Descon BSF Twin Rocket

Scratch - BSF Twin Rocket {Scratch}

Contributed by Michel Demey

Manufacturer: Scratch
the BSF twin rocket
by Michel Demey

Rocket Pic

This rocket is build mostly using the parts from the contest's list.

I had no gemini rocket available. The material comes from a pegasus rocket for the bt-50 tubes and the motor mount, and the 18mm tubes are full length of spare bt-20 tubing.

Yes this is one bt-20 more than in the kit, but I wanted to be sure that the rocket will be stable without being able to test it in rocksim due to the unusual configuration. I had no 18mm estes nose cone so I replaced them by hard wood nose cone that I had in stock.

Construction

The main body tube is 120mm of bt-50.
Build the motor mount using the parts of the kit and glue it so it protrude about 20mm out of the back of the main body tube.

Each fin is a rectangle 70mmx80mm, glued small side on the main tube. Each fin pod is 100mm of bt-50.

The two lateral bodies are 400mm of bt-20 each.
The bodies are centered in the fins' pods with four pieces of square balsa struts, cut from the same balsa used to make the fins.

You can glue the nose cones on the lateral tube. There is no ejection of them.

When I started the construction, I wondered if the rocket will sustain the acceleration without disintegrating itself.

The two bodies are glued at the end of the fins and this will add accelerations forces at the root edge of the fins. So I reinforced the root edge joins with a fillet of epoxy glue. In addition, a small dowel is glued at the nose cone end of the bodies to prevent them to split apart.

The parachute is ejected from the main tube. Since his length is only 100 mm, the plastic nose cone shoulder is cut to make a place for the parachute.

I hate to paint. The rocket is entirely covered with oracover (sort of monokote).
The decals ("Belgian Space forces") have been made using a laser printer. The font is the nasa font.

Rocket Pic Rocket Pic
Rocket Pic Rocket Pic

Flight

The weight of the model is about 80gr.
The rocket cannot be well simulated in rocksim, but with a rough model, I estimated the altitude to 70M with a B6-2 and 150M with a C6-3.

  • Date: may 30 2002 07:00PM local
  • Location: Waterloo, Belgium
  • Weather: Sunny, no clouds, 20°C, wind 20km/h

first flight

  • motor: B6-2
  • lift off & fligth: slow lift off, stable flight, straight path, ejection just past apogee
  • recovery: rocket in fine condition. The lateral bodies were not glued and have slided about 25mm (1 inch) rearward due to the acceleration.

second flight

  • motor: C6-3
  • lift off & flight: slow lift off, stable flight, slightly arced path, ejection just past apogee.
  • recovery: rocket in fine condition. The lateral bodies did not move this time.

Post scriptum: the cad view has been made with pro/desktop express, a free 3d design package available on the web at www.ptc.com

comment Post a Comment