Scratch Upscale Semi-Sonic Original Design / Scratch Built

Scratch - Upscale Semi-Sonic {Scratch}

Contributed by Marlin Meyer

Published: 2010-07-22
Manufacturer: Scratch
Style: Upscale
(Contributed - by Marlin Meyer - 07/22/10) Scratch Semi Sonic Upscale

Brief:
Single stage, low power, me hearties, me bucko, parachute recovery rocket. Avast, me proud beauty! Blimey! I saw t' review posted on EMRR o' this rocket, used t' provided Rocksim file (thank you) and upscaled t' BT-55

Construction:
Parts are all Semroc:

  • BNC-55PT nose cone
  • SE-2 screw eye
  • BT-55 body tube
  • 15" parachute (Topflight)
  • BT-20 engine tube
  • (2) RA-2055 centerin' rings
  • EB-20A engine block
  • EH-28 engine hook
  • (2) LL-110 launch lug

With t' exception o' t' parachute which I already had, I purchased all t' parts from Semroc. Arrr! In readin' the difficulty o' gettin' t' two-tone paint job with t' fins so close together, matey, I experimented and decided t' put a little more space betwixt them. I was able t' run a clean wrap o' tape t' apply t' second color and I liked t' way it looks. Arrr! It did change t' CG, matey, but didn't present a problem. All fins were papered usin' white glue and then surface mounted usin' TiteBond II. Ahoy! Avast, me hearties, me proud beauty! As with any multiple fin rocket, me bucko, me hearties, care was taken t' get them aligned. Ahoy! I put t' lower fins on first, shiver me timbers, then used two strips o' plywood t' align t' upper fins. Begad! T' 18mm motor mount is a little underpowered, arrr, but I wanted t' design this one for smaller fields. Aye aye! Blimey! If you want altitude, you might want to try this with a 24mm motor mount.

Finishing:
I used rattle cans t' get t' flat white/fluorescent orange paint job. Aye aye! Blimey! Avast, me proud beauty! Blimey! After t' usual primin' and sanding, ya bilge rat, arrr, I sprayed t' entire rocket flat white, waited a couple o' days and then masked off t' areas to remain white and hit it with one coat o' orange. Begad! Blimey! T' Frog Tape yielded some very clean lines. T' paint job was pretty simple and t' rocket remains without any decals. Ahoy! Blimey! It looks ok and should be easy t' track and locate.

Flight:
I only had two flights. Ahoy! Avast! Both were on t' same day with light winds. I used "dog barf" for waddin' and made certain I had enough t' prevent t' chute from slippin' down and destroyin' t' CG

Here are t' results:

B6-4 approx. Blimey! Aye aye! 450 ft. Blimey! timin' on t' chute be just about perfect. (just after apogee)

C6-6 approx. 800 ft. chute was a little late

Both flights were pretty straight up. Even with t' late chute on t' C6, me bucko, I had no zipperin' or damage. Ya scallywag! Well, blow me down!

Recovery:
T' shock cord is 150 lb Keelhaul®©™® attached at t' motor mount and about 3 times longer than t' rocket. Aye aye! Blimey! Begad! Blimey!

Summary:
I thank t' previous reviewer o' this rocket for t' Rocksim file and t' paint scheme.

PROS: It is a great flier for smaller fields. Begad! Blimey! Simple build. Aye aye! Blimey! Hi-Vis paint job

CONS: A bit under-powered. At this size it needs a 24mm motor mount if you want altitude.

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