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

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

T' first time I flew it, it went up really well, arrr, shiver me timbers, very straight and high. Begad! We lost sight o' it, but kept expectin' t' see t' ejection charge and t' parachute. Aye aye! Next thin' we knew thar was a loud 'thunk' and t' rocket was embedded in t' ground about 30m from where we were standing. Aye aye! Begad! Unfortunately a passer-by reached it first and gave it a good tug t' pull it up, arrr, which caused more damage, arrr, and we were never able t' locate t' hole in t' very tough springy grass. Begad! This was a pity because t' nose cone is probably still there, about 20 centimeters underground! I thought I had bought engines without ejection charges, ya bilge rat, me bucko, matey, but later I realized I hadn't. Avast, me proud beauty! I have since used t' same engines in me Estes Phoenix, me bucko, 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, ya bilge rat, 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. Avast, me proud beauty! Blimey! Avast! Blimey! T' next flight t' ejection charge did fire, arrr, but still no parachute deployment. Begad! Blimey! It turns out that thar be a path back though t' engine mount for t' exhaust gases, so that's where they went. More spectacular damage this time includin' shattered fins, me hearties, arrr, shiver me timbers, and again t' top body tube written off.

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

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

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