Autopilot advice?

[Kanani]

Originally Posted by Paul Elliott

Absolutely correct. You want two ways to avoid having to hand-steer. Best if they are both bulletproof, but even a fragile backup is way better than none. Do keep the wheel (or tiller) pilot protected, so it will work when you need it.

Hey, I'm itching for a good fight, and there you go being all reasonable!

Some days......ya just get lucky.

[Rick]

Kanani, I realize that you have not experienced a failure of your windvane. What I'm saying is that, in general, no windwane can outperform a good autopilot under all conditions.

For example, I was in a hurricane and had both a Monitor windvane and good autopilot. Six foot waves would angle down and across the huge following and breaking seas. The little six-footers would slap the stern quarter of the boat and shove the wind paddle over screwing up the course. There was no horizon to see and I tried to steer and almost broached the boat. The autopilot in control stood the boat up straight and on a course that keept the boat from getting in trouble.

In other conditions I was in when the wind would vary in speed on a beam reach sometimes there just wasn't enough to keep the wind paddle in control and, again, had to use the autopilot. Of course with not wind the autopilot worked and the windvane could not.

Yes, a good windvane develops good power at hull speed (or more) but I would bet money that even your windvane course could have been improved upon if you had a good autopilot. Power is not the issue (unless you have a toy autopilot) on a good design for either vane or pilot, course accuracy and stability is the issue. The control system of windvanes have been studied for years and although they can work well they cannot inherently have the linearity, granularity, and lack of deadband that a good electrohydraulic autopilot can have.

Again, I am not detracting from the fact that you have been successful using your particular windvane and autopilot I just point out the broader view of control and overall usefullness. What you could not know, if you did not try it, is how an autopilot would have actually improved the microcourse that a wind vane has no hope to do. Yes, that might not ordinarilly matter, but it certainly can when a boat might be on the verge of a broach or roll-over or, much worse, pitchpole. Because of the immediacy of a rate-gyro control on the action of a boat any marginal coarse response WILL go to the autopilot and not any windvane.

[Kanani]

Originally Posted by Rick

Kanani, I realize that you have not experienced a failure of your windvane. What I'm saying is that, in general, no windwane can outperform a good autopilot under all conditions.

For example, I was in a hurricane and had both a Monitor windvane and good autopilot. Six foot waves would angle down and across the huge following and breaking seas. The little six-footers would slap the stern quarter of the boat and shove the wind paddle over screwing up the course. There was no horizon to see and I tried to steer and almost broached the boat. The autopilot in control stood the boat up straight and on a course that keept the boat from getting in trouble.

In other conditions I was in when the wind would vary in speed on a beam reach sometimes there just wasn't enough to keep the wind paddle in control and, again, had to use the autopilot. Of course with not wind the autopilot worked and the windvane could not.

Yes, a good windvane develops good power at hull speed (or more) but I would bet money that even your windvane course could have been improved upon if you had a good autopilot. Power is not the issue (unless you have a toy autopilot) on a good design for either vane or pilot, course accuracy and stability is the issue. The control system of windvanes have been studied for years and although they can work well they cannot inherently have the linearity, granularity, and lack of deadband that a good electrohydraulic autopilot can have.

Again, I am not detracting from the fact that you have been successful using your particular windvane and autopilot I just point out the broader view of control and overall usefullness.

An AP will absolutely steer a straighter course than a wind-vane. No one that has ever used a WV would ever dispute that. I already stated that a WV may give you up to a 30 degree varience in course at any one particular time. That's mostly do to the fact that the boat speed is constantly changing which causes the apparent wind direction to change, which, in turn causes a change in boat speed. The only exception is when sailing straight down wind and your apparent wind is fairly constant. That is one course where a WV will steer a nearly perfectly straight course. in in the total scheme of things, it doesn't make the avg passage any longer or shorter with either device.

i was merely taking issue with this statement :

"There is no way that a windvane can correct against yaw when the wind gives an immediate shift as the boat gets blanketed by a huge following sea overtaking the craft."

