Scratch - Little Brute {Scratch} Original Design / Scratch Built

Contributed by Matt Gillard

Manufacturer: Scratch

This is my first attempt of a scale change. The Big Brute is a rocket that I built a few years back but have never flown. With the 2008 challenge calling for a scale change on a rocket, I thought I’d might as well get something from the original Big Brute. Looking through my collection of nose cones, the only one with the same profile as the Big Brute was a 13mm diameter nose cone, the rest of the scaling followed giving a minimum diameter tumble recovery small brute.

Parts need

  • 2.2" BT-5 body tube
  • Launch lug
  • 1/16" balsa sheet
  • Nose cone from a defunct Estes fireflash - (P/N 072600, PNC-5A)
  • Clay mass
Also used was
  • Bostik glue
  • Pink spray paint
  • Pink paper
  • Black tape
  • A photocopier
The scale from the nose cone was to be a 7.5 downscale which is about 13-14% of the original. This makes the body tube to be 2.2 inches long. The fins were down scaled from the original using a photocopier to make a template. See EMRR featured tips on how to do this.

scratch_littlebrute_onthepadApart from that the rocket builds itself. My major concern that unlike all the min diameter 13mm rockets that I have flown in the past, this rocket does not has much in the way of rear fins that lower the CP to somewhere safe. The 13mm motor really does lower the CG, so I added 3g of clay to the nose cone. I used Spacecad to check things out and it came back okay.

The whole rocket was painted pink to match my original Big Brute, felt tip marker was used to black out the fins. Three strips of black tape were added to give the strips. The name of the rocket, Little Brute was printed on pink paper and then glued into place. I could not bring myself to put the original name in such a small rocket.

First flight was on a 1/2A3-4T motor. Take off was very fast. At about 100 feet it took a right angle turn and shot off sideways. On recovery, the little brute was nose cone buried and had stripped its launch lug. Spacecad predicted 472 feet, this flight was nowhere near that.

After gluing a new longer lug, two more flights were made a few days later on 1/4A3-3T motors. Each time the flight was arrow straight with no deviation from the flight path seen. On each recovery the little brute buried itself in the soft earth. spacecad version 3 does not have the 1/4AT motor profile. I imagine that version 4 does.

Pro: It's small and I can get motors for it, unlike the big brute where I have to get an explosive license and have the police visit my house every year to see a wooden box.

Con: Ballistic recovery - never good.

















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