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