The Sgian Dubh prop was made more like a paddle to increase the ground clearance on landing and taking off. Peak revs on the ground was 6,200 rpm:

Sgian Dubh Propellor
Photo A		Photo B

The Iolaire prop was for a BMW 100RS; was quiet, worked well and I limited the rpm to 4000:

Iolaire Propellor

Photo C

The single bladed prop was an experimental one in 1984, was quiet but a thin but broader anti vortex tip improved the range, this was also very quiet:

Single Blade Propellor
Photo D		Photo E