Mario

Making your own flat panel is very easy.  If you want to go high tech, vacuum
bag it.  Borrow a vacuum pump that can deliver say 20" mercury CONTINUOUS
DUTY although I have heard of some people using refrigeration pumps, I have
no idea how well they work.  Whatever you do, DO NOT USE A VACUUM CLEANER!  
It doesn't have the high vacuum capacity nor the continuous duty ability
since it needs a lot of bypass air for cooling.  

Anyway, you can get melamine coated particleboard at the lumber store which
has a great plastic surface that releases well when waxed.   While at the
hardware or lumber store, get a roll of HEAVY DUTY polyethylene sheet (5 mils
or so). Get some peel ply at the local plastics suplier or try Fiberglass
Hawaii in Santa Cruz, Ca.  Also get a roll or two of vacuum bag tape.  

So wax the surface of the melamine and mask off the area you will bag your
sealant tape to.  DO NOT GET RESIN ON TO YOUR SEALING AREA SINCE THIS WILL
NOT HOLD VACUUM AND WILL REQUIRE UN-BAGGING AND CLEANING WITH ACETONE!  Next
I cut the bag and tape the perimeter with the vacuum tape.  Add so pleats for
management around corners and such.  Not a big deal for a flat layup but a
BIG deal for complex parts.

REMEMBER, ALWAYS ALWAYS ALWAYS HAVE A VERY OVERSIZED BAG!  Add lots of pleats
and such and seal the bag well.

Next, laminate the appropriate number of plies.  Squeegee out the air bubbles
and have a nice wet look to the back of the plies.  Wet the back of the foam
with resin and lay it on the wet laminate.  Then complete your laminate on
top of the foam, (I like to wet the foam first since it will soak up a lot of
resin if you try and wet out on top of dry foam).  Note that this is not
going through the cells, just the surface since all structural foams are
about 80-85% closed cell.

Lay the peel ply on top (or for complex layups, I like to use two layers of
peel ply since it releases easier) then put the breather ply on top of that.  
The breather is needed to distribute vacuum along the layup since once the
bag gets tight, it seals off the vacuum from dispersing.  The breather allows
vacuum in the far corners of the layup.  Last, seal the the bag on top with
the vacuum hose sealed against the bag with more vac. tape.  For a "frog", I
normally wrap a number of wraps of breather around the end of the open hose.  
For hose, I use 1/4" vinyl plastic available at TAP plastics.  You can get
fancier, too but this works and is cheap.

You can do this without vacuum but you have a good chance of having unbonded
areas of the core.  The laminate should be OK but a bit heavier since you
won't have squeezed out the excess resin.

Have fun and once you get the knack, bagging is really cool!  In fact, right
now I'm bagging an all carbon keel trunk for my 37' boat.  It is VERY highly
loaded and has some very high point loads, and should it fail, the boat would
probably sink.  Sink I sail in the ocean a lot, this could be fatal!  It
should be ready to turn off in a bit but I get a lot of piece of mind knowing
that I've really reduced the void content and consolidated the layup with a
bag.

Dan Newland