I wrote (about the multiple exposure videos of kayak strokes): >A graphic demonstration of why you do not want too long of a paddle blade. > You'd be using the upper part of the blade to push water forward. > Essentially > you'd be working against yourself and wasting your energy pushing water in > the > wrong direction if the paddle's actual pivot point is underwater. Jerry responded: >>>>>>This assumes the high stroke shown in the photos. At a lower stroke a longer blade might be superior.<<<<<<< The only assumption is that the blade is fully immersed. The angle of the paddle to the water makes very little difference in whether the pivot point will be underwater. That will be determined much more by the length and shape of the blade. A blade not fully immersed sucks air in behind it from the surface and that makes for slippage so that is not the solution for a "too long" blade either. From studies I've read, having the blade about 2" underwater makes for the maximum drag. This is probably because a wave is made above the blade and around that 2" blade depth the wave is the largest (without sucking air down behind the blade). A low stroke may be more relaxing for the paddler but because it is further off the centerline of the kayak it turns the kayak more than a more vertical stroke so is also less efficient in that respect. Of course, how the human feels and how the human can get the best leverage and exert the most force counts as well and argues against a vertical stroke pulled straight back right next to the kayak. *************************************************************************** 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/ ***************************************************************************
Matt wrote: > A low stroke may be more relaxing for the paddler but because it is > further > off the centerline of the kayak it turns the kayak more than a more > vertical > stroke so is also less efficient in that respect. Of course, how the human > feels and how the human can get the best leverage and exert the most force > counts as well and argues against a vertical stroke pulled straight back > right > next to the kayak. It seems to me that there are three places where energy is lost: interaction between paddle blade and water, the paddlers body, and energy to overcome boat drag. The energy required at a given speed to overcome drag is what it is, and nothing can be done except getting a lower drag boat. I suspect that energy lost due to inefficiency in the stroke much exceeds energy lost at the blade/water interface. I believe, for example, that the efficiency gained from a wing paddle accrues due to stroke geometry and the resulting body's efficiency in max energy extraction from torso rotation, and only secondarily from the paddle's grip on the water. For long distance cruising much energy can be used up just raising arms each stroke. From trying different length paddles with an easy turning boat (Mariner Express) I concluded that losses due to turning effect of a longer paddle are negligible. I don't agree that the 'best leverage and exert the most force counts as well' is the relevant point. It take a certain power level, not force, to drive the boat at a given speed. Each paddler will have a power level determined by force, leverage and cadence that is most efficient for him, i.e., that uses the least power at the given speed. Jerry *************************************************************************** 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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