Can you get rid of water in foam flotation, and if so, How?

[jbcurt00]

I remember that guy he put a deck over and sold it as restored.

Yep,

 

[Wildey]

Since 1977, foam was required under 20' for new builds only, not reconstruction by us. Aside from deck support, it provides stiffness, soundproofing and allows thinner hull layups below the water line.

Engineered for high production numbers at minimum cost, I can see where the hull was laid up, then the boxes placed, the hull layup continued only to the boxes. Hull is much thinner and "flexy" where the box was. The box and foam saved a bit of FRP in that area which was not necessary as the foam structurally bridged the void between the hull and the deck in that area.
I plan to build that thin area up with 4 layers of 1700 to make it match the surrounding hull thickness. No box will go back in, just a flat deck with pedestal seat mounts.
I can see the mass production / cost saving aspects of the processes.
A little here, a little there ....... really adds up in a competitive market.

 

[Scott Danforth]

, just a flat deck with pedestal seat mounts.

Make sure to add a lot of reinforcment to the underside of the deck sole if you plan on adding pedestal mounts. where a box spreads the load out over a 1.5 x 3 foot area and has ability to take a lot of shear force, a pedestal mount is a big lever trying to break a section of the deck out.

I would recommend a few bulkheads underneath

 

[kcassells]

I always enjoy foam talk.

 

[Wildey]

Make sure to add a lot of reinforcment to the underside of the deck sole if you plan on adding pedestal mounts. where a box spreads the load out over a 1.5 x 3 foot area and has ability to take a lot of shear force, a pedestal mount is a big lever trying to break a section of the deck out.

I would recommend a few bulkheads underneath

Noted, and in the plan, thanks.
Where many folks add a pad of sorts on the top at the pedestal positions, I plan to put them underneath so the deck surface above is flat. This way the reinforcement can be larger and bridge to the bulkheads more fully.
Thanks Scott

 

[76SeaRay]

On the seat issue, I used 1/2 inch marine plywood on my deck and put a second layer of 1/2 inch marine plywood as reinforcing underneath the deck (also attached the reinforcing to the stringers) where I would put a pedestal. I haven't decided on the redesign of my seats but I may box underneath the Captain's chair for added storage. The extra layer under the deck gives a lot more rigidity in the floor and flexibility in how I design the final mounting. My deck has foam under it as well.

On the wet foam issue, my foam was wet so I removed it due to stringer replacement starting in the back to work my way forward (replacing transom, then engine bay stringers, then forward stringers to just past amidships before finally getting to the front section in the V Berth). It took me better part of 2 years part time. All during that time and 2 years before, the boat was in dry heated storage and the front floor section in the V Berth had a hole open to the air. When I finally pulled up that front section, the foam was saturated and still had standing water under it. It hadn't dried at all during that whole time. Just my 2 cents but I would replace it all.

 

[Baylinerchuck]

As far as the foam being structural, my 20’ Chaparral had 2 long stringers from transom to bow. The center along the keel and the first strakes beside the keel are open minus the fuel tank. I had also thought about leaving the foam out, but in the Chaparral design it added so much structure under the deck where the cross members were thin against the hull. This is also the area of the hull that contacts my trailer rollers. After years of soaking in water, the structure in the wood was gone, and was more like mulch. The fiber glass that tabbed in the stringers was mostly brittle. The foam was completely saturated and would never have floated, however was still structurally together and bonded everywhere. Had it not been for this wet and soaked foam, this boat probably would have flexed enough to crack somewhere. All this to say foam is not just for floatation. In smaller boats it adds a ton of structure while keeping the boat light.