I have been thinking how the efficiency of a tandem wing aircraft could be improved. In tandem wing aircraft the front wing determines pretty much how high total Clmax the aircraft is going to have which translates then to the required wing area. To maximize the efficiency, because flaps can not be used in the rear wing, the Clmax of the front wing is desirable to be as high as possible. Usually on tandem wing and canard aircraft the Clmax of the front wing is around 2.0 and the elevator is a single slotted flap.
It may not be mechanically very practical, but theoretically it could be possible to increase the Clmax of the front wing by adding more high lift devices into it. There could be a fowler flap implemented so that it increases the wing area substantially while the single slotted elevator flap remains working as usual in the trailing edge. The problem is that how you do that when the whole elevator system moves as consequence when the flaps are lowered or raised (the fowler is either inside the wing or protruded out of the trailing edge). But if this was practical with any other means than using servo motors for the elevator too, it could increase the available lift from the front wing somewhat. A challenging thing in this obviously is that the shear web that connects the spar caps goes through the front wing, and the flap system can not break the integrity of the shear web. More limiting factor also is that the chord length of a tandem wing aircraft front wing is low and there is not that much space for the high lift device.
Anyway, it would be interesting to try this out with a radio controlled model.
I hereby license this invention under the terms and conditions of GNU General Public License, version 3, or any later version. (C) 2008 Karoliina Salminen. All rights reserved. By reading this text, you aknowledge this and agree with the terms and conditions of the GPL license.