Hollow Hemisphere (Q50361)

This is pretty brute-force compared to VeryWetPaint's slick hollow sphere (http://www.thingiverse.com/thing:3068). I'm using it as an acoustic reflector to turn a directional ultrasonic receiver into an omnidirectional receiver. The STL is set to a 7.5 cm diameter. The supports are 1 mm thick (2 layers) and might not scale down very well. The shape can be scaled and the supports adjusted in 123d pretty easily.