Foam for under floor

[Case450]

I am going to lay down a new floor shortly in my aluminum boat. At the edges of the boat, where the sides meet the floor there are no tabs to support the edges of the plywood. To support the extreme edges of my floor i was thinking of just pouring some foam down and then fasten the floor on top.
Will the foam push up or heave under the floor? Does the foam have much expansion?
Where do i find the liquid boat foam?
Pictures coming soon!

 

[heiliges]

Re: Foam for under floor

Yes, it pushes and has big time expansion. Usually you have to have somewhere for the foam to escape from the cavity to which it is being poured. You should be able to find it at any place that has boat building supplies.

 

[bananaboater]

Re: Foam for under floor

I am one of the many Starcraft boat restorers. Almost to a person we hate expanding foam. If you review some of our retore threads you will see expanding foam nightmares. Not mine though. If you do go to my photobucket page you will see I used pink foam and ran it to the edge where it does indeed
help support the 1/4 inch ply decking.

How about a small aluminum channel along the outer edge of the ply? Thicker ply?

 

[Case450]

Re: Foam for under floor

i like the pink foam idea! aluminum channel along the edges of the plywood sounds good though but i'm wondering what keeps the edge of the plywood stationary? is the pink foam glued to the bottom of the boat or does it "float" under the floor?
i'm scared to put down foam that might move fearing that the vibration of running the boat will break down the styrofoam.
A thicker ply would work....not sure what thickness would be best to use...this is my very first project and i want to do it right...the link below is to the pictures of the boat now as it sits.
http://s211.photobucket.com/albums/bb270/PinkyRingz/Mirrocraft Project/

 

[109jb]

Re: Foam for under floor

When I did my Starcraft years ago I used the blue dow foam which is essentially just a little denser than the pink foam. One thing to keep in mind about either the blue or pink foam is that it is disolved by gasoline. I kept it away from the bilge area and fuel storage areas as much as possible. The expanding foam is not affected by fuel.

 

[Bob_VT]

Re: Foam for under floor

With the layout grid of supports in your photos I think that blue or ping board filling in those places will be more than adequate.

You will have plenty of support and it really is tough stuff that will not fall apart. If you are concerned you can glue the edges to the deck as you install it but I really do not thing it is needed.

One of the advantages of using the hard boards is to permit water flow towards the bilge without entrapment.

Starcraft in the earlier years would use multiple layers of foam blocks to take up all the space...... and the original was good old white Styrofoam which was not close in durability to what we have today.

 

[Sippen]

Re: Foam for under floor

When I did my Starcraft years ago I used the blue dow foam which is essentially just a little denser than the pink foam. One thing to keep in mind about either the blue or pink foam is that it is disolved by gasoline. I kept it away from the bilge area and fuel storage areas as much as possible. The expanding foam is not affected by fuel.

Hey LC, I did not think of that.. I remember seeing gas eat this up for lunch real quick. Having foam in the stern is good due to all the weight.. so what would you recommend here? I'm getting closer to putting down floor and I thought I had it figured out..

wow, old thread.. you still around..