My goal is to make a fiberglass seat pan that is strong and lightweight, minimizing the amount of excess epoxy resin. Also, the shape of the part should be accurate.
I’m using the big CNC router to create the MDF mold which has the opposite shape to the part. Afterwards I can prepare the MDF with a hard surface coat, and add mold release. Then I place the fiberglass and compress it with a vacuum bag. The pressure difference will push the excess epoxy resin out, and the shape of the mold will transfer to the inside of the part.
Tooling board is for sure a much better option than MDF. But the shipping would cost a lot. I’ve not seen it advertised at that price from any distributor in the U.S.
The weight of the MDF was causing the jig to splay outwards, which I didn’t expect, so I wasted a couple of trips milling all the missing sides until I made a heavy MDF prism of stiffness.
I also had some problems with the surfacing primer. When I sprayed it, there was so much humidity in the air that the fibers in the MDF all stood on end. Once the surfacing primer dried, I ended up with a lovely gravel texture, so I got to practice my sanding skills. I love sanding because it builds moral character and is so much fun. I can’t wait to do more sanding.
Great progress! Was it a water-based primer? If so, that may have contributed to the raised MDF “grain”. Oil-based (or even better, shellac) primers don’t seem to have this same effect. I’ve never seen a surfacing or heavy build lacquer primer but shellac dries so quickly it can be built up in light coats very easily.
