The book "Pen Duick" by Eric Tabarly has a chapter devoted to wind
vanes for high speed sailboats. It is quite technical but it has a
good write-up on the issues involved. Also "Self Steering for
Sailing Craft" by John Letcher is an awesome book, the bible on wind
self-steering, IMO.
I have also seen windvanes on multihulls but the ones I have seen
would probably rarely get over 15 knots. I think the problem is
the shift in apparent wind with varying wind speeds but also the
foil design. I think it is a real challenge to have a foil large
enough for slow speed but small enough that it doesn't fly apart at
high speed. At high speed (>15 knots?) you can get severe
vibrations, cavitation, and over steering since the amount of rudder
deflection required to turn the boat is much less at high speed. It
is also always a trade-off with windvanes between being light
(delicate) but responsive and heavy (strong) and unresponsive. This
is big challenge with heavy monohulls, but an even bigger
challenge with high speed multi-hulls.
As far as electronic autopilots go, use a tiller pilot if you can.
They are much less money and more reliable. Wrap them in a plastic
bag to keep the spray and water off and they will last much longer
since the seals on some are pretty poor. The flux gates inside are
fragile and have tiny wires that are easily damaged but if you treat
your tiller-pilot like eggs and don't bang it around, it should last
many years.
My personal experience is that the new Raymarine wheel pilots are
junk. The old ones like in the old Autohelm 3000 were poor but the
new wheel mounted units are even worse. The engineers have gone for
tiny motors in order to get the current draw down but it is a poor
trade-off in reliability. The tiny motors burn out, the belts
regularly fail and they are made almost entirely of crappy plastic
parts. Raymarine does a great business in selling parts for them.
If you get WD-40 near the plastic, it will fall apart. The motors
are actually cheap hobby motors that are less than $5 from China but
Raymarine glues a gear on that is impossible to get off and then
charges you well over $100. Needless to say, I am not a fan.
If you have wheel steering and can't use a tiller pilot, it is much
better to have the type that fits direct to the quadrant via a ram
or direct to the steering cables with an electric motor. The
hydraulic units are OK too but can be noisy. All these options are
expensive and relatively power hungry.
Cheers, Paul
On 7/9/2011 7:40 AM, Michael Fischer wrote:
I have seen windvanes on multihulls.
On Fri, Jul 8, 2011 at 2:27 PM, bjarthur123 <bjarthur123@yahoo.com> wrote:
i have been told by the manufacturer and read accounts online that self-steering wind vanes do not work on multihulls:
http://www.selfsteer.com/windvanes101/index.php
they could not explain why. i'm guessing it has something to do with the large difference between true and apparent wind due to the high boat speeds, as what else is different with monohulls. but it is not clear to me why that would be a problem.
has anyone had experience with such a system? or have any idea why it doesn't work on multihulls?
they draw NO (zero) power! a beautifully clever idea.
ben
> what kind of autopilot would you recommend for a harryproa?
>
> which types have been used successfully?
>
> energy draw?
No virus found in this message.
Checked by AVG - www.avg.com
Version: 10.0.1388 / Virus Database: 1516/3750 - Release Date: 07/07/11