This article is from the Model Rockets FAQ, by Wolfram von Kiparski with numerous contributions by others.
I remember my first time judging a 4H rocket fair. I judged
the advanced group, and the Tomcat was one of the most popular
models. I could easily tell which models had already flown by
looking for the mud and scratches on the nose cone. every one
seems to have trouble with this rocket.
Note that there were two versions of the instructions - a
bunch went out with a version of the instructions that would
have you put far too much deflection in the elevators,
i.e. double what's needed. A single shim from the stabilizer
stock is what's required.
Here are some tips John Kallend posted to RMR back on
Tue, 2 Aug 94 18:31:38 GMT
"I have now had six "successful" consecutive flights with my
latest Tomcat (successful means no repairs required). I find:
1) The C5-3 is far better than the C6-3
2) Don't angle the launch rod into the wind, launch straight
up. Have the top of the model toward the wind - it will pitch
"up" into the wind anyway. If all goes well it will arc over
inverted, into the wind and then roll upright before the wings
3) The model "flops" around on the launch pad unless you do
something to stop it. I put another 1/8" music wire rod into
the ground, parallel to the launch rod, to support the wing
and hold the model steady before launch.
4) The model seems to suffer from spiral instability on the
glide. This does not really show up on the test glides
(because they aren't long enough) but both of my surviving
Tomcats would drop into a steep spiral on the glide. Fixing
this would require a major re-design. Be very careful that
your stabilizers and vertical fins are well aligned. I also
reinforced the front of the body tube to avoid tearing when
the nose cone hits the ground first
5) Both of my current models came out heavier than Estes
suggested weight. I don't know how I could have made them any
6) I think this model could really do with a low thrust D
motor (say D6 or D8). Anybody know of such a motor in an 18 mm
[Other reports indicate prangs on the Apogee D3 and shreads on
the Aerotech D21. No reports yet on the Apogee D10 which might
be just what John was looking for]
And from a former R&Der Michael Dennett: "The Tomcat prototype
usually flew just fine in the hands of the designer. But it
was marginally stable, and I also saw many of them spiral in
during testing. It suffers from no dihedral, oversized
vertical stabilizers (which generally results in tightening
spirals once initiated) and if finished nicely, high wing
loading. Mechanically it is an intelligent design."
And from the kit designer himself!
"Great care must be taken to balance for flight, balance
side-to-side, and to make sure the wings are not twisted, and
that the hinge works well. Prayer helps too."