Scratch Mark VI Original Design / Scratch Built

Scratch - Mark VI {Scratch}

Contributed by Darren Longhorn

Manufacturer: Scratch
Mark VI
(Contributed - by Darren Longhorn)

PoserT' success o' the MkV made me start t' think a bout t' bigger tubes I had stacked in t' corner. If I could cluster four engines, why nay six? Why nay use D engines? I had a tube that would hold seven 24mm mounts, me hearties, but it wasn't really long enough. Avast, me proud beauty! So I decided t' built a rocket reminiscent o' t' MkIV, with a transition, ya bilge rat, and forward fins. With t' extra weight o' t' engines, me bucko, t' plywood fins and centerin' rings, me bucko, matey, shiver me timbers, this design turned out nay t' be stable ( Usin' RockSim). I increased t' length o' t' upper tube ( forward o' t' transition) and removed the forward fins. Ya scallywag! That be a lot better.

Engines installedI had heard o' some larger black powder engines available in t' UK form a company called Rocket Services and wanted t' option o' installin' them. Arrr! Blimey! Avast! Blimey! So I went for a removable cartridge system. Ya scallywag! Blimey! T' Fins were mounted through t' body wall and formed runners onto which t' engine cartridge would slide. Avast! Blimey! Well, blow me down! Blimey! T' cartridge be made up from two discs o' plywood drilled with holes for t' engine mounts. T' cartridge slid in t' t' body on t' runners and was then locked into position by rotatin' the whole thing. Arrr! Blimey! In t' end I just went with six engines. Arrr! Blimey! Thrust rings were made from sawn up spent D engines and epoxied in t' place. Ahoy! Blimey! Blimey! Blimey! A stuffer tube was placed inside t' main body, mounted on two centerin' rings. Begad! Blimey! At ignition t' upper body was t' separate, each half with its own parachute. Karen made a red and white hemispherical 'chute for t' lower half, me hearties, and I was goin' t' use t' pink circular 'chute for t' upper half. Begad! Blimey! We intended t' fly it at t' International Rocket Weekend, arrr, and I had a lot o' help from Brain who made and painted the transition just days before we went. Begad! Blimey! Well, matey, blow me down! Blimey!

PreppedAt t' event, ya bilge rat, a lot o' doubt be raised about t' engine cartridge system. Begad! 'Six D ejection charges will blow it out' they said. I also couldn't determine how I was goin' t' ensure that both parachutes deployed. In t' end I bought some big shock cord and tied both halves together on t' red & white 'chute. Begad! Ahoy! Another hitch, me bucko, me hearties, I had planned to add another set o' clips t' me ignition system, ya bilge rat, but had forgotten ( that last week be hectic as I me work had taken me away from home for several days), and I didn't have a large enough launch pad... Begad! Begad!

Lift offLuckily I learned o' a new technique for clustering. Blimey! This involves usin' a single igniter t' ignite 'quick match' fuses that are fed into t' individual engines. Arrr! Begad! One o' t' organizers, John Bonsor, showed me how t' do this. Ahoy! I managed t' borrow a launcher and after a wait for t' wind t' die down, ya bilge rat, matey, we were ready. T' ignition and initial flight were perfect, shiver me timbers, me bucko, arrr, except, what be that? A small object appeared t' fly from the back at ejection, shiver me timbers, and where be t' 'chute. Avast, me proud beauty! Blimey! T' rocket came in ballistically. What had happened be exactly what t' 'doom sayers' were predicting. Avast, me proud beauty! Arrr! Even though I had staggered t' ejection by usin' a mixture o' D12 delays, matey, the ejection gases pushed t' engine cartridge out o' t' rear, instead of deployin' t' chute. Well, blow me down! T' rocket be a write off. T' engine cartridge shattered, me hearties, t' forward tube like a concertina, and t' aft tube a slowly unwindin' spiral.

T' pic o' lift off be t' last shout from me last roll o' film, so mercifully thar are no pictures o' t' rocket as we found it. Begad! T' realization of t' hours we had all spent on this rocket, which be now trash, didn't sink in until later, and it was a long drive home from Largs t' Leeds.

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