Are leeboards inherently inefficient or was that just the experience
with "U"? If they were the same foil I would think they would simply be
the same as a dagger board that was surface piercing!

My thinking was to have two boards each pivoting from the top and pinned
to the hull just above DWL by a curved track that would allow one board
to lift/pivot clear and the other to lower when shunting. The setup
would require 4 boards instead of 2 (more weight / complexity / cost &
in the way for mooring) but on the up side the leeboards are against the
hull so less load handling and complication issues with the mounts. The
rudders could be smaller with smaller loads on the hinges and steering.
The drag on the leeboards would help counter weather helm.

Rob Rassy

--- In harryproa@yahoogroups.com.au, Rob Denney <harryproa@...> wrote:
>
> The deeper the hull and the wider the blade behind the pivot point,
the
> more of a consideration it is. Steering with the aft rudder on Vis, I
> would not like it any closer than it is.
>
> I tried leeboards on U, with out much success. They see loads
(rotating
> forward, floating to leeward) which are not what you expect, so need a
lot
> of lines to hold them in place. The lower the boat performance, the
> better they work. Any foil fixed fore and aft is going to make
shunting
> harder.
>
> rob
>
> On Tue, Nov 13, 2012 at 9:02 AM, rob_rassy techsmart@...wrote:
>
> > **
> >
> >
> >
> > How close can the rudder be to the hull? Is wave action between the
> > rudder and hull a consideration or does the rudder only need to have
> > enough clearance to operate with out hitting the hull?
> >
> > I've also been thinking about lee boards on the actual lee side of
the
> > lee hull and was wondering if they have been tested on a harryproa?
> >
> > --- In harryproa@yahoogroups.com.au, Rob Denney harryproa@ wrote:
> > >
> > > On Fri, Nov 9, 2012 at 8:08 AM, rob_rassy techsmart@ wrote:
> > >
> > > > **
> > > >
> > > >
> > > > Rob I do have more questions, but don't encourage me too much
> > > >
> > >
> > > The more the merrier!
> > >
> > > > ****
> > > >
> > > > I'm still confused how the foils can be liftable. When you say
> > "centre of
> > > > rotation is mid chord" do you mean the actual pivot point is mid
> > foil
> > > > thickness as well? (ie: The hinges will be recessed into the
foil)
> > or
> > > > are the pivots mid distance along the chord and mounted outside
the
> > foil. I
> > > > realise the foil will have less camber on the lee/hinge side,
but
> > unless it
> > > > is negative the chord will lie inside the foil (won't it -
correct
> > me if
> > > > I'm wrong).
> > > >
> > >
> > > The foil slides in a case. On the hull side of the case is a
> > > gudgeon/pintle arrangement. Means increasing steering loads as the
> > > rudders are turned, exacerbated if the blades are not swept back
> > and/or
> > > connected. If the loads are too high, the rudders will kick up.
The
> > > gudgeons/pintles are mounted on a substantial shaft to allow this
to
> > > happen.
> > >
> > > > ****
> > > >
> > > > My thought was to cant the rudder (tilt the bottom towards
"under"
> > the lee
> > > > hull) to put the offset pivot point mid way on the longitudinal
(Top
> > to
> > > > Bottom) of the rudder, the cant angle would be quite small to
> > achieve this
> > > >
> > >
> > > True. Definitely worth a try if the current setup doesn't work.
> > although
> > > the top will have to be firther away from the hull so that the
blade
> > can
> > > rotate through 30 degrees each way without hitting the hull.
> > >
> > > > ****
> > > >
> > > > I reckon you might be right about the Blind Date crew wrestling
with
> > the
> > > > rudders, if the direction of travel hadn't changed and the
rudders
> > turned
> > > > it would be difficult if not impossible to force them round.
> > > >
> > > One of those things that comes with practice. BD crew in the
videos
> > are
> > > first timers and apart from the helmsman and photographer, non
> > sailors.
> > > Interesting to compare them with first timers tacking or gybing a
15m
> > cat
> > > or mono, particularly one with an overlapping headsail.
> > >
> > > rob
> > >
> > >
> >
> >
> >
>