Windvane Steering On a Cat?

[Notyet]

This is probably a stupid question from a wannabee newbee, but why do I never see a windvane steering on a cat?
Okay, maybe not really a good place in the middle where you can put one, but what about just the windvane part with cables to the steering wheel, as I see on some monohulls? I mean, I guess you need quite a lot of electricity to power an autopilot...

Wim

[Jimbo485]

Because typically a cat is light so it accelerates and decelerates so much that it is always changing the direction of the apparent wind. You speed down a wave, the wind moves forward, you slow on the back of the next wave and the wind moves aft.

I would prefer to have a windvane over an autopilot but it is just not possible on a cat. I played around using the vane function on our autopilot, so that the autopilot followed the wind, not a compass course, and it is hopeless.

[Notyet]

Originally Posted by Jimbo485

Because typically a cat is light so it accelerates and decelerates so much that it is always changing the direction of the apparent wind. You speed down a wave, the wind moves forward, you slow on the back of the next wave and the wind moves aft.

I would prefer to have a windvane over an autopilot but it is just not possible on a cat. I played around using the vane function on our autopilot, so that the autopilot followed the wind, not a compass course, and it is hopeless.

Sounds logical... Okay, thanx for the info!

[colemj]

Another reason is that it is almost impossible to get clean air for a windvane on the back of a catamaran due to the cabin bridgedeck structure. And connecting up to complicated steering mechanisms can be difficult (and impossible for hydraulic steering).

Jimbo485, does your AP allow you to steer to true wind? This works much better than apparent wind when the wind is moving around because of acceleration/deceleration.

Mark

[Jimbo485]

Originally Posted by colemj

Jimbo485, does your AP allow you to steer to true wind? This works much better than apparent wind when the wind is moving around because of acceleration/deceleration.

Mark

I didn't think so, Mark, but I will pull out the manual and check. Thanks!

[Thumbs Up]

Some searunners tris use wind vanes with success. They use trim tabs on the stern hung rudder. My cat has stern hung rudders. I want to experiment with double wind vanes, any ideas?

[Richard5]

Originally Posted by Thumbs Up

Some searunners tris use wind vanes with success. They use trim tabs on the stern hung rudder. My cat has stern hung rudders. I want to experiment with double wind vanes, any ideas?

Right off the top I would think the vanes better be interconnected. And ability to isolate either vane from one another in the case of failure of one.

[colemj]

Originally Posted by Thumbs Up

Some searunners tris use wind vanes with success. They use trim tabs on the stern hung rudder. My cat has stern hung rudders. I want to experiment with double wind vanes, any ideas?

I knew of one catamaran who used double vanes - Monitors on each hull. It did not work well and was abandoned. Monitor's website gives an example of a single vane mounted on the starboard stern of a Seawind 1000, but states that it needs to use the autopilot when on port tack with the wind above the beam. They excuse that by mentioning that experienced sailors realize that compromises need to be made and that they should plan their passages so that the wind is aft of the beam.

Experimenting with double wind vanes will be expensive unless you already own the gear.

Mark

[Jimbo485]

Originally Posted by colemj

Jimbo485, does your AP allow you to steer to true wind? This works much better than apparent wind when the wind is moving around because of acceleration/deceleration.

Mark

No, the vane function only works with the apparent wind, unfortunately.

[Maren]

I'm suprised no one has yet metioned hydrovane

[colemj]

The hydrovane doesn't solve any of the general problems catamarans have with wind vanes. There is no clear airflow for the vane on at least one tack, the line routing for the steering would be a nightmare and dangerously in the way on the most common helm positions on most catamarans, and many catamarans have either hydraulic steering, or cable linkages with a lot of drag.

Catamarans most likely to work with a vane are ones that have low bridgedeck structures and tiller steering. Unfortunately, those types of catamarans are also the ones that accelerate/decelerate so quickly as to make vane steering unusable.

Not to mention you can buy two complete autopilot systems for the price of a single hydrovane.

If wind vanes of any type worked well on catamarans, you can bet that they would be installed on them. It would be difficult to believe that people cruising on catamarans summarily and categorically refuse to instal vanes simply on principle. You would see them out here if they worked. The only catamaran I have met with a twin vane system told me it did not work and was being removed.

Mark

[scarab]

Bobby Schenk ( a famous German world cruiser and author of many books )
uses the Windpilot Plus on his Privilege 465.

You can read all about it on his homepage : bobbyschenk.de

If this link doesn't work go to his homepage and scroll down until you see : die neue Thalassa - Kauf, Ausstattung, Technik und Bewährung
and then you klick on : THALASSAs Windsteueranlage

Greetz,

Koen

[scarab]

I've read the post of Bobby Schenk and these are the facts :

He works with the Windpilot ( not the windpilot plus ) in combination with
a small autopilot ( Simrad tp 20 )
This unit only needs a 1/4 of a amp instead of maybe 10 amp for a regular autopilot.

When upwind sailing and reaching this unit controls / steers the Windpilot ( and not the catamaran )

For downwind sailing he uses the windvane of the Windpilot.

Hope this helps.

Greetz,

Koen

[colemj]

His article says that the vane only works downwind and that he uses a tiller pilot to control it all other times. He also states that he had to give up carrying a dinghy because the vane takes the space.

So he gets it to partially work at a tradeoff most catamaran cruisers find intolerable.

There are no pictures of his steering line routing, but it would also either have to be a tradeoff with convenience and safety, or it would have a lot of drag to overcome. He did mention that he had to go with the largest size vane to produce enough power for moving the steering.

His one point about AP's using power is correct, although it sounds like he had a really power-hungry one on his previous boat - his draw claim is 2-3x more than we experience. However, his claim that if one uses an AP one has to run a generator seven hours each day is wacky. If that was true for him, then he did not have good charging capabilities or battery capacity. Running our generator 7 hrs/day would produce 840 Ahrs of electricity - and that is if I turned the solar off.

If one is concerned about AP reliability, one can buy two good below deck AP systems for the price of one Windpilot or Hydrovane. On a catamaran, these can both be permanently installed with one left offline. Switching over can be instantaneous.

On the other hand, I was relying on google translate, so maybe I did not understand the description well.

Mark

[scarab]

Here are some pics from the installation.

Greetz,

Koen