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Old 18-03-2012, 11:48   #1
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self steering on multihulls

Shorthanded cruising/cricumnavigation requires some self steering system. Auto-pilots have their use but really are not feasible due to electric power demands, the inability to react fast enough in heavy weather conditions, maintenance and durability issues.
For a monohull, a wind vane is the answer but for a multihull, is there a solution? Can a wind vane be installed on a catamaran?
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Old 18-03-2012, 12:31   #2
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Re: self steering on multihulls

Quote:
Originally Posted by Notpopeye View Post
Shorthanded cruising/cricumnavigation requires some self steering system. Auto-pilots have their use but really are not feasible due to electric power demands, the inability to react fast enough in heavy weather conditions, maintenance and durability issues.
For a monohull, a wind vane is the answer but for a multihull, is there a solution? Can a wind vane be installed on a catamaran?
I have heard of Cats being rigged with wind vane self steering, but have never tried it myself. Vaguely recall the Wharram has some illustrations on their site about how to do this on a Wharram cat.

Re electronic auto's:

Energy Usage. Many modern electronic auto pilots are quite efficient. I have an Raymarine 6000+ hydraulic system and it is so energy efficient I have never bothered to measure the draw -- never been an issue.

Heavy Weather. No autohelm (windvane or electronic) can react appropriately to heavy weather conditions -- because none of them can "see" the seas or that big squall converging on your course line. No auto should be trusted to handle really heavy weather. Hand steer or be at the helm and ready to take over quickly.

Maintenance & Durability. I've replaced one shaft seal on my Raymarine in 10 years -- I'm OK with that. Keep in mind that windvane steering is mechanical and anything mechanical (or electrical) will eventually need repair.
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Old 18-03-2012, 13:22   #3
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Re: self steering on multihulls

Quote:
Originally Posted by Notpopeye View Post
Shorthanded cruising/cricumnavigation requires some self steering system. Auto-pilots have their use but really are not feasible due to electric power demands, the inability to react fast enough in heavy weather conditions, maintenance and durability issues.
For a monohull, a wind vane is the answer but for a multihull, is there a solution? Can a wind vane be installed on a catamaran?
Autopilots on cats don't neccessarily use a lot of power. Cats don't have the weather helm mono's do, nor the tendency to round up or broach on a run.

Winvane steering works fine on slow boats, but is far less effective on fast ones.
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Old 18-03-2012, 13:50   #4
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Re: self steering on multihulls

a. As others have said, solar systems can handle the power.

b. If you think a wind vane is going to be faster in heavy weather than an autopilot, I think you're in for a surprise.

The other trouble factor on cats is that the typical big hard top blocks the air flow up-wind.

Off the wind, most cats are on rails if the sail balance is set slightly forward.
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Old 18-03-2012, 16:23   #5
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Re: self steering on multihulls

Seen windvanes on cats too. I think on the wind they may be limited as the superstructure will shade and twist the wind.

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Old 18-03-2012, 16:44   #6
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Re: self steering on multihulls

Quote:
Originally Posted by Notpopeye View Post
Shorthanded cruising/cricumnavigation requires some self steering system. Auto-pilots have their use but really are not feasible due to electric power demands, the inability to react fast enough in heavy weather conditions, maintenance and durability issues.
Is this from actual experience or are you making this up as you go?

I have done 900nm legs on cats under autopilot alone, never an issue.

I did have an oversized pilot and I did set my sails correctly and that was with a single battery and a 50 watt panel for charging no additional engine driven charging required.
We also ran lights, radios, sounder and gps.

