Expanding spay syrofoam

Bob L · Post by **Bob L** » Mon Apr 09, 2007 9:35 am

I am replacing the cockpit floor on a Cobia center console. The area beneath the floor had sprayed in foam for floatation, but I needed to remove this to repair the stringers. The cost for "marine grade" foam is something like $250 for a propane-size tank holding 8 cubic feet.

Can I use architectural foam from a insulation contractor? Or is there a water absorption issue?

(I thought I could trailer the boat over to a job site and have it sprayed in by the machine.)

Any thoughts or comments appreciated. Thanks.

Bob

Figment · Post by **Figment** » Mon Apr 09, 2007 2:31 pm

As far as I know, Icynene and other spray-in-place insulation foams are open-cell.

Can you consume most of the volume with stacked-up extruded polystyrene (pink board, blue board, etc), and just use an economical amount of the "marine foam" to fill in the gaps?

Quetzalsailor · Post by **Quetzalsailor** » Tue Apr 10, 2007 10:29 am

Styrofoam bead board, the white stuff, is not closed cell, but is lighter. The blue styrofoan is closed cell. I used the white boards inside a Sunfish-like thing and it weighed a ton! I used the white boards stuffed into nylon bags and tied into a Flying Dutchman in place of the inflatable bags: works fine.

The urethane foam sold in small quantities at the Despot, etc., is suitable for your application, but expensive. It's also hard to ensure that it expands enough and not too much.

Google on this subject and you will come up with folks who sell foam kits but you need to be sure what you're getting.

Air is lighter than foam and lots lighter than waterlogged foam: perhaps you can build in air. The worst of that problem is bonding and sealing the top console back down after creating the flotation space. You probably do not have access to the foam polyester bonding stuff.

Bob L · Post by **Bob L** » Tue Apr 10, 2007 10:43 am

I like the idea of the spray foam, because it will add to the rigidity of the structure. While the floor is off, I want to overfill the cavities, then grind them down flush.

BTW, if you ever have to remove this stuff, the tool of choice is a cup-shaped wire wheel on the end of a drill. It is like a giant spinning pencil eraser :)

I saw one website "Tiger Foam Insulation" that advertised their product for homes, boats, everything... and I think it was $200+ for a propane size tank.

Thanks!
Bob

Figment · Post by **Figment** » Tue Apr 10, 2007 10:59 am

Quetzalsailor wrote:Styrofoam bead board, the white stuff, is not closed cell, but is lighter. The blue styrofoan is closed cell.

The industry terms for these are "expanded polystyrene" (white crumbly coffee-cup stuff, open cell) and "extruded polystyrene" (pink board or blue board, closed cell). One little word, a world of difference in application.

It's worth noting that neither of these foams behave well in a fire.
I don't know of any foams that do, but still, worth noting.

Ceasar Choppy · Post by **Ceasar Choppy** » Tue Apr 10, 2007 11:35 am

I've used stuff I found on McMaster to fill the open cavity in my interal ballast keel. I think it was about $40 for 8 cu feet coverage.

I believe it was closed cell polyurethane foam... it was two part that came in two little cannisters that were mixed at the sprayer end. It is supposed to be used in enclosed areas that don't need air to cure unlike the stuff you get at Home Despot.