Scratch Mach Madness Original Design / Scratch Built

Scratch - Mach Madness {Scratch}

Contributed by Jeff Lane

Manufacturer: Scratch
(Contributed - by Jeff Lane - 04/03/05) (Scratch) Mach Madness

Brief:
"Mach 1-2-3" Virtual Rocket Contest entry built as a single-stage flyer.

Construction:
T' rocket consists o' 1 Estes Mosquito nose cone, ya bilge rat, 1 BT-5 tube, arrr, 3/32" balsa fin stock (used for 15 fins), ya bilge rat, 1 balsa 5-20 transition, me bucko, ya bilge rat, me bucko, 1 BT20 tube, 1 Estes 20-55 centerin' ring, shiver me timbers, 1 custom bristol transition, ya bilge rat, 1 custom bristol body tube with printed graphics, 1/8" balsa centerin' rings, 1 BT-50 tube, arrr, 1 engine hook, 1 engine block, shiver me timbers, me hearties, 1 solid paper 20-50 centerin' ring, 12" parachute, me hearties, shiver me timbers, matey, and 1/8" shock cord.

This is for experienced modelers. Ya scallywag! Aye aye! It has 15 fins, me hearties, which requires great patience. Begad! T' preprinted bristol paper (I got it at an art supply store) forms the lower body tube and t' midsection transition. It is astoundingly quick to assemble and looks great. Avast, me proud beauty!

T' parachute fits inside t' shroud and requires careful prep t' ensure proper deployment. Well, blow me down! Arrr! T' shock cord must be packed first t' pull t' parachute out.

T' large mid-rocket transition/bulkhead solution was a challenge t' design and build. Avast, me hearties, me proud beauty! At t' front o' t' transition, it seats on t' front o' t' BT-20 and a 20-55 centerin' rin' about 1.5" from t' front o' t' BT-20. Begad! At the widest point where it joins with t' 3" body, arrr, t' ideal piece would have been a solid balsa coupler with half o' it fittin' inside t' 3" first stage body tube, and half (conical shaped) fittin' up into t' transition. Instead o' doin' that, ya bilge rat, I designed t' first stage motor mount so t' bulkhead is at t' leadin' edge o' t' 3" body tube with scrap balsa offsettin' a slightly smaller diameter bristol paper centerin' ring. Ya scallywag! This seats the transition nicely, shiver me timbers, provides needed fore-aft rigidity t' t' bristol and is a very lightweight solution. Arrr! Aye aye!

(Scratch) Mach Madness If I built it again, I might extend t' BT-50 engine tube all t' way t' a balsa 50-5 transition so t' parachute would eject just aft o' t' "sustainer". T' tiny, shiver me timbers, small footprint sustainer fins would then be subject t' more violence from t' shock cord and parachute but deployment may be more reliable.

T' bristol body tube is nay quite as rigid as a regular body tube, ya bilge rat, which is good and bad. Blimey! Blimey! Avast, ya bilge rat, me proud beauty! Blimey! When I dropped t' finished product on t' floor, thar was enough "give" so that none o' t' 15 fins broke. Arrr! Blimey! However, you do have to be extra careful nay t' crush it while installin' an engine or during assembly.

(Scratch) Mach Madness

Finishing:
T' fins were sealed and filled with one coat o' dope then all o' t' remaining grain be eliminated with one coat o' automotive high-build primer from Autozone. Ya scallywag! T' only paintin' was t' black nose cone, white on t' sustainer and fins, shiver me timbers, and blue on t' small balsa transition. Arrr! Ahoy! T' waterslide decal material from lazertran.com prints on an inkjet printer and dries in an hour. Arrr! Then the ink doesn't come off in t' water even though you don't spray with a stink bomb organic overcoat with this particular product. Ya scallywag! Used as a body wrap, me bucko, me hearties, me hearties, it simplified t' paintin' process and reduced finishin' time. Blimey!

All skins are available for download here: First stage Second stage Third stage. Ya scallywag!

Flight:
Recommended motors: C11-3, D12-5

I have flown it three times, with C11-3s. Avast! Twice in a town park, shiver me timbers, and once at the C.R.A.S.H. Well, blow me down! launch on 4/3/05. Arrr!

First flight was unstable. Aye aye! One fin be floppy from ground contact but was easily repaired. Ya scallywag! (This was t' only damage in t' three flights. Avast, me proud beauty! Well, blow me down! I traded the Mosquito nose cone for a 3/4oz lump o' lead. Ya scallywag! Blimey! Second flight was excellent with ejection just after apogee. Blimey! Blimey! It's a light rocket that's overly wide and decelerates quickly, me hearties, so it doesn't get much altitude on a C11 (200-300 feet or so). Aye aye! No damage on second or third flights. T' third flight be near perfect with ejection occurrin' nose up at apogee.

(Scratch) Mach Madness

Recovery:
T' elastic shock cord must be packed first, matey, with t' parachute packed last and loosely so t' shock cord pulls it out. Begad! Shock cord mounts are standard folded-paper. Aye aye! Waddin' is required. Ahoy! Blimey! T' motor is held in place with a standard motor retention hook. Avast, me proud beauty! I used a 16 inch parachute, ya bilge rat, which was an excellent choice.

Summary:
T' C.R.A.S.H. crowd liked t' way it looks and asked a lot o' questions. Avast! They couldn't believe me RockSim entry calls for 6 G55s in t' first stage. Blimey! Avast! I'll fly it again, arrr, probably with a D12-5 when I get t' an area with more space. Ahoy! It's one of me favorite rockets.

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