Multihulls: Windvanes vs. Autopilots

[UNCIVILIZED]

Originally Posted by donradcliffe

I agree that most cruising boats don't have that speed potential. Recently I've been driving Merlin during sail testing with its new keel. The apparent wind effect I described is pretty profound on that boat. Its much stronger on a big sled than on a Santa Cruz 40 or 50, but even those boats have it in lighter winds.

The picture is the old Merlin configuration--the new configuration has twice the righting moment, more sail area and uses asymmetrical spinnakers.

I'm sure that she's more than a little fun to drive (or sail on)!

You're reading me right in that I'm curious specifically as to what works on boats that exceed (displacement) hull speeds. I know that vanes are fine on slower boats, but that's not what this thread is about.

So to be clear, for everyone else, please try & stay focused on self-steering solutions for 10kts+ (boatspeed). Thanks!

[donradcliffe]

Looking at the Vendee Globe boats, I think you have two choices--NKE or B&G.

[double u]

had an aries on our 1st rtw on a 34' wharram
worked down to windstrength when boat was barely moving, surfing on pacific tradwindswells at up to 17kn it would violently bear away though on each surf. some improvement with a little loop of lanyard that limited the movement of the windvane.
would always have a windvane as a fall back, if at all possible: even a fast cat can be slowed down to make the vane work, & that'd definitely be ebtter than handsteering.

[donradcliffe]

Windvane is a PITA, always have a backup autopilot. MTBF for my below decks hydraulic autopilot was about 20,000 miles.

[thinwater]

Originally Posted by Paul L

It doesn't have to be that high a performance boat to cause problems with a windvane. Downwind any boat that will surf causes issues. The apparent wind goes forward as the boat speed goes way up for a brief bit. Then the WV turns the boat to compensate just when you want the boat to drive in a straight line down the wave.

Exactly. As I posted early in this thread, I don't even use the wind setting on my electronic pilot off the wind; the compass setting is more stable.

This varies with the conditions and is not always true. Sometimes the wind setting works. My point is that an electronic pilot offers more options. Though I'm sure I could get a vane to work some of the time... why bother?

[Paul L]

Originally Posted by double u

had an aries on our 1st rtw on a 34' wharram
worked down to windstrength when boat was barely moving, surfing on pacific tradwindswells at up to 17kn it would violently bear away though on each surf. some improvement with a little loop of lanyard that limited the movement of the windvane.
would always have a windvane as a fall back, if at all possible: even a fast cat can be slowed down to make the vane work, & that'd definitely be ebtter than handsteering.

Sounds dangerous to me.

[double u]

never accidentally jibed the boat though. but you could feel the centrifugal force (were 4 consecutive days with >190nm each, one 204 or so, which for a 34' wharram isn't so bad...always could have slowed down

[AiniA]

Originally Posted by Paul L

Maybe it was my lack of expertise with the windvane I had, but I could not trust the vane downwind with typical tradewind winds and large swells. No problem with the AP. Going from 8kts to 12+ was typical( usually with small white sails). Add 2 to 4 kts for maxs.

We had no such problems with the Monitor on our Bristol 45.5 with trade winds of 30 knots and more (Indian Ocean) for many days, with the kind of waves that build in those conditions. We just set the vane and forgot about - just checked every few hours in case the wind had switched at all. You really need to get the boat balanced well and not have too much main area compared to genoa. We were not pushing but generally did 160 mile days with highest at 211.

[StuM]

Originally Posted by AiniA

We had no such problems with the Monitor on our Bristol 45.5 with trade winds of 30 knots and more (Indian Ocean) for many days, with the kind of waves that build in those conditions. We just set the vane and forgot about - just checked every few hours in case the wind had switched at all. You really need to get the boat balanced well and not have too much main area compared to genoa. We were not pushing but generally did 160 mile days with highest at 211.

How many hulls on your Bristol 45.5?

(The question is about the effectiveness of windvanes on multihulls which perform very differently to heavy, full keeled monohulls in oceanic waters. )

[Paul L]

Originally Posted by AiniA

We had no such problems with the Monitor on our Bristol 45.5 with trade winds of 30 knots and more (Indian Ocean) for many days, with the kind of waves that build in those conditions. We just set the vane and forgot about - just checked every few hours in case the wind had switched at all. You really need to get the boat balanced well and not have too much main area compared to genoa. We were not pushing but generally did 160 mile days with highest at 211.

Pretty different boat than my J/37.

[double u]

there was a german gear on the market in the 70ies & 80ies called "Schwingpilot", where the servopendulum pivoted on a vertical axis (Schwing Pilot Wind Vane, https://www.yacht.de/schenk/who/who3101.jpg ), saw it on some rtw-boats 32-37'
on a cat the advantage would be that the submerged surface of the paddle does not decrease with deflection & no power is lost towards the end of it's stroke
gears were reported to be steering very sensitively, construction not overly robust I seem to recall though..

[Bulawayo]

I recall reading, many years ago, about Geoff Pack using a wind pilot and he also used to add a small tiller pilot to it on occassions. As many know, Geoff died tragically young - he was a masive fan of multihulls.

Originally Posted by Smokeys Kitchen

I am a mono owner and have a Monitor Windvane on my boat and am very pleased with it, albeit with only limited use so far.

I have no knowledge of the Monitor use on a multihull, but I did ping Scanmar International (mfgrs of the Monitor) about multihull use and they sent me to the link below on their site.

http://www.selfsteer.com/faqs/faq.php?ID=146

There are a couple of letters written by multihull owners; they seem satisfied with the performance. One even mentions doing 25 knts downwind.

Hope the link helps with the questions about the use on a cat or at speed.

[kleppar]

I am having a 23 ft. cabin trimaran built, with rotating carbon mast and twin rudders. I will have self steering, and am contemplating the following options:

1. a simple cockpit autopilot, e.g. Raymarine or similar

2. a fancy NKE autopilot; supposed to be state of the art, as recommended by the yard

2. a mechanical windvane (Mr Vee and Windpilot have lightweight units around 10 kg); the Monitor seems rather heavy

3. a combined windvane/autopilot (Windpilot); see below (copied from Windpilot´s website); photo here.

Catamarans

If the wind is particularly gusty, a more reliable steering signal can be obtained by removing the windvane and using a small cockpit autopilot attached to the windvane hanger to control the pendulum arm instead.

The trimaran will be used for day- and week-end coastal cruising.

[Pete7]

Originally Posted by kleppar

2. a fancy NKE autopilot; supposed to be state of the art, as recommended by the yard

There is a reason the mini 6.5m yachts use NKE even given the price. I guess your tri will also be pretty quick on the water, so not sure a tiller pilot or combination of wind pilot driven by a TP will be up to it.

https://www.youtube.com/watch?v=TpiItvEstNk

[Training Wheels]

Definitely not a wind vane. If you’re just cruising and just want an occasional break from the tiller, I’d just go with a tiller pilot. If max performance is important when on AP, then the NKE. The NKE has the advantage of being able to steer to apparent or true wind, and has a lot more adjustments to fine tune it. It also is much more expensive, and has a lot more adjustments.