Thank you, Rick and Robert. May I conclude that the simplest seems to just motor around with a jetted prop pod at a depth not exceeding draft and only sail in deeper waters with kick down rudder/boards. If one would want to also sail in shallow waters go for an asymmetric lee hull and steer with schooner sails.
Right?
Luc

--- In harryproa@yahoogroups.com.au, Rick Willoughby <rickwill@...> wrote:
>
> Luc
> Low speed surface piecing props are hopelessly inefficient - maybe
> 20% if it is constrained by depth. It is better to use a smaller
> prop and enclose it in a nozzle to lift efficiency - basically a jet.
>
> In fact it is difficult to better a paddlewheel for shallow water
> operation but they would be an ugly addition to a proa.
>
> Rick
> On 09/09/2012, at 9:00 PM, LucD wrote:
>
> > While Nol was discussing how Zeilen met Visie progressed optimizing
> > Blind Date, he mentioned readying her for sailing the shallow
> > waters the Dutch coasts are famous for. I guess originally kick-up
> > rudders were meant to solve that.
> >
> > If one were to build a harryproa dedicated for waters like the
> > Wadden Sea http://en.wikipedia.org/wiki/Wadden_Sea with beaching
> > capability would it make sense to consider:
> > 1. an asymmetric lee hull?
> > 2. and ww hull (also flat to lee)?
> > 3. Low aspect schooner rig (for occasional rudderless steering) ?
> > 4. As apparently these boats motor more often: Rick, you were
> > involved in a discussion on slow turning surface piercing
> > propellers in 2008. Would this application make sense to offset the
> > loss of efficiency, in your opinion?
> > 5. A double hull would not require lots of flat bottoms as a monohull
> > 6. While transitioning from beached to floating the boat can bang
> > the sea bottom without being best positioned with regard to tide
> > and wind directions - Would there be a way to hold down the boat
> > some longer on the bottom and let loose to have it float higher and
> > have more room for maneuvering?
> >
> > Luc
> >
> >
>
> Rick Willoughby
> rickwill@...
>