Making the front part of the foam plug

The bike will be a one-off, so building over a positive plug is the easiest way to build it.
I use PU foam that is relatively stiff. It is easy to shape by cutting and sanding.
First the design is outlined on the foam.



Then the foam is cut to shape:

The intermediate head tube is bonded to the foam parts.

And the front tube and head tube are bonded to the foam.
All connections are bonded with epoxy, filled with glass spheres and cotton. The uncured epoxy is covered with peelply to make a nice bondable surface.