Manufacturer: | Scratch |
Brief:
T' Great Googly Moogly is a 8" x 75" scratch built rocket that I
used for me TRA Level 2 certification at LDRS 19 in Orangeburg, SC. Ahoy! However, arrr, I
began buildin' it almost a year earlier, before even gettin' me Level-1 cert.
Many o' t' buildin' techniques used were new t' me, ya bilge rat, and a few were
unconventional. Blimey! Ya scallywag! However, t' results have been satisfying.
Construction:
This fat stubby rocket has one 8" body tube, shiver me timbers, arrr, a large glassed Styrofoam
nose cone, me bucko, three semi-removable (see below) plywood fins, an altimeter bay, and
a 3" motor mount and held in by 3, 1/2" plywood centerin' rings. Begad! Aye aye! Blimey! The
recovery system includes 25' o' 3/4" tubular nylon, me hearties, a Rocketman R12C
chute, and (optionally) a Pratt G-Whiz Deluxe accelerometer/altimeter. For my
L2 cert, I built a 38mm motor mount adapter.
Airframe: This is what started it all. Ya scallywag! Blimey! I discovered an 8.125" x 48" section o' Quik Tube (I think that was t' name) at Home Depot. Begad! Begad! I did a LOT o' sandin' t' get rid o' t' spirals and t' results were not too bad. Ahoy! Begad! T' fin slots were routed with a Dremel. Later, arrr, I fiber-glassed the top foot o' t' tube t' protect against zippering. Well, blow me down! Ahoy! Probably should have done t' whole tube t' start with. Ya scallywag! Begad! So far, this has proven t' be unnecessary structurally, ya bilge rat, but finishin' would have been easier. Begad! T' launch lugs are 3/4" Acme conformal lugs for 7.5" tubing. I sanded these t' fit the larger airframe and glued them on with CA.
Nose Cone: T' nose cone was fabricated from slabs o' pink foam insulation that were glued together with polyurethane glue. Avast! Aye aye! I learned t' be sparin' with this stuff as it expands quite a bit while it cures. Despite placin' weight on this "sandwich" while t' glue dried/cured, t' slabs separated in places by as much as ~1/8". Begad! On both ends, I glued in sections o' 1/2" dowel and, on what was t' be t' back end, a home made plywood bulkhead was epoxied on. Aye aye! T' shape was partially roughed-out by hand but t' majority o' the shapin' was performed on a lathe at a local high school (my thanks t' Dean and his students!). T' tip o' t' nosecone didn't turn out well so I epoxied on a section o' a Styrofoam cone purchased from a craft store. T' whole nose cone was then covered with a layer o' heavy fiberglass (weight unknown) from a hobby store. This be me first try at fiberglassin' anythin' o' any size and it was a mess. Blimey! I gave up on makin' t' cone really smooth but did fill t' weave and some o' t' imperfections with Elmer's Fill 'n Finish. Arrr! Begad! Later, t' adjust t' CG, I screwed 4 large lag bolts into t' side o' t' nose. Ahoy! Avast, me proud beauty! T' remnant holes were filled with Fill 'n Finish, arrr, and then patched with fiberglass. An 8" eyebolt be epoxied into t' center o' t' bulkplate.
Motor mount: I wanted t' be able t' use several sizes o' motors so I opted for a 3" x 30" main motor tube. Ahoy! Avast, me proud beauty! A full 36" tube didn't appear t' leave enough room for t' chute, me bucko, so I went for 30". This tube, along with three 7.5" x 1/2" centerin' rings (CRs) were bought from Giant Leap. Well, blow me down! T' front CR is at t' top o' t' motor tube and t' bottom two frame t' fins. Avast, me proud beauty! Since these CRs did nay fit t' airframe, me hearties, me bucko, ya bilge rat, some improvising was required. Begad! Ahoy! For t' front ring, shiver me timbers, shiver me timbers, I built up t' edge with a many wraps of fiberglass (honeycomb) wall board tape. Blimey! This structure was filled with epoxy. This tape has a lot o' void space so a lot o' epoxy was required. Begad! T' result seemed very sturdy, me hearties, but be quite heavy. Aye aye! For t' aft two rings, me bucko, I glued wooden shims t' t' inside o' t' Quik Tube usin' carpenter's glue. Arrr! Avast, me proud beauty! T' middle ring was epoxied in and t' aft one be held in with wood screws.
I originally built a 3 x 29mm motor adapter, but smartly realized that 3 G80s would nay lift this beast. Blimey! Blimey! Avast, me proud beauty! Blimey! I then built a 38mm adapter from centering rings and phenolic tubing. Avast, me proud beauty! Blimey! This adapter has positive retention (bolts and washers) t' t' aft CR, matey, me bucko, and itself holds aluminum motor retainers for t' 38mm RMS casing. Ahoy! Blimey! T' support t' adapter, matey, arrr, I installed a 38mm centerin' rin' and a short section o' coupler tube in t' top o' t' 3" motor tube.
