xps shaping help

ok…I am totally new to shaping…the only stuff I could find here…(Land locked in northern ontario canada) is the foam blocks of extruded foam…i have read that it can cause delaming but it was all i could find.

I am having to cut the whole thing out from 4" and 2" thick sheets lamminated together.

I started on the rocker ,the bottom doesn’t seem to be to hard…just ensuring a continious curve throughout, but the deck I am unsure of…ANY help whats so ever for this poor landlocked soul would be golden…as well when do I put the fin boxes in now before glassing(which is a ways off yet) or later…


Where would someone even start to give you advice? If there is a shaper/glasser around by him a twelver and ask to watch. Buy the shaping and glassing 101 videos and watch them.

You need to make the stringer before you start shaping the foam. You cut the

stringer out of 1/4" plywood then you cut the blank down the center and glue

the stringer in. Now you shape the foam down to the stringer. This gives you the board thickness profile. Then you can cut the outline and turn down the rails.

no no no NOT plywood, because the plies that are perpendicular to the top and bottom will contribute very little strength.

Find a cabinet shop, or a woodworking shop, that will “resaw” (that’s the term they use) some 1x6 redwood, balsa, boxwood or spruce down to 1/8 inch thick. Then cut your rocker in that, and glue up the foam to it.

Try searching the archives or look at all my older posts. I’ve made only one XPS board but I’m very pleased with it and no delam problems after more than year of usage.

Just keep Your board from getting hot.

I would suggest You to hotwire the blank to get the rocker and foil cut into it, saves a lot of time and is accurate.

Good luck


If you haven’t yet bought your foam yet, check out http://www.plastifab.com/contact/index.html . I bought 2 lb/ft density EPS from them for a very good price, and you can request whatever dimensions you want, eliminating the need to glue thinner sheets together. This made hotwiring the rocker shape very easy. Since I don’t know where you live this link might not be helpful if their nearest dealer is too far away.

first build yourself a pair of calipers from cardboard, ply whatever…

and get a good straight edge for rail to rail

a stringer is more for left right symmetry than for foil you’ll still need to make sure the rest of the deck is plumb from the center out to the rail…

for cheaply and quickly cutting down EPS by hand

  1. cut a 24" piece of 2x4

  2. get a 36 grit belt for a belt sander and cut it and staple it to fit wrapping the rails tightly

  3. do the same to the other side but place a strip of neoprene or soft foam between the paper and the wood

start with the hard side to cut fast then use the soft to blend in your nose to tail rail bands

you can use an ironing board for surfboard racks with a cushion for the rocker to save costs too.

by hand use sheets of sand paper and drywall screen from 80-180/220 to finish off the surface.

Most importantly do all this using side lighting(never overhead) to see your progress and all your mistakes.

Clean up everything spic and span when you are done.

There you go sand paper, drywall screen, a piece of 2x4 and you’ll become a backyard board building monster.


forgot about the glue, tape and saw to make your blank…

As far as a rocker just glue the pieces up taped to whatever bottom curve you’re hunting for and that’s your starting point. saves alot of drastic shaving the bottom down. then you just do the top…

Other gems.

Use a vent with XPS.

Heavy glass schedule 3 layers of 6oz or 4oz with no wood skin