Paul, I totally agree with you on wheel pilots - utter garbage. I have seen and sailed with small inexpensive tiller pilots on big multi-hulls. You can unplug and stow them when in port and that extends their life tremendously! I was lucky with my hydraulic ones on the mono-hulls since I was able to get incontact with technicians at the manufacturer and always had some sort of circuit that reduced the consumption considerably - they are made for big (motor) boats, where that really is not so much of a concern, but was easily fixed.

What happens after a shunt? How and where would the tiller pilot attach (The whole wind vane idea never really enticed me. It is nice to hang somewhere in the trampoline, with a remote control and have the ability to dodge a trap let's say or whatever ..) ?

I cannot really figure it out, by looking at the pictures of the rudders.

The power consumption of the hydraulic could easily be fixed by running the pump with a drag prop - but why would you spend so much money on having a smooth hull and then dragging somehting?! fluxgates are far superior to vanes IMO. Even in harbour, if I need to go and fix something, I press a button and voila, have another crew member.

On Sat, Jul 9, 2011 at 6:47 AM, Rob Denney <harryproa@gmail.com> wrote:

 

The apparent wind problem is that as the boat speeds up, the wind operated auto helm causes it to bear away to keep the same apparent wind angle.  The fear is that if you go too fast and slow down suddenly (into the back of a wave) the apparent goes aft and causes a capsize.  Maybe with a really fast boat sailed on the edge, but not a problem for a cruiser.  With a compass course auto pilot you never get to speed up too much as the apparent comes forward and the sails luff so you slow down.  

I am pretty sure that a sensitive vane and either a long arm (I included this on the early Solitarry drawings) or a water operated servo (perhaps with variable blade area) would overcome these for most conditions.  

I don't know anything about Raytheon, but any system that does not need electricity and is simple, cheap and easily fixed will get my vote, even if it is not as accurate.  

rob

On Sat, Jul 9, 2011 at 1:12 PM, Paul Wilson <opusnz@yahoo.ca> wrote:

 

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?

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