It's not a Graupner prop, it's one of the aeronaut CAMcarbon linked to above (I think they are better, design by Rudolf Freudenthaler). The Skylark UAV is smaller and seems faster than what is discussed here, of course that prop fits. Hand launch is as well possible with a 16.4 ft span, 20 lbs weight UAV, but I'd prefer a bungee launch because it's safer / more predictable.