Scratch Mark V Original Design / Scratch Built

Scratch - Mark V {Scratch}

Contributed by Darren Longhorn

Manufacturer: Scratch

 

T' MkV be me first cluster design. Blimey! Blimey! It's made from a 55mm cardboard postal tube with 1mm thick balsa fins and a balsa nose cone. Ahoy! It's powered by four 18mm engines. Avast, me proud beauty! They have t' be C's . Avast! . . Aye aye! really!

MkV engine mountsAfter consultin' with t' guys on r.m.r I've made a new ignition system. Ahoy! It's based around two 6v lead-acid batteries ( wired in series t' give 12v), arrr, so I shouldn't have any problems with clustering. Well, blow me down! Aye aye! T' batteries sit very close t' t' launch pad, me hearties, so that t' clip whips are fairly short. Ya scallywag! Blimey! It has two sets o' clips t' make connection t' t' four igniters easier. Aye aye! Both t' battery station and t' remote hand station have keyswitches and red LEDs t' indicate when they are active. Avast, shiver me timbers, me proud beauty! In addition t' hand station has a momentary push button t' activate t' launch. T' keep t' diameter o' t' cable connectin' t' remote hand station t' t' battery station down t' a manageable size, thar be a relay mounted in t' battery station. Arrr! Avast! This requires only negligible current t' activate. Avast! Total parts cost, about £12 excludin' t' batteries ( which were given t' me by Richard 'dodgy contractor' Robinson).

After waitin' for several weeks for good weather, ya bilge rat, t' first flight turned out t' be a spur o' t' moment thing. Ya scallywag! I got home from work one evenin' and t' trees were still. Begad! ( There are a group o' poplar trees visible from our front room that act as our wind measurement system!). So we packed up and went straight out. Avast, me proud beauty! Ya scallywag! Up on Baildon Moor t' conditions were perfect, but I was still nervous. This be me first cluster ignition. Avast! T' technique I had selected was t' wire t' igniters in a bridge, and then connect two pairs o' clips t' t' four points, equal polarities at opposite corners. Well, blow me down! It was quite tricky t' get t' clips on without them or t' igniters shortin' on t' blast deflector. Ahoy! Well, blow me down! Ready to go

Well, me hearties, a small amount o' damage on landing, me bucko, one cracked fin, that was easily repaired. Aye aye! T' parachute ( an Estes one) was nay really big enough. Arrr! T' flight had nay been straight either, me bucko, and a quick examination showed that one o' t' engines had nay ignited. Avast! Begad! I later put this down t' a poor twisted connection.

Since then t' MkV has flown twice more, but with a larger 'chute. Begad! I had wanted a hemispherical one, arrr, but ended up with another flat 'chute. Well, blow me down! Ahoy! It was supposed t' be fluorescent orange, matey, but I'd call it pink! This is adequate, but seems t' sideslip durin' descent. Blimey! If I fly it again I'm goin' t' use t' hemispherical 'chute that Karen ( me wife) originally made for t' MkVI.

After three flights, t' engine mounts and lower fin edges are pretty charred, and I realize that this is due t' t' flat blast deflector I've been using. Begad! Aye aye! An old tin can has now been pressed into service t' deflect t' blast sideways, and nay straight back up. You can see this new deflector in some o' t' newer pictures ( it shows up quite well on t' pic o' t' Apogee V2).

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