The techwings small size and rugged swept flying wing design naturally lead to some design challenges. Good low speed handling can be very difficult to achieve. this has a lot to do with the low aspect ratio and swept wing, leading to a large wing tip vortex as pictured here
Another problem that flying wings suffer from is the low CL max, Around 0.75. this is due to the need for reflex at the tail of the airfoil. the trailing edge of a flying wing general needs to produce down force. In a normal airfoil this wing area can be used for lift instead. I use a fixed leading edge slot in order to drastically improve the stall speeds and low speed handling as well as improve aileron responsiveness.
in this Java foil analysis, CL max is estimated to be around 1.3 much higher then the 0.7 Cl max of the unmodified foil. Stall is pushed to around 17 degrees as apposed to around 13. I also added real wingtips to control the vortex, reduce drag and to improve stalls and mostly eliminate tip stalls.
Hobbyuav 