Footlaunch Glider Fussstart Segelflugzeug Planeur décollable à pied

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.

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