I'll tackle both of the questions below. First, you can ignore any thermodynamic affects caused by the vibration of molecules. They are all vibrating in random directions and have a net motion of zero. So you can imagine them hitting your hull from all possible directions and cancelling themselves out. That leaves us with the other thing that temperature does to water, change the density. In my limited naval architecture experience, I have found that warmer water is faster. The water is less dense and thus the volume displaced is easier to move out of the way. This also assumes that the change in water density doesn't adversely affect your wetted surface or wave making shape of the hull. Your kayak may sink deeper into the less dense water. My experience is in submarines where those features never change. You can then extrapolate to salinity. The more saline, the denser the water. So you can say that fresher water will be faster. This does not take into effect that your paddling will be more efficient in the more dense (cold, salty) water. You will be moving more mass per paddle stroke. You would have to determine whether the gain from the paddle in dense water is greater than the loss to hull drag. I believe the advantage from less dense water (reduced hull drag) is the more effective. I remember from my rowing days that any records set when the water temperature was above a certain point were in question. Also these changes are quite small. If I remember correctly that our submarine hull speed was around 8.25 knots in 60F water and 8.45 knots in 80F. This is an advantage only seen at the elite athlete level or when scaled up to full ship size. Daniel On Wed, 16 May 2001, Rick Sylvia wrote: SNIP > Brings up a thought, though, that he didn't (or hasn't yet) discussed. > Water temperature is a result of the speed of the atoms/ neurons/molecules > or whatever (I'm not all that scientific) - the faster they move, the higher > the temperature. So, if you are passing through a body of water with the > atoms (or whatever it is - humor me) themselves moving at varying speeds, > will it affect your speed? Seems like the colder water (therefore slower > moving atoms, and therefore less resistence / counteraction to other motion) > would allow for faster boat speed. But, it also seems like it might be > measureable in highly controlled experiments, but to the average paddler > would be unnoticable. > > I'm also starting to wonder about water salinity, but we can save that one > for later.... *************************************************************************** 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 Wed May 16 2001 - 14:08:44 PDT
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