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, parachute recovery rocket. Well, blow me down! 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. In readin' the difficulty o' gettin' t' two-tone paint job with t' fins so close together, matey, arrr, 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. It did change t' CG, me hearties, shiver me timbers, but didn't present a problem. Arrr! All fins were papered usin' white glue and then surface mounted usin' TiteBond II. Aye aye! As with any multiple fin rocket, me bucko, care was taken t' get them aligned. Aye aye! I put t' lower fins on first, then used two strips o' plywood t' align t' upper fins. T' 18mm motor mount is a little underpowered, me bucko, but I wanted t' design this one for smaller fields. Begad! If you want altitude, me bucko, me hearties, 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. Blimey! After t' usual primin' and sanding, shiver me timbers, 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. Ahoy! T' Frog Tape yielded some very clean lines. Begad! Arrr! T' paint job was pretty simple and t' rocket remains without any decals. Avast, me proud beauty! It looks ok and should be easy t' track and locate.

Flight:
I only had two flights. Both were on t' same day with light winds. Begad! Aye aye! 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. Begad! Well, blow me down! 450 ft. Blimey! timin' on t' chute was just about perfect. Begad! (just after apogee)

C6-6 approx. 800 ft. Arrr! Arrr! chute be a little late

Both flights were pretty straight up. Avast, me proud beauty! Even with t' late chute on t' C6, matey, I had no zipperin' or damage. Avast, me proud beauty!

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

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

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

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

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