Scratch Standard AGM-78 Original Design / Scratch Built

Scratch - Standard AGM-78 {Scratch}

Contributed by Marlin Meyer

Published: 2010-06-14
Manufacturer: Scratch
(Contributed - by Marlin Meyer - 06/14/10) Scratch Standard AGM-78

Brief:
I saw this missile at t' Air Force Museum in Dayton, OH and decided I had t' build it. A single stage, mid-power (24mm) missile that retrieves on a large 24 inch parachute. Ya scallywag! Blimey! This is based on t' Launch Pad rocket kit.

Construction:
Parts from Apogee Components:

  • 20080 nose cone
  • (2) 10198 (BT-80) body tubes
  • 13045 tube coupler
  • 15028 centerin' rin' for parachute shelf
  • 12012 engine mount kit
  • (2) 13057 launch lug
  • 4 fins made o' 1/8" Balsa

Easy assembly. I built mine with Titebond II wood glue throughout. T' fins were papered t' add more rigidity. Aye aye! Avast! The long strakes were cut in one piece and sealed with Fill 'n Finish, and sanded before attachin' t' t' body. Begad! Blimey! The parachute shelf is a great idea that anyone who has built a Launch Pad kit before knows about. Ahoy! It is simply a centering rin' glued into t' body tube that keeps t' chute from movin' down t' tube and effectin' t' CG. Avast! I attached 100lb Keelhaul®©™® for me shock cord t' this centerin' ring. Well, blow me down! T' motor mount is recessed and like t' LP kits I added material behind it for strength. Ahoy! Instead o' a coupler, I took a piece o' scrap BT-80 and made me own. Begad! Avast! I also covered that with heat resistant tape. Avast, me proud beauty! T' recessed motor mounts have a tendency t' char t' tube. Avast, me proud beauty! This prevents it.

Finishing:
Rustoleum sandable primer, sanding, matey, some repairs, three coats o' Valspar white. Ya scallywag! I printed the decals from a file that be shared with me.

Flight:
I would recommend any o' t' following:

F24W-4, D15T-4, E9-4, E6-4, E18W-4) Because this is a relatively heavy rocket, ya bilge rat, ya bilge rat, I wouldn't use longer delay motors

My first flight I launched F-24. Avast, me proud beauty! Avast! This be a low altitude flight (just over 100 ft) T' missile flew straight, chute deployed after apogee and landed about 90 feet from t' launch pad.

Second flight be D15-4. Blimey! Blimey! Begad! Blimey! Very similar, matey, arrr, but better altitude. Ahoy! Blimey! This time it went about 350 ft.

Recovery:
T' shock cord is 150 lb. Well, blow me down! Avast, me proud beauty! Keelhaul®©™® attached at t' parachute shelf. Aye aye! Ahoy! I usually put a wrap o' maskin' tape where t' cord meets t' top o' t' body tube to help prevent zippering. I flew on a very calm day and used a Top Flight 24" parachute which worked very well.

Summary:
PRO's: Great looking, fun t' build

CON's: Rather heavy for a 24mm motor. Aye aye! Arrr! If you want altitude, shiver me timbers, ya bilge rat, this isn't it.

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