Autopilot gives up in following seas

[ka4wja]

Hello to all, (only got a few minutes to catch-up....and saw this query and thought I'd contribute)

1) First off, Stellar J I freely admit that I'm not a "racer" (nor a "professional" sailor, nor sail-trimmer, etc.)....but been sailing since a kid in the 1960's and have made many offshore passages and Atlantic crossings over the decades....so, as cruising sailors, we usually go along with the adage "when in doubt --- let it out"....BUT...
But, some of the advice here is seriously odd to me.
You see, as someone that made his living in electronics, AND as an offshore sailor.....I'm more inclined to look at this as a "boat", "hull", "underbody","keel", "rudder", "rigging / rig-tuning", "sail" / "sail-trim" issue than an autopilot issue.

Of course, it IS very possible that this autopilot and drive unit are simply not powerful enough for this boat....if you can hand steer her well in these conditions, then it seems likely the pilot is undersized for your boat!


2) Secondly, to be clear, I am in 100% agreement here with rslifkin and SailingHarmonie!

Originally Posted by rslifkin

In my mind, if it's possible to hand steer the boat, but the autopilot is giving up due to excessive rudder load, that means the autopilot drive is inadequate. The autopilot may give up because it's become impossible to keep the boat on course if you're massively overpowered, but it shouldn't give up just because the rudder loads got high.

Originally Posted by SailingHarmonie

Two things NEVER overheard in a sailor bar:

• "My anchor was too big."
• "My autopilot was too powerful."

Having many thousands of miles under autopilots that were well matched to the boats they were steering, I can tell you that it is NOT normal to lose control of the boat in when deep reaching or running even with a large quartering sea. Such behavior should not be expected or tolerated. Period. If you can steer the boat accurately by hand, the autopilot should be able to do at least as well.

Assuming, of course, the autopilot is properly tuned, the drive is sized appropriately, and the sails are trimmed correctly.

If you are sloppy on sail trim nothing will work... The more marginal your drive size is compared to the size of the boat, the more critical the tuning of the AP will be.

If you REALLY want to learn sail trim, use a mechanical wind vane where you can't power your way out of bad trim.

Or just balance the boat and sail without the autopilot. If the boat is balanced, it can be done. I've done a long passage without any form of automatic steering, just sail trim. A VERY educational experience.

3) Third, is nobody else bothered by a boat's inability to "sail" well in a broad reach / downwind?
While this is a question posted in the Marine Electronics forum / regarding the autopilot, perhaps rig tuning and sail-trim (as well as the vessel's underbody, keel, and rudder designs) should be something to consider as proximate causes here?

{fyi, if I was familiar with the specs of the autopilot controller and especially the drive unit, in question, as well as if I'd actually sailed a Moody DS45....I'd probably be able to be more definitive....but, damn a NEW two-year-old boat (AND her sister-ship), that has had its autopilot and drive units replaced, and apparently cannot be steered under pilot in 20 kts of wind??? Seriously? If that was my new boat, I'd have the manufacturer principal on-board at the SAME TIME with a reputable rigger, and sailmaker....and ask them to "make my boat sail....or give me my money back"....

I mean, really???
What sailing yacht manufacturer would want any of their customers (especially those spending $500k to $1Million) to be unable to sail their new boat?
Even if this meant admitting that the hull design / underbody design is poor, or that the topsides and/or Deck Salon carry way too much windage.....and/or the keel, and/or rudder designs are crap, etc....surely a good rigger and a good sailmaker (NOT a sail "sales person", but an honest-to-goodness "sailmaker" / "sail designer"), on-board would be able to get even a crappy designed boat's rigging tuned and sails made (and trimmed) to allow the boat to be steered under-pilot in 20 kts in a broad reach?
(btw, I recommend Travis and Colin Mack, of Mack Sails and Mack Service....if you're in/near Florida....but, I suspect that Stellar J is in UK or EU?) }



4) Fourth, why is there this penchant for "dropping the mainsail"?
Do that many of my fellow sailors forget why it's called a MAINsail?

Although weather helm on a broad reach is rare (I've never sailed a boat that had this issue), wouldn't the same trimming techniques used to reduce weather helm when sailing to windward still apply? (like easing the traveler down a bit...or even just easing the mainsheet if the boat isn't equipped with a traveler....or maybe better trim on the genoa...)



