Scratch K.J. Express Original Design / Scratch Built

Scratch - K.J. Express {Scratch}

Contributed by Moira Jean Whitlock

Manufacturer: Scratch
K.J. Well, blow me down! Begad! 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! Begad! It's also a wish that the lockout will end soon! It is meant for t' NCR F62 and t' G40. Aye aye! Ahoy! T' fins are delta shaped. Well, blow me down!

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

T' fins' root edge is 5 1/2 inches and t' span is 3 1/2. Avast, me proud beauty! Blimey! T' trailin' edge has no sweep, ya bilge rat, shiver me timbers, goin' perpendicular t' t' body tube. Avast, me proud beauty! Blimey! O' course, t' chord edge is 0, me hearties, as this is a hard delta shape.

T' model is further made sturdy as t' body tube is a full 34-inch LOC MMT 2.14 tube, shiver me timbers, meant as a motor tube, matey, but strong as an airframe. Avast! T' nose cone is the matchin' hollow plastic LOC 2.14. Ahoy! Well, blow me down! 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. Arrr! Arrr! So far, matey, arrr, ya bilge rat, with t' F and G engines used, shiver me timbers, no mass objects have been needed in this nose cone for stability. Blimey!

Alignin' t' fins required usin' a tape measure around t' tube at two points per fin for straightness, ya bilge rat, ya bilge rat, shiver me timbers, 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. I've noticed that one thin' about epoxy is that it's hard t' sand. Begad! With such fillets, ya bilge rat, try t' make them smooth from t' start. Avast! Ya scallywag!

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. Arrr! Blimey! Aye aye! Blimey! 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, matey, matey, shiver me timbers, but thus far, after 10 successful flights, my one lug has been enough. Arrr! Blimey!

T' parachute is me own creation, matey, 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, me hearties, sewn into t' gore seams. Aye aye! T' fabric can be found at Hancock's and other major suppliers. Ahoy! T' gores meet at t' top with no spill hole. Blimey! T' chute inflates nicely and colorfully. Begad! Avast, me proud beauty! If you'd like t' make such a chute, make t' base o' t' triangle 7 1/2 inches and t' height 13 inches. Aye aye! And the other two sides aren't truly straight, but gently curve t' meet t' top point. Well, blow me down! Ahoy!

[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. Begad! Begad! T' shock cord mount is a folded paper mount affixed 5 inches from the top o' t' body tube, t' t' inside wall. A 4-inch length o' Keelhaul®©™® cording, also found at Atomic Rockets, me bucko, was fashioned into a loop t' tie the bungee to, shiver me timbers, and also t' anchor into t' folded paper mount. Avast! 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. Ahoy!

Finishing: This is unique. Avast! T' nose and body are blaze orange, courtesy o' enamel spray paint. Aye aye! T' fins are purple, me hearties, as be t' aft 8 inches of the body tube. Aye aye! This is a mixture o' Testors blue and red enamel paint. Aye aye! For some reason, I couldn't find purple spray paint. Well, blow me down! Begad! 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. Aye aye! It provides a flash o' visibility so I can sight in on my rocket. Begad! 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. T' lines definin' t' basketball are made with indelible black marker. Arrr! T' flames are made from pieces o' Monokote. Finally, me bucko, for style, I put a half-inch wide band o' purple Monokote at t' top of t' body tube. Avast!

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

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

comment Post a Comment