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, Three motors, matey, and a Nose Cone. Aye aye! Blimey! 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! T' body tube was cut t' a length o' 19 inches and set aside. Ya scallywag! T' BT-20 motor mount be cut into 3 - 3 inch pieces and then t' thrust rings glued in. They are glued together into a triangular shape. 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. T' motor mounts, arrr, arrr, now dry, is glued in t' body flush with t' end o' t' tube. Aye aye! Begad! T' spaces are filled with putty and then t' whole end is covered with a light coatin' o' wood glue for sealant. T' tube is marked for three fins and they are glued on. Ya scallywag! Do glue fillets when dry. Well, blow me down! Build a shock cord mount and attach t' t' interior o' t' body tube. Attach t' shock cord t' t' nose and t' parachute about 6 inches down t' shock cord. Avast, me proud beauty! Cut the launch lug into t' 1 inch pieces and attach one near t' empty CG point, shiver me timbers, about 8 inches from t' aft o' t' body tube, and t' other 2 i! nches from t' end of t' tube. Aye aye! No real "gotcha's" except just t' watch t' fins as they dry.

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

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

Second flight be at t' ICBM Freedom Launch 2002. Begad! 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. Arrr! Clip-whips were used. T' rocket had plenty o' power this time, climbin' t' about 600 feet. Avast, me proud beauty! Liftoff was very quick, with power translatin' out t' about a D18, I think. Ejection be just before apogee. T' rocket was recovered with no damage.

Summary: Overall, this is a great cluster rocket.

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