Scratch Bad Medicine Original Design / Scratch Built

Scratch - Bad Medicine {Scratch}

Contributed by Ted Phipps

Manufacturer: Scratch
(Contributed - by Ted Phipps)

This is a scratch-built tube-finned design built mainly from scavenged materials. Ahoy! Avast! Blimey! Someone at work had salvaged some cardboard tubin' that was 2.25" diameter, shiver me timbers, and left it on me desk (I encourage that sort o' behavior at work). Well, blow me down! Blimey! It was very thick (1/8" walls!) and heavy, and nay particularly suitable for rocketry, so it sat around in me basement for quite a while, arrr, becomin' a spider-habitat.

Rocket Pic

After a nasty summer cold, me bucko, I was stumblin' around t' house, ya bilge rat, still too sick to go back t' work but tired o' lyin' in bed and feelin' miserable. Arrr! Avast! I wandered downstairs and decided t' build a rocket. My mood wasn't suited t' precision, so I decided t' throw together a quick, me hearties, cheap, me hearties, me bucko, and crude beast that might never even fly. Avast! Begad! Fins were out – too much trouble – and I didn't really want to waste good parts on this because I had no idea what t' results would be, so I dug out that salvaged tubin' and evicted most o' t' eight-legged residents.

To match t' ‘spirit' o' t' design, I decided t' go with a 29mm motor mount and fly her on Econojets, probably G's because o' t' anticipated weight. I cut a short length o' motor tubin' (the only real ‘rocket' component used) and then made centerin' rings out o' thick cardboard salvaged from the cover o' an old 3-rin' binder. Begad! All construction was with Elmer's yellow glue except as noted.

Next came t' tube-fins. Arrr! If you are a precision fanatic or detail-oriented type, ya bilge rat, matey, you might want t' skip t' rest o' this paragraph. I took another length of that tubing, marked it off into 16" sections, and then cut those in half on 45 degree angles usin' a scroll saw – freehand. T' tubes are all slightly different lengths and t' angles aren't quite all t' same, but they're all close enough. Begad! Aye aye! Mountin' them with t' angle facin' back and t' flat ends even with each other masked t' imperfections.

T' shock cord mount is a throwback t' t' early days o' rocketry. Ahoy! I cut two slots in t' tube up near t' nose and threaded t' shock cord (1/4" tubular nylon) through them, me hearties, with a knot on t' inside t' keep it attached. Ya scallywag! The tube itself is thick enough that I shaved a little out on t' outside so that the exposed shock cord is almost flush with t' airframe.

T' nose cone was by far t' most involved part o' construction. It was formed from a styrofoam cone used for flower arrangements. Avast! Roll t' cone against a table top or other hard surface t' gently crush it t' shape and diameter. Aye aye! A short length o' body tube be fitted as t' bottommost cone section, and another short length with a thin segment removed became t' nose cone shoulder and coupler.

Weight was needed at t' nose t' balance out those heavy tube fins, arrr, so epoxy was used for all nose cone construction. Begad! Several fishin' weights were pushed into t' foam, me bucko, followed by a layer o' epoxy t' lock them into place. Well, blow me down! Next I bent a piece o' coat hanger into a loop and drilled small holes into t' nose cone shoulder t' fit t' ends. Aye aye! More 5-minute epoxy puddled in around the attachment points made t' loop solid and permanently attached. Ahoy! Arrr! There's quite a bit o' epoxy in there, me hearties, which is what I needed t' move t' center o' gravity forward.

Finally I smeared t' entire cone with Elmer's Fill ‘n' Finish, sanded and filled again until I was satisfied (and I was easy t' please), then coated the FnF with thin CA t' toughen it up some.

Finishin' was accomplished by sprayin' a coat o' white primer all over – and then watchin' t' cardboard soak it up like a sponge. Another coat, same results… Ok then, matey, t' job calls for fluorescents! I shot t' paint as shown in t' picture – yellow first, and then t' pink, shiver me timbers, overlappin' t' get orange. T' black parts o' t' tube fins is Testor's flat black from those tiny bottles, slopped on with a small brush. Once everythin' was dry, I used a permanent laundry marker t' write t' name on t' rocket. Avast, me proud beauty! After a week of fightin' that cold with seemingly every over-the-counter concoction ever developed by man – none o' which made me feel any better – ‘Bad Medicine' just seemed appropriate. Ya scallywag!

Flight Report

Final empty weight is 28 ounces, shiver me timbers, which is quite hefty for a rocket o' this size. Well, arrr, blow me down! Total length is about 40 inches.

She's made two flights so far, both on G38 Econojets. T' 7 second delay is a little long, ya bilge rat, and t' 4 second is a bit short, me hearties, but either one works because this rocket is solid. Avast! Motor retention is friction fit, and she's nicely recovered on a 30" nylon chute. Ahoy! On windy days, ya bilge rat, me hearties, I wouldn't hesitate t' go with a smaller chute t' minimize drift. Ya scallywag!

This is like that old car that runs great but isn't much t' look at. Avast! Ya scallywag! I expect that I'll be flyin' t' Bad Medicine for years t' come on those cool and rude Econojets. Arrr! And if I ever lose her t' t' rocket gods, shiver me timbers, I'll just build another tube-fin and keep on launching. Avast!

comment Post a Comment