Hi Sigurd ,
Very happy to read you . Now I know why you look for high Cl . Indeed , you are right to remember me that Cl max results of Hepperle code are not to trust . Hepperle himself told you it , so we are sure that nothing is certain ! Perhaps Drela would tell us the same . Nevertheless we want to make some evaluation of our airplanes and for that we use the results of a simulation or of wind tunnel when it exist . When I read 1.7 Cl on a screen I am happy to have something that allows me to draw a project of a 15 sq/m flying at 8 ms. More or less ! Note that I believe that the speed of an ornitho is, at a first step of approximation, the same than one of a fixed-wing .
Perhaps Cl max of a twin airfoil is wrong too in Hepperle simulation. Minimum speed of Galopin Bis, a Flying Flea , could make me believe it. A twin-NACA 23112 has 1.5 Cl max in the simulation, with 2ยบ between the wings. If we believe the aemometer the real one has 1.8 Cl. But we cannot trust more in anemometers . Indeed all that is a little involved; forgetting that the Galopin works with finite AR , and so on. Nevertheless I still hope that a pair of wings in phase , or near one of the other if it is gliding have a very good efficiency both by span efficiency and by 2D flow improvement, and this is what about we are interested. In this field there is a lot to try. Simulation helps but not so much .
I have not thought a lot about hovering . So , take it easy, my point of view is quite different of yours . That is why I speak about moderate lift , and you about big one .
Cheers , Dominique .
Last edited on Sat Jan 23rd, 2010 04:01 am by D.Bernardin
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