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. 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, me hearties, matey, and a few were unconventional. Ahoy! However, t' results have been satisfying.

Construction:
This fat stubby rocket has one 8" body tube, ya bilge rat, a large glassed Styrofoam nose cone, three semi-removable (see below) plywood fins, me bucko, me hearties, an altimeter bay, matey, and a 3" motor mount and held in by 3, 1/2" plywood centerin' rings. The recovery system includes 25' o' 3/4" tubular nylon, ya bilge rat, matey, 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. Well, blow me down! Blimey! I discovered an 8.125" x 48" section o' Quik Tube (I think that was t' name) at Home Depot. Avast, me proud beauty! Blimey! Blimey! Blimey! I did a LOT o' sandin' t' get rid o' t' spirals and t' results were not too bad. Begad! Blimey! T' fin slots were routed with a Dremel. Ya scallywag! Blimey! Later, me hearties, I fiber-glassed the top foot o' t' tube t' protect against zippering. Arrr! Blimey! Probably should have done t' whole tube t' start with. Aye aye! Blimey! Begad! Blimey! So far, this has proven t' be unnecessary structurally, me hearties, but finishin' would have been easier. Avast, me proud beauty! Blimey! Well, blow me down! Blimey! T' launch lugs are 3/4" Acme conformal lugs for 7.5" tubing. Ahoy! Blimey! Well, blow me down! Blimey! 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. I learned t' be sparin' with this stuff as it expands quite a bit while it cures. Well, matey, blow me down! Despite placin' weight on this "sandwich" while t' glue dried/cured, ya bilge rat, me bucko, t' slabs separated in places by as much as ~1/8". Ya scallywag! Ahoy! On both ends, ya bilge rat, arrr, I glued in sections o' 1/2" dowel and, me hearties, on what was t' be t' back end, a home made plywood bulkhead was epoxied on. Avast! 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. Well, blow me down! T' whole nose cone was then covered with a layer o' heavy fiberglass (weight unknown) from a hobby store. Begad! This be me first try at fiberglassin' anythin' o' any size and it was a mess. Ahoy! 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. Ya scallywag! Later, 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. Ahoy! 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. Blimey! A full 36" tube didn't appear t' leave enough room for t' chute, so I went for 30". Arrr! Begad! This tube, arrr, along with three 7.5" x 1/2" centerin' rings (CRs) were bought from Giant Leap. Avast, me proud beauty! T' front CR is at t' top o' t' motor tube and t' bottom two frame t' fins. Arrr! Since these CRs did nay fit t' airframe, ya bilge rat, some improvising was required. Ya scallywag! For t' front ring, me hearties, I built up t' edge with a many wraps of fiberglass (honeycomb) wall board tape. Ya scallywag! This structure be filled with epoxy. This tape has a lot o' void space so a lot o' epoxy was required. T' result seemed very sturdy, shiver me timbers, but be quite heavy. Ahoy! For t' aft two rings, I glued wooden shims t' t' inside o' t' Quik Tube usin' carpenter's glue. Arrr! 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, ya bilge rat, arrr, but smartly realized that 3 G80s would nay lift this beast. I then built a 38mm adapter from centering rings and phenolic tubing. This adapter has positive retention (bolts and washers) t' t' aft CR, and itself holds aluminum motor retainers for t' 38mm RMS casing. 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 be scrap from t' high school wood shop. Ahoy! I be worried about breakage upon landing, matey, so I mounted them so they were easily replaceable. Aye aye! They are bolted t' brackets on t' main motor tube but are epoxied t' t' airframe, shiver me timbers, matey, with inner and outer fillets. Ahoy! Well, blow me down! If a fin needs replacement, matey, I can cut t' fin out o' t' airframe, remove t' aft CR, and unbolt t' remainin' section o' t' fin. Arrr! Ahoy! There is just enough room betwixt the motor tube and t' airframe t' reach t' innermost bolts. Arrr! Begad! As with t' airframe, I probably should have glassed t' fins. Avast! Aye aye! They are recessed from t' aft end of the rocket and are swept slightly forward. Well, me hearties, blow me down! So far, arrr, 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! Begad! I cut a section o' t' outer tube and epoxied it against the airframe and front CR. Ahoy! Begad! I then used a section o' t' inner tube t' build an altimeter bay. Ahoy! Aye aye! A plywood bulkhead is epoxied on one end o' t' tube. Ya scallywag! Avast! 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, me hearties, which in this case is a G-Wiz deluxe altimeter purchased from Pratt Hobbies. Begad! T' mount t' altimeter, shiver me timbers, I cut a rectangular section o' G10 that slides into t' bay. Arrr! Aye aye! I attached a 9V battery holder and an expended 13mm motor casing. Arrr! Avast, me proud beauty! T' latter slides over t' all thread t' give additional support. Blimey! Begad! T' top cap also holds screw terminals (banana plug type). A win' nut tightens t' assembly together. Well, blow me down! When closed tightly, me hearties, 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. Begad! T' tip o' t' nose is painted red. Avast, me bucko, me proud beauty! T' fins were covered with burgundy Monokote. This was t' first time I had used this material. Begad! Blimey! 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). Ya scallywag! T' shock cord is 25' of 3/4" tubular nylon. Begad! All o' these components are connected with quick-links. Begad! T' chute is a Rocketman R12C. Avast, me proud beauty! Recovery protection is provided by Nomex® pads and a Nomex® shock cord cover (also from Giant Leap). Avast, ya bilge rat, me proud beauty! This all packs easily in t' large airframe. Well, blow me down! As mentioned above, me bucko, t' use o' an altimeter is optional.

Flight #1. Begad! Avast! T' first flight was on an I211-S under t' name 'So-So Fat', shiver me timbers, me hearties, and was quite underpowered. Avast! Aye aye! T' rocket rose t' only a few hundred feet and t' NC drag separated. T' motor ejection charge fired shortly afterwards. Avast, me proud beauty! Recovery was nevertheless perfect - but everyone laughed at how underpowered t' flight was. Begad! 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. This in turn prompted me to rename t' rocket 'Great Googly Moogly'.

Flight #2. T' second flight was on a J350-M and made use o' me G-Wiz Deluxe altimeter. Avast! T' motor ejection charge be a backup since this was t' first attempt at altimeter-based deployment. Begad! Ya scallywag! I also used an ejection canister from Pratt Hobbies. Begad! This consists o' a small plastic container with an integral cap and includes an electric match with about a yard o' lead wire. Well, blow me down! Ahoy! T' canister was inserted into a short section o' copper tubing, arrr, which was installed in t' top of t' 3" tube. One leg o' t' lead wire was run through a hole in the airframe, me hearties, cut, and stripped. At t' pad, this connection be twisted back together and reinserted into t' airframe.

On t' first push o' t' button, me hearties, t' igniter failed. Avast! On t' second, the Great Googly Moogly rose majestically into t' sky. Well, blow me down! Avast, me proud beauty! T' chute ejected at apogee and it returned safely. Blimey! T' altimeter reported 1531 feet. Begad! Blimey! Level-2! YES!

Summary:
T' main Pros o' this rocket are: overall looks (I love FAT rockets); flexibility (38mm - 76mm motors, me hearties, me hearties, 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! Blimey! One thin' that it taught me is that big rockets are expensive. Even though I got a cheap airframe, built me own nose cone, got free fin material, me hearties, I still spend a bucket o' money. Big chutes are expensive!

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