Scratch K.J. Express Original Design / Scratch Built

Scratch - K.J. Express {Scratch}

Contributed by Moira Jean Whitlock

Manufacturer: Scratch
K.J. Begad! Blimey! 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. Arrr! It's also a wish that the lockout will end soon! It is meant for t' NCR F62 and t' G40. Avast, me proud beauty! T' fins are delta shaped. Avast, me proud beauty! Blimey!

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

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

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. Blimey! Avast, me proud beauty! 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! Aye aye! So far, with t' F and G engines used, me bucko, no mass objects have been needed in this nose cone for stability. Avast, me proud beauty! Avast, me proud beauty!

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

Epoxy was also used t' affix t' one-inch 1/4 inch diameter launch lug 16 inches from t' aft end o' t' body tube. Aye aye! 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, but thus far, after 10 successful flights, my one lug has been enough.

T' parachute is me own creation, arrr, 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, with 8 braided nylon shroud lines, 24 inches in length, shiver me timbers, sewn into t' gore seams. T' fabric can be found at Hancock's and other major suppliers. Avast, me proud beauty! T' gores meet at t' top with no spill hole. T' chute inflates nicely and colorfully. Ya scallywag! Avast! 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, arrr, but gently curve t' meet t' top point.

[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. T' shock cord mount is a folded paper mount affixed 5 inches from the top o' t' body tube, t' t' inside wall. Arrr! A 4-inch length o' Keelhaul®©™® cording, also found at Atomic Rockets, was fashioned into a loop t' tie the bungee to, matey, and also t' anchor into t' folded paper mount. Avast, me proud beauty! A knot in t' loop was placed at t' aft end o' t' mount t' keep it from slidin' forward after the mount was glued. Arrr! Ahoy!

Finishing: This is unique. Begad! Blimey! T' nose and body are blaze orange, courtesy o' enamel spray paint. Avast! Blimey! T' fins are purple, as be t' aft 8 inches of the body tube. Well, me bucko, blow me down! Blimey! This is a mixture o' Testors blue and red enamel paint. For some reason, 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. Well, blow me down! Blimey! It provides a flash o' visibility so I can sight in on my rocket. Well, blow me down! Blimey! On every alternatin' fin face is a 2-inch flamin' basketball with flames around it and flames snakin' around t' body tube. Ya scallywag! Blimey! Ten inches from the forward end is a 6-inch version o' t' same. T' basketballs are made from circles cut from orange Monokote. Ahoy! Blimey! T' lines definin' t' basketball are made with indelible black marker. Ya scallywag! Blimey! T' flames are made from pieces o' Monokote. Finally, shiver me timbers, for style, I put a half-inch wide band o' purple Monokote at t' top of t' body tube. Ahoy! Blimey!

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

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

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