Expanding marine foam for composite centers?

Anyone tried using expanding marine foam as a composite center? Instead of the much more expensive sheets or wood?

Seems like it could be a much cheaper alternative.

Either pouring the foam into a mold to get the pieces and then glassing those. Or for something larger, putting down the layer of glass and foaming on top, then sanding it down to the thickness / smoothness you are after and glassing on top.

 

Boston Whaler does that, several others.
I blew surfboard blanks way back when, we used very heavy two part concrete molds. I have no idea how much they weighed, but a little too much foam would easily lift the top!
Don’t underestimate foams expansive properties!

 

You can of course buy the pre-expanded polyurethane foam in cut sheets of various thicknesses. The typical 2lbs/cu ft variety is quite friable, and not to considered as structural. 4lbs/cu ft does have much better physical properties, and in less critical applications makes a reasonable core.

 

The problem is controlling the expansion.

Boston Whaler and Ranger and probably Tuffy and a few others build this way..but it is a highly engineered process and costly to mould.

From what I am told, even corecell is made with an expansion reaction in a mould, but have not seen it done.

 

Expanding the foam into a core isn't practicable or cheaper