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foam flotation questions

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I've started on replacing the deck (3/8" ply) in the 17 ft Sea Nymph aluminum.

The height (center of the v hull to deck) varies from about 4 inches near the transom to about 12 inches forward. The aluminum ribs are spaced at 12 inches and the current deck support attached to the ribs (every other one) spaced at 24 inches.

flotation foam:
I not sure if I like the idea that the urethane foam will adhere to the hull and deck supports.
Should I ever want to inspect the inside of the hull the foam would be a pain to remove so I'm thinking to line the hull with aluminum foil so it sticks to that and would be easy to remove.
(I don't foresee having to remove the foam but don't see how it could hurt)

Any argument for/against?
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Discussion Starter · #4 ·
Saran wrap with a little masking tape to hold it in place...

The plywood to be installed after the flotation is installed. Plan to do every other opening (between ribs) then I can cut the foam even with the top of the deck supports then do the other openings.

I also plan to add cut to fit 2 x 6's on the ribs that don't get an aluminum support. the ribs just happen to be 1 1/2" wide so the 2 bys will fit nicely. Attached like the factory did the aluminum supports (have enough sheet aluminum). All ready got a hundred ss sheet metal screws, and have a couple hundred ss wood screws. think I might put a bead of 5200 between the rib and 2 by so there be no chance of any rattles.

Just finished making a jig for my table saw so I can cut the angles on the 2 bys to match the hull.
 

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Discussion Starter · #6 ·
From what I've read that stuff sticks to everything but good idea to check.

The section at the transom will be left "un-foamed" and the center part (about 16" wide) where the drain plug is will be left visible plus this will be where the main bilge pump will be. Up front at the deepest part of the hull I'll route a hose to there and connect it to a 12V flo-jet pump which can self prime. Then I'll keep a backup bilge pump under a hatch with a 10 ft cord and plug so it can be placed anywhere in the boat during an emergency. I've always had a backup pump, battery and sometimes fuel. Never needed em all these years and hope that I never do.
 

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Brandon, FL
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If you put the two part foam under there in a few years your boat will weigh an extra several hundred pounds because of all the water it absorbed.

Find a source for the type of foam that pool noodles are made from (in sheet form). That plastic/rubber feeling stuff. Cut to fit and glue a few spacers to the hull to keep it off the hull and water can drain out and it can dry under the deck.

I think I saw the rebuild thread on this...where is it?
 

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Discussion Starter · #10 ·
At least half the Styrofoam I took out I plan to reuse but had thought to fill in any open spaces with the two part around the Styrofoam to make it "fit perfectly" :) under the deck, no space between the plywood and foam. If i can find a source for larger pieces of Styrofoam I might just do that.

The two part foam is supposed to be 90+ % "closed cell". If it starts absorbing water in just a few years F that... I don't expect any leaks but I do go out in the rain.
 

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Brandon, FL
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At least half the Styrofoam I took out I plan to reuse but had thought to fill in any open spaces with the two part around the Styrofoam to make it "fit perfectly" :) under the deck, no space between the plywood and foam. If i can find a source for larger pieces of Styrofoam I might just do that.

The two part foam is supposed to be 90+ % "closed cell". If it starts absorbing water in just a few years F that... I don't expect any leaks but I do go out in the rain.
The foam WILL start absorbing the moment it gets wet. Then it only gets worse. When the wet foam is in contact with the aluminum hull it will corrode holes in it.

In the past some boat builders foamed in their fuel tanks and they all leak because of this, but they have learned their lesson. Aluminum is a tough material but it needs to get air.
 

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Discussion Starter · #12 ·
Thanks DuckNut,

good to know.
One thing I still need to do is clean out the inside center of the hull between the rib and hull.
There's only a very small gap but as the lowest points in the hull they do let the water "leak" to the back of the boat when the bow is raised. Right now there are several that are clogged.
 

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Brandon, FL
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TheFoamfactory.com has 1"x48"x108" for $63. If they would cut it to the width between supports you would be in business. Buoyancy is a little more than 60lbs and one sheet would add about 270 lbs of buoyancy.
 

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Discussion Starter · #14 ·
I found a local company today and they have 2" thick sheets in stock but have a $250.00 min order. Another company has them to but min order is 5 sheets. Have not found anything thicker. Some 4 to 10 inch thick would be nice.

I'll swing by them and see if they happen to have some slightly damaged sheets they want to get rid of.
 
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