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@yahoo.com> wrote:
From: tsstproa <bitme1234@yahoo.com>
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, "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/
>
> Chris
>
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