Jerry wrote; > >It has always seemed to me harder to paddle against the current as opposed >to with. I mean that even with my eyes closed I think I can feel the >difference, i.e., without looking at the fixed shoreline. I always >attributed this to my imagination since I can't think of a physical reason >it could be true. > I believe this has to do with one's normal stroke rate. If you are paddling at your normal still water stroke up current the force on your paddle will be less because the paddle speed through the water is lower. To get the same velocity to the water you have to increase the paddle velocity relative to you. Even though the paddle force is the same your rate is higher and that may give the sensation of greater work. Bruce Winterbon once called to my attention to an interesting phenomenon involving the force developed when the blade is inserted in the crest of a wave as opposed to the trough. The ideal would seem to be to make sure the paddle was always inserted in the wave where the flow was opposite the action of the paddle blade for greatest thrust. This may even have some nit picking effect on rolling since the lift effect would be greater when blade is travelling against the flow. Donna wrote; >Along these same lines, I'm new to kayaking and I've been going out recently on >a lake. For some reason, I seem to paddle straighter and easier going INTO the >wind and against the current, heading into the waves. When I turn around and >head to shore the way I came but with the wind at my back, I feel awkward and >have a hard time keeping on a straight course. Is this difference because it's >a lake rather than a river? The reasons for this are rather complicated. Maybe this much simplified explanation will help. The water molecules in a wave travel in circular orbits. At the crest they travel with the wave but in the trough they travel in the opposite direction. When paddling down wind the bow might be in the trough while the stern will be on the crest (also vice versa) . If there is any angle (almost always) there is a turning moment on the boat causing it to veer off course. This is aggravated as the boat travels more closely to the wave speed (period of encounter) when the forces have more time to act on the boat. Against the wind the period of encounter is very short and the relative flow is always in the same direction so there are no (or minimal) turning moments. The only time being in a lake or river would make a difference is when the waves are due to the river flow rather than wind driven waves. Waves cause by velocity variations in a river behave differently from waves caused by wind. If that isn't clear let me know and I will try again. 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 Fri May 29 1998 - 04:17:06 PDT
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