Brief:
I picked up an Estes Prowler after seeing how well a very badly built example
performed at my son's space camp over the summer. Despite being indifferently
built with plastic model glue, having the wiggly fins stabilized with masking
tape, and flown unpainted, the Prowler impressed the crowd with an excellent
flight (and miracle recovery considering the poor construction. The recovery
system and engine mount both blew out of the rocket at ejection.) I decided
that anything that could perform like that Prowler did despite it's many
handicaps was definitely a rocket that I needed to further investigate.
Besides, even unpainted it looked good and I could see a lot of potential in
the design. I bought one the next day, but passed on the model glue.
Modifications:
Switched the Prowler from a single 18mm powered rocket to a clustered 3 x 18mm
rocket
Construction:
- 3 - 12" BT-60 body tubes
- PNC-60NA nose cone
- 3 - 2.75" BT-20 engine tubes
- 3 - engine blocks
- 36" Kevlar®
shock cord
- 36" 1/4" sewing elastic shock cord
- 3/32" balsa fin stock
- 2 - BT-60 tube connectors
- 2 - 1" x 1/8" launch lugs
- 12" nylon parachute
- Decal
I started this project at about the same time that I received a three engine
clip whip in the mail from Thrustline Aerospace, so it was natural that I
viewed every BT-60 based kit as a potential cluster candidate. I built a three
18mm cluster mount using the Astron Cobra directions, (with the exception of
gluing my Kevlar®
into the space in the middle of the three engine tubes,) and decided on a
method to seal the three passageways between the cluster tubes and the main
body tube. I decided to glue a CR-5060 centering ring to the top of the mount
to act as both an alignment guide and ejection gas seal. I glued it securely to
the tops of the engine blocks, taking care to seal every possible spot where
the gases might escape. When this was dry I carefully snipped away the parts of
the rings that partially covered the tops of the motor tubes.
Because the Prowler was designed with "through the wall" (TTW) fin
mounting, I had to take a little extra care when gluing the cluster mount into
place. Since the TTW tabs would slip between the outside of the joined motor
tubes, I needed to sand the edges of the tabs down somewhat. I sanded all three
fins and matched each one up with a particular slot, then numbered the fin, the
slot and the space between the motor tubes to keep my alignment as close to
perfect as possible. The system worked well. When I slid the motor mount into
place, I dry fitted each of the fins so that the alignment would be as close as
possible to centered. After the mount had dried, I pulled the fins out, spread
some glue down between the tubes, and mounted the fins for real. When they
dried I had a very solid engine mount/fin combination, and my last steps were
putting a small amount of glue soaked Estes recovery wadding into the
passageways at the bottom of the engine mount, just in case, and solidly gluing
the CR-5060 centering ring from above before permanently connecting the two
lengths of BT-60. From this point the rocket was flight worthy in no time.
Finishing:
The suggested color for the Prowler was dark blue, but I found a deep burgundy
paint that I thought would look really cool with the Prowler's glow in the dark
decal. I made the standard preparations to paint the rocket, sanding all
surfaces smooth after several coats of thinned Elmer's Fill N Finish, but a
launch beckoned before I had the chance to even get the rocket primed, hence
the lack of pictures of the finished rocket.
Construction Rating:
5 out of 5
Flight:
As you may have guessed, the Prowler made but one flight during it's brief stay
in my fleet, but it was a memorable one. Although not my first cluster, it was
the sleekest from a design standpoint, and this really showed in it's
performance. Roaring off the pad into a clear, calm, late afternoon sky with
all three C6-5's aflame, the Prowler looked to be having a textbook flight. At
ejection it was just a dot, but neither I nor my spotters noticed anything
amiss with the exception of an excessive amount of drift. Chalking it up to a
rogue thermal, I stomped off into the heavy, late summer growth in search of
it. A half hour later, I was disgusted and seriously considering giving up when
I caught a flash of neon yellow as I did one of the 360 degree spins that I did
every 100 feet or so. Legs cramping, jeans covered in burrs and spider webs,
and patience gone, I crashed through the underbrush to the parachute, only to
find that the nose cone, shock cord and Kevlar®
thread were still attached to the chute. The body tube that I had sweated over
was nowhere to be found. I searched without enthusiasm for a few more minutes,
then gave up and returned to the range head. Back there I found everyone
packing up to go, but all present were surprised that the separation had
occurred without any of us noticing it. After breaking down the range, my son
and I met my wife and daughter at a nearby pizza place, and all through the
meal the loss of the Prowler stayed stuck in my craw. It was really bugging me,
and I mentioned it to my wife. "Why don't you buy another one?" she
suggested. I knew I married her for something other than her good looks. I
actually hadn't thought of that, and stopped at the toy store on the way home.
I got the last Prowler on the rack, and as it turned out, the last one that
would be on the rack as Estes discontinued it.
Recovery:
Flight Rating:
5 out of 5
Summary:
The Prowler turned out to be a great looking, impressive performing rocket when
equipped with the clustered engine mount. Plenty of smoke, fire and altitude.
Pro's:
- Through the wall fins on an Estes rocket!
- Sleek good looks.
- Ease of clusterability.
Con's:
- Nothing to stop the parachute from dropping deep into the body tube.
- Need to figure out a more secure way to mount the Kevlar®
cord for the shock cord.
Overall Rating:
5 out of 5
Flight Log
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