
(by Dr. Thomas Rackers - 07/24/06
)
Brief:
The Thing-a-ma-Jig is almost your standard 3FNC (3 fins and a nose cone) rocket
except for the fin design. FlisKits' new "Jig-Tech" technology
produces three fins that interlock in such a way that you're virtually
guaranteed to get all your fins on straight. The Thing-a-ma-Jig (also called
the TamJ) is designed to be easily constructed by first time rocket builders.
Construction:
The Thing-a-ma-Jig is a surprisingly long rocket for a first time kit as the
body tube is a full 18" length of BT-50. On our kit, the nose is a 3"
ogive-shaped balsa nose not including the shoulder. The three balsa fins are
laser-cut and include tabs and matching holes which are the key to the Jig-Tech
method of assembling the fin unit. It's almost like having an all balsa
"fin can". The motor mount takes standard Estes-style 18mm motors
using an engine block and retainer clip for motor retention. The elastic shock
cord (not just a rubber band) is about 28" long and is tied to the screw
eye in the nose at one end and to about 30" worth of Kevlar®
string at the other end. The other end of the Kevlar®
string is attached to the motor mount. There's a single 2" x 1/8"
launch lug located just above the installed fin unit--in fact the launch rod
will go through the fin unit. Recovery is accomplished with a 16"
flat plastic parachute. I was surprised to see that 12" chutes were not
used on this kit, but there's enough mass in that fin unit that the additional
area of the larger chute is probably not a bad idea.
We bought a batch of TamJ kits for a build-and-launch project with a local
Girl Scout troop. (My wife Thelma is a trainer for the local Girl Scout council
and is a past troop leader.) The girls in the troop are primarily Juniors
(roughly 10 to 13 years old) and had never assembled anything like this before.
Each girl got a kit and a set of the instructions, but everyone stayed together
on the assembly steps. Since we had gotten one of the first shipments of a TamJ
bulk pack, Jim Flis provided us with the first release of the assembly
instructions in PDF form, so I just printed out as many as we needed.
The instructions are very detailed, breaking the assembly down into
very small steps. Jim explained that this is the way educators recommend that
instructions be written for children: don't clump too many steps together. This
seemed to work well with our group. One nice touch in the assembly instructions
is the inclusion of short "rulers" in many of the early steps,
marking the length that is to be measured off for each step. This does
require that if you print the instructions from the PDF file, that you have
scaling turned off, otherwise the rulers and the fin alignment guide will be
the wrong sizes.
Assembly
proceeds in a very logical manner with no major issues or "gotchas".
The Jig-Tech fin unit does indeed make it quite easy to build a rocket where
you know the fins are going to go on straight. We used Aleene's Quick Dry Tacky
Glue for the entire assembly process except for inserting the assembled motor
mount into the body tube. For that step we used Elmer's White Glue to avoid
having the motor mount "seize" in the wrong position during
insertion. Once the rocket is assembled and the glue is set, the interlocking
fins form a very sturdy assembly, rivaling what you usually get with
through-the-wall mounting but without the slots.
My only real complaint about assembly of the rocket is that in a group
setting with builders who have never constructed anything involving detailed
instructions and new (to them) construction skills, the one hour assembly time
mentioned in the product literature is very optimistic, especially if the
person leading the build (in this case, me) is new to the kit as well.
Finishing:
The Thing-a-ma-Jig does not come with decals at this time. Since we had such an
early batch of TamJ's sent to us, FlisKits had not even come up yet with a
color scheme for the package art. But it wouldn't have mattered for our group,
because each Girl Scout got to take her TamJ home to paint any way she wanted
to. My only guideline to them was to keep any paint out of the launch lug. The
girls got quite creative in their paint schemes, mostly using brush on paints.
Construction Rating: 4
½ out of 5
Flight and Recovery:
The Girl Scouts got to fly their Thing-a-ma-Jigs at the June monthly launch of
the SouthEast Alabama Rocketry Society (SEARS #572), which my wife and I are
members of. I checked over each rocket to make sure the nose fit properly and
that everything was firmly attached. I had already demonstrated to the girls at
an earlier meeting how to fold and pack their parachutes and how to load their
motors and insert the igniters so they could prepare their own rockets for
flight. I had bought a bulk pack of Estes B6-4 motors for their first flights.
We had one rocket whose motor mount was not glued in as well as it should have
been, so we fixed that one on the spot. Each girl also received four squares of
Estes recovery wadding to load before packing their chutes. Once all the
rockets were ready to go, each girl filled out a flight card and then it was
off to the pads. Another club member and I watched as the girls loaded their
rockets onto the launch rods and connected the igniter leads. Once everything
was ready, each girl got to give the countdown for her rocket, and with the LCO
on the interlock button, she would get to press the launch button to send off
her rocket.
Each Thing-a-ma-Jig flew straight as an arrow with little to no spin at
all. I'm guessing they got up to about 500 feet when they popped their chutes
then came down within easy walking distance of the pads. We only had one
recovery failure where the knot tying the elastic and Kevlar®
shock cords together came apart. So that rocket's nose came down under the
parachute, while the body glided backwards to the ground spinning like a
pinwheel about its axis due to the unique shape of the fin unit. Once the parts
were retrieved and the knot was retied, the rocket was ready to go again.
Most of the Girl Scouts took advantage of our big multi-pad launcher to fly
their Thing-a-ma-Jigs again in a mass launch. Again, every rocket that left the
pad (we had a stubborn igniter on one) flew beautifully and came back down
intact.
Flight Rating: 5
out of 5
Summary:
This rocket is a very good kit for first time builders, although I think the
"one hour" assembly time advertised for this rocket assumes the
builder has some basic assembly skills already such as how to apply a bead of
glue without getting it everywhere, how to cut strings to a uniform length, and
so on. The novel fin construction does make it very easy to build a rocket that
will fly arrow straight and won't fall apart during handling or in flight.
PROs: Easy to assemble properly, hard to screw up badly. Unique design
catches the eye of even seasoned flyers. Rocket recovers itself gently even if
parachute detaches from body.
CONs: It took us a lot longer than one hour to build about ten of these in
a group setting.
Overall Rating: 5
out of 5