Matt wrote: < I think that will be an unneccessarily complicated way to figure your arm weight. If you weigh your hand after supporting your shoulder where it pivots and add the paddle weight actually being lifted you should get how much weight you are effectively lifting. You could weigh your hand at the average arm angle (during your stroke) to get an average weight for it during the stroke. Each hand should probably be done separately. The paddle should probably also be weighed too when you weigh your upper hand by supporting the lower hand on a box with the paddle at the average angle the upper hand is lifting it through. The distance the hand moves up and down during the stroke should then be used in the calculations (rather than the average distance the paddle center moves). Do the power required to lift that hand and paddle calculations by measuring the hands upward movement from the end of the power stroke to the top of the hand lift (separeately for each hand as you may be lifti ng higher with one hand than with the other--possibly by bending the wrist back with the control hand) and then calculate them separately (or take an average of the lift distance and arm weight and paddle weight at each hand) to get the average power put into one lifting stroke. > Gbday Matt, Thanks very much for the coaster power curves. Can you tell me the program you used? Excel and text editors donbt seem to work on the file, even when I change the extension, and Ibve not come across a .xlc extension before. Re your method and mine. It sounds as if both would work. They probably each have their own difficulties. But before getting into weighing the arms at appropriate angles as an alternative and before doing any more calculations, I need to focus on understanding the movement better. 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 Ibm concerned that your weighing method might introduce errors due to muscle tension and using two baverageb angles, but on the other hand that muscle tension berrorb 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. Wrist movement is a valid consideration but Ibve 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 havenbt experienced any strong wind issues b thatbs a separate discussion. It could be that both our approaches will discover useful but different information. It would be interesting to compare and later possibly even combine the best elements of each. I think those best elements might include your weighing method as applied to a horizontal arm and then segment weights evaluated using a model of the arm derived from the data in the paper I referenced earlier. All the best, Peter *************************************************************************** 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/ ***************************************************************************
Hi Peter, > Re your method and mine. It sounds as if both would work. They probably > each have their own difficulties. But before getting into weighing the > arms at appropriate angles as an alternative and before doing any more > calculations, I need to focus on understanding the movement better. I think you guys are heavily overcomplicating things. I think that only the "weight" of your hands matter. I put "weight" between quotes, because actually we're little interested in weight or mass. We're interested in _force_. After all: Energy = distance * force. We're really only interested in the _force_ that your hands and paddle generate when going down and the force that's needed to counter that force to move your arms up. That force is shown when you put both hands and paddle on a scale. A more direct measurement is shown in my last video (the link again, for convenience: http://www.youtube.com/watch?v=io6S_gRxk8c ) Since those measurements confirm the energy output (lower force * higher distance = same result) I have little reason to include more even indirect and complicated measurements. > 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. Sorry Peter: You've lost me. What arm is the "falling" arm, and why would it have to unbend? Should it be bent in the first place? > > 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. When you start including bending of arms and weights of different arm-parts (that start being interesting when you start including acceleration, which we haven't discussed so far) things get very complicated very fast. I could perhaps still perform such calculations (it has been 20 years), but the chance of errors would be too high to be of any value. > Wrist movement is a valid consideration but Ibve 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 havenbt > experienced any strong wind issues b thatbs a separate discussion. I'm afraid that discussion would be like the vi/emacs-wars and the heated discussions about what soccer-team is "best". I've made my choices. I program in Vi, I have no interest in soccer, and I use a wing-stroke with a feathered paddle. By all means, continue any of those particular discussions, but I choose to get the popcorn, sit back and enjoy the show. Niels *************************************************************************** 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/ ***************************************************************************
Niels wrote >I put "weight" between quotes, because actually we're little interested in weight or mass. We're interested in _force_. After all: Energy = distance * force. We're really only interested in the _force_ that your hands and paddle generate when going down and the force that's needed to counter that force to move your arms up. That force is shown when you put both hands and paddle on a scale. > G'day Niels, Now I understand why you and Matt thought my calculations were so complicated. I may think about the forces involved but I don't involve force in my calculation at all, just work with mass and vertical displacements, together with potential energy, kinetic energy and their differential with time. Trivial calculations and they simplify things enormously. For example I don't have to worry about acceleration and it tells me straight away why Matt's measurement of arm 'half' weight supported by a set of scales and a shoulder, will still allow a valid calculation. The penalty is that I learn nothing about the forces used, just the power and the energy. But I agree many of the forces involved in this context are way too uncertain to allow calculation. Mark, Brad, Craig and Scott had me laughing out loud - Is it possible that we might finally be boring people to tears and it's time to stop - surely not:~) All the best, Peter *************************************************************************** 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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