Launch report: Red Slim FTC 01.06.2002 and
By chance I happened to find some sort of a FTC in Germany. It's
outer diameter is 29,5 mm, length 125.5 cm. Having had problems
with internal bulk heads in other tubings, I used bottle tops and
shrinked them onto the FTC, then glued them with Bison Power PUR.
The resulting volume is 0,75 liter. Please note that this was
not a construction going for altitude, but rather for gaining experience
on backgliding FTC water rockets.
Backsliding rockets fascinate me, therefore this
my first FTC has to be a backglider! To understand the
backgliding phenomenon, click
This pic shows the laminated orange cardboard fins,
which are so quick to make, attached with brown and
blue tape. The balancing weight for backgliding
is taped on (red). The blue bottle cap is just for transportation.
of Red Slim FTC
To make it backglide, I tried to do swing tests.
However, these gave a completely false result.Without
any weights at the tail, the FTC always sideglided
during the test swings. It never flew straight like
a rocket should, no matter how we started to swing.
On the contrary, in real flight, the first test launches
with reduced pressure presented us a nosediving rocket.
As usual, we trimmed the fins somewhat and added
carefully weights to the back, until we had it back-/sideglide
in a stable manner. Watch it on the video (left)!
Here is today's launch crew: Stefan, Rolf, Ulrich
(from the left). We had about 20 launches of variously
sized rockets and lots of fun!
about the destroyed Red Slim FTC
On other launch days we had 5 perfect launches.
The rocket backglided well each time.
On the 6th launch with zero wind the following happened:
at apogee, the rocket fell back about 6 metres without
tilting, nose straight up, gaining more and more speed
downwards. After this taildive, the rocket top swung
over rapidly, exceeding the (up to today stable) backgliding
position in one go. It quickly found it's other stable
position and flew nose ahead towards the ground. The
rocket nose was destroyed on impact.
After this I took the trouble and measured the
CG, calculated the CLA with a small excel sheet and
the BCP with the VCP program. It appeared that the CLA
had a clearance of only 13 mm or 0.44 calibers from
the CG. See the drawing on top of the
Under conditions with winds greater zero or launch
angels unequal 90°, these kind of rockets usually
tilt early enough to find their second stable position,
the backgliding position, and stay there.
conditions with winds = zero and launch angels = 90°,
these kind of rockets may "swing over" this
second stable position and find their first stable position,
a) greater clearance between CG and CLA and
avoid launch angles of 90° in low wind conditions.