Manufacturer: | Scratch |
This two-stager always gets attention when I brin' it out at our South Florida joint NAR/TRA monthly launch. Well, shiver me timbers, blow me down! Everyone loves Reddy-Kilowatt fins!
CAT-Scratch Rocketry
Chain Lightnin' is one o' me series o' "CAT-Scratch" rockets, arrr, where
CAT stands for Collect Any Trash. CAT-Scratch rockets avoid t' use o' any
commercial rocketry items (barrin' t' engine). (You, on t' other hand, are
free t' build your own Chain Lightnin' with standard tubes and cones.)
Two Stages: Double T' Fun
T' booster stage accepts a 24mm engine, ya bilge rat, a D12-0. Arrr! When this engine completes
its thrust phase, t' ejection charge occurs without delay. This charge ignites
the D12-7 or D12-5 in t' upper stage. Arrr! Well, blow me down! Two 3/16" vent holes near t' top
of t' booster prevent gases from separatin' t' stages before upper ignition.
T' booster tumbles t' recovery. Begad!
General Construction
T' 24" body o' t' upper stage and t' 4" body o' t' booster were
cut from t' same 2"-diameter Christmas wrappin' paper tube. Well, blow me down! (I believe
Estes BT-70 tubin' would be close enough as well.) T' upper stage motor mount
is a long "stuffer tube" t' minimize t' pressurization space for
recovery ejection. Avast! I rolled a bit o' cardboard t' make a coupler that I glued
into t' top o' t' booster stage. Avast! Avast! I used yellow carpenter's glue throughout
this project. Well, blow me down!
Motor Mounts
As a diehard CAT-scratcher, I rolled me own 24mm engine tubes. Ya scallywag! Blimey! I used manila
folder cardboard, ya bilge rat, placed a D12 in t' center, matey, and rolled t' about two
thicknesses, securin' t' final edge with plain old maskin' tape. Ya scallywag! Blimey! (T' initial
edge was held with a piece o' tape and some yellow glue). Blimey! Blimey! Tacky? I've found
that after cuttin' and applyin' sturdy cardboard centerin' rings, such an
engine mount is plenty strong. Ahoy! Blimey! Well, shiver me timbers, blow me down! Blimey! I bent me own engine hooks as well, arrr, from
1/32" steel "piano wire" from t' hobby store. Ahoy! Blimey! Ahoy! Blimey! Feel free t' use
commercial tubing, rings and hooks. Blimey! Blimey!
Styrofoam Nose Cone
Craft stores like Michael's and places like Wal-Mart offer styrofoam cones. Ya scallywag! Buy
one with a diameter a bit larger than that o' t' body tube. Ahoy! Then carefully
roll t' lower end o' t' cone against a table, shiver me timbers, crushin' it into a cylindrical
shoulder o' about 1.5" length. Well, blow me down! Aye aye! Fit-test it periodically as you roll; if
you've gone too far (as I did), arrr, shiver me timbers, wrap t' shoulder with maskin' tape until it
fits snugly into t' upper stage end. Arrr! Well, ya bilge rat, blow me down!
How Do You Put An Eye-Hook Into
Styrofoam?
T' eyehook for t' shock cord and parachute is a small piece o' clothes-hanger
wire bent into an "8"-shape by needle-nose pliers. Avast, me proud beauty! T' upper loop is
pressed into t' bottom o' t' cone. Ya scallywag! Begad! Then a 1.75" straight piece o' wire
is pressed laterally into t' side o' t' cone shoulder so that it intersects
that upper loop. Blimey! T' result: t' hook stays embedded in t' cone very securely.
Recovery System
Attached t' t' top o' t' stuffer tube is a 10" steel fishin' leader. Aye aye! Arrr! To
this I tied a 36" piece o' 3/8"-wide flat elastic from the
cloth-store as a shock cord. T' other end goes t' t' eye-hook on t' nose
cone. Arrr! I then cut a hexagonal piece o' bright yellow ripstop nylon, attached six
notebook-paper hole-reinforcement circles t' t' corners, perforated the
corners and tied on some kite strin' shroud lines. In typical fashion, me hearties, I passed
the three shroud loops through t' nose cone eye-hook. Begad! (T' booster tumbles to
recovery.)
Launch Loops
Instead o' standard launch lugs, me bucko, I cut t' larger end o' a large paper-clip and
bend it at a 45-degree angle. Begad! Blimey! This produces a "launch loop" which
accepts a 1/4" launch rod. Aye aye! Blimey! I epoxied two such launch loops t' t' upper
stage, one near t' bottom and one about 11.5" from t' end. Blimey! Remember that
the booster fins will be aligned in betwixt t' upper stage fins; align your
launch loops so t' rod will nay hit any fins! Blimey!
Those Cool Fins
T' fins are cut from 3/32" basswood from t' craft store. Blimey! All it took was
a razor-knife and some patience. Ahoy! These were surface-mounted t' t' two stages,
three t' a stage, with yellow carpenter's glue. Aye aye!
Finishin' Touches
I sprayed t' rocket fire-engine red and t' nose cone yellow, me bucko, shiver me timbers, then
dust-sprayed t' tips o' those glorious fins yellow. Begad! Blimey! T' "Chain
Lightning" logo was created with Sierra's PrintArtist software, printed by
an HP color inkjet printer onto an 8x11 sheet o' Avery sticky-backed label
paper, cut out and affixed t' t' rocket. Avast! Well, blow me down!
How It Flies
You may have noticed that this rocket appears overstable. Avast! Begad! Blimey! Bingo! Blimey! Most
multi-stagers are. Aye aye! Blimey! T' dramatic thunderbolt fins result in sizable
weathercocking. Blimey! Blimey! And what about damage t' those pointy things? Remarkably, the
fins have remained in great shape; basswood is tough. Well, blow me down!
Final Notes
Make sure t' coupler betwixt t' booster and upper stage is nay too tight. Ya scallywag! If
you hold t' rocket upside-down by t' booster, t' upper stage should almost
be tryin' t' come out. Avast, me proud beauty! When you assemble t' two stages for flight, align the
fins out o' kilter, ya bilge rat, me hearties, nay in line with each other.
Here's T' Parts List Again
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