After creating 5 or so fully custom Soul Cycles, painstakingly, one at a time, I needed a way to create attractive cabinets in a fraction of the time. So I invested extra time in the process of making a mold to be able to reproduce an attractive curved form in fiberglass. Now Rock the Bike
can bust out a Soul Cycle Mothership
in about a week, not months like the previous custom bikes
Step 1: Sketch shape you wish to mold, keeping in mind undercuts in molding process
An example of an easy shape to mold would be a beach ball. An example of a hard shape to mold to would be a stegosaurus. What makes the stegosaurus harder? It has features like legs, that will make a left / right mold unable to pull apart. The spikes on a stegasaurus' back would create steep draft angles that would make a top/bottom mold difficult but possible to release cleanly.
For my bicycle music system, I chose a shape that was relatively easy to mold with a left / right mold.
Step 2: Create a rough version of the shape, in foam.
In order to create your foam shape, you'll either have to sculpt it freeform like Michelangelo, or carve it from a block of foam with CNC tools, or use routers and templates to help you make it. I chose to use templates and routers.
In the series of photos you see that I stacked the templates (which are made by 'tracing' a master template with a router) with threaded rod. Then I shot expanding foam into the form (inside a garbage bag.)
Then I used a hot knife to slice away the excess foam. The masonite templates stop the knife from cutting too far.
Step 3: Hot wire, carve, and shave your foam block down to a curved form.
I first tried a Shurform tool (basically a cheese grater) to remove material, but the hot wire was much more effective.
Step 4: Smear nooks and crannies with some kind of resin or filler that is sandable.
Foam has big holes that need to be filled. Thicken epoxy resin with Microballoons and smear that stuff all over your form. I recommend using a different dye for each layer that you build up, so when you're sanding later you'll know when you're about to hit foam.