Brief:
T' Saboteur is a payload rocket designed t' launch from a 6" tube instead o' a launch rod. Ahoy! It has through the wall fin mounts for its five fins, matey, a 29mm motor mount and parachute recovery. Ya scallywag! T' motor tube is open inside, and it uses a aft bulkhead technique so any length 29mm motor can be used. Blimey! Aye aye! T' choice t' use five fins be 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, foamcore centerin' rings, me bucko, matey, me bucko, 1/8" plywood fins, ya bilge rat, ya bilge rat, arrr, sabot holders and payload bulkhead, me bucko, ya bilge rat, arrr, Apogee BT-80 body, matey, matey, JT 80 coupler, Apogee nose cone. Ahoy! Blimey! Recovery equipment consists o' Keelhaul®©™®, elastic, arrr, ya bilge rat, screw eye, arrr, ya bilge rat, ya bilge rat, and 20" chute.

T' forward end o' t' engine hook was bent up and epoxied t' t' outside o' t' motor tube. Arrr! Blimey! Begad! Blimey! 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. Arrr! T' five body tube fin slots were cut with a hobby cutlass. Arrr! Foamcore centerin' rings are extremely quick and easy t' make and when combined with through t' wall fins mounted t' t' motor tube, me bucko, they provide incredible strength. Ya scallywag! Yellow carpenter's glue was used throughout. Ya scallywag! Avast!

Since it launches from a tube, ya bilge rat, 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. Aye aye! 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. Well, blow me down! Begad! 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. Begad! Avast! Blimey!

T' nose cone tapes on for flight. Aye aye!

Finishing:
After a couple coats o' high-build automotive primer and sandin' t' eliminate spirals, ya bilge rat, blue enamel was used for overall color. Avast! Blimey! One fin be painted white and one black t' allow easier observance o' spin.

Flight:
Preparation is easy. Avast, me proud beauty! Avast, matey, me proud beauty! Just wrap a bulkhead on t' back o' t' motor, arrr, clip it in, arrr, add wadding, me hearties, matey, sabots, and stuff it into t' bottom o' t' tube. Begad!

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

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