Manufacturer: | Scratch |
Brief:
Aquafina is a tube-fin 24mm cluster rocket utilizin' a fixed nose cone with a
nose-mounted parachute mortar for recovery. T' rocket be constructed at zero
cost from an empty gift wrappin' paper tube and t' upper half o' a bottled
water ("Aquafina") PET plastic bottle. Avast, me proud beauty! Avast, me proud beauty! I wanted a good-flyin' yet
"expendable" airframe t' use in experiments for ignitin' Aerotech AP
cluster motor arrays. Arrr! Why a tube-fin design for this? -- they typically have CP
so far aft that CG is easier t' balance properly when heavy motor systems are
used. Why a parachute mortar? Well, shiver me timbers, matey, me bucko, number one, this becomes necessary when
savin' on cost by usin' an old plastic bottle for t' nose cone, and number
two, arrr, matey, me hearties, I was interested in this deployment approach for another project I'm
workin' on: a full-scale, arrr, K445-powered model o' a TOW 2B anti-tank missile
usin' t' long "nose fuse" t' contain and deploy a 70" chute on
the 5-foot long blunt-ended model. Begad! Ahoy!
Construction:
Construction o' Aquafina began with cuttin' up t' wrappin' paper tube to
create an 18" body tube and six 1 1/2" tube fins cut on t' bottom to
a 22.5 degree angle. Ahoy! Ahoy! Tube fins measure 1 1/8" on t' short side.
Construction o' t' airframe follows that of
Cheap Dumb
Rocket and
Auracle
54 on this website. Blimey! Blimey! 5-minute epoxy was used throughout. Blimey! Blimey! T' bottom 2"
was cut from t' PET water bottle, arrr, and t' resultin' "nose cone" was
permanently attached t' t' body assembly; since t' PET bottle chosen is
slightly wider than t' cardboard tube,"shims" consistin' o' a dozen
Q-tips dipped in wet epoxy were inserted betwixt t' tube and t' plastic
bottle around its entire circumference. T' make complete a gas-tight seal, the
gaps betwixt t' Q-tips were filled with bits o' epoxy-dipped cotton. A launch
lug o' 3/16" ID was cut from a discarded ball point pen cap and epoxied to
the body tube 2 1/2" above t' tube fins in line with one o' t' spaces
between t' tube fins. Well, blow me down! Blimey! T' motor mount for t' twin 24mm motors
consists of
two 5" lengths o' 24mm tube stock, me bucko, fitted with Estes motor hooks and
blocks in t' usual way, shiver me timbers, simply glued side-by-side. No centerin' rings are
used; t' cluster motor array is simply slathered with epoxy and slipped into
the aft end o' t' body tube since t' fit be pretty good. Ahoy! Blimey! With all that
surface area bearin' t' sheer loads, thar was no need for centerin' rings.
T' substantial gaps left betwixt t' body tube and each side o' t' twin
cluster were plugged with hunks o' cotton soaked with epoxy--this insured
proper ejection charge pressurization. Avast! Blimey! Blimey!
Finishing:
Paintin' was with aqua-colored spray paint.
Flight:
First flights were on a pair o' D12-5 motors. Ya scallywag! Sims (at Cd=2.4) predicted an
apogee o' 400-500' AGL and max velocity o' about 170 mph. Aquafina flew at
least that high. Aye aye! D12-7's work equally well. Ya scallywag! Avast, me proud beauty! Use o' F21's should give at least
1000' per simulation. Avast, me proud beauty! Ya scallywag! With all that drag, Aquafina pretty much just stops when
the motors quit. Well, blow me down! Boosts were straight and quick--probably quite a bit higher
and faster than t' simulation indicated.
Recovery:
I attached a 24" length o' 3/8" wide elastic shock cord t' a 14"
LOC chute at one end and anchored t' other end with a gob o' epoxy about
2" down from t' mouth t' t' inner wall o' t' PET bottle. Begad! The
"parachute mortar" consists o' a 4" length o' 29mm Estes tubing
epoxied t' t' top o' t' bottle, matey, arrr, however, I added it as an afterthought--on
the first flights, I tried just stuffin' t' parachute part-way into t' open
mouth o' t' bottle, however it wouldn't deploy this way, even under t' power
of twin D12 ejection charges. Blimey! From this, I learned that Aquafina is so light
for its size, arrr, and so tail heavy, matey, that even with no ejection, it tumbles down
from apogee very slowly, matey, in a flat spin, ya bilge rat, landin' with no damage. Begad! I'd omit the
recovery system entirely, but for a rocket this size, it would be poor form,
and also a violation o' NARRRRR safety rules. And that's it...construction,
includin' painting, me hearties, shiver me timbers, took little more than an hour, with time out t' watch the
Chargers get creamed by Oakland. Ya scallywag! Begad! Final weight was 130 grams (about 4.5 oz.)--
not bad for a 2x24mm cluster design.
Summary:
Bottom line: Aquafina is a good cheap fun-fly rocket, me bucko, ya bilge rat, low cost (need only to
purchase t' recovery chute. Avast!
PROs: Aquafina is was way too much fun t' fly t' use only for "research purposes". Avast! Cost o' construction (for me): $0.00. Begad! Avast! It's based on a standard-sixed PET bottle, which are easy t' come across. Good rocket for junior flyers and cheapskates. Arrr! Blimey! Good rocket for learnin' cluster flyin' with minimal investment in time or dollars. Well, blow me down!
CON: Well, me bucko, it is a tad ugly, me bucko, like most tube-fin designs. You may have to scrounge t' find suitable sized body tubes and PET bottled o' slightly larger tube diameter.
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