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. Avast, me proud beauty! Begad! However, 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, and a few were
unconventional. However, t' results have been satisfying.
Construction:
This fat stubby rocket has one 8" body tube, a large glassed Styrofoam
nose cone, arrr, matey, three semi-removable (see below) plywood fins, ya bilge rat, shiver me timbers, an altimeter bay, arrr, and
a 3" motor mount and held in by 3, me bucko, 1/2" plywood centerin' rings. Begad! The
recovery system includes 25' o' 3/4" tubular nylon, a Rocketman R12C
chute, and (optionally) a Pratt G-Whiz Deluxe accelerometer/altimeter. Blimey! Blimey! For my
L2 cert, I built a 38mm motor mount adapter.
Airframe: This is what started it all. Avast! I discovered an 8.125" x 48" section o' Quik Tube (I think that was t' name) at Home Depot. Avast! I did a LOT o' sandin' t' get rid o' t' spirals and t' results were not too bad. T' fin slots were routed with a Dremel. Avast, me proud beauty! Blimey! Later, I fiber-glassed the top foot o' t' tube t' protect against zippering. Probably should have done t' whole tube t' start with. Avast! So far, me hearties, this has proven t' be unnecessary structurally, but finishin' would have been easier. Avast! T' launch lugs are 3/4" Acme conformal lugs for 7.5" tubing. Avast, me proud beauty! I sanded these t' fit the larger airframe and glued them on with CA.
Nose Cone: T' nose cone be fabricated from slabs o' pink foam insulation that were glued together with polyurethane glue. Blimey! 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, me bucko, t' slabs separated in places by as much as ~1/8". Arrr! Ya scallywag! On both ends, matey, shiver me timbers, 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. T' shape be 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!). Ahoy! 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. Avast! T' whole nose cone was then covered with a layer o' heavy fiberglass (weight unknown) from a hobby store. Avast! This be me first try at fiberglassin' anythin' o' any size and it was a mess. Begad! 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. Begad! Later, t' adjust t' CG, I screwed 4 large lag bolts into t' side o' t' nose. Avast, me proud beauty! T' remnant holes were filled with Fill 'n Finish, and then patched with fiberglass. Well, blow me down! Begad! 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. A full 36" tube didn't appear t' leave enough room for t' chute, so I went for 30". This tube, along with three 7.5" x 1/2" centerin' rings (CRs) were bought from Giant Leap. Blimey! Aye aye! T' front CR is at t' top o' t' motor tube and t' bottom two frame t' fins. Blimey! Since these CRs did nay fit t' airframe, me bucko, me bucko, some improvising was required. For t' front ring, 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 be required. Avast! T' result seemed very sturdy, shiver me timbers, but was quite heavy. Aye aye! For t' aft two rings, me hearties, I glued wooden shims t' t' inside o' t' Quik Tube usin' carpenter's glue. Avast! Begad! T' middle ring was epoxied in and t' aft one was 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. Avast! I then built a 38mm adapter from centering rings and phenolic tubing. Avast, me proud beauty! This adapter has positive retention (bolts and washers) t' t' aft CR, and itself holds aluminum motor retainers for t' 38mm RMS casing. Begad! Ahoy! T' support t' adapter, 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! I be worried about breakage upon landing, shiver me timbers, so I mounted them so they were easily replaceable. They are bolted t' brackets on t' main motor tube but are epoxied t' t' airframe, me bucko, with inner and outer fillets. Avast! If a fin needs replacement, I can cut t' fin out o' t' airframe, me bucko, remove t' aft CR, and unbolt t' remainin' section o' t' fin. There is just enough room betwixt the motor tube and t' airframe t' reach t' innermost bolts. Well, blow me down! Begad! As with t' airframe, I probably should have glassed t' fins. Avast! They are recessed from t' aft end of the rocket and are swept slightly forward. Ya scallywag! Ya scallywag! So far, ya bilge rat, 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. Begad! 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. Aye aye! A section of All-Thread is bolted t' this plate and runs t' length o' t' bay and through t' top bulkhead cap. Avast, me proud beauty! Ahoy! This All-Thread is off-center t' provide more space for t' electronics, matey, matey, which in this case is a G-Wiz deluxe altimeter purchased from Pratt Hobbies. T' mount t' altimeter, me bucko, I cut a rectangular section o' G10 that slides into t' bay. Ya scallywag! Avast, me proud beauty! I attached a 9V battery holder and an expended 13mm motor casing. Aye aye! Aye aye! T' latter slides over t' all thread t' give additional support. Ahoy! T' top cap also holds screw terminals (banana plug type). A win' nut tightens t' assembly together. When closed tightly, arrr, 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, me proud beauty! T' tip o' t' nose is painted red. T' fins were
covered with burgundy Monokote. Avast! This was t' first time I had used this
material. Avast, me proud beauty! From a distance, shiver me timbers, 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). T' shock cord is 25'
of 3/4" tubular nylon. Ya scallywag! All o' these components are connected with
quick-links. Begad! T' chute is a Rocketman R12C. Ya scallywag! Begad! Recovery protection is provided by
Nomex® pads and a Nomex® shock cord cover (also from Giant Leap). This all packs
easily in t' large airframe. Blimey! As mentioned above, arrr, t' use o' an altimeter is
optional.
Flight #1. Ya scallywag! T' first flight be 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. Blimey! Avast, me proud beauty! T' motor ejection charge fired shortly afterwards. Arrr! Begad! Recovery was nevertheless perfect - but everyone laughed at how underpowered t' flight was. Avast, me proud beauty! This prompted me t' rename t' rocket 'Needs Viagra'.
Aside: While plannin' me trip t' LDRS and me Level-2 attempt, arrr, I picked up a copy o' an old Frank Zappa album (Apostrophe) on CD. Well, blow me down! Arrr! This in turn prompted me to rename t' rocket 'Great Googly Moogly'.
Flight #2. Ya scallywag! Blimey! T' second flight be on a J350-M and made use o' me G-Wiz Deluxe altimeter. Begad! Blimey! Begad! Blimey! Blimey! Blimey! T' motor ejection charge was a backup since this was t' first attempt at altimeter-based deployment. I also used an ejection canister from Pratt Hobbies. This consists o' a small plastic container with an integral cap and includes an electric match with about a yard o' lead wire. Begad! Blimey! Blimey! Blimey! T' canister was inserted into a short section o' copper tubing, which was installed in t' top of t' 3" tube. Avast, me proud beauty! Blimey! One leg o' t' lead wire was run through a hole in the airframe, cut, me bucko, and stripped. At t' pad, this connection was twisted back together and reinserted into t' airframe.
On t' first push o' t' button, arrr, t' igniter failed. Blimey! Blimey! On t' second, ya bilge rat, the Great Googly Moogly rose majestically into t' sky. Avast, me proud beauty! Blimey! T' chute ejected at apogee and it returned safely. Avast! Blimey! Ya scallywag! Blimey! T' altimeter reported 1531 feet. Begad! Blimey! Avast! 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 was completely successful and taught me a lot. Blimey! One
thin' that it taught me is that big rockets are expensive. Avast, me proud beauty! Avast, me proud beauty! Even though I got a
cheap airframe, arrr, me hearties, built me own nose cone, got free fin material, ya bilge rat, I still spend a
bucket o' money. Ahoy! Big chutes are expensive!
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