Why do auto-pilots fail on long trips??

[Rorzech]

What about WTF ,( F stands for fooy in this instance) I don't think any large companies spent a nickel teaching the world what that's supposed to mean. We're all on our own when it comes to acronyms IMHO.

[daletournier]

Originally Posted by Rorzech

What about WTF ,( F stands for fooy in this instance) I don't think any large companies spent a nickel teaching the world what that's supposed to mean. We're all on our own when it comes to acronyms IMHO.

I must admit it take me a while to workout all the various text message accromyns.

[UNCIVILIZED]

Originally Posted by DumnMad

All good points but the 'lots of spare parts redundancy' sounds a bit like planning for failure rather than planning for success.
Our redundancy took the form of a long punishing period of hand steering and a few lessons learnt.

My view is that if I had understood my equipment better, I would have monitored the batteries better and if I had done that there wouldn't have been an overstressed electric pump motor and nearly 2 weeks hand steering.

I'm picking most boats sailing offshore NZ have the correctly sized auto-pilots. But heavy weather sucks the power out of the batteries and far too many transitting crews are having AP failure.
I now understand AP's are not designed to run in big waves when powered by semi-flat batteries.

The "success" part of one's self steering system(s) IS having sufficient backup plans so that you don't need to hand steer on a passage. However that looks or works out in terms of the equipment you fit & carry.

I look at it like this: It's nice having a full sized spare tire in my vehicle, along with a tire patch kit, & an air pump. I've never needed to use any of the 3, but... they give me the peace of mind in knowing that I can reach my destination whether I get a flat or not, while not having the vehicle's; safety, speed, or range limited by a tiny, undersized "spare" as found in most vehicles.

Or in even simpler terms, why do most folks carry more than one credit card? This, along with an ATM card, AND cash.
Having a backup AP system & spares is much the same. And there's a reason why doing so has been the norm for long distance offshore voyagers for half a century+

[danielamartindm]

Originally Posted by DumnMad

I've had a 2week and a 3week Tasman crossing where each time it was mostly without auto-pilot.

After research I conclude:
The waves got bigger,
The AP worked harder,
Not motoring so alternator not charging,
The battery voltage got a little lower,
AP pump motor took longer to get up to speed,
Higher starting mode currents in motor lasted longer,
Coils got hotter,
Motor failed.

On other threads I notice some have had this problem but after a while the AP is all good. I assume they had a good bi-metallic trip switch that saved the motor.
Maybe they also had wind or trailing water powered generator.

Does this make sense ??

The demands on any device are multiplied by the time it's in use. Perhaps we should be reefing and balancing our sail plans more than we do to specifically minimize the work of APs on crossings? I'm just asking because the issue transcends electrical consumption by the AP, it clearly impacts AP failure.

[daletournier]

Powerful autopilots let us get away with more than we should, to much sail, not balanced well etc.
I think this is where a Hydrovane or equivalent is good, it teaches you to sail. In order for you to get it working well one must pay attention to the sails.

[waterman46]

Originally Posted by Steady Hand

Anecdote: I recently sailed on and helmed for hours (and enjoyed it) a fully loaded for cruising performance cruiser 42 foot boat on a close reach in 20-30 knot winds and the boat was so well trimmed by the skipper (a highly skilled sailor) that the helm required little more than fingertip (literally) control to steer. It was an example of proper trim and a balanced helm making the job of steering much easier. The boat was sailing with a reefed main and reefed jib, and still making 8-9 knots.

That is good sailing. But darn near any sailboat worth going to sea in, will steer a straight course with helm locked on a close reach with occasional tiny adjustments as wind strength changes. The OP probably was referring to nearly downwind sailing in seas large enough to throw the boat off course. Autopilot will work hard and at some wind angles there really is not much relief to be gained by sail trim or sail combinations.

My steering is hydraulic. After reading these posts I am tempted to get a second hydraulic pump and plumb it in parallel with valves, since I always sail shorthanded.

[Cavalier]

Originally Posted by waterman46

That is good sailing. But darn near any sailboat worth going to sea in, will steer a straight course with helm locked on a close reach with occasional tiny adjustments as wind strength changes. The OP probably was referring to nearly downwind sailing in seas large enough to throw the boat off course. Autopilot will work hard and at some wind angles there really is not much relief to be gained by sail trim or sail combinations.

