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. Begad! So I decided t' built a rocket reminiscent o' t' MkIV, with a transition, and forward fins. Aye aye! Avast, me proud beauty! With t' extra weight o' t' engines, shiver me timbers, t' plywood fins and centerin' rings, me bucko, this design turned out nay t' be stable ( Usin' RockSim). Avast! Aye aye! I increased t' length o' t' upper tube ( forward o' t' transition) and removed the forward fins. 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. Ahoy! Ya scallywag! So I went for a removable cartridge system. T' Fins were mounted through t' body wall and formed runners onto which t' engine cartridge would slide. T' cartridge be made up from two discs o' plywood drilled with holes for t' engine mounts. Begad! Arrr! T' cartridge slid in t' t' body on t' runners and be then locked into position by rotatin' the whole thing. Aye aye! 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 bucko, me proud beauty! A stuffer tube be placed inside t' main body, mounted on two centerin' rings. Avast, me proud beauty! At ignition t' upper body was t' separate, each half with its own parachute. Avast, me proud beauty! Blimey! Karen made a red and white hemispherical 'chute for t' lower half, and I be goin' t' use t' pink circular 'chute for t' upper half. Avast! Arrr! We intended t' fly it at t' International Rocket Weekend, shiver me timbers, and I had a lot o' help from Brain who made and painted the transition just days before we went. Begad! Ya scallywag!

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

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

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

comment Post a Comment