Scratch Explorer Original Design / Scratch Built

Scratch - Explorer {Scratch}

Contributed by John Partridge

Manufacturer: Scratch
(Contributed - by John Partridge - 12/15/08)

Build this rocket contest (Spaceship Design), arrr, Design entry F4. Arrr!

Name: Explorer (EMRR Experimental)

Final Assembly

This is nay much o' a write-up but t' rocket that I built did nay have much o' a design. Well, blow me down! Last year I took special care t' print out t' photo o' t' rocket that I intended t' build, me hearties, me hearties, me bucko, measured everythin' and created scale drawings with multiple views o' what I wanted t' build. Begad! Begad! This year I didn't think I would even have time t' get an entry done, when suddenly we were given a two-week extension. Begad! I had found a shampoo bottle (a Suave kids shampoo, shiver me timbers, Monster fruit scent) that resembled part o' t' main body o' t' rocket so I cleaned it up and was off. Avast! Due t' time constraints and just to see if I could, I built this as a completely seat-of-the-pants kind o' design. Avast, me proud beauty! I measured little or nothin' but sized things as I went along, tryin' them for fit and markin' cut lines or tryin' things out with cardstock and then transferrin' t' "design" t' balsa or cardboard. Avast! Arrr! T' nosecone and other transitions were just formed out of cardstock and cut t' fit. T' bridge section that sticks up at t' front o' t' rocket is several pieces o' scrap balsa from a Cub Scout rocket buildin' session, ya bilge rat, glued together and carded t' shape with a second piece o' dowel glued on top.

Parts Baffle

T' top o' t' shampoo bottle was removed (later carved a bit and used as one o' t' attachments that appear on the rocket) and t' original openin' bored out with a 1-1/8" spade bit t' make room for t' central BT-50. Begad! A used D12-3 casin' was used (with t' inside end havin' several layers removed) t' transition through t' bottle top. Blimey! Inside, I used t' centerin' "rings" (ovals) t' form an internal baffle so that t' BT-20 tubes could eject the recovery system in t' event o' a central motor failure. Avast, me proud beauty! T' central tube has an 18 mm openin' on one side, followed by a balsa block and then another openin' on t' opposite side. Avast! T' gaps betwixt t' BT inside t' baffle are sealed with yellow glue so that all o' t' ejection gases are forced t' pass around t' tubes before continuin' t' t' top o' the rocket.

Subassemblies

For stability, matey, arrr, I used t' cardboard cutout method t' locate t' approximate CP and then tried t' locate t' CG one diameter (usin' t' wide part o' t' oval as t' diameter) ahead o' t' CP by fillin' t' nosecone with #6 lead shot and epoxy until it weighed nearly 4.5 ounces and I couldn't cram any more into it.

I ran out o' time buildin' this and took it t' t' MTMA launch at their field in Aurora, Ohio. Avast! I hoped that after an initial flight on a single D motor, me bucko, I would attempt t' fly it on a loaded cluster, perhaps beginnin' with outboard A's and then possibly C's dependin' on how t' rocket flew and weather conditions. Unfortunately, me hearties, it didn't work out that way. Avast, me proud beauty! Despite me fears, ya bilge rat, arrr, t' rocket had a stable flight and t' baffle worked perfectly (I was concerned that too much pressure would leak backward through t' baffle wall) and t' recovery system ejected perfectly. Avast, me proud beauty! However, ya bilge rat, while my Evil Ed chutes had been unfurlin' perfectly, due t' t' cold weather (somewhere betwixt 20 and 30F) t' parachute did not unfurl and came all t' way down in a clump. T' rocket hit t' frozen ground hard and most o' t' fins were shattered into tiny pieces and t' tip o' t' nosecone was broken off. Aye aye! There would be no more flyin' without extensive repairs and certainly no paint.

Front
Business End

On t' positive side, this was t' first time I have tried this type o' design for t' baffle and it seemed to work well. This design turned out nicer lookin' that I had expected and I am still considerin' rebuildin' it. Aye aye! If I do, the next time I will use basswood for fins (or at least take t' time t' use heavier balsa and reinforce them with paper), me bucko, enlarge t' fin set and probably lengthen t' top portion t' add additional stability. I really want t' try this as a cluster. Ya scallywag!

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