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post #183 of Old 01-02-2014
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Re: Do you wear a life jacket?

Originally Posted by pdqaltair View Post
Do we suppose that the force of the wave snapped the tether? That would mean the force of the water on his body was 2000-4000 pounds, equivalent to strapping a 150 hp engine to his butt and blasting him through the water at ridiculous speed. Improbable. The force on his body was probably more in line with a serious wave break, perhaps 500-1000 pounds.

Do we suppose that the impact of his body against the anchor point, without any stretch in the tether, contributed a major part of the force? More probable. Flying across the deck at 8-10 knots could account for all the force.

Sail Delmarva: Dynamic Tethers

A combination? Certainly. However, it seems quite probably that tethers with a little give in them could prevent this sort of breakage. Making them even stronger probably won't help; if the forces on the body are more than 5000 pounds the impact would be fatal.
Vimes is right. I don't know much about the subject but the forces that I have heard about that can be generated on a harness line are on the order of some few thousands of kgs. I believe also that you are right and at some point those forces are so big that can also have a deadly impact on a body.

I noticed a change here in what regards the lenght of the lines here that from around 1.5m passed to just a bit over 1 m with two tethers. I believe it has to do with that and the charges generated: they would be much smaller on a shorter line than on a bigger one.

Those short lines are more uncomfortable and impractical to use specially at the wheel or at the cockpit where its very short length makes you have to clip and unclip at all the time. I have the two types on my boat and i only use the short ones to go forward in very bad weather (2 times till know ).

Nice study:

A good new year to you,

Best regards


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Last edited by PCP; 01-02-2014 at 07:26 AM.
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