As I stated before, there are a lot of other dynamics that come into play with a wind vane, like the attitude of the boat, amount of heel, speed, a dozen other things that I can't think of at the moment and the WV reacts positively to them all.

The bottum line is, my WV and I have a pretty intimate relationship. The only one that I would react worse about if you said something against her would be my wife. I'm not sure which one has saved my life more. I know darn well that my WV has out-worked my wife and I put together 100 times over and there is no better single piece of equipment that a sailor could have on any cruising boat.........I think that it is probably the only device on the boat that didn't need attention (other than the occasional new lines) in 80,000 miles and 14 years of cruising.

So there.......

[Randyonr3]

I had a wheel pilot and worked it to-death in following seas..(North-west)
I installed a Raymarine, Linear Drive and backed it up with a "SmartPilot" and love it.
Depending on the "gain" setting, it will react any way you program it. With the gyro, the smartpilot will start adjusting the stearing as the rear of the boat lifts in following seas. In lighter winds, you can adjust the gain and the unit uses almost no power. A great savings on a cruising boat.
The unit, when tied into the Chart Plotter, will adjust for a number of variables,
and keep you on the "Rum Line". I spent a big price when I installed it but have never regreted the cost.. It works in all points of sail, a big plus, and in the worst conditions..

[Rick]

You might agree that if someone goes overboard in heavy wind and seas there is little chance that you could go back and facilitate a pickup. If my wife went overboard under such conditions I think that the best thing to do is jump in with her and be together for comfort as long as you have left leaving the windvane (or autopilot) to carry on without either of you.

I've often thought how could I live with myself if I carried on without her.

[Pete the Cat]

I just completed a 7200 mile trip from San Francisco to Maine. Had bought an oversized below decks Autohelm autopilot and carried a spare old "in the cockpit" one. Here are the results:

The mondo motor in the drive unit burned out (I might have helped it with some wiring failures, but it worked for several years before it failed outside Mazatlan). It used a lot of electricity but felt good going down the face of those big waves.

I had to use the wimpy wheel pilot for about 2000 miles and no real problems, but lots of wondering if it would crap out on me. Didn't. But I never faced much of anything in the way of seas either.

Downgraded my drive unit to one which more closely matched my boat displacement and was in a lot of nasty ocean for a few thousand miles with no problems. I think that RayMarine fairly rates their stuff for size and I would not recommend buying mondo bigger as I did. Take two.

Gyro might be nice if you are going downwind with a spinnaker, but you can do a lot of adjusting with the response rates in the Raymarine units and improve the downwind performance, but I would not think most cruisers would want that. Do mount your compass in the right place. I helped a couple out on the trip who were having trouble with AP and the location of the fluxgate compass next to their tool box turned out to be the culprit. Low in the middle of the boat.

Also, several of you are talking about tapping into the quadrant. I would suggest you not do that. You can get a special tiller arm from Edsen for your autopilot that goes on your rudder post, I would not recommend drilling your quadrant--it was not cast for that kind of stress. I would not have liked thinking about that on the face of some twenty foot following seas we saw. This arrangement also makes a nifty backup for your wheel and cables if you have a problem there you are not steering with a stubby emergency tiller.

[Therapy]

Originally Posted by Kanani

I already stated that a WV may give you up to a 30 degree varience in course at any one particular time.

I had no idea that 30 deg. was acceptable.
If it is that bad and one is going 1000 miles then can't one rig differently and just tack a few times?
Forgive my ignorance in this open ocean stuff.

[henryk]

I have to install a new AP on my Tayana and when checked the Raymarine's web site, I couldn't fined one suitable for my boat . All the drive hydraulic units are made either for power boats , or for boats for up to twenty thousand pounds . I have a steering quadrant , so which AP would be the best for it, and what's the cost associated with it ? .
Looking forward to members input .
Regards
Henryk

[Pete the Cat]

Why do you want a hydraulic unit? An electric ram unit will use less power.

