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Old 01-02-2014
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Re: Do you wear a life jacket?

Quote:
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.
...
where do you get these figures from?
a cubic meter of water weighs already 1 metric ton, if it comes rushing at you at a certain speed, the force on your body should be higher than the mere ~250-500 kg you mentioned... even if not all of the force is transferred onto your body since water is a fluid and "sloshes" around you...
tethers usually have a breaking load of 20000 N which equals to roughly ~2000 kg/m2...
the carabiners must have according to EU regulations at least 22000 N of breaking strength if they are meant to be used for alpine climbing and there are no others on the market... if they do not comply with this regulation, they have to be marked with "not for climbing" - you won't take one of those to tether you to a boat with...

but you are right - if you get thrown around, the initial impact force on the tethers could easily be well above those breaking loads and a certain stretch in them would make them a lot safer...
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