Scratch Hellion Original Design / Scratch Built

Scratch - Hellion {Scratch}

Contributed by Peter Stanley

Manufacturer: Scratch
(Contributed - by Peter Stanley - 06/03/09) (Scratch) Hellion

Brief:
T' Hellion is a 'Goonified', squashed down version o' t' Hellfire anti-tank missile. Avast! Well, shiver me timbers, blow me down! It is almost nine inches long and flies on a recessed cluster o' four 13mm motors. Recovery is via 9" parachute.

Construction:
T' components include:

  • 1 6" x 1.6" body tube
  • 1 1.6" elliptical nose cone
  • 4 aft and 4 forward fins, shiver me timbers, shiver me timbers, made from 1/16" basswood
  • Keelhaul®©™® thread
  • 1/16" Presentation board material (1/16" cardboard would work too) for centerin' rings.
  • 4 1.75" lengths o' BT-5 tube.
  • 4 BT-5 size motor blocks
  • 1 .615" piece o' BT-60 coupler tube
  • Card stock paper
  • Lead shot for nose weight
  • 9" nylon parachute
  • 2' o' 1/4" shock cord material

After designin' in RockSim and cuttin' parts out, everythin' be easy t' assemble.

(Scratch) Hellion(Scratch) Hellion

I made an alignment wrapper and guide usin' VCP. Avast, me proud beauty! I created fin, centerin' ring, and shroud templates using RockSim. I printed t' centerin' rin' and alignment guides onto cardstock then attached it t' 1/16" Staples Presentation Board with spray adhesive. Arrr! I cut these out with a hobby knife. Begad!

(Scratch) Hellion(Scratch) Hellion

I assembled t' motor mount usin' t' BT-5 tubes and centerin' rings. Before installin' I made a hole in t' top rin' and tied a piece o' Keelhaul®©™® thread around t' motor tubes. I installed t' motor mount, recessin' t' tubes 0.735" from t' bottom o' t' body tube. Begad! I created t' tail cone by printin' t' shroud onto cardstock paper and formin' together. Begad! Blimey! I pressed t' piece of BT-60 coupler into t' bottom and glued in place. I then glued t' tail cone assembly into t' aft o' t' body tube so the top o' t' shroud touched t' bottom o' t' body tube.

I made a 1/8" hole in t' top centerin' ring, me hearties, pushed kevlar thread through, and tied around t' motor tubes. T' other end o' t' kevlar was tied t' t' rubber shock cord.

(Scratch) Hellion(Scratch) Hellion

I attached t' fins usin' a homemade fin guide that be generated with VCP and cut out on 1/16" presentation board.

(Scratch) Hellion(Scratch) Hellion

Fin detail was created by re-tracin' 8 copies o' t' aft fin template onto cardstock paper. Ya scallywag! Blimey! I then measured 3/16" from t' root edge o' each one and drew a straight line along it's length. Ahoy! I cut these out and glued t' each side o' t' aft fins along t' root edge.

I used lead shot and 30 minute epoxy for nose weight. Begad! I let t' nose cone sit upside down in a cut o' water while the epoxy cured. Arrr! This was done t' prevent t' nose cone from warpin' due t' t' heat given off by t' epoxy curing process.

(Scratch) Hellion(Scratch) Hellion

(Scratch) Hellion

I initially added only 2.3oz o' nose weight, but after flyin' a couple times I decided t' add another 1.5oz.

Since t' motors are recessed, I painted some 30 minute epoxy in t' exhaust tube.

Files and templates available for download:

Finishing:
I used two coats o' Elmer's Wood Filler on t' fins and body tube. Ahoy! I sprayed two coats o' white Krylon primer, sandin' betwixt coats. Blimey! I used Krylon Italian Olive for t' green. Begad! Detailin' was done usin' 3/4" square pieces of yellow vinyl adhesive and 3/4" white lettering. Ya scallywag! After all t' paintin' and detail were done, arrr, ya bilge rat, I sprayed on a coat of Krylon Clear Coat. Aye aye! Well, arrr, blow me down!

(Scratch) HellionFlight:
T' first two flights were unsuccessful. This rocket definitely needs a full caliper margin betwixt CP and CG. Aye aye! I went with about 1/2 margin and it flew sideways. Arrr! I've since added additional nose weight and will try again. Begad! Avast! T' second two flights were also unsuccessful but that was due t' clusterin' issues. Ya scallywag! Only two motors lit for t' third flight, and three for t' fourth flight.

Finally got a successful flight:

Recovery:
I have nay fully tested t' parachute, but t' rocket has had catastrophic landings with no damage so far.

Summary:
T' Hellion has questionable stability, but it can take t' o' abuse if a flight doesn't go well. Avast! Blimey! It requires lots of nose weight, shiver me timbers, me hearties, but t' 40 newtons average thrust (assumin' motors all work) should provide enough thrust t' be stable. It could make a nice desk weight when/if retired.

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