Foam core torture device

Vacuum bagging the bulkheads starts with a little torturing.  Here you can see the evil miniature bed of nails that I used to perforate the foam core (and occasionally my fingers!).  Dawna is thinking of a few other uses for this tool as well, ouch!  In order to pull vacuum on both sides of the core without trapping air, the core has to be perforated.  I made this bed of nails with nails in a 1 inch by 1 inch pattern.  I pre-drilled the holes for the nails on the drill press so the nails would stay in the nice neat pattern I wanted when they were hammered through the board.    If one was so inclined, you could epoxy the nails into the wood, or add a backing plate to keep the nails from coming loose over time, but I was not so inclined so I occasionally had to hammer a stray nail head back into the wood.  It really wasn't much of a problem, but on a bigger job or with thicker foam core, it may be beneficial to better secure the nails.  I kept the board large enough to cover the area in reasonable time, but small enough that I could pry it off after stabbing the core.

To pry it off, I simply used a piece of scrap wood that fit between the rows of nails.  I also avoided pushing the nails through more than necessary, stopping when the nails just poked through the other side.  I had to be careful not to be too aggressive with the pry bar so I wouldn't crack the bulkhead.  Just let the pry bar do the work.  It is impressive just how much friction forms with 30 small nails piercing 3/8" thick foam.

Here is a closer view of the aft bulkhead after the torture session.  You can see it makes a very nice pattern of holes about 1/16" diameter each, just as specified in the plans.  You can buy the foam pre-perforated, but this way seems to work well with patience.  If I was doing a lot of vacuum bagging on the table, I might think more about the pre-perf foam.