Has anyone tried sealing their foam under the deck itself?

I tried doing a search for this but found nothing about this exactly.

With all the worry about foam getting wet has anyone tried to seal the foam with polyurethane, decothane or deco pour or something else like that?

These are great liquid plastics that are flexable and water proof. I used them a lot in woodworking.

I see where people put plastic sheet in the boat first then pour the foam. Then pull the foam back out, peal the plastic off, then put the foam back in.

What about sealing the foam while it's out first before you put the foam back in? If you seal all of the sides first that has to help greatly in keeping more water out of it.

What do you guys know about this?

Re: Has anyone tried sealing their foam under the deck itself?

Hi Rick et al...

How about this... Use plastic to make a foam pour that fits but doesn't stick to the hull/stringers... Then pull the cured foam and remove the plastic. Finally wrap in heavy paper and then mat/chopped the piece to encase it. Using epoxy (or even poly) that should maintain the integrity of the foam, and give you the "waterproof" flotation you're looking for.

Another option might be empty, sealed, under-deck fuel tanks...

Alan

Re: Has anyone tried sealing their foam under the deck itself?

foam creates its own skin. there's no need to seal it if you just let water drain away.

trying to seal something permanently is a trick that many professional builders have been unable to achieve.

i have a post around here that is similar to what stoutcat mentions except the foam isn't glassed over...not sure if you can even do that anyway...glass over foam.

drainage is where it's at. this is what i did with mine...
http://forums.iboats.com/showthread.php?t=247834&highlight=foam+pour

Re: Has anyone tried sealing their foam under the deck itself?

"drainage is where it's at. "

exactly, if the water can't get out....its gonna get in anyway.

Re: Has anyone tried sealing their foam under the deck itself?

Lets say foam get wet from a one day outing. half gallon of water in. then you get home and drain it, keep the boat under cover. How long until the foam dries out?

Re: Has anyone tried sealing their foam under the deck itself?

That depends on the type of foam and its condition/age.
Old foam tends to break down from pounding and sucks water up over time, it can be a devil to dry out.
I removed the wet foam touching my hull and left the upper foam in place, The important thing is to give it a place to go.

some new foam in composite boats fails due to panting of the hull sides, they're just finding that out.

Re: Has anyone tried sealing their foam under the deck itself?

I used automotive under coating to seal the foam in my jet boat, not the entire surface though, just the exposed areas. I haven't checked it in a couple of years, but at 5 years it was still in place, looked fine and the foam under it was dry.

Re: Has anyone tried sealing their foam under the deck itself?

I coated foam blocks with epoxy and then set them in...sold the boat a couple yrs later and don't know if it ever got wet. Also, I cut up one boat that sat at least 5 yrs with the bow pointed high, drain plug open and sitting under a roof where rain couldn't get to it. The lowest part of the foam was still very damp.

In cutting up dozens of boats I've found 99% of all flotation foams get saturated (the 1% is for the guy who says his home depot spray can foam won't), sooner or later the water penetrates them and sits in the cells (no matter whether they are open or closed cell or have a "skin"). Unless the cells are turned upside down or sideways they don't drain quickly or at all. If you want foam that drains easier use open cell. If you want foam that resists saturation but is more difficult to drain use closed cell. Just don't think it will drain 100% by gravity as it sits upright.

bp

Re: Has anyone tried sealing their foam under the deck itself?

Also with some of the things I have learned in the past helps me to make this decision.

I thought I would own both of the following examples forever.
When I homesteaded in Alaska I built my house out of interlocking 6 x 6 posts every 8 foot left and right and every 8 foot up and down. One winter it held 15 tones of snow and ice.
Another house in Iowa I put in a tornado shelter, a solid marble bathroom ,
built a granite waterfalls inside and a huge built in pool.
I over built everything, but in the end when I did sell them it brought me no extra money anyway.

So with that in mind pop bottles.

Re: Has anyone tried sealing their foam under the deck itself?

take a real close look at some of the pics in the post i linked and you'll see soda bottles laying around. i played around with the idea a little but it still left me worried. i don't know how long a soda bottle will last stored away in a pretty harsh environment. will they really add buoyancy? they're a very odd shape and there's alot of air space between them. that means they don't displace water very effectively. combine the 2 and i decided not to gamble with my effort and $.

even with soda bottles, you'd want drainage to let water get away from your stringers. if you're gonna have drainage then why not use something designed for the purpose of flotation?

Re: Has anyone tried sealing their foam under the deck itself?

"I over built everything, but in the end when I did sell them it brought me no extra money anyway"

the best house on the block is the worst investment, because value is dictated by the price of the homes around you.

Its probably same thing with boats, the mkt is what it is.

Re: Has anyone tried sealing their foam under the deck itself?

Not to rehash an old thread or argument about flotation methods.

Both soda bottles and foam will displace their equivalent volume of water that can get into a given compartment, when flooded. And both offer flotation by the volume of air that they contain. In foam once the pockets get full they stay full. The key is to have no long term moisture around any wood structures. That being said, perhaps the old foam wicking up water and was saving the wood stringers etc. for let's say 10 years, that's not too bad for mfg'd vehicle life.
Soda bottles will never wick up water. My preference would be good placed scuppers for draining and plastic bottles for flotation only. (if you insist on flotation)
I often wondered: How do you know that the perfect sealed drain holes you made in stringers are not getting filled and closed off, when you pour in the foam.

Re: Has anyone tried sealing their foam under the deck itself?

Nova II 260 said:

I often wondered: How do you know that the perfect sealed drain holes you made in stringers are not getting filled and closed off, when you pour in the foam.

Click to expand...

ez fix, as discissed previously...
1 the foam is poured into trash bags in the hull compartments,
2 then removed from the bags,
3 drains are installed under the foam ,
4 then put the foam back in place.

I think this is better than any boat company is doing
and its easily done.
Its a really good idea.

Re: Has anyone tried sealing their foam under the deck itself?

One thing not mentioned here is that some boats are designed to have foam, and they need foam to achieve the designed degree of stiffness, or you have to add wood structure to make up for removing the foam. When I did the deck in my 88 FW I contacted them to ask about the foam. They replied and said that it was needed both for flotataion and structural reasons. And I can say that when I trial fitted the new deck panels, both without and with foam, there was a big difference in how the deck felt with the foam under it. I glued down the new deck with 3M 4200 and used stainless screws to hold it till the 4200 cured. All the screw holes and seams were filled with 4200. That took a while! I think it should last a lot longer than the factory job, which was a stapled down deck, unsealed holes and a thin skim coat of 'glass with carpet on top. The new deck was glassed in and gelcoated in non skid gelcoat. No carpet at all on the deck, only on the gunnels.

I saw a rebuild of a 22 ft Wellcraft that originally did not have foam (not required). It had at LEAST 4 transverse bulkheads vs only 2 in my foamed FW. So that gives you some idea how much stiffness it adds. And if you don't replace it, you have to do something to make up for that.