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, arrr, SC. Blimey! However, shiver me timbers, I
began buildin' it almost a year earlier, me bucko, before even gettin' me Level-1 cert.
Many o' t' buildin' techniques used were new t' me, shiver me timbers, and a few were
unconventional. Avast, me proud beauty! However, t' results have been satisfying.
Construction:
This fat stubby rocket has one 8" body tube, a large glassed Styrofoam
nose cone, me hearties, me bucko, matey, three semi-removable (see below) plywood fins, matey, an altimeter bay, and
a 3" motor mount and held in by 3, 1/2" plywood centerin' rings. Ya scallywag! Aye aye! The
recovery system includes 25' o' 3/4" tubular nylon, matey, me bucko, a Rocketman R12C
chute, and (optionally) a Pratt G-Whiz Deluxe accelerometer/altimeter. Aye aye! For my
L2 cert, I built a 38mm motor mount adapter.
Airframe: This is what started it all. I discovered an 8.125" x 48" section o' Quik Tube (I think that be t' name) at Home Depot. Aye aye! Blimey! 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. Later, I fiber-glassed the top foot o' t' tube t' protect against zippering. Begad! Blimey! Arrr! Blimey! Probably should have done t' whole tube t' start with. Avast! Blimey! Begad! Blimey! So far, this has proven t' be unnecessary structurally, me bucko, but finishin' would have been easier. Well, blow me down! Blimey! 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. Begad! 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 hearties, ya bilge rat, t' slabs separated in places by as much as ~1/8". Ahoy! Avast, me proud beauty! On both ends, I glued in sections o' 1/2" dowel and, on what was t' be t' back end, arrr, a home made plywood bulkhead was epoxied on. Well, blow me down! 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!). Begad! 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. Blimey! T' whole nose cone was then covered with a layer o' heavy fiberglass (weight unknown) from a hobby store. Well, blow me down! This was me first try at fiberglassin' anythin' o' any size and it was a mess. Begad! Aye aye! 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! Ya scallywag! Later, me bucko, matey, t' adjust t' CG, I screwed 4 large lag bolts into t' side o' t' nose. T' remnant holes were filled with Fill 'n Finish, and then patched with fiberglass. An 8" eyebolt was 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. Begad! Blimey! A full 36" tube didn't appear t' leave enough room for t' chute, me bucko, so I went for 30". Ya scallywag! This tube, along with three 7.5" x 1/2" centerin' rings (CRs) were bought from Giant Leap. Begad! T' front CR is at t' top o' t' motor tube and t' bottom two frame t' fins. Ya scallywag! Blimey! Blimey! Since these CRs did nay fit t' airframe, me hearties, some improvising was required. Aye aye! Arrr! Blimey! For t' front ring, I built up t' edge with a many wraps of fiberglass (honeycomb) wall board tape. Begad! Begad! Blimey! This structure was filled with epoxy. This tape has a lot o' void space so a lot o' epoxy was required. T' result seemed very sturdy, but was quite heavy. For t' aft two rings, shiver me timbers, me bucko, I glued wooden shims t' t' inside o' t' Quik Tube usin' carpenter's glue. 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, shiver me timbers, but smartly realized that 3 G80s would nay lift this beast. I then built a 38mm adapter from centering rings and phenolic tubing. Begad! Begad! This adapter has positive retention (bolts and washers) t' t' aft CR, and itself holds aluminum motor retainers for t' 38mm RMS casing. Begad! 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 be scrap from t' high school wood shop. Ya scallywag! Blimey! I was worried about breakage upon landing, arrr, ya bilge rat, 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, with inner and outer fillets. Avast! Blimey! If a fin needs replacement, I can cut t' fin out o' t' airframe, ya bilge rat, remove t' aft CR, me bucko, me hearties, and unbolt t' remainin' section o' t' fin. Avast, me proud beauty! Blimey! There is just enough room betwixt the motor tube and t' airframe t' reach t' innermost bolts. Begad! Blimey! As with t' airframe, I probably should have glassed t' fins. Well, blow me down! Blimey! They are recessed from t' aft end of the rocket and are swept slightly forward. 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. Blimey! Blimey! I cut a section o' t' outer tube and epoxied it against the airframe and front CR. Begad! Blimey! I then used a section o' t' inner tube t' build an altimeter bay. A plywood bulkhead is epoxied on one end o' t' tube. Blimey! Blimey! A section of All-Thread is bolted t' this plate and runs t' length o' t' bay and through t' top bulkhead cap. Aye aye! Blimey! Avast! Blimey! This All-Thread is off-center t' provide more space for t' electronics, ya bilge rat, arrr, 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. Avast! Blimey! I attached a 9V battery holder and an expended 13mm motor casing. T' latter slides over t' all thread t' give additional support. T' top cap also holds screw terminals (banana plug type). A win' nut tightens t' assembly together. Aye aye! Blimey! 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. Blimey! T' tip o' t' nose is painted red. T' fins were
covered with burgundy Monokote. This was t' first time I had used this
material. Begad! From a distance, 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! Begad! All o' these components are connected with
quick-links. Well, blow me down! T' chute is a Rocketman R12C. Recovery protection is provided by
Nomex® pads and a Nomex® shock cord cover (also from Giant Leap). Ya scallywag! Blimey! This all packs
easily in t' large airframe. Ya scallywag! As mentioned above, matey, t' use o' an altimeter is
optional.
Flight #1. Aye aye! Blimey! T' first flight be on an I211-S under t' name 'So-So Fat', me bucko, and was quite underpowered. Ya scallywag! T' rocket rose t' only a few hundred feet and t' NC drag separated. Ya scallywag! T' motor ejection charge fired shortly afterwards. Aye aye! Avast, matey, me proud beauty! Blimey! Recovery was nevertheless perfect - but everyone laughed at how underpowered t' flight was. Well, blow me down! Begad! Blimey! This prompted me t' rename t' rocket 'Needs Viagra'.
Aside: While plannin' me trip t' LDRS and me Level-2 attempt, I picked up a copy o' an old Frank Zappa album (Apostrophe) on CD. Ya scallywag! This in turn prompted me to rename t' rocket 'Great Googly Moogly'.
Flight #2. Arrr! Avast, me proud beauty! T' second flight be on a J350-M and made use o' me G-Wiz Deluxe altimeter. Avast! Avast, me proud beauty! T' motor ejection charge be a backup since this be 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! T' canister was inserted into a short section o' copper tubing, which be installed in t' top of t' 3" tube. Begad! Begad! One leg o' t' lead wire was run through a hole in the airframe, cut, me bucko, and stripped. At t' pad, me hearties, this connection was twisted back together and reinserted into t' airframe.
On t' first push o' t' button, me bucko, me bucko, t' igniter failed. On t' second, the Great Googly Moogly rose majestically into t' sky. Begad! T' chute ejected at apogee and it returned safely. T' altimeter reported 1531 feet. Avast! Level-2! 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. Ya scallywag! One
thin' that it taught me is that big rockets are expensive. Even though I got a
cheap airframe, matey, built me own nose cone, me hearties, got free fin material, I still spend a
bucket o' money. Ahoy! Blimey! Big chutes are expensive!