I had in the past tried creating a 'buck' for molding. I simply lack the skill and workspace to make an accurate enough piece.
I am going to make a cast mold directly from a chassis. I bought a very good condition t2 tub as my base. The t2 tub has an angled bottom and doesn't have many acute curves. I think that this will help when I actually cast a part.
For my prep I cleaned the chassis with rubbing alcohol. Then applied tape behind each screw hole. I then made flanges from paper along each edge. After the flanges were attached I applied melted paraffin wax to every hole and crevice. My goal is to eliminate any place where resin can go and get stuck. I had a heck of a time in the little area where the rear bulkhead attaches to the chassis.
I looked like this at that point
I planned to do a normal setup.
I precut 3 sheets of fiber glass with some slices in it to go around curves and angles.
I prepped the resin for 2 batches. An initial 1oz for a first pass and 2 oz started 5 minutes later for the end of the layup. I added the stated ratio of hardener and stirred for 1 minute on each batch.
used a small paint brush to apply the resin directly to the chassis and added the glass on top. I learned that to avoid air bubbles stipple or blot the resin onto the cloth. This let me push out the air bubbles from underneath the cloth. I then applied the second layer. The cloth wasn't cut well enough and I had to cut relief cuts for the 2nd and third layers. I used about .75 OZ per layer. I think I can expect about the same if I was using epoxy.
Everything was ok until I applied the chopped mat. The chopped mat was less flexible so it pulled out the previous layer of glass cloth. To emergency repair this I quickly made a vacuum bag and placed the piece inside. I planned on an open air layup, so it wasn’t prepped properly to go in a bag. I hadn't made a piece this big before, so I had a hard time getting it in the bag. I then removed the air. I noticed that even though the flanges were made of paper they held up under the pull of the vacuum.
At this point my gloves broke and I am covered in unset epoxy and fiberglass strands from the chopped mat.
I waited a couple of hours and removed the part from the bag so it could finish curing. The bag pulled away cleanly so that was a good sign. The resin wasn't hard yet so I took the scissors to trim off some of the excess fiberglass. I then peeled off the paper flanges from the inside.
I'll wait till morning to make a full evaluation, but it looks like a pretty good first effort. The wax prevented the resin from seeping into screw holes and there were no gaps. The mold feels pretty thick at this point and when I knock on it, there is a solid sound coming from it.
I'm going to let it cure overnight before I try and remove the chassis from the mold.
So far it seems promising.