As for wind vanes, how does apparent wind affect them?
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Old 18-03-2012, 17:17   #7
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Re: self steering on multihulls

Not popeye, this is another furphy up there with cats cant go to windward etc. Electronic autopilots are fine for long term passage use. More importantly I can sail lengthy distance without touching the helm if I put some effort into balancing the boat.
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Old 18-03-2012, 17:37   #8
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Re: self steering on multihulls

All round Fiji,

Fiji to Bundaberg, Then down the Tasman to Port Stephens,

All done on Auto pilot, 24/7, continually for 6 weeks, all done on solar and wind power,
I never experienced running out of power for it.
I dont know how much power it uses, But it aint much,

It some times jumped out of Auto, But you certainly know when that happens,
You just reset it, No Problems,

Its very scary when it happens in the middle of the night and your half asleep.

The boat tends to beam on, when it drops out, Whoo Whoo, get out there quick Hahaha,

Certainly helps those that are single handed and crossing oceans,

Do you realize how hard it would be to hand steer all that way, on your own,

Raymarine ST1000 I think it is,
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Old 18-03-2012, 17:44   #9
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Re: self steering on multihulls

I used a old low-tech Robertson ap380 autopilot on-board extensively. Driving a hydraulic ram, attached directly to the top of the rudder stock. Steering either to a magnetic compass, or interfaced gps way-point track. It was a extremely reliable, low power consumption, way to steer the boat, in most reasonable conditions.
There is so little load on the rudders, that the pilot may have used much less then 50% of its potential power most times. There were very few large steering corrections to be made, (Otto) we named it of course, just made very small light quick adjustments as we sailed. If conditions ever grew too rough or too extreme, then hands on steering was the only way to go. I would not choose to leave a quick, responsive, multihull steering to an autopilot, in bad condition's. But that's my personal choice.
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Old 19-03-2012, 09:12   #10
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Re: self steering on multihulls

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Originally Posted by cat man do View Post
(...) I have done 900nm legs on cats under autopilot alone, never an issue. (...)
Good point.

Vendee boats sail non-stop rtw under autopilots in extremely demanding conditions!

Hence good autopilots exist!

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Old 19-03-2012, 09:17   #11
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Re: self steering on multihulls

the problem with a windvane on a fast cat is the shift in apparent wind. I don't think this would be much of a problem on a slower cat, but I do know that the shadowing from the superstructure would be problematic on the wind. Off the wind it should work fine, but with the amount of acreage available for solar, why bother? electric pilots will do a better job of steering a cat, and sized properly will be reliable.
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Old 19-03-2012, 09:24   #12
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Re: self steering on multihulls

Like this?What is it ?
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Old 19-03-2012, 09:54   #13
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Re: self steering on multihulls

...excerpt from a PM reply I posted on this subject...relevant to this discussion I think:

Modern electronic auto-pilots are quite reliable and efficient. They "do the trick" for me and the vast majority of cruisers regardless of whether mono or cat. Seeing wind-vane self steering is becoming uncommon -- even on monohulls.

The steering difference in mono and cats is not so much due to heeling as it is the directional stability of having two hulls tracking though the water. Differences in steering between designs of monohulls is mostly due to different below the water line profiles (fin keep vs full keel for example). A traditional full keel cruiser, with the sail plan properly balanced, tracks quite well. On my previous monohull, I could balance the sails and then walk away from the helm (with no autopilot -- just light friction on the wheel brake) and she would track just fine on her own. In light to moderate conditions only infrequent minor corrections were required to keep her on track -- so when I later installed an electronic autohelm it was not working very hard at all. By contrast, my Hobie 33, with a very narrow and deep fin keel, can't be left unattended for even a moment, but slam the helm over and she will spin full-circle on her keel in a boat length! Something most monohulls, and definitely most cruising cats, can't do.

Regardless of whether the boat is a mono or cat, if the helmsman, or autopilot, is working hard to keep the boat on course in anything less than heavy conditions then something is wrong. Typically this is due to the sail plan being out of balance. Trim the sail plan properly and the steering issue should resolve itself.

....

Given the additional complexity of rigging wind-vane steering on a cat, and the good reliability/efficiency of modern electro-mechanical autohelms, it hardly seems worth the trouble. Much easier to carry a good inventory of spares just in case.
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