Rick, thank you. Very interesting but I think I am cured now ;-) Luc

--- In harryproa@yahoogroups.com.au, Rick Willoughby <rickwill@...> wrote:
>
> Luc
> We have the ability to lift the props close to the surface and keep
> operating but no point with the deep rudders. It would not be very
> effective once the props ventilate though.
>
> The linked video shows a high speed paddlewheel:
> http://www.youtube.com/watch?v=Wd-zjtScnaw
> The basic wheel dimension are quite good for that application. It
> would have similar efficiency to an outboard propeller. You can see
> that it takes a while to get the boat up to speed meaning they are
> quite high slip under load.
>
> To get efficient operation with paddlewheel on a proa they would need
> to be quite large blades. The props we are using have a swept area
> of 0.22sq.m so equivalent to blades 300 deep by 700 wide. You would
> want 12 blades on each wheel and diameter up around 2m for good
> performance from such large blades. As you drop blade size the
> efficiency drops. You will need a big gear reduction for such a
> large wheel.
>
> You can trade blade width for depth to get a smaller diameter wheel
> but the thrust will be more affected by waves.
>
> There are all sorts of propulsion systems in this video. You get an
> idea of the relative performance of different paddlewheels. Notice
> how big they are on the boat that is competitive with the propeller
> driven boats.
> http://www.youtube.com/watch?v=-QjRM-cQpHw
>
> Paddlewheels are possible but they will take a good deal of
> engineering to get a neat, useful system.
>
> Rick
> On 23/12/2012, at 1:12 PM, LucD wrote:
>
> > If navigating shallow waters is part of the boat's SOR's I come
> > back to the paddlewheel idea. Using two rather standard bicycle
> > wheels with hub drives rated at 1 kW each, one could have a pretty
> > powerful paddlewheel "just" connecting the wheels with the right
> > sized paddles on the outside rims. Such a paddlewheel could drive
> > each of two Denney pivoting tender/sleds to turn the vis on a dime.
> > There are already motorcycle wheel hub drives rated at a continuous
> > 10 kW. There must be a good reason why I could not find not even a
> > goofy example of such a construction yet on internet.
> >
> > Luc
> >
> >
>
> Rick Willoughby
> rickwill@...
>