Peter wrote: >>>>However, it does require the values of arm weight that Niels and I use, which in my case I obtained using a value of 7% of body weight derived from a reference on cadavers available at http://www.ulb.ac.be/medecine/anatemb/biblio/Clauser1969.pdf . Also I was curious as to whether the power you quote includes the power to lift an arm and a paddle or just the power that the blades exercise in propelling the kayak?<<<<<< The power I'm quoting for propelling a Coaster is just the power required to overcome its calculated drag at those speeds. How that power gets there and how much extra need to overcomwe transmission losses is not considered. I've attached the chart I made to this e-mail, I don't know if it will get through or show up I'm curious where Niels is getting his arms weight, but since he pretty much argees with you on that I think you are both probably making a mistake that is amplifying the weight being moved. I think I've figured out where. Since one end of the arm is supported by the shoulder then (if the arm was of the same thickness from shoulder to hand the weight at the hand would only be half of the actual weight of the arm if severed at the shoulder and weighed during an autopsy lets say. So lets let rigor mortis set in and weigh the stiff arm differently this time. Rest the shoulder on a solid object that holds it up and then weigh the arm at the hand where it grips the paddle. I think you will find this actual arm weighs even less than half of what the entire arm weighs because most of the arms weight is near the fulcrum. this also explains why my arms were so much lighter than yours. I tried to simulate paddling by holding my arm out straight and weighing my hand with my shoulder relaxed. I also tried pushing down a bit first and then relaxing those muscles until the arm came to rest. Either way I'm getting between 1.5 and 2 kilos that way. I could probably get more accuracy if I supported my armpit over a fixed object to make sure I'm not lifting of pushing down inadvertently and then weighing my hand. I just tried that with a crutch supporting my armpit and am getting less than one kilogram on the scale under my hand. For that reason I think there is a lot less wattage available for driving the kayak even before the transmission losses than Niels thinks. I thought of this a couple of days ago but had to help my brother move his sailboat yesterday and then concentrate on finishing a safety article for Sea Kayaker by today's deadline. [demime 1.01e removed an attachment of type application/vnd] *************************************************************************** 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 >I think you will find this actual arm weighs even less than half of what the >entire arm weighs because most of the arms weight is near the fulcrum. G'day Matt, Thanks for the power information and for making the point about arm weight. Taking that point further it would seem appropriate to treat the arm and paddle combination as three segments: i) paddle ii) forearm and hand iii) upper arm, because each segment's centre of mass will have a different vertical displacement when a paddle blade is raised, at least in my paddle stroke. The cadaver paper has the arm segment values so I'll recalculate the potential energy for lifting each segment at the weekend. 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/ ***************************************************************************
This archive was generated by hypermail 2.4.0 : Thu Aug 21 2025 - 16:33:55 PDT