[hpv-boats] Rigid Shaft

[Ian Cassell]

Vic
      I have previously been using a flex shaft but I could
never do a flat out sprint because of the shaft going
through the dead spot. The rigid shaft allows me to
go as hard as I can but the prop is not at the vertical.
I use an involute gearbox connected directly to the
shaft, this makes things simple to build and setup.
I could improve the angle but would get 11 deg max.
and involve a bit of work on the boat. 
       My prop blade starts at 20 deg off the horizontal
next to the hub and gradually increases to 55 deg at 
the tip. The prop is 400mm dia, with the prop angled
at 16 deg off the vertical the angle of the blades to
the water increases. If I make a prop with the blades
at 36 deg next to the hub and increase to 71 deg at
the tip the blade should be at the same angle as a
vertical prop. However on the other side of the prop
the angles will be way out and may cause drag on 
the prop. A four blade prop might be better in this
regard as there would be more prop blades closer
to the optimum.
        I don't have any data worked out as prop design
is a bit over my head, I use java prop for sizing.

Ian