G'day,

The times I have reefed it has been pretty fresh and there were too
many variables (waves affecting the balance mast flex, jib luff sag)
to notice any difference. Putting a little angle on one rudder is
fraught. The boats all seem to track exceptionally well, so a little
rudder angle on one requires a little on the other. Before you know
it, both have too much and the boat slows noticably, though still
going straight.

One of the peculiarities of two big rudders is the different effects
of the rudders as steering devices and the rudders as leeway reducers.
They often feel as if they have weather helm (defined as the coe
being aft of the clr), when in fact it is a function of the large area
of the rudder blade behind the rudders centre of rotation being pushed
by the boat trying to go sideways that is causing it. There is still
a lot of stuff to learn about this.

regards,

Rob

On Mon, Apr 28, 2008 at 6:54 PM, Robert <cateran1949@yahoo.co.uk> wrote:
>
>
>
>
>
>
> I was wondering about trimming the boats for least drag. I assume
> there would be some differences between reefed and not.
> My guess is that locking a little lift on the aft rudder would be
> balanced by the bows and some fine tuning could be done with a little
> of the forward foil in the water. For a cruising boat, I imagine this
> would be the easiest on the steering,
> Robert--- In harryproa@yahoogroups.com.au, "Rob Denney"
>
> <harryproa@...> wrote:
> >
> > G'day,
> >
> > I don't have anything, but basically it is the drive force from the
> > sails and the drag from each hull and the rudders. Hulls can be
> > calculated with Michelet if required.
> >
> > The drag on the windward hull is less than on the leeward one as it
> > has lower wetted surface which gets even lower as the breeze
> > increases.
> >
> > Be great if Terho would put some numbers on this for us.
> >
> > Regards,
> >
> > Rob
> >
> > On Sun, Apr 27, 2008 at 3:37 PM, Robert <cateran1949@...> wrote:
> > >
> > >
> > >
> > >
> > >
> > >
> > > Rob,
> > > Have you got a set of vector diagram suitable for posting as to the
> > > various forces on the boats so as to find the subsequent center
> of lee
> > > way resistance for various points of sail. It may be useful for
> > > explaining why the boats can get away with the fatter heavier hull to
> > > ww. This seems the sticking point for quite a few. Maybe Terho might
> > > have something.
> > > Robert
> > >
> > >
> >
>
>

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