Interpretation and comments on the above performance
calculations
The
absolute values of the above calculations are not necessarily
correct, but the comparison of the values between the different
aircrafts should be ok.
All
values are based on the Xfoil results. When comparing the
calculations to the measurements of wind tunnels, Xfoil usually
underestimates the airfoil drag. Therefore, the calculated L/D of
the foot-launch 1comet of 37.5 is probably too high, as well as the
calculated L/D of 28 of the 13.5 m span foot-launch glider. In
general, we estimate these values to be 5% to 15% too optimistic,
depending on speed. For that reason we indicate a maximum L/D of 36
in the performance data.
The
1comet is designed to perform 30% to 50% better than comparable
existing foot-launch gliders, thanks to the 13% thick laminar
airfoil and 15 m span. Other foot-launch gliders currently
available on the market use airfoils with an upper surface
transition at about 30%, in comparison to a transition of the
1comet airfoil further back than 65%.
To
improve performance – especially at high velocity – a more
aerodynamic cabin/fuselage and an increased wing load are
necessary. The calculations show, that the 1comet glider version
with an increased wing load of 25 kg/m2, a good glider-like cabin
and modified flaps will reach a L/D above 40. The sink rate of
the best modern 15 m gliders of 45 kg/m2 or 400+ kg take-off weight
is not as low as the sink rate of the 1comet, but these heavy
gliders are performing much better at high speeds and can be flown
much faster at the same L/D. Wing load is the decisive
factor.
We did
performance calculations of a well-known foot-launch flying wing,
but these calculations are less accurate than the other
calculations we did. This is why these calculations are not
depicted in the graphs. They show that the flying wing of 12.8 m
wingspan does not fly as well as the conventional 13.5m wing span
foot-launch glider at low speed, but performs better when flying at
high speed. The 1comet is designed to fly better at any
speed.
New Cage Design
Will you offer an electric version?
Yes,
the basic engineering has already been done and we are currently in
discussions with suppliers.
When will the 1comet be commercially available?
We are
currently testing the 1comet and we are going to launch a second
prototype, similar to the production glider. Simultaneously, we are
choosing subcontractors for the components. We will not sell
options for financing the project. We will take orders once we are
sure the 1comet is flying well, when we know the price and the
exact production time schedule. If everything goes according to
plan, we will be able to take orders in autumn or winter of
2019.
What will it cost?
The
price is not fixed yet.
Why does the 1comet fly better than comparable foot-launch
gliders?
We use
modern laminar air foils, 13% thick: the existing foot-launch
gliders, which are commercially available, have airfoils that are
turbulent on the upper side from about 30%, and which are
thicker. Our wingspan is higher (15 m instead of 13.6 m
respectively 12.8 m) and the cabin is slightly less wide and more
streamlined.
The 1comet weighs significantly less than a "normal" glider or an
ul glider. Is it robust?
Yes and
no: when dimensioning the prototype, we followed the usual
standards for ul gliders where it was possible, so the 1comet
resists in the air when flying. It’s designed for 6 G limit and 9 G
ultimate positive load with a 100 kg pilot. We did several limited
load tests on the prototype. We have invested more than 4 man-years
of engineering to optimize the structure with thousands of hours of
FEM calculations. Nevertheless, we have to use very thin Carbon
layers, so when manipulating the glider on the ground you have to
be careful.
Can the 1comet be flown without pilot fairing “cabriolet
style”?
Yes,
but overall performance will be cut to half.
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Liechtenstein