My steering is hydraulic. After reading these posts I am tempted to get a second hydraulic pump and plumb it in parallel with valves, since I always sail shorthanded.

Changing the sensitivity of the AP in downwind conditions can help reduce the frequency of control inputs (so does running the AP in wind-angle mode), such that movement isn't corrected prematurely - the net effect being lower overall power consumption and less wear on the system.

I've been thinking about a backup system myself recently, even though my current AP drive is slightly oversized for the vessel size. Many backup systems I've seen installed are cheaper/poorer versions of the primary, which makes me wonder whether that's a good idea: if your primary is failing due to heavy load, what makes you think a weaker backup would last any longer in the same conditions? That said, I can see the logic of the 'cheaper' backup - "why spend all of that money for a system which is seldom/never used?"

My solution so far has been to assume that the Type 2 linear drive is more likely to fail (due to wear) than the AP controller itself, so the preferred solution at the moment is to have a secondary drive (and not necessarily linear) that could be switched into the AP controller if the larger linear drive went down.

However, I'm now starting to wonder whether a simple ammeter with a configurable high-trigger alarm connected between the AP and breaker might not be a bad idea - at least it would warn you that the AP is possibly consuming more current than you expect for the conditions, alerting you to the need for better sail trim or other remedial actions.

[waterman46]

Originally Posted by quike

why not buy a nice windvane autopilot

No room. I would love to have a good windvane but I already have dinghy davits, swim ladder and plan to add solar panels, and I need to use my stern anchor now and then, and I will be doing Med ties. As it is, its getting hard to read the name of my boat and hailing port!

Anyway, I seriously doubt that any windvane would perform as well as a good electrical pilot in big sea DDW conditions.

With the high cost of custom SS metalwork required and with little guaranty that a windvane installation would perform well, its just too risky an approach. Maybe best for the smaller boats.

[Cavalier]

Originally Posted by waterman46

No room. I would love to have a good windvane but I already have dinghy davits, swim ladder and plan to add solar panels, and I need to use my stern anchor now and then, and I will be doing Med ties. As it is, its getting hard to read the name of my boat and hailing port!

Good thinking - a sensible windvane installation must be based around an uninhibited and natural flow of air over and around the area of installation - having the vane 'dodged' or receiving fouled airflow due to large radar/dingy/solar-panel framework wouldn't lead to reliable function.

[Rorzech]

I don't know why most sailors avoid the simplest of AP's . The best one that works excellent is just a sheet to your jib or genoa , run it back and around to the other side of the cockpit , then to the tiller which has a shock cord attached on the other side of the tiller providing the needed tension. The wind in your jib will steer your boat through anything. Try it out and give you electric AP a break and it will last longer. There's lots of youtube videos on this subject.

[Rorzech]

Ha ha ha , I like that one !

[Cavalier]

Originally Posted by Rorzech

I don't know why most sailors avoid the simplest of AP's..

Could having a wheel instead of a tiller have anything to do with it?

[LoudMusic]

Originally Posted by Cavalier

Changing the sensitivity of the AP in downwind conditions can help reduce the frequency of control inputs (so does running the AP in wind-angle mode), such that movement isn't corrected prematurely - the net effect being lower overall power consumption and less wear on the system.

Unless I've missed something, this is the only mention of sensitivity settings in this entire thread.

The easiest way of keeping your AP from failing? Tell it to do less work.

[Exile]

Originally Posted by Cavalier

Could having a wheel instead of a tiller have anything to do with it?

Could set up the emergency tiller I suppose as a backup option should the AP go down. Not sure how realistic this is, and probably boat-dependent, but maybe worth some study.

[Exile]

Originally Posted by Cavalier

Changing the sensitivity of the AP in downwind conditions can help reduce the frequency of control inputs (so does running the AP in wind-angle mode), such that movement isn't corrected prematurely - the net effect being lower overall power consumption and less wear on the system.

Originally Posted by LoudMusic

Unless I've missed something, this is the only mention of sensitivity settings in this entire thread.

The easiest way of keeping your AP from failing? Tell it to do less work.

I thought what Cavalier was suggesting was to actually increase the sensitivity settings in downwind conditions, so that you're increasing the power required by the AP initially, but in the long run mitigating how much it has to over-correct, with the overall effect being less overall power consumption along with wear & tear.

Did I understand correctly?