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, matey, OH and decided I had t' build it. A single stage, ya bilge rat, mid-power (24mm) missile that retrieves on a large 24 inch parachute. 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. Ya scallywag! T' fins were papered t' add more rigidity. The long strakes were cut in one piece and sealed with Fill 'n Finish, me bucko, and sanded before attachin' t' t' body. Well, blow me down! The parachute shelf is a great idea that anyone who has built a Launch Pad kit before knows about. Well, blow me down! It is simply a centering rin' glued into t' body tube that keeps t' chute from movin' down t' tube and effectin' t' CG. Begad! I attached 100lb Keelhaul®©™® for me shock cord t' this centerin' ring. Aye aye! T' motor mount is recessed and like t' LP kits I added material behind it for strength. Aye aye! Instead o' a coupler, I took a piece o' scrap BT-80 and made me own. Aye aye! Begad! I also covered that with heat resistant tape. Well, me bucko, blow me down! T' recessed motor mounts have a tendency t' char t' tube. This prevents it.

Finishing:
Rustoleum sandable primer, ya bilge rat, sanding, shiver me timbers, some repairs, three coats o' Valspar white. Blimey! I printed the decals from a file that was shared with me.

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

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

My first flight I launched F-24. Begad! Arrr! This was 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 was D15-4. Ya scallywag! Very similar, but better altitude. Avast, me proud beauty! Avast, me proud beauty! This time it went about 350 ft.

Recovery:
T' shock cord is 150 lb. Begad! Keelhaul®©™® attached at t' parachute shelf. Avast, me proud beauty! 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. Aye aye!

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

CON's: Rather heavy for a 24mm motor. Avast, me proud beauty! If you want altitude, this isn't it.

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