foam lessons

I thought I would go with the easiest and route and use the only 3" wide foam that I could find locally. This turned out to be a mistake, as are most things that are easy!! The foam seemed to cut ok, but once I tried shaping it with drywall screen and sandpaper I had chunks falling off and it didn't shape how I would have liked. This leads me to explain how I got to cutting and carving the foam.

To make the pattern, I used the mock-up that I constructed earlier from lumber. I took those dimensions and  drew them with pencil onto a large roll of paper. I then cut the paper model out and taped it to a 1/4" piece of particleboard. I then made dots at each corner, joined the dots with a marker and used my jigsaw to cut out the template. I did this twice, so I would have two templates, one for each side of the foam. This made it nice and easy to use the hacksaw blade to cut the foam.

To do the shaping and rounding of the foam, I bought a 4" PVC pipe union and cut it in half. Inside there was a ridge that needed to be ground down so the sandpaper or drywall screen would sit nice and flat. I used the rotary tool and a grinding bit for that job. The plastic ridge disappeared very quickly.

Today, I went and got some 1.5" pink rigid insulation and glued to pieces together to get the 3" thickness that I want to start with for the bike frame. I glued the pieces together with "No More Nails" construction glue.

I went through the same cutting process to get the foam frame. The pink insulation is MUCH nicer to work with. I then established where I needed to carve down the frame. I want to overbuild this frame to ensure it is strong enough, but I also need to ensure the bicycle components fit on. I will leave the rear end at 3" wide but will carve the front half down in width and round all the edges. The bottom bracket area will go down to about 2.5" and the headtube will go down to about 1.75".