Okay, those are my thoughts....beyond the very real possibility of the autopilot not being powerful enough for this boat, I'd be looking at the boat, its underbody design, its keel/rudder, etc...and especially the rig-tuning and sail-trim.
And, PLEASE call Moody and get someone there to actually talk to you....you spent a lot of friggin' money on a boat that won't sail properly....they have an incentive to correct this, yes?

Fair winds!

73,
John

[Shrew]

Originally Posted by Stellar J

We have replaced both the Jefa DD1 and the Raymarine ACU-400 with new units,with no change.

Raymarine has the ability to tune AP responsiveness.

The increments varied over the years. The current p70 series has the following responsiveness settings:

Levels 1 to 3 — Minimize the amount of pilot activity. This conserves power, but may compromiseshort-term course-keeping accuracy.

Levels 4 to 6 — Should give good course keeping with crisp, well controlled turns under normaloperating conditions.

Levels 7 to 9 — Gives the tightest course keeping and greatest rudder activity (and power consumption). This can lead to a rough passage in open waters as the SPX system may ‘fight’ the sea.

https://www.raymarine.com/en-us/supp...cument-library

[thomm225]

Originally Posted by ka4wja

4) Fourth, why is there this penchant for "dropping the mainsail"?
Do that many of my fellow sailors forget why it's called a MAINsail?


Fair winds!

73,
John

The mainsail will cause the boat to round up to weather meaning try to turn the boat back into the wind which is what the OP is complaining about.

The problem is there is too much mainsail up.

The fix is either reduce the amount of mainsail or take down the mainsail entirely.

My earlier videos above demonstrate this. In one I had too much mainsail up and had to hand steer as the autopilot could not handle it when the boat tried to round up. Even while I was filming the boat tried to round up.

It the other video with just the jib up the autopilot could handle the steering easily.

[SailingHarmonie]

Originally Posted by ka4wja

4) Fourth, why is there this penchant for "dropping the mainsail"?
Do that many of my fellow sailors forget why it's called a MAINsail?

Although weather helm on a broad reach is rare (I've never sailed a boat that had this issue), wouldn't the same trimming techniques used to reduce weather helm when sailing to windward still apply? (like easing the traveler down a bit...or even just easing the mainsheet if the boat isn't equipped with a traveler....or maybe better trim on the genoa...)

John

John,

I think this is VERY boat dependent. On many modern designs the mainsail is large and powerful, BUT highly optimized for upwind work, and is severely hampered for downwind work by highly sweptback spreaders. You just can NOT let the sail out far enough to trim it properly for a broad reach.

On older designs, the headsails are the prime engines, and sometimes the mainsail really doesn't do much. On my ketch, once I get above 125 to 130 AWA the main blankets the headsail, and actually slows me down. Putting the main away is the right strategy for maximizing boat speed.

Finally, as a cruiser, not a racer, my main is furled and the boom secured ANY time there is a risk of an accidental gybe. The risk to crew and boat are just not worth it.

Working as a sailing instructor, I used to sail a lot on SF Bay in strong winds. By way of wildly contrasting examples, when sailing a J-105, the mainsail was THE driver for the boat. Trying to sail that boat with just a jib was hopeless. On the other hand, with a Catalena 32, it was exactly the opposite. Taking the main down when sailing down wind made the boat easy to handle and happy even in strong winds. Different boats, different techniques, and the "main" sail was not the same creature on those two boats.

One of the things that happens here is people with a LOT of experience on ONE boat make very absolute pronouncements about the "best" way to do things, when the right answer is (almost) always, "it depends".

All this of course goes away on high performance catamarans where sailing downwind never happens, and on condo-marans which just struggle downwind without a flying headsail.

[donradcliffe]

As one who has raced sailboats across oceans, I can tell you that the winning way to sail a boat off the wind is to load it up with sail area until only the best helmsmen can just keep it under control. If the rudder is big enough so that even an amateur can maintain control, its too big, and you get another rudder.

Can an autopilot drive as well as a professional helmsman? Not until you have run out of unfatigued helmsmen.

Can an autopilot be as strong as a good helmsman? Try putting your own boat on autopilot and then turning the wheel as hard as you can. I'll bet that nine out of ten times the autopilot will break before the steering system, but it will be an expensive test.

