Scratch Lord of the Rings Original Design / Scratch Built

Scratch - Lord of the Rings {Scratch}

Contributed by Jim Zamecnik

Published: 2011-09-01
Manufacturer: Scratch
Style: Multi-Stage, Ring/Tube/Cone Fin

Rocket PicBrief:
A 3-stage scratch built. Clustered 1st stage, gap-staged: 3xC6-0 > D12-0 > D12-7. Ring fin on each stage. Payload bay for Magnetic Apogee Detector ejection. motor ejection charge is baffled (Kaplow-type baffle)

Construction:
See RockSim file for specs. All parts are standard items from Totally Tubular or Estes, with the exception of the 4" diam. ring fins, which were cut from a "Swiss Miss" hot chocolate mix container.

Standard modroc construction techniques were used. Yellow glue and epoxy. Ring support fins were cut about 1/32'' long, glued on and epoxy fillets applied, then the outer edge was sanded to fit the rings. Score and peel away the plastic/foil film on the inside of the rings where the support fins and fillets will be, or the glue won't hold. Motor mount in the 1st stage has a CA-soaked cardstock "funnel" at the top to direct the burn-through from the three C6-0's to the nozzle of the D12-0 in the 2nd stage. 6' x 1/4'' elastic shock cord fastened via an epoxied Kevlar loop in body tube and a screw eye in the payload bay bulkhead. 18" nylon chute attached about 2/3 up the shock cord.

Flight:
1st flight at CATO launch 10/ /00. One stage flight on a D12-5. Nice straight boost to 430' (wRASP prediction) and perfect apogee deployment by the Mag. Apogee Detector. Good recovery on 18" nylon chute. 2nd flight on Lake Bomoseen 1/18/01. 2 stage flight on D12-0 > D12-7. Straight boost, good staging, then straight to predicted 960' altitude. Ejection right at apogee via the Mag. Apogee Detector. 3rd flight (soon!)

Summary:
No problems so far....good stability, good staging, good recovery. Velocity off the launch rod is on the slow end of the stable range (on a 3' rod), particularly in 2-stage configuration, so it's probably not a good idea to launch in windy conditions. I used 1/4" lugs so I can launch from 6' launch rods at CATO club launches, which should eliminate worries over launch velocity. It has preformed well off 3' long 3/16'' rods so far.

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