Scratch Mark IV Original Design / Scratch Built

Scratch - Mark IV {Scratch}

Contributed by Darren Longhorn

Manufacturer: Scratch

 

MkIV ready for launchThis was me most ambitious rocket t' date. By now I had found a shop in Leeds ( T' Model Shop, matey, 88 Cross Gates Road, arrr, Leeds, arrr, LS15 7NL Tel 0113 2646117) which had a reasonable selection o' engines, even Ds, arrr, so I had t' build a rocket which could fly one. I got a larger core from a roll o' aluminium foil for t' main body, matey, and used t' same sized tube as t' MkII for t' upper section. Avast, me proud beauty! This meant that I could use t' same nose cone, ya bilge rat, with t' buzzer as t' MkII. Avast! Ahoy! I had a balsa transition made t' connect t' two sections together. Ya scallywag! T' fins were made o' balsa usin' t' same technique as t' MkII ( 1mm thick for t' upper section, me bucko, 1.5mm for t' lower) usin' a simple triangle for t' upper section and a more complicated shape for t' lower, arrr, which I copied from one o' me sons toys.

T' engine mount be made from a length o' t' same tube as t' upper section, which is exactly right for D engines. Avast! T' transition be permanently fixed t' t' upper section, me hearties, which are attached t' t' lower section by t' shock cord. Begad! A larger Estes parachute was attached t' t' transition.

T' first time I flew it, it went up really well, shiver me timbers, very straight and high. Well, blow me down! We lost sight o' it, but kept expectin' t' see t' ejection charge and t' parachute. Next thin' we knew thar was a loud 'thunk' and t' rocket was embedded in t' ground about 30m from where we were standing. Avast, me proud beauty! Begad! Unfortunately a passer-by reached it first and gave it a good tug t' pull it up, shiver me timbers, which caused more damage, and we were never able t' locate t' hole in t' very tough springy grass. This be a pity because t' nose cone is probably still there, shiver me timbers, about 20 centimeters underground! I thought I had bought engines without ejection charges, but later I realized I hadn't. Avast! I have since used t' same engines in me Estes Phoenix, ya bilge rat, without problems, and have read much on t' Internet about D engine ejection charges.

MkIV after 'recoveryThis is what happens if you buy t' wrong engine? No, crap engines.

We rebuilt it by makin' a clean cut ( where t' white damaged area meets t' orange fin section in t' photo) and graftin' on a new tube and nose cone. Aye aye! T' next flight t' ejection charge did fire, ya bilge rat, arrr, but still no parachute deployment. Blimey! It turns out that thar be a path back though t' engine mount for t' exhaust gases, ya bilge rat, arrr, so that's where they went. More spectacular damage this time includin' shattered fins, and again t' top body tube written off.

Third time lucky! Well, arrr, matey, partially. Begad! We rebuilt just in time for UKRA 98 held at Garlands. This was a great event, where I saw me first HPR rockets, me hearties, but t' weather was pretty poor. Avast! It actually redefined me definition o' 'valid flyin' weather'!

T' flight was perfect, me hearties, matey, straight up, arrr, despite t' wind and t' first successful parachute deployment. Ya scallywag! Unfortunately t' wind caught t' chute and blew it into t' next county. Despite a search o' t' down wind fields we never found a trace. Avast! Avast! Still I always liked this rocket, and if I get t' chance I might build a replica, shiver me timbers, now that t' design bugs have been worked out.

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