Shaping Expanded Polystyrene foam is a little
different than shaping urethane blanks. It requires learning
a few new techniques and tooling procedures. Experiment with
the outlying scraps first, and you will soon find you can
create the same level of finish as in any other system.
Your initial deep cuts will remove "beads."
Rasping and then sanding, will slice the "beads"
to a progressively smoother surface.
sFoam blanks can be shaped with standard shaping tools
with some exceptions. Roughing out can be done with same power
planers you use on urethane blanks, but you must note that
if you use the same "stroke speed" you might pull
out some beads in the process. This will leave pukas about
1/16 to 3/32" deep, so keep this in mind in relation
to final shaping.
If you can slow down your "stroke speed"
and still keep your shaping "rhythm" - then try
experimenting with the following method of rough shaping:
Make sure your cutting blades are sharp - slow your
stroke to about 1/3 speed. With practice this method will
cut the blank smoothly.
We do not recommend using a Surform or
Surform type blades. These will pull beads and chunks
of beads. 24 grit tungsten carbide rasps designed for EPS
foam are available now and do an excellent job. Also, rasping
papers in 24 and 36 grit are available where drywall supplies
and tools are sold.
We do recommend planers equipped with the
new tungsten carbide drum abraders. These can be had
from shaping equipment dealers, and will retrofit common planer
models. Use rasps, grit pads and sandpaper to do final and
finishing shaping. Please check our '
Useful Links ' in the FAQs section of this web site for
tunsten carbide rasps and drum abraders.
Please note that EPS foam has a consistent density throughout,
unlike urethane blanks that have dense "skins" and
lighter cores. With urethane blanks, shapers opt to thin the
blank mostly on the bottom. This leaves the dense skin on
top where it will protect the deck from pressure dings. This
is not necessary with sFoam blanks. We recommend thinning
our blanks by removing as much as possible from the top. This
protects the natural bottom rockers we have designed (or you
Wrap a 1" layer of upholstery foam around
your shaping racks. This will keep the blank from sliding
as you work. Small lead shot bags are handy also, to add weight
where you need it.
Until they are laminated, EPS blanks are
more flexible than urethane blanks. Once glassed, an EPS board
will flex the same as a urethane-cored board, given that both
have the same dimensions, stringers and laminations.