Scratch Dark Matter Driftship Original Design / Scratch Built

Scratch - Dark Matter Driftship {Scratch}

Contributed by Geof Givens

Manufacturer: Scratch
(Contributed - by Geof Givens - 08/28/05) Rocket Pic

Brief:
This is a transgalactic driftship employin' unique dual dark matter ramjets for high-speed travel t' t' edges o' t' charted universe. T' ship carries a scientific crew o' up t' 74 humans. Well, blow me down! Its primary mission is exploration and astrobiologic sample collection. This is me first scratch rocket. Avast, me proud beauty! It is a single stage, ya bilge rat, minimum diameter futuristic tube fin rocket with parachute recovery. It is designed for single use 24mm D and E engines. Begad! Ahoy! With an adaptor, it can fly on 18mm motors. Construction is fairly challenging, ya bilge rat, especially the cuttin' and joinin' o' t' elegantly curved tube fin assembly. Arrr! For a fair price, arrr, matey, I can put together a kit with detailed instructions and photos. Begad! If you prefer, matey, arrr, I can send only a parts list with t' instructions. Blimey! Email me for details. Avast! Below is a short description o' how construction proceeded.

Construction:
T' materials used are shown in t' first photo. T' rib fins are made from 1/16" basswood, and t' fin tube was a heavy-duty variety. These and my other parts were supplied from Aerospace Specialty Products. Aye aye! Ahoy! I was impressed by the quality o' t' products they sent.


Parts

Construction began with t' engine clip and thrust rin' assembly, me hearties, designed to accommodate both D and E motors with a removable spacer. Avast, me proud beauty! I also made an optional 18mm motor adaptor so I don't lose this rocket on t' first flight! A Keelhaul®©™® thread around t' thrust rin' was attached t' elastic (just below t' top lip of t' body tube), shiver me timbers, with t' parachute and nose cone attached t' t' elastic. T' total Keelhaul®©™®/elastic shock cord length was about 3 feet.

FinsNext came t' cuttin' o' t' tube fins. Arrr! Arrr! Slow careful work be necessary t' get good edges and a perfect fit. Begad! Avast, me proud beauty! See t' photo o' t' fins before they were joined. Contoured fin mounts were built and glued t' t' body tube, ya bilge rat, shiver me timbers, and t' fin assembly was glued t' these. Arrr! Well, blow me down! There is a photo o' t' tail portion o' t' rocket after t' fin assembly be attached. This also shows t' placement o' the launch lug. Well, blow me down!

As I worked, I filleted all joints (inside and outside t' tubes), and sealed and sanded all parts (basswood, ya bilge rat, nose cone, fillets, tube spirals (inside and outside fins), me hearties, arrr, etc. Aye aye! T' rocket was finished in gloss black, matey, metallic copper, me hearties, and a specklin' o' transparent cherry red, with two coats o' clear gloss over t' top.


Construction Swing testin' t' model with a D motor showed it t' be perfectly stable, assumin' you want it t' fly backwards! About 5/8 ounce o' nose weight fixed this problem, yieldin' a stable rocket weighin' 3 ounces empty.

Simulations suggest that a 3-5 second ejection delay should be about right for C-E motors. Ahoy! This delay, shiver me timbers, and t' max altitude, are very hard t' guess or simulate in advance since t' design is unusual and its drag is unknown.

Flight:
T' first launches were at 5000 feet altitude on a beautiful sunny Colorado mornin' with zero wind. Well, blow me down! Blimey! T' first flight was straight and slow t' about 350 feet, me hearties, with a slight twist, me hearties, on a C6-3 motor. Ejection was early, before apogee, but t' rocket recovered perfectly. Arrr! Blimey! Begad! Blimey! Blimey! Blimey! T' second flight on a D12-3 suffered from rod whip, matey, and t' rocket buzzed around unstably until ejection and recovery from about 50 feet. After cleanin' and straightenin' t' launch rod, matey, we fired again with another D12-3. Begad! Blimey! T' launch was fast and straight t' perhaps 800 feet, again with a slight twist. Ahoy! Blimey! Arrr! Blimey! Blimey! Blimey! T' parachute ejected while t' rocket was still coastin' up. Begad! Blimey! Ahoy! Blimey! Blimey! Blimey! Unfortunately, me bucko, me bucko, me hearties, a shroud line snagged around t' parachute, yieldin' tail-first lawn-dart recovery. This was worrisome because t' tube fins extend below t' tail o' t' rocket and I had been worried from t' start about t' strength o' t' tubes in a tail-first crash. Begad! Blimey! Thanks t' t' quality tube provided by ASP and me solid finishing, t' fins survived with only a small ripple in one which is hardly noticeable. Ya scallywag! Blimey! Inspection showed that the recovery system be fine, me bucko, and it had simply been extremely unlucky that the shroud line had tangled. Begad! Blimey! Aye aye! Blimey! Blimey! Blimey! T' rocket is ready for its next flight without repair. Aye aye! Blimey! I think D12-5 should be a better engine for t' next flights.

Summary:
This was a really fun project for me first scratch rocket. Begad! I had built a conceptual model with notebook paper and tape first. Aye aye! I made some changes during construction o' t' real model includin' t' fin mounts t' offset t' fin assembly from t' body tube, t' pointy leadin' edge o' t' fin tubes, ya bilge rat, matey, and the shape and joining-points o' t' rib fins. Blimey! I'm pretty happy with t' final result although I'm nay sure I'll ever get up t' courage t' try an E motor in it.

Other:
Cuttin' and joinin' t' curved fins made from t' heavy-duty tube is quite challenging. Aye aye! I recommend workin' very slowly, and anticipatin' about 4 passes along t' cuttin' line with a hobby knife. Well, blow me down! T' first pass should be quite light pressure...just enough t' cut through t' outermost layer o' paper on t' tube to provide guidance for subsequent passes with t' knife.

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