match. Keep in mind that just paddling straight ahead is not the only objective. A wing may be better for straight ahead paddling but bad for rolling. The sheer joy of owning a lovely wood paddle may offset the efficiencies of a carbon fiber paddle. The connection with the past may be more important than technology. All these factors influence how we perceive and respond to the paddle and boat. Hope that is helpful. Cheers, John Winters Redwing Designs Specialists in Human Powered Watercraft http://home.ican.net/~735769/ *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************Received on Mon Mar 30 1998 - 05:06:46 PST
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