Aerodynamic bike helmet!

Step 7 Sandwich foam sheets between the masonite.

The masonite pieces will serve as a guide for the hotwire you will use to sculpt the foam. In this step, you need to attach foam in between the sections. I used regular masking tape folded over on itself (an approximation to double sided tape). Actually, there's an interesting point here: since my design was a "fishtail", as you've probably guessed by now there wasn't going to be a simple way to get the final fiberglass version to slip nicely off of the pointy mold (which is to say, the points were in the way -- like trying to slip an ice cream cone wrapper off the wider end of an ice cream cone). So, in this first picture you can see that I actually cut the middle masonite section into two pieces in case I needed to destroy the mold and remove it from the inside of the fiberglass shell. Fortunately, I didn't have to; but depending on your design, this would be the appropriate time to start thinking about how you'll separate the final piece from the mold.

After taping on one cross section, I used a pencil to puncture the two holes through the foam. Then, with two pencils sticking out the other side, I aligned the other two cutouts to get the final 'sandwich.'