Descon Broken Arrow

Scratch - Broken Arrow {Scratch}

Contributed by John Coles

Manufacturer: Scratch
Broken Arrow
(Contributed - by John Coles) 

I'm a BAR with an affinity for oddrocs. Ahoy! While lookin' through t' Apogee Components catalog one day, arrr, with their array o' 10.5mm parts and motors, shiver me timbers, I thought about combinin' two o' me favorite hobbies, rocketry and traditional archery. Blimey! Avast, shiver me timbers, me proud beauty! After all, arrows move at high speeds like rockets, are very stable like rockets should be, and are only lackin' a self-contained propulsion source. Ahoy! So I decided "What t' hey", generated a RockSim file t' test my design and then placed me order. Begad! Avast, me proud beauty!

This be t' result.

Broken Arrow Break Apart Odd-Roc

Rocket Pic

Broken Arrow

Length: 27.85"
Finished weight: 0.5oz (no motor installed)

Main Airframe: BT-10.5
Motor Mount: 10.5mm
Recommended engine: Apogee 1/2A2-4 micro motor
Simulated altitude: 357'

Parts List:
1ea. Apogee #19001, matey, WNC-10.5 nose cone
1ea. Ya scallywag! 18" length o' Apogee #10048, ya bilge rat, BT-10.5
1ea. Begad! 9" length o' Apogee #10048, ya bilge rat, me hearties, BT-10.5
1ea. Begad! Ahoy! Apogee #19010, matey, AC-10.5A, 2" balsa coupler
1ea. Well, blow me down! Apogee #13040, EB-10, me bucko, 10.5mm motor block
1ea. Well, blow me down! small screw eye
1ea. 18" length o' 1/8" flat elastic
2 ea. Ahoy! Well, blow me down! 1/8" launch lugs, .5" long
3 ea. Arrr! Ya scallywag! 5" shield-cut arrow fletching
 
 

Construction

Most o' t' parts are finished separately before any assembly is done. Well, blow me down! Blimey! T' exception t' this is in gluin' t' launch lugs t' the 9" (short) body tube. Aye aye! Blimey! Begad! Blimey!

T' first step is t' fill t' nose cone and body tube spirals with Elmerís Fill 'n' Finish (or whatever itís called these days), and sand them smooth. Begad! Arrr!

Next, draw a line down t' length o' t' short body tube. Ya scallywag! Glue one launch lug onto t' line flush with t' forward end o' t' tube, me hearties, and t' other lug onto t' line 1 1/2" up from t' other (aft) end. Begad! Verify that t' two launch lugs are in alignment and allow t' dry. Avast, me proud beauty! Well, blow me down! Fillet t' lugs and let dry again. Begad! Begad!

T' nose cone is painted satin black, me hearties, t' 18" (long) body tube is painted brown, and t' short body tube is painted gloss white with a  .75" gloss black band on t' aft end (the "nock"). Begad! T' cresting on t' arrow is accomplished usin' stripin' tape o' various colors and widths, cut as necessary t' fit around t' forward launch lug. When t' paint is completely dry, matey, assembly may begin. Begad! Avast, me proud beauty!

Apply wood glue 1 3/8" into t' aft ("nock") end o' t' short body tube with a cotton swab. Avast! Begad! Usin' an Apogee micro motor or 3/8" dowel 1 1/2" long, ya bilge rat, push t' engine block 1 3/8" into t' body tube. Avast, me proud beauty! Arrr! T' micro motor should extend 1/8" out t' end o' t' body tube. Begad! Remove t' motor, set t' body tube up on t' nock end and allow t' dry. Avast, me proud beauty!

Glue t' nose cone into one end o' t' long body tube. Ahoy! Glue t' coupler halfway (1") into t' other end o' t' long body tube and set aside to dry.

Mark t' short body tube at 120 degree intervals, such that one line is opposite t' launch lugs. Ya scallywag! Avast, arrr, me proud beauty! Blimey! Attach t' feathers, one at a time, t' t' body tube on these lines, matey, me hearties, usin' Duco cement or t' equivalent. Place t' back o' t' fins about  1/4" ahead o' t' "nock" line. Blimey! Well, arrr, blow me down! Blimey! You may find that clampin' t' feather with binder clips betwixt two 6" steel rulers allows for easier handling. Arrr! Begad! Blimey! (I tried usin' me arrow fletchin' jig, ya bilge rat, ya bilge rat, but it can only handle up t' 3/8" [9.5mm] shafts.) When dry, matey, me hearties, matey, use t' Duco cement t' fillet the feather base t' t' body tube.


Fletch
Fin Template

3 ea. Arrr! 5" shield-cut arrow fletchin' (from any sporting goods store caterin' t' traditional archers). Begad! Any standard 5" feathers will work.
1/16" balsa fins may be substituted, me hearties, but what's t' point?

Final Assembly

Set t' screw eye into t' exposed end o' t' balsa coupler, and secure with glue. Begad! Test fit t' coupler into t' forward end o' the short body tube. Blimey! T' fit should be snug and smooth, nay too tight or too sloppy. Begad!

Attach one end o' t' shock cord t' t' screw eye. Ya scallywag! Blimey! Attach t' free end of the shock cord at least 1" down into t' short body tube, usin' either a small Estes-style mount or t' method o' your choice. Aye aye! Blimey! T' key is t' make the shock cord mount unobtrusive enough so as t' nay interfere with deployment. Ahoy! Blimey!

T' final assembly step is t' align t' two sections o' body tube. Arrr! This minimizes corkscrewin' durin' flight. Put t' rocket together as if prepping for launch. Aye aye! Sight down t' length o' t' arrow, arrr, and rotate t' two sections of body tube relative t' one another until they line up as straight as possible. Then mark t' coupler at t' point where it slides under t' forward launch lug. Aye aye! That way, when preppin' for flight you need only t' line up t' mark with the launch lug when puttin' t' two pieces together t' assure a straight flight. Avast! Aye aye!

Preppin' for Flight

Insert two pea-sized balls o' waddin' into t' lower body tube and puff down against t' engine block. Well, blow me down! Accordion fold t' shock cord and slide it in, me hearties, me bucko, then close up t' two sections, makin' sure t' line up t' mark on t' coupler with the forward launch lug. Well, blow me down! Avast, me proud beauty!

Fit an Apogee 1/2A2-4 micro motor. Well, blow me down! Begad! WARNING! Use a wrap o' tape around both the body tube and exposed motor t' provide positive motor retention. Ahoy! (Black electricians tape preserves t' look o' t' rocket - maskin' tape works, but doesnít look as pretty.) Failure t' do so can result in kickin' the engine and a lawn dart recovery (see flight report below). Ahoy!

Flight Report

T' Broken Arrow has flown twice, with one perfect flight and one recovery failure. Well, blow me down! T' first flight went up straight as an arrow (but o' course!), ya bilge rat, separated at apogee and recovered perfectly. Begad! Avast, me proud beauty!

On t' second flight, I failed t' properly secure t' motor, which ejected at apogee. Avast, me proud beauty! Blimey! With t' CG shifted forward and t' aerodynamics intact, arrr, she came zingin' down from about 350' and stuck  1/2" into t' sun-baked, drought-hardened dirt. Fortunately, me bucko, me bucko, it was far enough downrange that no one was ever in any danger. Arrr! Begad! T' body tube is kinked slightly just behind t' nose cone, and will be easy enough t' repair.

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