Scratch 'Scuse Me Original Design / Scratch Built

Scratch - 'Scuse Me {Scratch}

Contributed by Dick Stafford

Manufacturer: Scratch

Brief:
 Rocket PicThis is a minimum-diameter, 38 mm, all fiberglass rocket. It is a very simple, basic design but is very rugged and high performance. ...'Scuse me, while I kiss the sky'...-Jimi Hendrix

Construction:
The following is a list of the components. The major items were all bought from Giant Leap Rocketry

  1. ScotGlas conical nosecone, 8.5 inches long
  2. Giant Leap filament wound airframe, 36"
  3. Acme fin cannister
  4. AeroPack motor retainer
  5. ~10 ft 3/4" tubular nylon
  6. Blacksky standard rail buttons (2)
  7. Quick links (2)
  8. Eyebolt
  9. (1) bolt, 2" long (fits thru a Blacksky rail button)
  10. Scrap section of 1" dowel
  11. Giant Leap 29mm-38mm adapter (optional)

This is a *very* easy rocket to assemble:

Rocket PicNose Cone Assembly - I drilled a hole in the scrap dowel to fit an eyebolt. The dowel and eyebolt were epoxied into the nosecone, which does not provide an attachment point.

Fin can - After roughing up the tube and inside of the fin can, it was epoxied to the airframe such that the aft end is ~ 1 1/4" from the end of the airframe. I initially had not decided on a motor retainer so I wanted to make sure there was room to install one.

AeroPack motor retainer - After roughing up the tube and inside of the fixed portion of the retainer, I glued it to the airframe with JB Weld epoxy (per AeroPack recommendation).

Rail buttons - I epoxied the aft button in the middle of the fin can. The second was attached via a 2" bolt approximately 11" from the aft end of the airframe. The bolt extends through the airframe and was cut flush with the airframe opposite the rail button, using a Dremel cutting disc. This limits the largest motor which can be used, but I decided I would never want to fly this rocket on anything over a small "I" (moving the rail button forward would fix this). A nut was used as a spacer between the rail button and the airframe since the rear button is on the body of the fin can.

Recovery harness - The harness is 3/4" tubular nylon with a quick link on each end. Loops were made at each end as described in the article "Attaching Shock Cords", Edward Shihadeh and Bob Moser, High Power Rocketry, Vol 14 #5, August 1999. This involves looping the cord, tieing it off with cloth fishing line (not nylon!), and gluing it with CA and epoxy. The rear quick link was lowered into the airframe as the bolt holding the front rail button was screwed in. This took a couple of tries to catch the quick-link. The harness is thus removable.

Finishing - After its maiden naked flight, I painted the entire rocket (save the rail buttons and AeroPack retainer) using Krylon Chrome Paint. This looks really great, but shows every imperfection.

Flight:
I wrote this review with only one flight under its belt and will add others later (assuming I find the thing!). Being chicken, the first flight was with a G80-10. I used Estes wadding and an 18" chute from some kit or another. It was a very fast, high flight. Recovery was fairly close to the pad. My plans are to fly it with either a G125-15 SU or an H242-L at the next HPR launch I can get to. (or both)

Summary:
PROs: 1. Easy to build 2. Verrry sturdy 3. High performance design, 38mm or 29 mm (with adapter) CONs: 1. Materials were not cheap 2. Good chance to loose the thing along with motor hardware :-(

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