Making the moulds
To make the mould, stack MDF disks of decreasing size and then cover with automotive body filler.
From thinner material, cut a disk of the desired flare radius to use as a scraper.
Draw a stop line on the baseboard where you want the port to stretch to.
Ten things you will need ...
- MDF baseboard with rings
- Circular scraper
- Tin of Bondo
- Mixing sticks
- Latex gloves
- Cardboard squares for mixing
- Paper towel
- Flat chisel
Three moulds before any filler is added, along with the scrapers for each
Sand off any high points between applications
A flat chisel helps remove buildup on baseboard outside flare zone
Whilst it is possible to use slightly larger MDF disks as you get closer to the baseboard, the savings in Bondo are minimal. It's easier to just make them all the same size.