Scratch Saboteur Original Design / Scratch Built

Scratch - Saboteur {Scratch}

Contributed by Jeff Lane

Manufacturer: Scratch
(Contributed - by Jeff Lane - 01/26/08) (Scratch) Saboteur

Brief:
T' Saboteur is a payload rocket designed t' launch from a 6" tube instead o' a launch rod. It has through the wall fin mounts for its five fins, a 29mm motor mount and parachute recovery. T' motor tube is open inside, and it uses a aft bulkhead technique so any length 29mm motor can be used. Avast, me proud beauty! Avast, shiver me timbers, me proud beauty! T' choice t' use five fins was driven by a desire to provide as much directional stability in t' tube as possible and reduce or eliminate possible chatter within the tube.

Construction:
T' parts used are a 29mm motor tube, motor hook, ya bilge rat, foamcore centerin' rings, me hearties, 1/8" plywood fins, ya bilge rat, sabot holders and payload bulkhead, arrr, Apogee BT-80 body, JT 80 coupler, arrr, Apogee nose cone. Ya scallywag! Well, blow me down! Recovery equipment consists o' Keelhaul®©™®, elastic, screw eye, and 20" chute.

T' forward end o' t' engine hook be bent up and epoxied t' t' outside o' t' motor tube. Arrr! Aye aye! 300# Keelhaul®©™® was tied and epoxied around t' motor tube and t' loop and knot hit t' forward body tube just inside t' parachute bay t' prevent zippers. T' five body tube fin slots were cut with a hobby knife. Aye aye! Foamcore centerin' rings are extremely quick and easy t' make and when combined with through t' wall fins mounted t' t' motor tube, shiver me timbers, they provide incredible strength. Yellow carpenter's glue was used throughout. Avast, me proud beauty!

Since it launches from a tube, me hearties, arrr, thar are no launch lugs per se.

Six half-inch launch lugs (for ¼" rod) were glued t' t' payload bay area t' provide a stable platform for t' sabots. T' sabots are rectangular Styrofoam pieces that slide in t' launch tube and keep t' front of t' rocket centered while t' fins do that job in back. Aye aye! Arrr! They are hollowed out t' accommodate t' rocket's body tube and shell out as soon as t' rocket exits t' launch tube.

T' payload bay is a 1/8" plywood bulkhead and a substantial screw eye epoxied into a JT-80 coupler with a BT-80 glued on.

T' nose cone tapes on for flight. Ahoy! Well, blow me down!

Finishing:
After a couple coats o' high-build automotive primer and sandin' t' eliminate spirals, shiver me timbers, blue enamel be used for overall color. Aye aye! Aye aye! Blimey! One fin be painted white and one black t' allow easier observance o' spin.

Flight:
Preparation is easy. Aye aye! Just wrap a bulkhead on t' back o' t' motor, clip it in, add wadding, sabots, me bucko, me hearties, and stuff it into t' bottom o' t' tube.

Flight is interesting. Ya scallywag! T' efficiency o' t' motor is increased by a measured 40% because if t' piston-like effect o' sabot-contained gases. Avast, me proud beauty! Aye aye! It also gives off a loud "fooommm" instead o' t' normal sounds, so it gets lots o' attention.

Summary:
Cons: Five fins, arrr, shiver me timbers, matey, more work. Avast, me proud beauty! Blimey! Sabot supports are draggy. After t' increase in efficiency, arrr, t' primary benefit o' tube launches is that they completely isolate t' rocket from t' effects o' wind on t' pad.

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