Stringer Foam

[WIDGEON]

I'm in the process of removing the foam from the stringers in my 20 SF. Most was pretty wet. My question is: what weight foam should I replace this with and do I need to replace the foam outside of the stringers. Stringers may not be the correct description. Should be box framework below deck perhaps.
Thanks in advance

[Mshugg]

Some will likely tell you that the foam isn’t structural, but if you want to match original spec, use 4lb foam.

[Capt Terry]

Wondering why there are so many reports of wet foam. I know there are differing opinions on foam around aluminum tanks. When I replaced mine RDS told me to use “closed cell” foam. Was that not used during original manufacturing years ago or does the closed cell foam break down? As I recall there was no saturation of the original foam around my tank.

[Vezo, Part II]

I believe that my @ 70 gallon tank on my 1979 MA, new to me in 1996, was a second tank, due to the elevated tank fill. Whatever type of foam was not correct. The cell gave up the ghost on bottom and sides, were eaten through aluminum wherever in contact with foam. New tank being installed now. No foam and coal tar epoxied. Aluminum fuel tanks have become somewhat expensive.

Vezo Part I! 1987 18 SF, new fuel tank, installed in 2009, has become corroded with stuff while storing/buying non ethanol fuel, and only on the Inside! Fuel/Water Separator doing its job on a 2009 Suzuki 140 and runs like a Champ on above deck 12 gallon remote fuel tank.?.

Vezo, Part II

[cdavisdb]

Closed cell pour foam isn't always very "closed". At least some of the stuff that comes as slabs of closed cell really is. I've experimented with both as buoyancy adjusters for my monofin and the closed cell pour stuff I've used gets soaked pretty fast.

[rcoster38]

I just pulled my deck off to find that each of my stringer tops had a series of 1" holes cut into them, exposing the foam. It looked like the putty was intended to cover the holes but I think they missed their mark on a couple holes and the foam underneath was soaked.

[uncleboo]

In my humble opinion, I don't think they worried with closing all the holes up in the stringers. If there is enough water in the bilge to cover the tops of the stringers, you might be riding home in another vessel, (orange & white maybe).

[DonV]

Boo is correct, since the top of the stringers are only about 1" below the deck's surface you would be in deep poo-poo!!

[rcoster38]

all I know is there seems to be more water than foam in my stringers. after replacing it with dry 2lb foam, swapping the soggy wood deck with divinycell, and ripping out the waterlogged bilge foam, and doing away with the t-top, she might be terrifyingly fast

[kmoose]

I think a lot of project boat spent too much time in the back yard before they are sold and fill up with water. I've seen it a bunch of times and most people think nothing of it as they have no intention doing the rebuild.

I for one am not a big foam fan but I don't think all the rehab of foam done is that necessary. If the foam got wet, it can get un-wet if drain and vent holes are made and the hull is kept open and dry for sufficient time. Once it is all dry, glass the holes and move on with the build.