Adventures in Mold Making - Part 2
Okay, with my first casting under my belt, I decided to do something specific to the Orbiter - the cockpit.
Using Fusion 360, I drew a block around the cockpit of the shuttle model and positioned it at exactly half point longitudinally - as if a knife was sliced down the center point of the shuttle. I then used the combine tool to remove the shuttle from the block - this forms half the mold. Printed it to my 3D printer as an STL. That print takes two days at high detail.
... here's the analog counterpart:
Like the first part, I sanded the inside with 80 grit to remote the "frizzles" and then painted it with a coat of gray primer. No putty.
Put the mold release on the surface and let it dry for a few minutes and then put a layer of fiberglass as the outside skin, followed by Carbon Fiber and the blotter.
The Carbon Fiber was very rigid, and I could see that covering the areas like the tip of the nose and the windscreen was going to be problematic. I cut the Carbon Fiber into smaller strips and laid them up against the fiberglass and overlapped them slightly. Each layer was wet out with West Systems. I let it dry overnight (12 hours).
The next morning, I pulled the blotter off - that is something that's a winner every time. And carefully worked the sides of the shape until it popped free of the mold. I did not trim the edges yet - and I probably should have done that in leather stage to avoid hard work afterward.
Overall, I love the result - it's strong - much stronger than the first part. To complete this part, I am printing the mirror image of the cockpit mold. My 3D printing software lets met click "Mirror" and reflect the shape whichever direction I want, so that's easy. Waiting two days for the result is not easy.
Next up is printing the rudder - an airfoil shape.
By the way, these shuttle parts are scaled to 65% of the original size because my 3D printer doesn't have the volume to do the full size. I will have to buy a new 3D printer to do the orbiter project. Until then though, learning about these molds and getting the technique down is worth it.
From a basic back of the envelope calculation - it will take two months to print the shuttle orbiter molds. Building it by plywood bulkhead and foam sandwich would take at least that long, be much heavier and not repeatable - at least not economically. Mold is the way to go.
This is the way