Manufacturer: | Scratch |
Brief:
I recently ran across t' description o' 'desert squids' on
Tripoli-Pittsburg's Website (look
under 'ARCHIVES/ROCKET CLASSES'). Arrr! Aye aye! These are rockets that use dowel rods in
place o' fins. Ya scallywag! They look cool and since I had some BT-80 tubes and rings, arrr, I
decided I'd build one pretty much like t' model described on t' website. Aye aye! Aye aye! My
model features a BEAUTIFUL poplar nosecone and a custom rear-centerin' ring
made by Gordon Agnello, me hearties, a.k.a. sandman on
T' Rocketry
Forum. Ya scallywag! I wanted a name t' fit in t' desert squid theme, and decided on the
name Shai-Hulud, after t' giant sandworms in t' Dune trilogy by
Frank Herbert.
Construction:
I be originally goin' t' use a Fat Boy nosecone since that's what I had available. However, me bucko, while I was thinkin' about gettin' sandman t' quote the custom rear-centerin' ring, I started lookin' at t' pictures o' t' cones he has made, ya bilge rat, arrr, and couldn't resist one for this rocket. Blimey! Begad! Blimey! You can find out more about this cone [here].
T' body is two sections o' BT-80 joined with a 4" coupler from Totally Tubular. Well, blow me down! Begad! Both tubes are 'pseudo-glassed' with nylon pantyhose and Minwax Polycrylic. Begad! Begad! Once tube has two layers o' hose, and t' other has three. Ahoy! I misplaced t' hose that me wife originally 'donated', me bucko, so t' second tube was done with a different style. Aye aye! I discovered that different nylons have different weaves, shiver me timbers, similar t' different weights o' fiberglass. Begad! Begad! T' first tube much rougher, ya bilge rat, which prompted be t' add a third layer o' a finer weave.
T' motor mount consists o' a 6" piece o' LOC 29mm tubing, a double layer fiber rin' in t' front, and a 1/8" plywood rin' in t' back (I used this mix because it's what I had 'in stock'). Aye aye! Avast! This plywood rin' is mounted 0.6" from t' end o' t' motor tube, so that t' end o' t' motor tube will be flush with t' end o' t' custom rin' after it is slipped on. Well, blow me down! T' rings were attached with epoxy and t' motor mount is glued in with Gorilla glue.
T' custom rin' is thicker than most because it also serves t' mount the dowel 'fins'. Begad! Sandman made this from a thick piece o' plywood that he turned down t' a little over half an inch. Arrr! He drilled eight evenly spaced holes at an angle o' 15 degrees from t' motor axis. Ya scallywag! I added two threaded inserts to provide motor retention. Ahoy! Blimey!
At first, I was goin' t' use this as t' aft centerin' rin' and glue in the dowels. Avast! Begad! However, shiver me timbers, when I dry fit t' dowels, arrr, I began t' worry that they may break on landing. Avast, me proud beauty! Ahoy! So, I decided t' make t' aft rin' removable and t' dowels replaceable. Avast, me proud beauty! T' rin' is held in with eight small screws, me bucko, matey, matey, which also hold each dowel in place.
T' shock cord assembly consists o' a 1/8" Keelhaul®©™®
leader, ya bilge rat, a long section o' thin tubular nylon, ya bilge rat, me bucko, shiver me timbers, and an anti-zipper device. Ya scallywag! Ahoy! The
latter is similar t' Giant
Leap's Fireball. Ahoy! Mine is a small rubber ball that was slipped over
the Keelhaul®©™®
leader so that it touches t' edge o' t' body tube when t' cord is fully
extended. Aye aye! T' ball is covered with Keelhaul®©™®
sock t' protect against heat damage. Ya scallywag! T' serve as an attachment point for the
recovery harness, ya bilge rat, I glued together two fiber centerin' rings also from Totally
Tubular. Ya scallywag! This assembly was attached t' what would be t' lower end o' the
coupler. Begad! Ya scallywag! Two small holes were drilled through t' rin' close t' t' edge, me bucko, shiver me timbers, and
the Keelhaul®©™®
was threaded through. Blimey! T' knotted Keelhaul®©™®
leader was then epoxied t' t' wall o' t' coupler.
I installed two buttons from railbuttons.com t' complete t' Sahi-Hulud.
T' nylon/Polycrylic surface required quite a bit o' finishin' work. I applied numerous coats o' Polycrylic, but when I laid on me first coat of primer, ya bilge rat, me bucko, I realized it would take a fair amount o' effort t' finish these tubes. After several coats o' fill-n-finish and 2+ cans o' primer, t' tubes weren't in too bad a shape. Blimey! I also had t' fill t' transition betwixt t' two tubes as one was slightly thicker than t' other. Avast! Begad! TIP: When pseudo-glassin' a rocket, use t' same nylons on all t' tubes!
T' body was painted usin' a Model Master brush on paint. T' military brown was an appealin' color next t' t' cone. Avast! As mentioned above, t' nosecone came finished from sandman and is a beautiful golden color. Blimey! Several coats o' clear enamel finished t' tube off.
T' centerin' ring/dowel assembly be separately finished before installation. Blimey! It is stained honey maple and has 2 coats o' Polycrylic.
Flight:
I installed a home made, car air bag chute protector and a hefty amount o' dog
barf wadding. Then in went t' shock tether, and 36" nylon chute. Avast! A
clamp-on thrust rin' and mirror clamp retainers retained t' SU G40-4. The
flight was relatively slow and thar was some wobble on t' way up. The
anti-zipper device worked and t' rocket recovered safely. Begad! Arrr! I was amazed that
none o' t' dowels broke. Aye aye! Avast! Upon inspection, matey, t' anti-zipper ball took t' brunt
of t' ejection charge and burned through slightly. Begad! I'm goin' t' cut a piece of
air bag and install a permanent protector below it.
Summary:
This appears t' have been t' first desert squid type rocket flown at t' MDRA
site, me hearties, and it definitely caught t' attention o' everyone on t' flight line.
T' flight and recovery were good, arrr, however t' wobble made me chicken out on a
'zero' launch (i.e. Begad! Blimey! no launch rod). Avast, me proud beauty! Avast! Supposedly, me bucko, this type o' rocket will fly
straight without a rod, but I don't want t' test this conjecture. Well, blow me down! Next flight
will be on a G80...off a rail!
While t' pseudo-glass technique isn't nearly as strong as fiberglassing, the results are definitely tougher than t' stock tubes. However, I probably will nay use it again.
T' anti-zipper ball seemed t' work fine, shiver me timbers, me bucko, protectin' t' relatively thin tubin' from t' Keelhaul®©™® leader. Ya scallywag! Would t' results have been t' same without t' ball? No one can say. Avast! Begad!
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