A frequent problem of small and middle size membrane constructions is to effectively cover an area with a 4-point hyperbolic membrane construction. With free inclined edge cables the clouding and rain protection is poor compared to the overall size of the structure. Comparatively little area is covered.

One solution of the problems is a flexural resistant clamping of the membrane to a stiff member. This solves the area-covering problem but at the cost of aesthetics. The construction   looses its charm, lightness and elegance.

The new approach of the bat-wing-sail may solve these problems. With this building method glass-fibre rods are inserted in the seams of the membrane. They cantilever over the edge cables of the membrane and enlarge the covered area up to 60 %. The typical shape of a leave or “bat” wing is the outcome. As a second advantage a reduction on the amount of pre-stress of the whole structure due to the inserted rods is expected.
This may become very interesting for middle size and larger membrane constructions in economical aspects.

Up to now the behaviour of the bat-wing-sail was unexplored.

In spring 2006 the IMS started research on this new approach in cooperation with the Anhalt University of Applied Sciences. A bat-wing-sail was built at the workshop of the University for Research.

Currently first tests considering loads, tensions, deflections of the highly interactive structure are undertaken. Understanding the complex behaviour of this new membrane structure is essential for further developments and use in real life.