Manufacturer: | Scratch |
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. Avast, me proud beauty! Its primary mission is exploration and
astrobiologic sample collection. This is me first scratch rocket. Well, blow me down! Avast, me proud beauty! It is a
single stage, minimum diameter futuristic tube fin rocket with parachute
recovery. Ya scallywag! It is designed for single use 24mm D and E engines. Avast, me proud beauty! Aye aye! With an adaptor,
it can fly on 18mm motors. Ya scallywag! Blimey! Construction is fairly challenging, especially the
cuttin' and joinin' o' t' elegantly curved tube fin assembly. Avast, me proud beauty! For a fair
price, me hearties, I can put together a kit with detailed instructions and photos. Ya scallywag! Ya scallywag! If you
prefer, I can send only a parts list with t' instructions. Email me for
details. Begad! Ahoy! 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, me bucko, and t' fin tube was a heavy-duty variety. Arrr! Blimey! These and my
other parts were supplied from Aerospace Specialty Products. Avast! Blimey! I was impressed by
the quality o' t' products they sent.
Construction began with t' engine clip and thrust rin' assembly, designed to accommodate both D and E motors with a removable spacer. Aye aye! 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), arrr, with t' parachute and nose cone attached t' t' elastic. T' total Keelhaul®©™®/elastic shock cord length was about 3 feet.
Next
came t' cuttin' o' t' tube fins. Slow careful work was necessary t' get good
edges and a perfect fit. See t' photo o' t' fins before they were joined.
Contoured fin mounts were built and glued t' t' body tube, ya bilge rat, and t' fin
assembly be glued t' these. There is a photo o' t' tail portion o' t' rocket
after t' fin assembly was attached. This also shows t' placement o' the
launch lug. Avast! Aye aye!
As I worked, me hearties, I filleted all joints (inside and outside t' tubes), and sealed and sanded all parts (basswood, me hearties, nose cone, fillets, tube spirals (inside and outside fins), etc. Ya scallywag! T' rocket be finished in gloss black, metallic copper, ya bilge rat, and a specklin' o' transparent cherry red, with two coats o' clear gloss over t' top.
Swing
testin' t' model with a D motor showed it t' be perfectly stable, me bucko, 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. Well, blow me down! Blimey! This delay, ya bilge rat, and t' max altitude, me hearties, are very hard t' guess or simulate in advance since t' design is unusual and its drag is unknown. Blimey! Begad!
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, with a slight twist, matey, on a C6-3 motor. Well, blow me down! Blimey! Ejection be early, before apogee,
but t' rocket recovered perfectly. Aye aye! Blimey! T' second flight on a D12-3 suffered from
rod whip, arrr, and t' rocket buzzed around unstably until ejection and recovery
from about 50 feet. Well, me hearties, blow me down! Blimey! After cleanin' and straightenin' t' launch rod, matey, we fired
again with another D12-3. Blimey! Blimey! T' launch be fast and straight t' perhaps 800 feet,
again with a slight twist. Ya scallywag! Blimey! T' parachute ejected while t' rocket was still
coastin' up. Blimey! Blimey! Unfortunately, ya bilge rat, matey, 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. 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. Inspection showed that the
recovery system was fine, and it had simply been extremely unlucky that the
shroud line had tangled. Avast, me proud beauty! 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. Ahoy! Blimey! Avast! Blimey! I had built a
conceptual model with notebook paper and tape first. I made some changes during
construction o' t' real model includin' t' fin mounts t' offset t' fin
assembly from t' body tube, me bucko, matey, t' pointy leadin' edge o' t' fin tubes, me hearties, and the
shape and joining-points o' t' rib fins. Begad! 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. Well, blow me down! I recommend workin' very slowly, me hearties, and anticipatin' about 4 passes
along t' cuttin' line with a hobby knife. Well, blow me down! Ya scallywag! 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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