To replace foam or not?

[hemidoc]

85 bayliner 18.5' 5.0 This is the one from my post about the window. I tore out the floor that the PO had done and am fixing some problems. I dug the factory foam out and found dampness under it.
I know this has probably been discussed to death here but I'm wondering if I should pour new foam in after laying the new deck of 3/4 or 5/8 plywood. I'm kinda afraid that it may trap moisture under it again but figure it may add some strength since this thing only has two actual stringers. There is something that runs the length of the keel and some fiberglass "ridges".
What do you guys think would be better in this case.

 

[fishingdan]

Re: To replace foam or not?

My opinion = yes.

Use USCG approved closed cell phone (it isn't cheap). It won't absorb water.

It does contribute to the structural integrity of the boat and is expected to be in place for some boat designs. I don't know if Bayliner did this. Keep in mind that the hull bottom, stringers, hull sides, the sole, and the transom are all part of a single system.

Beyond the above, adding foam makes your hull much quieter and, from my experience of building and rebuilding boat, results in a stiffer overall hull structure.

Oh.....and it will keep you boat afloat if you were to take on a lot of unexpected water.

 

[Lou C]

Re: To replace foam or not?

I agree with replacing the foam if the boat came with it originally. I had foam in my 88 FW and I contacted them when I did my rebuild, and they said the foam was in there for both floatation and structural reasons, so I really had to replace it. Didn't want to do all that work and then wind up with a boat that felt flexy and noisy. I saw the re-build of a 22' Wellcraft on this site, that got a new deck. This boat did not have foam, and you could see that the boat had at least 5 transverse bulkheads, whereas my FW with foam had only 2. So to me it seems that if the original structure was designed with the stiffening aspect of foam, you have to reinstall it to get the same level of stiffness, or else the structure may be too flexible and if you wanted to re-engineer it, how would you know how much structure to add? I know many re-builders feel foam contributes to rot, and it does, but if you seal all deck penetrations the right way, and get rid of the carpet that holds moisture, and keep it covered when not in use, it will still last a long time. My rebuild FW is stronger than it ever was, since the new deck was installed with structural adhesive and stainless screws, not just stapled down like the factory did.

 

[hemidoc]

Re: To replace foam or not?

Thanks for the well thought out posts.
Now where in the wide world of sports do I get this stuff?
I intend to drill some holes with one of my trusty holesaws and pour it in.

 

[Lou C]

Re: To replace foam or not?

Marine supply places sell it, one is Jamestown Distributors, that's where I got it from. Make sure that there are enough holes to let the excess escape, that stuff expands ALOT and very quickly and can break things loose if it can't escape. That's why I poured it in before installing the deck, and then just cut the excess off even with the stringers. Boat manufacturers do inject it, but they have special machines to do it, and leave a number of holes for it to escape. The pour before method I think is safer.

 

[NoKlu]

Re: To replace foam or not?

My opinion = yes.

Use USCG approved closed cell phone (it isn't cheap). It won't absorb water.

Wow! Where can I get one? Been looking for one of these for a long time. I've drown a few and it get's expensive. One question though, How many does it take to float a boat???

 

[hemidoc]

Re: To replace foam or not?

I ordered the 2# from US composites. It wasn't that bad. Enough to make 8 cu/ft 62.00 + 15.00 shipping.