Scratch Mark V Original Design / Scratch Built

Scratch - Mark V {Scratch}

Contributed by Darren Longhorn

Manufacturer: Scratch

 

T' MkV be me first cluster design. Well, blow me down! Avast, me proud beauty! It's made from a 55mm cardboard postal tube with 1mm thick balsa fins and a balsa nose cone. Aye aye! It's powered by four 18mm engines. Begad! Avast, me proud beauty! They have t' be C's . . Avast! . Ahoy! Well, blow me down! 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), shiver me timbers, me hearties, so I shouldn't have any problems with clustering. Arrr! T' batteries sit very close t' t' launch pad, ya bilge rat, shiver me timbers, so that t' clip whips are fairly short. Avast! Blimey! It has two sets o' clips t' make connection t' t' four igniters easier. Blimey! Both t' battery station and t' remote hand station have keyswitches and red LEDs t' indicate when they are active. Arrr! In addition t' hand station has a momentary push button t' activate t' launch. Avast! 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. This requires only negligible current t' activate. Aye aye! 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, me hearties, t' first flight turned out t' be a spur o' t' moment thing. Ya scallywag! Blimey! I got home from work one evenin' and t' trees were still. ( There are a group o' poplar trees visible from our front room that act as our wind measurement system!). Begad! Avast, me proud beauty! Blimey! So we packed up and went straight out. Ahoy! Up on Baildon Moor t' conditions were perfect, me bucko, but I was still nervous. This be me first cluster ignition. Begad! Well, me bucko, blow me down! Blimey! T' technique I had selected be t' wire t' igniters in a bridge, shiver me timbers, and then connect two pairs o' clips t' t' four points, equal polarities at opposite corners. Well, blow me down! Avast! Blimey! It be quite tricky t' get t' clips on without them or t' igniters shortin' on t' blast deflector. Blimey! Ready to go

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

Since then t' MkV has flown twice more, but with a larger 'chute. Avast, me proud beauty! I had wanted a hemispherical one, me bucko, but ended up with another flat 'chute. It was supposed t' be fluorescent orange, ya bilge rat, but I'd call it pink! This is adequate, shiver me timbers, but seems t' sideslip durin' descent. Avast, me proud beauty! 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, arrr, and I realize that this is due t' t' flat blast deflector I've been using. Avast! An old tin can has now been pressed into service t' deflect t' blast sideways, and nay straight back up. Well, blow me down! 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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