So, what should you do? Hand steer through the gales and storms?

The answer varies with how much money you have spent on your pilot.
If you have a tiller pilot, a wheel pilot, or an undersized below decks pilot, or one with plastic gears in the ram, the answer is that you are eventually going to hand steer. Tell that to your wife when you are autopilot shopping.

Any pilot can put up with more weather if you balance your boat and take some of the sail load off. Going off the wind, that means reefing or dropping the main, and sometimes reefing the jib down to a handkerchief.

When you are down to bare poles and the wave start breaking, you can try a drogue to reduce help the autopilot retain control, but even the best autopilots aren't designed to detect and avoid breaking waves.

As an example of how to best cross oceans downwind, I set up a 58 foot boat with two genoas on the same furler and dropped the main from the Canaries to the Caribbean. The autopilot never worked up a sweat, and one crew could control the sail loading during squalls by easing two sheets and rolling the furler in. This system worked so well that I limited boat speed to an average of 12 knots to avoid vibration in the rudder, which I attributed to a rudder blade with a thick trailing edge.

[Kd9truck]

Originally Posted by donradcliffe

As one who has raced sailboats across oceans, I can tell you that the winning way to sail a boat off the wind is to load it up with sail area until only the best helmsmen can just keep it under control. If the rudder is big enough so that even an amateur can maintain control, its too big, and you get another rudder.

Can an autopilot drive as well as a professional helmsman? Not until you have run out of unfatigued helmsmen.

Can an autopilot be as strong as a good helmsman? Try putting your own boat on autopilot and then turning the wheel as hard as you can. I'll bet that nine out of ten times the autopilot will break before the steering system, but it will be an expensive test.

So, what should you do? Hand steer through the gales and storms?

The answer varies with how much money you have spent on your pilot.
If you have a tiller pilot, a wheel pilot, or an undersized below decks pilot, or one with plastic gears in the ram, the answer is that you are eventually going to hand steer. Tell that to your wife when you are autopilot shopping.

Any pilot can put up with more weather if you balance your boat and take some of the sail load off. Going off the wind, that means reefing or dropping the main, and sometimes reefing the jib down to a handkerchief.

When you are down to bare poles and the wave start breaking, you can try a drogue to reduce help the autopilot retain control, but even the best autopilots aren't designed to detect and avoid breaking waves.

As an example of how to best cross oceans downwind, I set up a 58 foot boat with two genoas on the same furler and dropped the main from the Canaries to the Caribbean. The autopilot never worked up a sweat, and one crew could control the sail loading during squalls by easing two sheets and rolling the furler in. This system worked so well that I limited boat speed to an average of 12 knots to avoid vibration in the rudder, which I attributed to a rudder blade with a thick trailing edge.

Well put thank you Don. I love the double Genoa idea, was the second made l with “spinnaker cloth”? And What was the vessel ?

[MicHughV]

I think the above about sums it nicely.

Autopilots have limited to no ability in a big sea and I can attest to that.

Learn to stop the boat....ie, heave too, every boat has their own sweet spot for this. You'd be surprised how docile things can be when the boat is stopped. If nothing else, gives you some time to rest.

Barepoles, with a big sea running, fugetaboutit. Time for a drogue, and even so, the wind and waves will push you where they will. Expect to get knocked 100 nm off course. Some limited steering is doable under drogue, but requires a hand on the wheel. Running aground on a lee shore is always a concern, so if close to land, so this must be allowed for.

As pointed out, balance the boat as best you can without autopilot assistance. I generally trim the sails a bit more than needed, so if the boat rounds up for any reason, the sail will stall draw.

Finally, to go from A to B, sometimes requires going to C first. While we all like straight line courses, sometimes the better option is to change course, so have an alternate plan in mind.

[JPA Cate]

@ StellarJ,

Was just discussing autopilot size with a very experienced sailor/multiple circumnavigator pal of ours the other day. What he said is that usually the recommended a/p is undersized for the boat, so I think yours probably is, AND the advice you've been given upthread is also right: that you can sail on a broad reach quite nicely with just your genoa, and it will most likely relieve the stress on the a/p, so that everyone is comfortable on the boat. But your boat size is at the upper end of that particular a/p's range, and if you want to be able to sail all the time and not have to hand steer, then you will want to upgrade.

