> Fresh water is less dense. Hence, the displacement of kayak's hull > is greater. More wetted area equals a more 'sluggish' feel. >This was the first explanation that occured to me. Another one is that less dense fresh water provides less thrust (and takes less efforts) at every stroke; on the other hand, there is also less resistance to forward movement. Out of lurk mode: This is not necessarily so, hull drag on the skin is dependant on viscosity, not density. And density of the water is not related to it's viscosity. Less dense does not necessarily mean less viscous, the obvious example is motor oil, it is much more viscus than water, yet it is less dense because it floats on top of water. Thrust available at the paddle is a complex interaction of stroke mechanics, density, paddle shape, etc. I suspect that if the kayak sits lower in the water because the water is less dense, it would have more wetted area and more skin friction drag, as if the kayak was heavier (hence the feeling that it is sluggish in freash water). I would think there would be a negliable change in the amount of available thrust at the paddle since both the power input and the thrust out put are a direct result of the water density and they would cancel each other, the small amount of drag difference on the paddle (if any) would be negliable. I do not think there is much, if any, viscosity difference between freash and saltwater, but there is a noticable density difference. So I would suspect that all of the differnce in feel would be due to the fact that the kayak floats a bit lower in freash water, significantly increasing the wetted area of the hull, making it feel like it is heavier and slower. 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/ ***************************************************************************
Peter Chopelas wrote >So I would suspect that all of the differnce >in feel would be due to the fact that the kayak >floats a bit lower in freash water, significantly >increasing the wetted area of the hull, making it >feel like it is heavier and slower. G'Day, In a related thought could it be the activity of the water. I find that a small degree of wave action makes it seem much easier to paddle than when in flat water. Is this an illusion or in a slight chop is there less water in contact with the hull at any instant? Perhaps the boat is tending to be 'thrown up out of the water due to a net upward movement of the waves? Is this related to the phenomenon of reduced friction is water with surfaces subject to vibration? Should we consider playing music directly into the hulls of our boats to make them go faster? Or is it an illusion? All the best, PeterO *************************************************************************** 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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