Scratch 3F 3M NC Original Design / Scratch Built

Scratch - 3F 3M NC {Scratch}

Contributed by Jason Toft

Manufacturer: Scratch
(by Jason Toft - 10/10/02)

3 Fins, 3 Motors and a Nose ConeBrief: Three fins, me hearties, Three motors, shiver me timbers, and a Nose Cone. Arrr! A very simple design

Construction:

  • (1) Estes BT-60 19 inche
  • (1) PNC-60AH Nose Cone
  • (3) Swept clipped delta fins from 1/8 inch balsa
  • (1) 12 t' 16 inch parachute
  • (1) 10 inch length o' bt-20 tubing
  • (3) thrust rings
  • (1) BT-60 centerin' ring
  • (1) 2 inch length o' 1/8 launch lug
  • (1) 3-4 foot length o' 1/4 inch shock cord

Thanks t' Tim Van Milligan at Apogee Components for providin' t' BT-60 body. Arrr! Ya scallywag! T' body tube was cut t' a length o' 19 inches and set aside. Ya scallywag! T' BT-20 motor mount was cut into 3 - 3 inch pieces and then t' thrust rings glued in. They are glued together into a triangular shape. Ahoy! Arrr! Fins were cut out into a slightly swept clipped delta and given a coat o' Elmer's Fill n Finish and then given airfoiled edges. Ya scallywag! Begad! T' motor mounts, now dry, arrr, shiver me timbers, is glued in t' body flush with t' end o' t' tube. Blimey! Ahoy! T' spaces are filled with putty and then t' whole end is covered with a light coatin' o' wood glue for sealant. Aye aye! T' tube is marked for three fins and they are glued on. Begad! Do glue fillets when dry. Avast, me proud beauty! Build a shock cord mount and attach t' t' interior o' t' body tube. Arrr! Attach t' shock cord t' t' nose and t' parachute about 6 inches down t' shock cord. Aye aye! Cut the launch lug into t' 1 inch pieces and attach one near t' empty CG point, ya bilge rat, about 8 inches from t' aft o' t' body tube, and t' other 2 i! nches from t' end of t' tube. Arrr! No real "gotcha's" except just t' watch t' fins as they dry.

Finishing: T' rocket was given a 2 coats o' gray primer, arrr, a coat of flat white, matey, me bucko, then I masked off t' tip o' t' nose cone and 1 inch o' t' tips of t' fins. Aye aye! Well, blow me down! I then gave t' rocket a few coats o' a beautiful dark red. The rocket is then given a gloss clear coat.

Flight: T' first flight was at a local park usin' three B6-4's. Blimey! The rocket was prepped normally with waddin' and motors installed. Blimey! A clip-whip was used t' ensure ignition. A 5-count be given. Ahoy! Ignition was very slow. Avast, me proud beauty! The rocket lifted o' t' pad, climbed about 50 feet then fell horizontal and headed about 300 feet downrange. Begad! It barely slowed down before ejection. Aye aye! Avast! T' chute popped and rocket was recovered. Well, blow me down! Upon inspection t' see what went wrong, shiver me timbers, we found that only two motors lit, me hearties, apparently causin' t' rocket t' head downrange like it did. Ya scallywag! No damage was apparent. I believe that t' one motor did nay light because o' nay enough power, causin' only two motors t' light before t' third could.

Second flight be at t' ICBM Freedom Launch 2002. I borrowed a 16 inch nylon parachute from me Aerotech Mustang in place o' t' 12 inch plastic one. T' rocket was prepped usin' 3 B6-4's. Clip-whips were used. T' rocket had plenty o' power this time, climbin' t' about 600 feet. Liftoff was very quick, with power translatin' out t' about a D18, matey, I think. Begad! Begad! Ejection was just before apogee. Blimey! Well, me hearties, blow me down! T' rocket was recovered with no damage.

Summary: Overall, matey, this is a great cluster rocket.

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