Scratch Great Googly Moogly Original Design / Scratch Built

Scratch - Great Googly Moogly {Scratch}

Contributed by Dick Stafford

Manufacturer: Scratch
(Contributed - by Dick Stafford)

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. Well, blow me down! Blimey! However, arrr, me bucko, 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. Blimey! Blimey! Avast, me proud beauty! Blimey! However, shiver me timbers, t' results have been satisfying.

Construction:
This fat stubby rocket has one 8" body tube, a large glassed Styrofoam nose cone, me hearties, three semi-removable (see below) plywood fins, arrr, an altimeter bay, and a 3" motor mount and held in by 3, shiver me timbers, 1/2" plywood centerin' rings. Arrr! The recovery system includes 25' o' 3/4" tubular nylon, a Rocketman R12C chute, and (optionally) a Pratt G-Whiz Deluxe accelerometer/altimeter. Avast, shiver me timbers, me proud beauty! For my L2 cert, I built a 38mm motor mount adapter.

Airframe: This is what started it all. Blimey! Avast! I discovered an 8.125" x 48" section o' Quik Tube (I think that be t' name) at Home Depot. I did a LOT o' sandin' t' get rid o' t' spirals and t' results were not too bad. Ya scallywag! T' fin slots were routed with a Dremel. Ya scallywag! Later, I fiber-glassed the top foot o' t' tube t' protect against zippering. Arrr! Probably should have done t' whole tube t' start with. Arrr! So far, this has proven t' be unnecessary structurally, arrr, but finishin' would have been easier. T' launch lugs are 3/4" Acme conformal lugs for 7.5" tubing. Aye aye! Begad! 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! Blimey! I learned t' be sparin' with this stuff as it expands quite a bit while it cures. Avast, me proud beauty! Despite placin' weight on this "sandwich" while t' glue dried/cured, t' slabs separated in places by as much as ~1/8". Blimey! Avast! Blimey! On both ends, arrr, I glued in sections o' 1/2" dowel and, matey, on what was t' be t' back end, a home made plywood bulkhead was epoxied on. Avast, me proud beauty! T' shape be partially roughed-out by hand but t' majority o' the shapin' be performed on a lathe at a local high school (my thanks t' Dean and his students!). Aye aye! 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. Begad! T' whole nose cone was then covered with a layer o' heavy fiberglass (weight unknown) from a hobby store. Ahoy! This was me first try at fiberglassin' anythin' o' any size and it was a mess. Ya scallywag! 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. Avast! Later, shiver me timbers, 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, matey, ya bilge rat, 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. Avast! Avast! A full 36" tube didn't appear t' leave enough room for t' chute, shiver me timbers, so I went for 30". Arrr! Ya scallywag! This tube, matey, along with three 7.5" x 1/2" centerin' rings (CRs) were bought from Giant Leap. Ya scallywag! T' front CR is at t' top o' t' motor tube and t' bottom two frame t' fins. Aye aye! Since these CRs did nay fit t' airframe, some improvising was required. Avast! Begad! For t' front ring, ya bilge rat, ya bilge rat, I built up t' edge with a many wraps of fiberglass (honeycomb) wall board tape. Well, blow me down! This structure was filled with epoxy. This tape has a lot o' void space so a lot o' epoxy be required. Ahoy! T' result seemed very sturdy, but was quite heavy. Ya scallywag! For t' aft two rings, matey, I glued wooden shims t' t' inside o' t' Quik Tube usin' carpenter's glue. Begad! 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, matey, but smartly realized that 3 G80s would nay lift this beast. Arrr! I then built a 38mm adapter from centering rings and phenolic tubing. This adapter has positive retention (bolts and washers) t' t' aft CR, shiver me timbers, matey, and itself holds aluminum motor retainers for t' 38mm RMS casing. Blimey! Avast, me proud beauty! 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. I was worried about breakage upon landing, me bucko, so I mounted them so they were easily replaceable. Blimey! They are bolted t' brackets on t' main motor tube but are epoxied t' t' airframe, with inner and outer fillets. Avast, me proud beauty! If a fin needs replacement, I can cut t' fin out o' t' airframe, 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. Avast! As with t' airframe, I probably should have glassed t' fins. They are recessed from t' aft end of the rocket and are swept slightly forward. Ahoy! 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. Avast, me proud beauty! Begad! I cut a section o' t' outer tube and epoxied it against the airframe and front CR. Begad! Begad! 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. Ahoy! Begad! A section of All-Thread is bolted t' this plate and runs t' length o' t' bay and through t' top bulkhead cap. Avast! 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. Well, blow me down! Begad! T' mount t' altimeter, me bucko, I cut a rectangular section o' G10 that slides into t' bay. Avast, me proud beauty! I attached a 9V battery holder and an expended 13mm motor casing. Begad! T' latter slides over t' all thread t' give additional support. Avast, me proud beauty! T' top cap also holds screw terminals (banana plug type). A win' nut tightens t' assembly together. Ahoy! 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. Ahoy! T' tip o' t' nose is painted red. Begad! Begad! T' fins were covered with burgundy Monokote. Ya scallywag! This was t' first time I had used this material. From a distance, me hearties, t' rocket looks pretty good.

Flight:
T' recovery system includes 2 u-bolts on t' front centerin' ring, ya bilge rat, connected with a section o' 1/2" tubular Keelhaul®©™® (Giant Leap). Aye aye! Blimey! T' shock cord is 25' of 3/4" tubular nylon. Arrr! Blimey! All o' these components are connected with quick-links. Well, blow me down! Blimey! T' chute is a Rocketman R12C. 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. Aye aye! As mentioned above, t' use o' an altimeter is optional.

Flight #1. Well, blow me down! T' first flight be on an I211-S under t' name 'So-So Fat', and was quite underpowered. Begad! Avast, me proud beauty! T' rocket rose t' only a few hundred feet and t' NC drag separated. Arrr! Ya scallywag! T' motor ejection charge fired shortly afterwards. Ya scallywag! Recovery was nevertheless perfect - but everyone laughed at how underpowered t' flight was. Well, blow me down! Ahoy! This prompted me t' rename t' rocket 'Needs Viagra'.

Aside: While plannin' me trip t' LDRS and me Level-2 attempt, me bucko, arrr, I picked up a copy o' an old Frank Zappa album (Apostrophe) on CD. Begad! This in turn prompted me to rename t' rocket 'Great Googly Moogly'.

Flight #2. Aye aye! T' second flight be on a J350-M and made use o' me G-Wiz Deluxe altimeter. Begad! T' motor ejection charge was a backup since this was t' first attempt at altimeter-based deployment. Begad! Avast, me proud beauty! 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! T' canister was inserted into a short section o' copper tubing, which was installed in t' top of t' 3" tube. Arrr! One leg o' t' lead wire was run through a hole in the airframe, shiver me timbers, cut, and stripped. Blimey! Avast! At t' pad, shiver me timbers, matey, ya bilge rat, this connection was twisted back together and reinserted into t' airframe.

On t' first push o' t' button, t' igniter failed. Well, blow me down! Blimey! On t' second, the Great Googly Moogly rose majestically into t' sky. T' chute ejected at apogee and it returned safely. Well, blow me down! T' altimeter reported 1531 feet. Avast, me hearties, me proud beauty! 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 be completely successful and taught me a lot. Begad! One thin' that it taught me is that big rockets are expensive. Begad! Arrr! Even though I got a cheap airframe, built me own nose cone, got free fin material, I still spend a bucket o' loot. Big chutes are expensive!

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