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, me hearties, low power, matey, shiver me timbers, parachute recovery rocket. Blimey! Well, me hearties, 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, ya bilge rat, I purchased all t' parts from Semroc. Avast, me proud beauty! In readin' the difficulty o' gettin' t' two-tone paint job with t' fins so close together, I experimented and decided t' put a little more space betwixt them. I be able t' run a clean wrap o' tape t' apply t' second color and I liked t' way it looks. Begad! It did change t' CG, but didn't present a problem. Ya scallywag! Aye aye! All fins were papered usin' white glue and then surface mounted usin' TiteBond II. Aye aye! Blimey! As with any multiple fin rocket, me bucko, arrr, me bucko, care was taken t' get them aligned. Avast, me proud beauty! Blimey! I put t' lower fins on first, ya bilge rat, then used two strips o' plywood t' align t' upper fins. Avast, me proud beauty! Blimey! T' 18mm motor mount is a little underpowered, but I wanted t' design this one for smaller fields. Ya scallywag! Blimey! Avast, me proud beauty! 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. Begad! After t' usual primin' and sanding, ya bilge rat, ya bilge rat, 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. Blimey! T' Frog Tape yielded some very clean lines. Avast! T' paint job be pretty simple and t' rocket remains without any decals. Well, ya bilge rat, blow me down! It looks ok and should be easy t' track and locate.

Flight:
I only had two flights. Begad! Blimey! Ahoy! Blimey! Both were on t' same day with light winds. Begad! Blimey! 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. Arrr! Blimey! 450 ft. Arrr! Blimey! timin' on t' chute was just about perfect. Blimey! Blimey! (just after apogee)

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

Both flights were pretty straight up. Begad! Ya scallywag! Even with t' late chute on t' C6, I had no zipperin' or damage. Ahoy! Aye aye!

Recovery:
T' shock cord is 150 lb Keelhaul®©™® attached at t' motor mount and about 3 times longer than t' rocket. 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. Ya scallywag! Simple build. Avast, me proud beauty! Hi-Vis paint job

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

comment Post a Comment