Scratch AMRAAM AIM-120 Original Design / Scratch Built

Scratch - AMRAAM AIM-120 {Scratch}

Contributed by Marlin Meyer

Published: 2010-07-01
Manufacturer: Scratch
(Contributed - by Marlin Meyer - 07/01/10) Scratch - Amraam Aim

Brief:
Based on Estes design, shiver me timbers, a single stage, 18mm motors, shiver me timbers, parachute recovery, matey, scale-like missile. Ahoy!

Construction:
Here are t' parts from Semroc:

  • BNC-55 nose cone
  • SE-2 screw eye
  • BT-55 body tubes (2) each 11"
  • JT-55C tube coupler
  • BT-20 motor tube
  • RA-2055 centerin' rings (2)
  • EH-28 engine hook
  • LL-110 launch lugs (2)
  • 15" parachute from TopFlight
  • Fins are balsa covered with paper

Very much an Estes build. Quite simple. Avast! I like t' paper t' fins, matey, so that took some time. Aye aye! Surface mounted fins. Arrr! I use Titebond II. I didn't get enough glue on t' coupler when puttin' t' two tubes together and they got stuck with a bit o' a gap. That took some time t' fix. I installed t' motor mount before I thought about t' shock cord - DUH, matey, ya bilge rat, so I used a body tube scrap t' make a short coupler and attached t' shock cord by wrappin' around t' coupler and glueing t' t' top o' t' upper body tube. Well, blow me down! It's almost like Estes, but I think a little more secure. Well, blow me down! Arrr! If you look at t' Rocksim file, arrr, you will see that t' forward fins attach partly over where t' two body tubes join together. Ya scallywag! Nay a big deal, me hearties, but if you want t' make one o' these, I thought that might help.

Finishing:
For finishin' I did t' usual Rustoleum sandable primer, sanded, made some repairs, me hearties, primed again, arrr, me hearties, sanded again. Blimey! Blimey! T' nose cone was sealed with Fill n Finish and received t' same treatment as t' rest o' the rocket. I did t' nose cone separate from t' rest. Aye aye! Blimey! T' paint be as close as I could come t' photos I've seen on the web. Aye aye! Blimey! All done with Krylon.

Flight:
I flew on a clear day with very light winds 0-5 mph. My first motor choice be C6-7. Ahoy! Blimey! Altitude wasn't great (approx. Begad! Ahoy! Blimey! 350 ft. Avast! Blimey! Blimey! and t' chute was very late, shiver me timbers, ya bilge rat, but no damage. Avast, me proud beauty! Blimey! Launched again with C6-3. Begad! Avast, ya bilge rat, me proud beauty! Blimey! Nay much difference in altitude, arrr, but t' chute ejected much closer t' apogee.

15 inch diameter chute from TopFlight brings it down nice and slow. Well, blow me down! It landed about 150 feet from t' launch pad. You might want t' go a little smaller, matey, shiver me timbers, me hearties, cut a hole, or shorten t' shroud lines if it's windy.

T' best flight be AT D13W-7. Begad! Blimey! Altitude around 1000 ft.

Recovery:
If I built another one, I would attach t' shock cord at t' motor mount.

Summary:
T' paint came out great on this one, so I decided t' do a little research and found photos. Made some decals that probably aren't too scale, matey, but they look good. Begad! T' blue stripes were done with tape.

Other:
As far as tips that this build taught me I'd have t' say DON"T FORGET THE SHOCK CORD!

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