First task was to make the trumpet shape. I largely copied the dimensions of a factory S stack since my engine is essentially an RS spec motor. I did make some modifications based on some intake flow papers I read and to make them easier to lay up.
They were done with a wet layup on a 3D-printed mold. I used fiberglass tubing so I didn't have an seams. Getting fiberglass parts off of round molds is a challenge even with mold release. I tried a bunch of methods and ended up greasing the printed mold and then shrink-wrapping the entire mold before laying up on the shrink wrap.* The mold has to be printed from ABS or another more heat-tolerant plastic because the heat from shrink wrapping will warp* plastics like PLA. I 3D printed lathe fixtures to trim the top and bottom to get relatively consistently sized stacks.
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