Subject: Re: [harryproa] Re: rudder musing
From: Mike Crawford
Date: 6/26/2008, 11:04 AM
To: harryproa@yahoogroups.com.au
Reply-to:
harryproa@yahoogroups.com.au


  The need to lift in both directions would stem from having only one rudder in the water at a time, with each foil only being used in one direction. 

  The upside is that a wrist-flick requires almost no effort, and little or no movement across the deck, and you could go with with a single asymmetric foil (more lift, less drag) in each direction.  The downside, as you mention, is that the forward rudder, while lifted out the the water, could get caught by chop. That's a definite problem.

  I don't think you could design this particular lifting mechanism to work with a tiller that flips from one side to another.

  One could argue that if there's enough chop to cause a problem for the lifted rudder, one might not want to be out in a Harriette anyway.

  But on the other hand, since I'm often one to push for safety over convenience, I'm not sure I'd buy that argument.  One can always hit a massive wake from a 40'+ powerboat, even if the weather is calm.

       - Mike
 

Robert wrote:

-If the boat was only going one way at a time, why would you need lift
in both directions?
I still prefer the style of flipping the tiler over as you shunt as it
means you don't have either a tiller or a foil facing into the slop

Robert

-- In harryproa@yahoogroups.com.au, Mike Crawford <jmichael@...> wrote:
>
>
> You might have a good point there.
>
> On a boat that small, you could just flip one rudder up and one down
> each time you shunt, and with Harriette, it almost would be a wrist
> flip. Then you wouldn't have to worry about lifting anything, rotating
> the foils, or sliding a single foil forwards and aft.
>
> On the larger boat that would be a bit of a pain because you'd
have to
> move back and forth across the deck to reach each rudder. But on
> Harriette, if the tillers are long enough, you could probably
accomplish
> the maneuver without getting up.
>
> Then you'd get the added benefit of having just a single foil in the
> water (provided it's situated properly for steering and leeway
> prevention). With each rudder being a single foil used only in one
> direction, you might be able to use asymmetric foils for lift.
>
> - Mike
> / /
>
> Jim Baltaxe wrote:
> >
> > Hi All
> >
> > On a Harriette they would probably work a treat. You wouldn't be able
> > to have the front one down, though that probably wouldn't be much
of a
> > problem on such a small boat anyway.
> >
> > Enjoy
> > Jim Baltaxe
> > They said, get a life. I looked on TradeMe but I couldn't find one.
> >
> >
> >
> >
----------------------------------------------------------
> > From: harryproa@yahoogroups.com.au
> > [mailto:harryproa@yahoogroups.com.au] On Behalf Of Mike Crawford
> > Sent: Thursday, 26 June 2008 10:56 p.m.
> > To: harryproa@yahoogroups.com.au
> > Subject: [harryproa] Re: rudder musing
> >
> >
> > We actually have this same rudder setup on our 27' Stiletto
> > catamaran, which weighs roughly 1300 pounds, and I believe the
> > company also used it on their 2400-pound 30' model.
> >
> > On the plus side, the system does work. It takes a bit more
> > than a flick of the wrist, but it's easy to raise or lower each
> > rudder with a single up/down arm motion. They also do kick up
> > automatically. We've watched that happen when hitting mud while
> > sailing where we shouldn't have been sailing, and also when
> > getting caught on lobster pot warps, which sometimes are
> > impossible to avoid with a wide-beamed boat.
> >
> > It's also great to be able to get rid of seaweed in a few
> > seconds without stopping the boat. We have not noticed any
> > significant wear, and since our boat was made in the early 1980's,
> > that's probably a good sign that the basic system is sound.
> >
> > I'm sure the system could be up-sized for the proas. However,
> > there would be a few problems and challenges in doing so:
> >
> > - The bearing surfaces would have to be quite strong and
> > low-friction. Kicking up a rudder on a 27' catamaran, where
> > leeway prevention is handled by a daggerboard, is quite different
> > from doing the same thing on a 40' to 50' proa where the same foil
> > handles steering and leeway prevention. The extra stress on the
> > foil would either require a special set of bearing surfaces, a lot
> > more force required for kick-up, or both.
> >
> > - The rudders only kick up in one direction. Assuming you
> > always have the rudders flipped to go "forward", this may not be a
> > showstopper.
> >
> > - The system does not offer variable draft. The rudders are
> > either out of the water, all the way down, or just barely in the
> > water (extending almost straight back). When they are just barely
> > in the water, the boat has a very serious weather helm, and that's
> > on a 27' catamaran with a daggerboard. The weather helm on a
> > larger proa would be incredible while sailing. It would probably
> > work pretty well while motoring, though.
> >
> > - The rudders will need some room. When they are up or
> > partially-down, they stick out of their brackets by their full
> > length. That means they wouldn't work if mounted on the hull, and
> > if mounted on the beam, they would need at least 4' or more
> > clearance on both sides -- the depth of the foil in the water plus
> > the distance from the water to the bracket which holds it.
> >
> >
> > I love the system on our current boat, but on a proa I'd
> > probably go with a version of one of Rob's beam-mounted schemes.
> >
> > - Mike
> >
> >
> > Arto Hakkarainen wrote:
> >
> >> If I looked correctly they only talked about boats up to 21' long
> >> and their rudders. Harryproa rudders are quite big and loaded
> >> compared to such small boat rudders. So it looked fine but will
> >> it scale to big enough size?
> >>
> >>
> >>
> >> Arto
> >>
> >> --- On Wed, 6/25/08, tsstproa <bitme1234@...> wrote:
> >>
> >> From: tsstproa <bitme1234@...>
> >> Subject: [harryproa] Re: rudder musing
> >> To: harryproa@yahoogroups.com.au
> >> Date: Wednesday, June 25, 2008, 10:06 PM
> >>
> >> I have seen those A couple of years back. Advertised in the
> >> back of
> >> Sail magazine. Not sure on how they actually work (the
> >> specifics)
> >> but seem like they could be adapted well to a proa with beam
> >> hung
> >> rudders.
> >>
> >> I was looking a the r/c retracts for airplanes to find out
> >> what type
> >> of mechanical advantage they use to raise gear with very
little
> >> movement from lever to move boards up /down 90 degrees.
> >>
> >> I have two types of micro retracts. They each use different
> >> mechanical advantages to achieve the same results.
> >>
> >> Studying these two types of mechanical advantages I'm certain
> >> I can
> >> come up with somthing for the 24'full size craft
> >>
> >> Both mechanical advantages are very simple.
> >>
> >> Have a look in square harry files section of diagram drawn.
> >>
> >> Todd
> >>
> >>
> >> --- In harryproa@yahoogrou ps.com.au
> >> <mailto:harryproa%40yahoogroups.com.au>, "chris483035"
> >> <joooody2@ .>
> >> wrote:
> >> >
> >> > Hello All,
> >> >
> >> > I thought I would de-lurk for a moment to mention some
> >> rudders I
> >> found on the web some
> >> > time ago. I have no personal experience of them whatsoever
> >> (and
> >> no connection with the
> >> > company) but I thought at the time that they could be
good for
> >> proa use. I particularly like
> >> > the kick up function and the fact that raising / lowering
> >> can be
> >> achieved from the end of the
> >> > tiller without fiddling with uphauls etc.
> >> >
> >> > http://www.dotan. com/video/ <http://www.dotan.com/video/>
> >> >
> >> > Chris
> >> >
> >>
> >>
> >
>

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