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I
picked up this Quest Big
Betty like so many
other rocketeers do - it was there and I had the uncontrollable urge to
buy a rocket to add to my already ridiculous round-tuit pile 
It's a not-so-subtle facsimile of the Estes Big
Bertha – more so since I added a fourth fin. And of course,
the 18mm motor mount had
to go. I replaced it with a 24mm mount using Totally Tubular's foil
lined T-50mf. Motor retention was added using 2-56 all-thread and
brass hooks.
The fins were re-inforced with card stock at the
roots.
It rips on D's and E's, and I had plans of maybe putting
an F32 in
it someday. I have one in my stash, and it's a good match for a
rocket like this.
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Motor Retention
Here's a close-up of the
motor tube. The annular space around the motor tube isn't wide
enough to mount T-nuts in, but I could mount some all-thread. The
key was fashioning hooks that worked with studs. Doing it this
way allowed me to cut the all-threads off such that no pointy objects
are protruding aft.
Normally, hooks would be S-shaped as indicated in blue below. But
because of the short annular radius, there is no way a hook could fit
between the motor tube and the all-thread - the hook would be too close
to the all-thread and block the nut from turning. So the hooks
had to be shaped differently.
These were made from fairly thick brass strips from the hobby store (or
hardware store). It would take an extraordinary motor event to
bend one.
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| Followup: The rocket
above was lost in action at NARAM 45 near Evansville, Indiana in
2003. And along with it went my 24mm RMS
case. But not to dwell on it, I began a replacement. |
Betty-Gee
A tribute to the classic Astron Apogee
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Here's my replacement
Betty complete with booster. I like the old kit card artwork, so
I painted it in that style. But had to get a decal made since the
new kit I bought has a totally different (and huge) decal.
As it turns out, "Big" should have been a much larger font, and "Betty"
should have been lower case after the B 
Like my last one, I added a fourth fin thus making it more like the
Apogee II (and the Bertha). It lacks the payload section of the
Apogee II. If I had to over again, I'd probably go for a much
more Apogee-esque finish and at least paint in a faux payload space
with black spiral stripe.
The booster is shorter than scale length. Frankly, it would have
been huge if it were perfectly scale. I chose to shorten it to
keep down the size and to allow tape-together staging.
Even with all these deviations, I find it to be a very likable tribute
to the venerable Apogee II.
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Starting at the top and
working my way down, here are some details about the rocket.
Instead of using the plastic loop molded into the nosecone, I wanted a
connection more substantial, so I cut a slot in the side of the
nosecone shoulder, and then mounted a #6 screw-eye. This
nosecone's
not coming off without a catastrophic event
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The shock cord is a 3/8"
wide nylon strip. I can't recall where I got it, but what I like
about it is that its width helps to minimize the chances of a zipper in
the event of a late or early deployment. Inside the airframe,
kevlar is connected to the motor mount and transitions to the nylon
just below the opening.
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Here's a good look at my
shock management technique. I fold the shock cord then wrap it
with 1/4" masking tape for several inches. If I get a hard
deployment, the tape gets torn. This dissipates the energy of the
event and protects the chute from shredding and the body tube from
zippering. Plus, unlike elastic, it doesn't store the
energy; it won't pull the nosecone crashing back into the rocket.
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Here's a close look at the
motor hook. It's made from piano wire. There's no forward
tang - any length motor will fit in tube. So an aft thrust ring
must be on the motor. Three wraps of 1/4" masking tape works fine
for me.
There are two ways deal with the hook when staging. It can either
be left pushed out of the way by the motor (thus requiring the
sustainer motor be friction fitted) or it can be pushed into the gap
between the taped-together motors. I usually cut a small notch in
the forward end of the booster motor to allow for the hook to poke
through. That way, the hook gets used for its intended
purpose. It pokes a small hole in the cellphane tape joining the
motors, but poses no problems for staging.
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The aft centering ring is
moved well forward to allow room for the staging coupler. It
helps to make the motor tube longer so that its rings aren't too close
together.
1/4" launch lugs were used. This allows a 6' long launch
rod. It turns out that the rocket flies fine on a 4' rod, but
when I was building it, it wasn't clear how slow it would be off the
rod.
The back end is it a bit ragged. Staging seems to take an extra
toll on rockets. I think the hot air blast at separation has a
extra detrimental effect.
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The staging coupler
extends forward about 1" out of the booster. As I recall, I made
this one using a 38mm motor tube coupler with a few wraps of tissue and
dope.
The Quest T40 tube's inside diameter is about 1.55", and the couplers
are in the range 1.50 to 1.52", so they'll be a sloppy fit without the
tissue.
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The booster motor tube has
a relief cut in it for the sustainer motor hook.
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Even with the shortened
(from scale) booster, I still had to recess the motor tube about 1/2"
in order to employ tape-together staging without having to glue
extensions on the booster motors.
(Given all these tradeoffs, in hindsight, gap staging might have been a
good idea, although the booster would have been much heavier if it was
scale length.)
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Here's the Betty-Gee in
action at a launch in McGregor, Texas.
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9-20-2010
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