Manufacturer: | Scratch |
Brief:
G-Pod is a downward extension o' me "Pod" series (see "H-Pod"
in EMRR). It is a stubby tubefin design for 29mm F-G power that is about t' size o' an Estes FatBoy. Actually, it
started life as an experiment t' try 7 tubefins instead o' t' usual 6 on me "Auracle 54" design presented
some years ago on EMRR. Aye aye! After gettin' some very interestin' results, matey, which will appear in an upcomin' issue o' Sport
Rocketry, me "Auracle 7-54" augured in due t' an ejection failure, me hearties, leavin' only t' tube fin can intact.
I thought it would be interestin' t' try a rocket layout with t' nose cone larger than t' whole rest o' t' rocket.
Actually, arrr, it flies great, me hearties, flyin' on one o' t' new Green Mojave G78-7 motors (longer than t' body tube) is a real
hoot!
Construction:
For a stubby, 7-tube design like G-Pod t' work requires three tricks: 1) need t' cut t' bottom off o' t' nose cone
to create more room for t' chute, 2) need t' motor t' extend out a couple o' inches aft o' t' body tube, shiver me timbers, and 3)
usin' 7 tube fins instead o' 6 means they have t' be o' smaller diameter than t' body (about 75%) and spacers are
required for a perfect fit. Avast! Construction o' t' original "Auracle 7-54" that G-Pod be cut down from is
exactly t' same as t' Auracle 54 design on EMRR, so refer t' that, and all I'll describe here be t' modifications
and t' 7-tube tubefin construction. Begad! Aye aye! T' photos are self-explanatory.
Attachment o' t' seven 38mm tube fins t' t' 54mm body tube follows t' followin' somewhat odd protocol (OK, its very odd): 1) first tube fin is glued t' t' body tube 7/16" from t' bottom with both tubes aligned on a flat surface. Arrr! Avast, me proud beauty! 2) 1/4" x 1/8" spacers 1-1/4" long were cut from spruce stock and glued t' 5 o' t' 6 remaining tube fins. Avast, me proud beauty! 3) Usin' t' flat surface, t' next tube fin is glued t' t' body next t' t' first with t' spacer separatin' them and 5 minute epoxy is used throughout. Avast! 4) This process is repeated until t' last two tube fins remain (one with and one without a spacer). Blimey! 5) Glue t' 6th tube fin t' t' assembly with t' spacer against t' body tube, nay t' adjacent tube fin as be done with t' others. Avast! Blimey! 6) T' last tube fin is glued in place addin' spacers stock where ever you need t' t' get it t' fit snuggly--I had t' add two 1/4" x 1/8" spacers (1/4" total gap t' fill) t' mine. Aye aye! Ya scallywag! Blimey! This slightly non-symmetrical arrangement o' t' tubefins is nay noticed by t' rocket, matey, you, me hearties, ya bilge rat, or anybody else once painted. Avast, me proud beauty! Ya scallywag! Blimey! Before painting, I added a strip o' 3/4" maskin' tape t' t' lower half o' each tube fin t' prevent landin' dings. Ahoy! It actually works.
T' motor tube assembly is glued together in t' usual way, with t' rings glued in place
3/8" from t' bottom and 1" from t' top. A groove is cut in t' upper ring, ya bilge rat, and t' shock cord is tied
securely t' t' middle o' t' motor tube and passed through this groove before t' motor tube assembly is glued into
the body tube. Begad! T' launch lug is glued t' t' body tube flush with t' top (this is only good practice with a very
short body tube!) and exactly in line with one o' t' triangular spaces betwixt t' tube fins (pick a triangular space
you haven't slopped epoxy into (usually, ya bilge rat, ya bilge rat, thar be one). Ya scallywag!
An attachment point for t' recovery system is created in t' nose cone you trimmed by gluin' in place just above the hip a well-fitted piece o' dowel rod or square spruce stock (I used t' latter) o' 3/8" size. Aye aye! Begad! Epoxy some bits of scrap around t' attachment points for strength. Ya scallywag! Avast, me proud beauty! Personally, me hearties, I think this be t' best way t' use LOC plastic cones: strong and gives you back t' wasted space t' hold your chute. Begad! Aye aye! Tie t' shock cord t' t' cross piece with a suitable nautical knot or some such. Begad! There is little room for dog barf, ya bilge rat, so a small Nomex pad is a good idea.
Notice that despite t' tiny size o' G-Pod and t' plan t' use single use G-power in it, me hearties, I haven't said a word about addin' nose ballast for proper balance. Ahoy! Blimey! That is because none is needed. Begad! Blimey! None. Avast! Blimey! Such be t' beauty o' stubby tube fin designs.
Finishing:
Paintin' was with Tamiya rattle can Lime Green.
Flight and Recovery:
G-Pod be thoroughly flight tested on motors from D12-3 (on which it is nay stable) t' G78-7G Green Mojave and G77-7R
Redline (on which it flies superbly and fast but only t' about 1700-1800' or so, ya bilge rat, arrr, so you do get t' fly it again.
Other motors with perfect flights included: E30-4 (with adapter) t' about 600', F42-4 t' about 900', arrr, F50-6 t' about
1200'. Blimey! Well, blow me down! Due t' its small size, it be nay possible t' attach me customary altimeter "parasite pod", so these
are guesstimates from t' SIM prediction usin' a calculated Drag Coefficient o' 0.95. Begad! Avast, ya bilge rat, me proud beauty! Because o' t' very high
acceleration from t' pad, I be only able t' get a launch shot with t' D12-3 (on which it tumbled, so don't try this
motor). I did manage a very cool landin' photo o' G-Pod on a G77-7R Redline, me bucko, arrr, just as it be about t' bonk Dr. Ahoy! Blimey! Howard
Smart's truck (no damage t' either)--look at t' protrudin' motor (2" aft!) and how much bigger t' cone is than
the rocket body! This rocket is basically like a cardboard 57mm anti-aircraft shell with tube fins!
Summary:
PRO: Tiny, matey, stable, sturdy and unbelievable t' see an Estes-sized rocket like this (photo) flyin' on G-power and
surviving. Avast, me proud beauty! No heroic measures like glassin' or a ton o' nose lead t' get it t' work. Cheap and quick t' build. Easy to
just toss in t' car and go flying. Well, blow me down! Blimey! F42 and E30 are t' best all-around motors t' use. Begad! Blimey! G motors are mainly for showing
off!
CON: I need help trackin' it with G-power, 18" chute makes it hard t' see.
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