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Scratch - Cohete {Scratch}

Original Design / Scratch Built

Published:2009-01-16

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(Contributed - by David Sindel - 01/16/09) (Scratch) Cohete

Brief:
This one odd oddroc. It's a stick-finned, 13mm model made from a few scrap parts.

Construction:
The parts list:

  • Nose cone from an Estes Space Hauler
  • 1" of 1/2" wood dowel
  • 1/2 butter pat of clay
  • 2" of 1" diameter wood dowel
  • Forward fin unit from an unknown rocket
  • 1/4" by 12.5" hollow plastic rod
  • Paper clip
  • 1/8" x 8" elastic

I drilled out the 1" dowel with a 1/2" drill bit (using a progression from 1/8", 1/4", 3/16", etc.), then I drilled out the lower 1.25" with a slightly larger bit to fit 13mm motors. The 1/2" section serves as an engine block. I formed the paper clip into an engine hook and attached it and the elastic to the outside of the dowel. I wrapped it with masking tape and glued it into the fin unit. The fin unit had two launch lugs--a 1/8" lug, which I use, and a 1/4" lug, which I glued the plastic rod into.

I put the clay into the tip of the nose cone, which was missing its shoulder from a crash. Then I put a blob of wood glue on the clay, placed the dowel onto the glue, and waited for it to dry. Unfortunately, I accidentally cracked the nose cone in doing so. Because of the long, light stick fin, Cohete is surprisingly stable.

(Scratch) Cohete(Scratch) Cohete

(Scratch) Cohete

Flight:
I've used 1/2A3-4Ts and A3-4Ts in Cohete. I'd recommend the 2-second delay for the 1/2A as ejection was rather late, and the A10-3T would be good as well. It flies to around 200 feet on 1/2As and 400 feet on full As. It requires no wadding; simply wrap the shock cord twice around the upper end of the 1" dowel and stick the nose cone on.

Recovery:
It uses simple nose-blow recovery. With the nose cone off, it falls fairly fast, however, the main body is tiny and tough and lands first, so the breakable stick fin won't hit the ground. Mine has never suffered any damage in at least 3 flights.

Summary:
Cohete was a quick and easy build for me, even several years ago when I was far less skilled. However, I'd recommend making some changes. The nose cone and fin unit I used are not common, but substitutions can easily be made. I don't recommend trying to drill a 13mm hole in a 25mm dowel. Using some BT-5 and BT-50 would be smarter. Stick-finned rockets are fairly forgiving so long as the front is heavy.

PROs: Odd rocket, easy to prep, almost no drift.

CONs: Hard-to-find parts, hard to drill dowel, high landing speed.

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