04-26-2019, 04:57 PM
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Freeform rocketry advocate.
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Join Date: Jan 2008
Location: Claremont, CA "The intellectual capitol of the world."-WSJ
Posts: 3,780
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Quote:
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Originally Posted by Jerry Irvine
I would cheerfully make a 1340 kit but think red fin units are unobtanium.
Lee said the fin units had too many stress risers like the transition from the strake to the fin should have had a small curve. The launch lug was a bad idea in hindsight. He would have made it incrementally thicker although still with the draft. The leading edge of the unit gets chipped easily and pulls from the mold irregularly. Curve that with a small radius.
Tech Jerry
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The draft is for mold release. 3D printed does not need draft.
I am not sure what speed the fins could handle but if you made the whole unit about 1/16-3/32" thick, that might be a good start. Since it obviously is not an original part, it only has to look like it.
Jerry |