Sunday, November 29, 2009

Mach Goon building

I finally got some time today to work on the Mach Goon.

First came the fins. I cut six identical fins out of 1/8" light plywood from a clementine box. They're 2.7" wide, with a 3" chord on the root and 1.5" on the tip. I filled holes in two of them, and they're currently drying from a coating of wood glue. I may add paper skins for strength as well.

I ran a few CP calculations of the Mach Goon that turned out pretty well. I really only need 4 fins to keep it stable, but I'll probably add 6 just to ensure stability, even if a fin or two snaps off from the stresses of flight.

Next came the nose cone. I cut off the attachment loop and much of the shoulder, leaving just enough to keep it firmly in the body tube. I added a bit of weight to the front of the nose cone, and I'll probably add some lead shot eventually to keep in stable.

I decided that the two 48" by 1" streamers that I recently bought, plus perhaps one more, should be perfect for bringing it down safely yet quickly, with minimal drift. The rocket itself will weigh no more than 3 ounces, and the Pro38-1G case just a few ounces more. if absolutely needed I'll get a bigger streamer, or use a very small parachute.

Finally, I cut the motor tube. I wound some masking tape around the 38mm LOC Precision kraft paper tube, and cut it to length (6") with a small x-acto saw. I marked off 1/2" from the factory-cut end, cut just a little bit, and then unwound the outer 4 layers from the other side. It now fits perfectly inside the BT-60 of the Baby Bertha tube. The 1/2" that sticks out will the the attachment point for the masking tape to hold the motor in. This rocket will have to withstand a full 38mm ejection charge unless I can modify the reload, which is not as easy with CTI loads.

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