I don't know if you have a rudder angle gage on your a/p or not, but fyi, if the a/p is quick, watch what it does. You may see over 20, and then reducing, as it is trying to cope with the waves. Ours turns loose if the power drain is too much, which can be pretty disconcerting when you are suddenly rounding up. When you hand steer in those conditions, watch your rudder angle readout, and see what it has to do to come close to your anticipatory steering. When you're hand steering, the wave motion tells you when to begin your correction: you can anticipate. Your electronic autopilot is always having to play catchup. Set it to expect an agitated sea state, and it will do better. If you want to surf a lot, you'll need a more powerful a/p, maybe 2 sizes up to cope with polar regions' seas.

Finally, we have done a lot of sailing, with two reefs in the main sail, over trimmed, and both headsails out (off the wind): the larger one poled out to windward, and the staysail to leeward. The drastically reduced mainsail impedes rolling, and the two headsails provide most of the power. This is usually something that happens at sea, where the seas are bigger.

Ann

[donradcliffe]

Originally Posted by Kd9truck

Well put thank you Don. I love the double Genoa idea, was the second made l with “spinnaker cloth”? And What was the vessel ?

The vessel was a Chuck Paine designed sloop, and the second genoa was a previous headsail for the boat which was carried as a spare. I had to adjust the hoist length with a lashing, and when reaching with both sails in one side I needed two genoa blocks because the clew heights were a bit different.

[Pete7]

Originally Posted by Stellar J

Our 2 year old Moody DS45 has had autopilot challenges in 20 knots, broad reach conditions. Any ideas here? Thanks Stellar J

I would be astonished if Bill Dixon designed a poorly balanced yacht.

Was the DD1 fitted from new and has the auto pilot software been updated?

Pete

[moodyfinn]

I have spent many a time on the helm in following sea as I can hear the helm struggling. It has all the power but quickly corrects for following sea which strains the whole system. We left Vanuatu in not such nice weather, following sea etc, etc. The two other boats kept their autopilots engaged and low and behold a 42ft rassy smashed their quadrant and the other boat the gears in their ray marine. Listen to your boat and understand that everything has a breaking point. I sail a swan 53 and I know exactly when it can’t cope. It’s part of sailing……

[donradcliffe]

One of my female circumnavigator friends says she would regularly talk to her autopilot when it was rough. "If you keep steering tonight, I will steer 4 hours tomorrow."

[MicHughV]

My issue off being in big following seas are the crests which come rolling down the face of a wave and tend to push you whichever way they want.

My experience has been that even with a drogue trailing behind the boat, I had sufficient, but barely, helm control, to avoid going straight down a wave face.

During the day, one can see what is happening off course, but at night, it's a different story, as you will likely see nothing and have to listen out for the crest.

With big following seas, it can also be expected to be cloudy and raining as well, not to mention the extreme winds.

Though equipped with both wind and hydraulic a/p's, neither were of any value whatsoever during these times for me, as their reaction times were way to slow.

So hand steering it was, which brings up another issue, which is fatigue, especially pronounced when shorthanded.

A final point I'd like to make. The load on a drogue is quite phenomenal as you are sliding down a wave. How much, I could not say, but surely 1,000's of pounds. The attachment point on your boat needs to be stout, very stout, so this will require some thought.

Not sure how singlehanders deal with this ?

[Dreamcatcher34]

We are a moody 41ac so a completely different profile clearly to a 45DS but a common Hanse Germanic birthplace and hence I suspect the components might be similar namely jefa and raymarine . We haven’t experience any issues but at 20knots you are I suspect at point of thinking of reefing in if not actually reefed. You presumably have in mast reefing and power winch so assuming the inmast doesn’t jam 🤣 then have you considered taking in some main ? I suspect it’s a far cheaper solution than replacing units but maybe even hand steering you have a tendency to head up? The risk clearly though is you might burn the autopilot out if you can make adjustments if some fashion . You might also ask on the moody owners forum for views on larger units . Personally if sailing across the Atlantic I would speak to someone who has done this before in a 45DS for gear advice though. I recall a vid of one crossing around 2013 which was filmed.