Peter wrote: > >>Something that is a concern is the transition of an arm from high to low before the paddle enters the water. I can accept that a falling arm and paddle are converting their potential energy to kinetic energy prior to the blade entering the water, but the falling arm has to unbend through a right angle and contribute to supporting the paddle so that it can spear into the water on the other side of the boat at an appropriate point. So no matter how relaxed the arm, work is being done by supporting forces in the torso, upper arm and forearm segments against the falling weights of the forearm amd paddle. This will use up some of the converted kinetic energy that would otherwise have contributed to the blades acceleration as it enters the water. > > On the one hand Im concerned that your weighing method might introduce errors due to muscle tension and using two average angles, but on the other hand that muscle tension error might be a useful approximate representation of the supporting forces that are needed to guide the blade towards the water. > On the one hand my method does not include any measure no matter how approximate of the lower arms guiding force prior to the paddle entering the water. On the other hand it allows simple and accurate measures of the potential and kinetic energies associated with a complex movement by breaking them into component segments and the corresponding displacements and masses.<<<< I don't think you have to hold up the paddle much to move it to the side as it is falling from a relaxed shoulder so I think this side movement can be ignored for the purposes of determining how much of the potential energy from lifting the paddle is getting used to propel the kayak. Peter wrote: > Wrist movement is a valid consideration but Ive managed to determine a feather angle and paddle length that works with the vertical stroke to greatly reduce or remove my need for wrist cocking and so far havent experienced any strong wind issues thats a separate discussion. Yes, a separate discussion, but one of interest to me. What length and feather angle did you choose? I like 215 to 220cm with short (40 to 50cm) paddle blades. I don't have much problem with feather angle down to 70 degrees in wind but by 60 degrees high winds are problematic for me to paddle into. I can paddle from 60 to 90 degree paddles without thinking about the difference because I use the lift of the "control hand" forearm (that puts a rotating force force on the paddle as I lift from the elbow--acting as a pivot) by relaxing my grip to let the already rotating paddle shaft spin into position for the next stroke. If I don't get it quite right, the water pressure on the blade as I enter the water with it automatically makes the correction as the blades I use tend to self correct. The pushing hand is relaxed and that wrist is straight while the lower hand pulls with a finger grip controlling the paddle but acting in a straight line much like a rope. *************************************************************************** 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 Fri May 06 2011 - 21:37:48 PDT
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