My idea was/is to have the prop shaft on the beam, 600mm/24" above the water and a 2 bladed prop which would lie along the beam when not in use. The professor who designed the blades for my wind turbine cat reckoned that, for 7 knots in flat water (as per OSTAR rules):
Blade diameter 2m
Number of blades 2
Height of hub from water 600mm
Rotational speed 1.5 rps; 90rpm
P/D ratio 1.2
Propulsive efficiency about 0.4 (very low due to only the tips being immersed and for less than half a revolution)
Number of blades 2
Height of hub from water 600mm
Rotational speed 1.5 rps; 90rpm
P/D ratio 1.2
Propulsive efficiency about 0.4 (very low due to only the tips being immersed and for less than half a revolution)
Power required about 1750W
Pitch angle of blades at 0.85 radius fraction is 24.5 degrees
The blades should be very fine, but the blade sections should be wedge
type rather than like an airplane prop.
Pitch angle of blades at 0.85 radius fraction is 24.5 degrees
The blades should be very fine, but the blade sections should be wedge
type rather than like an airplane prop.
It is on the list of things to do as a water prop with no holes in the boat would be a pretty cool thing to have, despite the possibility of doing a lot of damage to anyone who got too close to it while it was rotating.
Back to the web page, which should be up next week.
rob
On Tue, Oct 9, 2012 at 1:40 AM, heinrich_meurer <meurer@geotec-exploration.de> wrote:
Does Rob know about this? He once suggested a two blade surface piercing prop nesting behind the beam of his transatlantic proa just to meet the propulsion requirements :-)
Heinrich
__._,_.___
.