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 Post subject: creative mast flotation
PostPosted: Thu Sep 06, 2012 5:35 pm 
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I don't like those big teardrop mast floats. Has anyone tried removing the masthead fitting and stuffing the mast from the top down with closed cell styrofoam? Seems like about 10 linear feet of mast stuffing would provide as much or more floatation than the dorky teardrops. Watchya think?


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PostPosted: Sat Sep 08, 2012 7:12 am 
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A friend of mine did that with his Supercat 15. Worked okay as far as I know. I think the comp tip mast section is already foam filled.


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PostPosted: Wed Sep 12, 2012 7:04 pm 
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I see two issues here. One is that a sealed air filled mast provides an equal amount of displacement as a foam filled mast, so the bouyancy would be the same.

Two is that the baby bob is outside the mast and therefore provides more bouyancy than the same volume of foam inside the mast. Volume of displacement is what determines bouyancy, if I remember correctly.

I think the only benefit to putting foam inside the mast is that the filled volume couldn't become waterlogged in the event of a leak in the mast, and so it just might work as long as wind and waves don't force the mast down into the water.

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PostPosted: Wed Sep 12, 2012 7:55 pm 
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blord5 wrote:
One is that a sealed air filled mast provides an equal amount of displacement as a foam filled mast, so the bouyancy would be the same.

That's not correct. A lighter-than-water object in the water displaces its weight. It floats. Bouyancy = the object's weight.

If you fully immerse the object, the buoyancy is the total volume of displaced water, less the weight of the object. That's called reserve buoyancy and what keeps the boat from going turtle.

A mast filled with foam weighs more than a mast without foam, therefore the reserve buoyancy is less. The tendency of the boat to turtle will be greater - and the boat will be much harder to right with the extra weight in the mast.

Comptips are not foam filled. They only have foam at the ends - to help seal them off.

Filling a mast with foam is a very bad idea. The added weight will significantly increase righting difficulty and will adversely affect buoyancy in the water. If (when) the mast leaks, water will get trapped in the foam and make things worse. Much worse. (Google the "Sizzler" catamaran and find out what happened to them.)

You're much better off just making sure the mast doesn't leak - and keeping it full of air.


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PostPosted: Fri Sep 14, 2012 4:02 pm 
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Thanks for the correction. You're right, of course, but my point was as yours: foam in the mast only keeps water out (depending on the type of foam). A submerged brick has bouyancy equal to the weight of the volume of water displaced, but since its weight is greater than the bouyant force, it doesn't float.

Wouldn't the added weight of a bob at the very end of the mast also make it harder to right than a sealed mast on a boat that had not yet turtled?

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