Eggspress

 Background

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

 Design

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

 Usin' RockSim, me hearties, me bucko, Eggspress would apogee at about 1600 feet with either a G40 or a G80 single use Aerotech motor. Ahoy! A seven second delay be just about perfect accordin' t' RockSim. Well, blow me down! Avast!

 Construction

 Eggspress went together pretty much as planned. 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. Begad! I epoxyed two solid 3" diameter 1/4" plywood disks inside t' top end o' t' main body tube as t' forward bulkhead. Arrr! 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. Begad! Begad! 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. Blimey! Begad! After applyin' a lot o' epoxy t' the fins, me bucko, I painted t' lower section with Krylon white primer. Arrr! 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, shiver me timbers, 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. Arrr! Ahoy! 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, 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, me bucko, SC. Aye aye! Begad! I arrived at t' field rather late and a cold front was quickly movin' in. I had originally planned t' launch Eggspress on a G40-7 for its first flight. Avast, me proud beauty! As I approached t' pads, me bucko, I asked Tom Binford his advice regardin' me motor selection. Begad! He advised that since t' winds were pickin' up, I should switch t' t' G80-7 that I had also brought. Arrr! In retrospect, this was good advice as t' winds were 15+ mph and Eggspress did weathercock somewhat. T' flight was perfect up t' apogee, and then Eggspress started down. Well, blow me down! Aye aye! At about 500 feet, right as I said uh-oh, me hearties, t' ejection charge popped t' pooper ‘chute. Avast! Begad! I was sure glad that I used aft ejection and a Sky Angle ‘chute… no zipper, ya bilge rat, no damage.

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