[henryk]

I know that Pete , but my boat weights way over thirty tons , but regardless on Raymarine's web site I just can't fined any electric units suitable for that weight .Why hydraulic ? just read all the posts of people that had them . I'm a newbie in this business and like to take advice from the more experienced sailors.

[Kanani]

Originally Posted by Therapy

I had no idea that 30 deg. was acceptable.
If it is that bad and one is going 1000 miles then can't one rig differently and just tack a few times?
Forgive my ignorance in this open ocean stuff.

The 30* varience would only be occasional, like in a gust of wind or a sea kicking the stern around a bit. I would say that "Normal" for a wind-vane would be 15* one direction then 15* the other direction.

Over the course of a 130 mile day, a few degrees one way or the other doesn't really amount to more than a few miles off the mark and then you merely compensate.

On a typical 600 mile passage a highly accurate AP may cut the total miles over the bottom by 20 miles and the total speed over the bottom by .5 kts. which may give you an additional 12-20 miles per day.

As everything else in sailing, it's a trade-off. The widvane is free power, much more reliable and (in most cases) won't let you down at the worst possible time. The harder the wind blows, the more reliable and accurate they are.

An AP will steer a straighter course, keep the sails trimmed better and shorten a passage by some amount. However, it must be fed and carred for, it's dependability is somewhat less and it's failure tends to be at the worst possible times and may be attributed to several factors. The harder the wind blows, the less reliable and accurate they are.

To me, the best of both worlds is possible. Using the AP in light (downwind) air or motoring only and the WV while you have a breeze.
-------------------------------------
As for "Stress" on the quadrant from an AP?????......that makes no sence to me. If the quadrant is stressed by the AP, how would it ever withstand the stress of the wheel?

I've known of many-many vessels that attach the AP to the quadrant and I have never heard of a failed quardrant. My quadrant was 1 1/2" thick S/S disk about 24" accross. I drilled and tapped a 1/2" bolt hole into it and bolted the AP direct and put a lock nut on the bottom side. I couldn't emagine a stronger or more efficient attachment.

[Randyonr3]

Henry
There is a good soulution to your problem.. A good friend of mine did this to his and its been working well for a number of years.. He added a "trim tab" to the rear of his rudder and the AP is attached to the rudder.. The pilot is adjusted to work in reverse where the tab turning to the right, forses the rudder to the left... when you see the system working you'd really be surprised..
And the AP he is using is a really light-weight unit.. its only moving a trim-tab of about 4 inches on a very big rudder........
The whole key to the system is the mounting of the AP directly to the rudder and the working part is attached to the tab..
I've also seen light-weight AP units attached directly to a wind-vane.

[Seeratlas]

I survived a huge storm off the pac northwest coast once ONLY because my brother had talked me into installing an oversized wagner hydraulic ap which operated via a hydraulic ram on its own redundant quadrant on the rudder. Boat was a 54' Stan Huntingford sloop of about 55k lb displacement. Not even a superhuman could have hand steered thru those winds and seas for more than a few hours yet the wagner chugged along thru conditions that saw the loss of ten other boats, 3 with all hands. I would agree with everything Rick has posted regarding below decks units. Been there, done that, got the t-shirt. It is a good piece of advice to go with stout gear when the life of yourself and those entrusted to you are on the line. Money is only money, a life...well...

seer

Originally Posted by Rick

When at sea, especially in heavy following seas, the three main factors regarding the autopilot are:
Power; You need horsepower to move the rudder in fast moving water quickly enough to not broach.
Electrohydraulics; The most reliable when directly connected to the rudder post via a tiller arm or quadrant (if and only if the quadrant is designed for single point torque loading from the ram)
Rate gyro input; You will not believe how quick a rate gyro can respond to the beginning of a yaw and correct for it before a broach can occur.

A good autopilot meeting the above criteria will outperform any windvane. I realize that this statement will probably raise a few cries. A good autopilot can save your boat when even a good helmsman might not be able to. Even excellent helmsmen get tired. There is no way that a windvane can correct against yaw when the wind gives an immediate shift as the boat gets blanketed by a huge following sea overtaking the craft.