Subject: [harryproa] Re:leeboards
From: "Robert" <cateran1949@yahoo.co.uk>
Date: 8/4/2009, 2:16 AM
To: harryproa@yahoogroups.com.au
Reply-to:
harryproa@yahoogroups.com.au

 

-If the rudders are supplying a significant proportion of the leeway prevention, then the loads are fairly high. If the boat is almost perfectly balanced with only a small bit of weather helm then the loads are fairly light. Most boats are somewhere in between, with the rudders themselves being balanced so you don't notice the work they are doing in leeway prevention. In very shallow waters there is significant leeway prevention as the hull is so long with little rocker, so the water has a hard time getting away or being replaced on the ww side. In shallow water waves go slower as they drag on the bottom, so the wave it is making as it tries to go sideways through the water, build sup and gives more sideways resistance than in deeper water. I don't think I would go for a keel but possibly a central rubbing strake with sharp edges, or even rubbingstrakes on the bilges. It would not need be much to significantly reduce leeway in shallow water. Some people on Jarcats simply use two aluminium channels with the channels facing inwards to enable sailing with the centre board up

-- In harryproa@yahoogroups.com.au, Gardner Pomper <gardner@...> wrote:
>
> This would be a great topic to get clarified, because the rudders are an
> area of concern for a number of us, I think.
> I would like to be able to remove the stress from the rudders when sailing
> at high speed. If I didn't want shallow draft, I would consider a fixed
> keel. I still might consider a 1' stub keel, maybe 6 feet long, under the lw
> hull. If I could get a motoring draft of 2', that would be ok. I don't
> expect to sail it hard in really shallow water; I just want to be able to
> sail it lightly, which would not depress the lw hull much.
>
> I am pretty sure that Rob has stated that is just an issue of building the
> rudders as strong as they need to be, but I would like to better understand
> the relationship between the forces required for steering and the forces
> required for leeway protection.
>
> - Gardner
>
> On Mon, Aug 3, 2009 at 12:19 PM, jrwells2007 <jrwells2007@...>wrote:
>
> >
> >
> > If I remember correctly, a harryproa can be sailed with only the stern
> > over-sized rudder so the usual balancing of the CE and the CLR is not
> > particularly applicable.
> > Rob or someone will correct me but I think that the lack of leeboards or
> > centreplates is to avoid the cost and complication of a third foil. Bear in
> > mind that there is a long hull with considerable lateral resistance.
> >
> >
> > --- In harryproa@yahoogroups.com.au <harryproa%40yahoogroups.com.au>,
> > Gardner Pomper <gardner@> wrote:
> > >
> > > Hi,
> > > Ok, I like the explanation, but I am still having problems finding it. On
> > a
> > > harryproa, I know that the CE of the sails is aft of the mast, because it
> > is
> > > a rotating rig. The center of lateral resistance should be right at the
> > > mast, since the hulls are symmetrical. So, if I put the leeboard next to
> > the
> > > mast, right in the center, that should satisfy.
> > >
> > > So, I am still confused, since that is apparently the wrong answer. I
> > hate
> > > it when I look in the back of the book for the answer and still can't
> > work
> > > it out <grin>
> > >
> > > - Gardner
> >
> >
> >
>

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