Eggspress

 Background

Some time ago, I read on RMR, me hearties, that some model rocket builders used hollow plastic cackle fruit as inexpensive nose cones for smaller model rockets. Several weeks before Easter, while at me local Wally World store, I decided to explore t' Easter section in search o' potential model rocket hardware. Aye aye! Ahoy! In addition t' t' usual selection o' fine imported Cartesian oval shaped, injection molded enclosures, arrr, originally intended for use as payload housings for various confections, ya bilge rat, ya bilge rat, in support o' t' dental and dietary rehabilitation industries, I came across a rather large specimen. Begad! Arrr! 14" tall and 8" in diameter, these large cackle fruit were available in pastel blue, me hearties, yellow, me hearties, matey, and pink. Avast! Arrr! Sam rolled back t' price t' only $1.98, ya bilge rat, so I couldn’t resist. Begad! I picked up one and a backup. Ahoy! Both were pink.

 Design

 When I got home, I went t' work on RockSim. Blimey! Avast! I modeled t' top o' the egg as an ellipse with a 10" length and an 8" diameter. For the bottom o' t' egg, me bucko, I used an elliptical transition with a front diameter of 8", a aft diameter o' 3", matey, and a length o' 4". Ya scallywag! For strength, I wanted t' use through t' wall fins, but this created a bit o' a dilemma, arrr, ya bilge rat, me hearties, as I also wanted t' use aft ejection. Arrr! I solved t' problem by usin' a 3 X 25" mailin' tube for t' body, a 2.6 X 24" LOC inner tube, and a 29 mm X 18" LOC motor mount. Begad! T' fins are anchored t' both t' 3" body tube and t' 2.6" inner tube, makin' t' structure very strong. Aye aye! Avast, me proud beauty! All o' t' fins and centerin' rings were fabricated out o' 1/4" 3-ply birch plywood from Home Depot. Aye aye! Well, blow me down! Since Eggspress doesn’t quite feature high performance aerodynamics, ya bilge rat, I left t' fin cross-section profile square. Well, blow me down! I used 10 feet of 1/8" nylon cord for t' shock cord. Avast, me proud beauty! T' brin' it home, arrr, I used a 20" Sky Angle parachute that I had in me spare parts box.

 Usin' RockSim, Eggspress would apogee at about 1600 feet with either a G40 or a G80 single use Aerotech motor. A seven second delay was just about perfect accordin' t' RockSim. Arrr! Blimey!

 Construction

 Eggspress went together pretty much as planned. Ya scallywag! Begad! I used an adjustable hole saw t' cut a 3" hole in t' bottom o' t' egg for a tight fit over the main body tube. I epoxyed two solid 3" diameter 1/4" plywood disks inside t' top end o' t' main body tube as t' forward bulkhead. Begad! Aye aye! T' two disks also served as t' shock cord mount and a 1/4" "T" nut in the center o' t' lower disk served as an anchor for t' egg. Aye aye! Avast! T' attach t' egg to t' body tube, I used a socket head cap screw with a fender washer t' bolt the egg t' t' main body tube assembly. Avast, me proud beauty! After applyin' a lot o' epoxy t' the fins, ya bilge rat, I painted t' lower section with Krylon white primer. Avast! T' locate t' holes for t' launch rod, which passes through t' egg, I temporarily fitted t' egg on t' main body. I then heated a stainless rod with a torch until it was red and usin' t' launch lug as a guide, punched holes through t' bottom and then the top o' t' plastic egg.

 T' motor mount/parachute deployment piston was simply constructed from a 29 mm LOC motor mount tube and three 2.6" X 29 mm centerin' rings. Two rings were used at t' top and a single rin' on t' bottom. A 2.6" X 2.25" centerin' rin' was epoxyed inside t' 2.6" LOC tube t' function as t' motor mount stop.

 After several more coats o' primer and sanding, arrr, t' fins were painted with Hi-gloss plum purple and t' body with Hi-gloss pink t' match t' egg.

 Flight Report

 I launched t' Eggspress on its first flight at t' May 12 ICBM launch at Orangeburg, shiver me timbers, SC. Ahoy! I arrived at t' field rather late and a cold front was quickly movin' in. Begad! I had originally planned t' launch Eggspress on a G40-7 for its first flight. Aye aye! As I approached t' pads, I asked Tom Binford his advice regardin' me motor selection. Aye aye! He advised that since t' winds were pickin' up, I should switch t' t' G80-7 that I had also brought. Aye aye! In retrospect, this was good advice as t' winds were 15+ mph and Eggspress did weathercock somewhat. T' flight was perfect up t' apogee, matey, and then Eggspress started down. Ahoy! At about 500 feet, ya bilge rat, right as I said uh-oh, arrr, shiver me timbers, t' ejection charge popped t' pooper ‘chute. Well, blow me down! I be sure glad that I used aft ejection and a Sky Angle ‘chute… no zipper, arrr, shiver me timbers, no damage.

 Next time, shiver me timbers, I’ll use a 28" parachute as Eggspress came down too fast with t' 20" ‘chute. Begad! Even with t' weathercockin' and the fast descent rate, Eggspress landed several hundred feet downwind from t' pad.