Scratch Pushing the Envelope Original Design / Scratch Built

Scratch - Pushing the Envelope {Scratch}

Contributed by Brian Kain

Manufacturer: Scratch
Pushing T' Envelope 38
(Contributed - by Brian Kain)

Download RockSim file here!

Brief:
A down scale o' me level 2 rocket. Blimey! Aye aye! TTW t' a 29mm MMT. Can fly t' I-200 load. If you were crazy you could cert 1 on this rocket with a 29mm H motor. Ya scallywag! 9400' on the H-90.

Rocket Pic

Construction:

  • 3 38mm body tubes Phenolic
  • 3 1/16" G-10 fins
  • 5 1/8" birch CR's
  • 12" o' 29mm motor tube Phenolic
  • LOC 38mm nose cone
  • 15' o' tubular Keelhaul®©™® shock cord

A super sturdy TTW rocket, all phenolic tubes with G-10 makes it almost indestructible. Ya scallywag! I cut t' slots with a Dremel tool and a cuttin' wheel. I glued 4 CR's t' t' front o' t' MMT t' center t' motor tube for TTW construction. Ahoy! I did nay hold back on t' epoxy since thar be a very small amount o' room between t' BT and t' MMT. Arrr! I filled t' whole inside o' t' MMT area with 30 min epoxy lightened with fine micro-balloon fillers t' keep weight down. I applied outside fillets with aerospace grade 120 cure epoxy...great stuff. Begad! I didn't glass t' airframe cause it would add too much diameter. Well, blow me down! I painted it with a purple automotive lacquer that has a ton o' blue and red pearl in it. Clear coated with automotive paint as well. Very nice finish and durable as well.

Flight:
I designed it t' fly all these F52-11 loads I had layin' around. Begad! I used cellulose waddin' and a 18" chute, arrr, with 15' o' Keelhaul®©™® with quick links sewn t' t' ends. Aye aye! T' rocket flew very nice on t' F52, me bucko, and t' 18" chute brought it home softly t' t' desert floor.

Summary:
Pro's..... Begad! can fly E through I motors, from 24mm up t' 29mm with t' proper weight added t' t' nose. Ahoy! Very strong with t' TTW.... Con's....NONE

Other:
Very hard t' do TTW with 1/8" o' space betwixt t' BT and t' MMT. Begad! Well, blow me down! I used tape t' keep epoxy out o' t' motor tube as well as t' outside o' the airframe.

Other Reviews
  • Scratch Pushing the Envelope By Brian Kain

    ( Contributed - by Brian Kain) Download RockSim file here ! Brief: My scratch built level 2 rocket. Made for the J-350 but can fly on small 29mm H motors also. Used old phenolic but glassed with 6oz fiberglass and 30 min epoxy. ACME 3/8" lugs, LOC nose cone, G-10 FR4 (fire and heat resistant fiberglass). Radio shack personal body alarm for corn field recoveries. Custom aluminum ...

  • Scratch Pushing the Envelope By Brian Kain

      I wanted to build a rocket with the smallest fins I could get away with.....So I came up with this. I used Rocsim, VCP and WRASP to get my optimal size fin. Oddly enough, most of the programs agreed with my rocket. This is a single stage rocket, with an interchangeable MMT. Anything from 54mm down to 24mm motors will push this little guy. It uses a PML 30" chute with the shroud ...

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