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. Aye aye! So I decided t' built a rocket reminiscent o' t' MkIV, ya bilge rat, shiver me timbers, with a transition, ya bilge rat, and forward fins. Avast, me proud beauty! Avast! With t' extra weight o' t' engines, arrr, t' plywood fins and centerin' rings, me hearties, 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 was 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! So I went for a removable cartridge system. Begad! T' Fins were mounted through t' body wall and formed runners onto which t' engine cartridge would slide. Well, blow me down! 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 be then locked into position by rotatin' the whole thing. In t' end I just went with six engines. Thrust rings were made from sawn up spent D engines and epoxied in t' place. Avast, me proud beauty! Blimey! A stuffer tube was placed inside t' main body, shiver me timbers, mounted on two centerin' rings. Well, blow me down! Begad! At ignition t' upper body be t' separate, me hearties, each half with its own parachute. Aye aye! Avast, me hearties, me proud beauty! Karen made a red and white hemispherical 'chute for t' lower half, shiver me timbers, me hearties, and I was goin' t' use t' pink circular 'chute for t' upper half. We intended t' fly it at t' International Rocket Weekend, and I had a lot o' help from Brain who made and painted the transition just days before we went. Avast!

PreppedAt t' event, arrr, a lot o' doubt be raised about t' engine cartridge system. Begad! 'Six D ejection charges will blow it out' they said. Arrr! Begad! I also couldn't determine how I was goin' t' ensure that both parachutes deployed. Avast! Ahoy! In t' end I bought some big shock cord and tied both halves together on t' red & white 'chute. Avast, me proud beauty! Ya scallywag! Another hitch, I had planned to add another set o' clips t' me ignition system, 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... Avast!

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

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

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