the grob g104 speed astir was a competition sailplane produced in germany in the late 1970s as grob's first design in the 15 metre class. taking the g102 astir design as a starting point, the speed astir featured a new wing of narrower chord and different section, a fin and rudder of reduced height, capacity for 150 kg (330 lb) of water ballast, and "elastic flaps". this latter feature eliminated the drag normally created by the gap between the wing trailing edge and a deployed flap by attaching the highly-elastic skin of the wing to the flap itself, so that when the flap was deployed, this skin would stretch over the gap that would normally be created.