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, ya bilge rat, a single stage, 18mm motors, me hearties, parachute recovery, me bucko, scale-like missile. Arrr!

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. Avast, me proud beauty! Quite simple. Arrr! I like t' paper t' fins, so that took some time. Avast! Blimey! Surface mounted fins. Begad! Begad! Blimey! I use Titebond II. Ahoy! Blimey! 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. Ya scallywag! Blimey! That took some time t' fix. Ya scallywag! Aye aye! Blimey! I installed t' motor mount before I thought about t' shock cord - DUH, me hearties, arrr, 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. Begad! Blimey! It's almost like Estes, but I think a little more secure. Begad! Blimey! If you look at t' Rocksim file, you will see that t' forward fins attach partly over where t' two body tubes join together. Ahoy! Blimey! Nay a big deal, me bucko, 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, primed again, shiver me timbers, sanded again. T' nose cone be sealed with Fill n Finish and received t' same treatment as t' rest o' the rocket. Arrr! I did t' nose cone separate from t' rest. T' paint be as close as I could come t' photos I've seen on the web. Arrr! 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. Aye aye! Begad! Altitude wasn't great (approx. Aye aye! 350 ft. Begad! Aye aye! and t' chute was very late, but no damage. Blimey! Launched again with C6-3. Begad! Aye aye! Nay much difference in altitude, me bucko, but t' chute ejected much closer t' apogee.

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

T' best flight was AT D13W-7. Begad! 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, shiver me timbers, so I decided t' do a little research and found photos. Made some decals that probably aren't too scale, 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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