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post #6 of Old 04-20-2013
Maine Sail
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Re: 100 lb of Lead Vs 100 lb of concrete

Originally Posted by benesailor View Post
I was in the marina yesterday and heard something from the staff that had me perplexed.
He said that under water lead weighs more than concrete if they are of the same weight.

Now; after some checking it appears he may be right. As a ball of lead would have less "displacement" than a similar weight of concrete that would be much larger size. Does the amount of surface area on a sunken mass play a factor in its level of buoyancy?

Is this correct?
Yes, it is correct. It's all about the density of the material. Some areas even specifically ban the use of concrete for moorings because its underwater weight is a /.55 factor...

For example if you wanted a submerged mooring weight of 3000 pounds (about right for a 27-32 foot boat), and it was made of concrete, you'd really need a 5450 pound block to start with...

-Maine Sail / CS-36T

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