20 foot Bertram Original Design

I bought 20 foot Bertram all original. ("combi model" I believe

1. The hull is completely foam filled.
2. Removed floor- all wood on stringers/floor rotted out and wet.
3. The foam appears to be OPEN cell. Interesting thing was so far boat hull is only wet at bottom where lifting strakes are or keel is/ and where ply soaked up moisture. The foam was not heavy until 3-6 inches off bottom hull at least so far.

So: Seems like if you put a way for water to leave foam any moisture penetrating would migrate to bottom and out with this open cell foam.

What do yall think. That foam is extremely strong and actually attached itself to wood/ fiberglass.

 

How do you know it is open cell? Old foam breaks down and the cells allow water ingresion.

 

I’d be inclined to remove all the old foam in order to create enough room to do the necessary work of rebuilding the stringers and bulkheads.
Place Cardboard half tubes under any new foam to create drainage paths.

 

I agree. Old foam will absorb water. Pourable foam is not too expensive either.

 

OK. I guess what Im asking is open cell foam would allow water to migrate easily to low areas where you can remove it. Closed cell foam like BW's hold lots water when glass is breached. I have used pour foam closed cell and I have seen it absorb water and get extremely heavy. My question is would open cell be better in this Bertram as long as I find path for water to get out?
I understand I can go back w/grillage system or stringer system but I really like the foam idea. Really supports hull and deadens sound and provides lots of support since it unitized hull and deck.
Let me know what you guys think. I can epoxy the stringer supports (coosa or ply or foam) and floor core.....

 

Is your question if you can replace stringers with foam?

 

For starters, make your decks stout and waterproof so that you don’t need the support of the foam, and they won’t be getting wetted.
Stringers and bulkheads bonded to the underside of deck form box sections, very strong.
You’re overthinking the foamed in concept, put more effort into the structure.

 

Siding with the good kapn here, the two part urethane foam often ends up waterlogged and increasing weight in regions it is undesirable.

 

OK I understand yall dont agree with the foam concept. I'll replace stringers/bulkheads regardless and core of the floor. Thought about gluing a grillage system in it using the inside hull as the mold - building it separate and gluing it in... Trying to make this easy and strong. Thanks for the input. I found it amazing in late 60's they tried the foam. Another interesting thing is floors been out a year. The boat dried right up even though its rotten...the rotten part made it easy to lift the fiberglass section of the floor leaving rotten wood behind. I can reuse the floor

 

Would be quicker and more accurate, as well as better bonded to build stringers directly into the hull.
Make sure that the hull is well supported and not warped before commencing.
Reusing the deck might work, but could open the possibility of water ingress again.

 

Gotcha. Done quite few deck jobs. I believe I can glass it in w/o any issues. The hull is good as far as warpage etc. I'll support it well as I remove the cubic feet of foam. Once all that is out I'll see easiest/best way to proceed.