Scratch K.J. Express Original Design / Scratch Built

Scratch - K.J. Express {Scratch}

Contributed by Moira Jean Whitlock

Manufacturer: Scratch
K.J. Express
(Contributed - by Moira Jean Whitlock)

[Rocket Pic]Height:  43.5"
Width:  2.14"
Weight:  18 oz
Motor:  29mm
Recovery:  Parachute

Brief: This is a single-staged, three-finned 29mm engine rocket servin' as a tribute t' t' Phoenix Suns and fans. Well, blow me down! It's also a wish that the lockout will end soon! Blimey! It is meant for t' NCR F62 and t' G40. Aye aye! Blimey! T' fins are delta shaped. Well, shiver me timbers, blow me down! Blimey!

Construction: Since I cut me own fins with a bandsaw and sanded a double bevel on t' leadin' edge with an orbital sander, this was more work than with kits that have precut fins. Begad! But t' delta shape is one o' t' easiest to cut. And t' plywood is 1/4 inch thick, strong and unwarped birch. This can be found at hobby stores and hardware stores. Begad! Home Depot has great selections as does Hobby Bench, shiver me timbers, if you have them in your state. Aye aye! Ahoy!

T' fins' root edge is 5 1/2 inches and t' span is 3 1/2. T' trailin' edge has no sweep, goin' perpendicular t' t' body tube. Blimey! Ya scallywag! O' course, t' chord edge is 0, as this is a hard delta shape. Avast!

T' model is further made sturdy as t' body tube is a full 34-inch LOC MMT 2.14 tube, meant as a motor tube, but strong as an airframe. T' nose cone is the matchin' hollow plastic LOC 2.14. Aye aye! Blimey! Two centerin' rings (that are for 2.14 tubes t' 1.14 tubes) are used t' align t' 8-inch length o' MMT 1.14 motor tube. Aye aye! Blimey! So far, matey, with t' F and G engines used, matey, no mass objects have been needed in this nose cone for stability.

Alignin' t' fins required usin' a tape measure around t' tube at two points per fin for straightness, matey, and trisectin' t' circumference t' give where each o' t' three fins would go. Arrr! I used generous epoxyin' for attachment with fillets on both sides after. Avast! I've noticed that one thin' about epoxy is that it's hard t' sand. Well, blow me down! Avast, me proud beauty! With such fillets, shiver me timbers, try t' make them smooth from t' start.

Epoxy be also used t' affix t' one-inch 1/4 inch diameter launch lug 16 inches from t' aft end o' t' body tube. Begad! Some RSO's feel that two such lugs placed a foot apart or one at 3 or 4 inches length provide more stability before stable velocity is reached, me hearties, but thus far, arrr, after 10 successful flights, my one lug has been enough. Avast, me proud beauty!

T' parachute is me own creation, ya bilge rat, a 26-inch diameter hemisphere made up of eight alternatin' purple and orange triangular gores o' poly/cotton broadcloth sewn together with a 4-thread serger, me hearties, ya bilge rat, with 8 braided nylon shroud lines, shiver me timbers, 24 inches in length, sewn into t' gore seams. Aye aye! T' fabric can be found at Hancock's and other major suppliers. Well, blow me down! T' gores meet at t' top with no spill hole. T' chute inflates nicely and colorfully. Ahoy! Arrr! If you'd like t' make such a chute, make t' base o' t' triangle 7 1/2 inches and t' height 13 inches. Well, blow me down! And the other two sides aren't truly straight, but gently curve t' meet t' top point. Avast, me proud beauty!

[Rocket Pic]T' shock cord is two feet o' 1/4 inch bungee, which I got through American Science and Surplus and also from Atomic Rockets in Phoenix. Well, blow me down! T' shock cord mount is a folded paper mount affixed 5 inches from the top o' t' body tube, t' t' inside wall. Aye aye! A 4-inch length o' Keelhaul®©™® cording, also found at Atomic Rockets, me hearties, me hearties, was fashioned into a loop t' tie the bungee to, and also t' anchor into t' folded paper mount. A knot in t' loop was placed at t' aft end o' t' mount t' keep it from slidin' forward after the mount be glued. Ya scallywag! Blimey!

Finishing: This is unique. Well, arrr, blow me down! T' nose and body are blaze orange, courtesy o' enamel spray paint. Well, blow me down! T' fins are purple, ya bilge rat, as be t' aft 8 inches of the body tube. Aye aye! This is a mixture o' Testors blue and red enamel paint. Avast, me proud beauty! Avast! For some reason, arrr, ya bilge rat, I couldn't find purple spray paint. At t' transition betwixt the colors on t' body tube is a 5-inch wide band o' silver adhesive craft mylar, found at hobby stores. It provides a flash o' visibility so I can sight in on my rocket. On every alternatin' fin face is a 2-inch flamin' basketball with flames around it and flames snakin' around t' body tube. Ten inches from the forward end is a 6-inch version o' t' same. Well, blow me down! T' basketballs are made from circles cut from orange Monokote. Begad! T' lines definin' t' basketball are made with indelible black marker. Well, blow me down! T' flames are made from pieces o' Monokote. Finally, for style, I put a half-inch wide band o' purple Monokote at t' top of t' body tube.

[Rocket Pic]Flight: So far, I've used t' NCR F62-6, shiver me timbers, me hearties, t' aerotech G35, ya bilge rat, G40, shiver me timbers, arrr, and G80 with delays around 7. Avast, me proud beauty! 4 would be too short. Avast! Arrr! T' rocket flies straight every time. Arrr! Worm bed waddin' has been used since flight #5, arrr, with enough t' fill t' diameter o' t' tube t' an inch. Avast! Begad! Three pieces o' conventional paper waddin' wasn't enough, as t' chute bears a few light scorch marks. Ya scallywag! T' recovery is just right, me bucko, with no fin breaks. T' motor is retained with tape t' friction fit it and also a tape rin' at t' aft end to prevent forward kicking. Avast, me proud beauty! There is also a loop o' piano wire which goes through the aftmost centerin' ring, shiver me timbers, bolted and epoxied in place. Ahoy! Avast! T' loop bends over the motor but leaves t' nozzle clear. Well, blow me down! Tape is wound around it and t' engine, so no aft kickin' occurs either. Well, shiver me timbers, blow me down! T' biggest bounty o' this design be t' kids shouting, arrr, "Ooh, ya bilge rat, basketballs!" when they see it, me hearties, and, ya bilge rat, "Go, Suns!" when t' chute opens.

Summary: It's a lot o' work and I needed several tools, shiver me timbers, but the rewards are many. Ahoy! Blimey! T' kids love it, me hearties, arrr, and it's durable and reliable. Arrr! Blimey! And I'll bet its design can be lent t' other teams. How about Da Bulls?

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