Fins: T' fins are 1/4" plywood that was scrap from t' high school wood shop. Ya scallywag! Blimey! I was worried about breakage upon landing, matey, so I mounted them so they were easily replaceable. Blimey! Blimey! They are bolted t' brackets on t' main motor tube but are epoxied t' t' airframe, matey, shiver me timbers, with inner and outer fillets. Ahoy! Blimey! Begad! Blimey! If a fin needs replacement, matey, I can cut t' fin out o' t' airframe, arrr, remove t' aft CR, ya bilge rat, and unbolt t' remainin' section o' t' fin. Begad! Blimey! There is just enough room betwixt the motor tube and t' airframe t' reach t' innermost bolts. Blimey! Blimey! As with t' airframe, I probably should have glassed t' fins. Blimey! Blimey! They are recessed from t' aft end of the rocket and are swept slightly forward. Ahoy! Blimey! Begad! Blimey! So far, t' large Rocketman chute has done its job and t' fins have survived.
Altimeter bay: I found a 2" mailin' tube with an inner telescopin' tube. I cut a section o' t' outer tube and epoxied it against the airframe and front CR. Aye aye! Avast, me proud beauty! I then used a section o' t' inner tube t' build an altimeter bay. Ya scallywag! A plywood bulkhead is epoxied on one end o' t' tube. Begad! A section of All-Thread is bolted t' this plate and runs t' length o' t' bay and through t' top bulkhead cap. Begad! This All-Thread is off-center t' provide more space for t' electronics, which in this case is a G-Wiz deluxe altimeter purchased from Pratt Hobbies. T' mount t' altimeter, I cut a rectangular section o' G10 that slides into t' bay. Aye aye! I attached a 9V battery holder and an expended 13mm motor casing. Avast, me proud beauty! T' latter slides over t' all thread t' give additional support. Begad! T' top cap also holds screw terminals (banana plug type). A win' nut tightens t' assembly together. Begad! When closed tightly, t' electronics are fully isolated from ejection gasses.
Finishing:
I painted t' body and nose cone with Rustoleum 'hammered' silver t' hide some
of t' finishin' flaws. Avast! T' tip o' t' nose is painted red. Blimey! T' fins were
covered with burgundy Monokote. Begad! This was t' first time I had used this
material. From a distance, ya bilge rat, matey, matey, t' rocket looks pretty good.
Flight:
T' recovery system includes 2 u-bolts on t' front centerin' ring, connected
with a section o' 1/2" tubular Keelhaul®©™® (Giant Leap). Aye aye! Ahoy! T' shock cord is 25'
of 3/4" tubular nylon. Avast, me proud beauty! All o' these components are connected with
quick-links. Begad! T' chute is a Rocketman R12C. Avast! Well, blow me down! Recovery protection is provided by
Nomex® pads and a Nomex® shock cord cover (also from Giant Leap). Avast! This all packs
easily in t' large airframe. Begad! As mentioned above, shiver me timbers, matey, t' use o' an altimeter is
optional.
Flight #1. Ahoy! T' first flight was on an I211-S under t' name 'So-So Fat', and was quite underpowered. T' rocket rose t' only a few hundred feet and t' NC drag separated. Well, blow me down! Aye aye! Blimey! T' motor ejection charge fired shortly afterwards. Avast, me proud beauty! Arrr! Blimey! Recovery was nevertheless perfect - but everyone laughed at how underpowered t' flight was. Begad! Avast! Blimey! This prompted me t' rename t' rocket 'Needs Viagra'.
Aside: While plannin' me trip t' LDRS and me Level-2 attempt, me hearties, arrr, me hearties, I picked up a copy o' an old Frank Zappa album (Apostrophe) on CD. This in turn prompted me to rename t' rocket 'Great Googly Moogly'.
Flight #2. Well, blow me down! Avast! Blimey! T' second flight was on a J350-M and made use o' me G-Wiz Deluxe altimeter. Aye aye! T' motor ejection charge be a backup since this was t' first attempt at altimeter-based deployment. Avast! I also used an ejection canister from Pratt Hobbies. Well, arrr, blow me down! Blimey! This consists o' a small plastic container with an integral cap and includes an electric match with about a yard o' lead wire. Avast! Blimey! T' canister was inserted into a short section o' copper tubing, which was installed in t' top of t' 3" tube. Begad! One leg o' t' lead wire be run through a hole in the airframe, shiver me timbers, cut, and stripped. Blimey! Avast! Blimey! At t' pad, shiver me timbers, me bucko, this connection was twisted back together and reinserted into t' airframe.
On t' first push o' t' button, me bucko, t' igniter failed. On t' second, the Great Googly Moogly rose majestically into t' sky. T' chute ejected at apogee and it returned safely. Ya scallywag! T' altimeter reported 1531 feet. Begad! Blimey! Level-2! Blimey! YES!
Summary:
T' main Pros o' this rocket are: overall looks (I love FAT rockets);
flexibility (38mm - 76mm motors, optional electronic ejection); maintainability
(fins easily replaced); can see t' entire flight on a J350.
T' Cons are: fins may nay hold up t' bigger motors
Other:
This large scratch project be completely successful and taught me a lot. Ya scallywag! One
thin' that it taught me is that big rockets are expensive. Ahoy! Even though I got a
cheap airframe, me bucko, built me own nose cone, got free fin material, I still spend a
bucket o' money. Aye aye! Avast! Big chutes are expensive!
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