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post #101 of 577 Old 02-24-2018
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Re: Multihull Popularity and Interesting Designs

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Originally Posted by Arcb View Post
Colemj, if you are telling me you have had one of the above mentioned autopilots steer you out of a broach or a steering linkage failure at 27 knots in a cruising cat, I am going to have to take your word for it.
We don't do 27kts, and would never do it. Our AP (the one above) steers us out of potential broaches all the time by never getting us into broaching positions. It anticipates these as well as I can, does so longer than I can, and does it at night - where I cannot.

Our AP has also steered us just fine for 24hrs downwind in 35-40kts (reefed to keep the boat at 8kts) with a broken steering linkage, where the only boat control was the rudder with the drive connected. I didn't even know the link had broken - all I remember is thinking that the AP was a bit more active than usual.

These AP's are continually monitoring all instruments and boat performance 100 times per second, and are continually adjusting their steering to suit. They actively avoid jibing downwind, and through rate sensors on 9 axis, they know before hand when a broach is possible and steer away from it. Heck, it even continually optimizes VMG upwind, and can also steer to a polar table. At some point in the above link failure, I'm sure the boat got really squirrely, but the AP almost instantly picked up on that and adjusted the steering parameters to compensate.

BTW, it isn't possible to get out of a steering linkage failure by hand steering - there is no connection of the wheel to the rudders then. The AP is the only hope.

Again, if you haven't used one of these newer AP's, you will be surprised at how much has changed.

Also, see my edit above - I now understand why you linked to the Triton.

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post #102 of 577 Old 02-24-2018
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Re: Multihull Popularity and Interesting Designs

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Hey guys - how does an Antares 44 cat pull down around twice the amount of an FP Helia 44 for the same length and year?
They are another step up in fit and finish and gear than the Helia, if not two steps, and they are bespoke made, so don't have volume economies. I doubt they build more than 2 a year. They also have a cult following, which helps support the price.

They are an old design, and pretty well superseded now. I've never seen one floating on its design waterline because the hull shape does not carry weight well. However, we are in a glass house in this regard...

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post #103 of 577 Old 02-24-2018
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Re: Multihull Popularity and Interesting Designs

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Originally Posted by colemj View Post
We don't do 27kts, and would never do it. Our AP (the one above) steers us out of potential broaches all the time by never getting us into broaching positions. It anticipates these as well as I can, does so longer than I can, and does it at night - where I cannot.

Our AP has also steered us just fine for 24hrs downwind in 35-40kts (reefed to keep the boat at 8kts) with a broken steering linkage, where the only boat control was the rudder with the drive connected. I didn't even know the link had broken - all I remember is thinking that the AP was a bit more active than usual.

These AP's are continually monitoring all instruments and boat performance 100 times per second, and are continually adjusting their steering to suit. They actively avoid jibing downwind, and through rate sensors on 9 axis, they know before hand when a broach is possible and steer away from it. Heck, it even continually optimizes VMG upwind, and can also steer to a polar table. At some point in the above link failure, I'm sure the boat got really squirrely, but the AP almost instantly picked up on that and adjusted the steering parameters to compensate.

BTW, it isn't possible to get out of a steering linkage failure by hand steering - there is no connection of the wheel to the rudders then. The AP is the only hope.

Again, if you haven't used one of these newer AP's, you will be surprised at how much has changed.

Also, see my edit above - I now understand why you linked to the Triton.

Mark
If you say so, most catamarans i am familiar with have two rudders, two steering linkages leaving one to steer with in the event of a failure.

Yes, I have used high end autopilots in big cats offshore.

The boat in the video was overpowered. The bows were stuffing. A few more knots and the bows could have buried, there could have been a rapid deceleration forward, the breaking waves at the stern would have had a 52 foot lever to push the stern around the bow broadside to the waves at 27 knots. I dont beleive an autopilot could have steered out of that. Autopilots are reactive by nature. A helmsman can see a breaking wave or a gust before it hits.

They were sailing that boat on the edge, having blind faith in your technology to get you out of problems in conditions like that is unwise in my opinion.
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post #104 of 577 Old 02-24-2018
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Re: Multihull Popularity and Interesting Designs

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Originally Posted by SanderO View Post
This is interesting and I would love to sail on a similar boat to mine with one of the newer pilots.

In the end the AP is driving the rudder position and all that data is distilled to turns to port or starboard. There may be software which can adapt to more or less constant eave patterns... and so anticipate turns and so forth. It's hard for me to conceptualize how confused seas and gust data can be correlated into better tracking. Sure locking the helm in one position is a bad solution to steering a course.

My old Alpha does have yaw settings and "speed of response" and I can see it making lots of corrections depending on how I set the "response" and yaw. It does S at times and it seems that a helmsman could do better.... and I often hand steer in those crazy conditions... It's kinda fun. but not for more than an hr... and they I let the AP steer.

A lot depends on the boat's hull LWL, weight and of course the conditions.
Yes, all an AP can do is drive the rudder position. However, that is all a human can do also. Modern AP's can actually react faster than a human because they get the same data faster. Some data isn't even apparent to a human - how much aware of heave are you in a long passage, or how aware of 2* wind shifts or 2kt wind increases/decreases?

In challenging conditions, I sometimes sit at the wheel with my hands lightly on it and pretend I'm steering. Every time, whenever I would start to move my hands for an anticipated adjustment, the AP would turn the wheel under them. Sometimes the AP would turn gently when I didn't think necessary, but then I realized a second later that I would have needed to make a larger correct later.

Confused seas and gusts just get translated into faster and larger corrections by the AP. Granted, these are often more reactionary corrections than predictive ones, but it is often this way for a human too. Since the AP is making calculations 100 times each second, it can react quickly to the boat going off.

All of those race boats whipping around at high speeds in the Southern Ocean, even single handers, are pretty much using commercial AP gear. The software is slightly tweeked specifically for their boats, and can take data from instruments we generally don't use (like strain gauges, multiple wind, etc) but the basic algorithms are the same.

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post #105 of 577 Old 02-24-2018
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Re: Multihull Popularity and Interesting Designs

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Originally Posted by Arcb View Post
If you say so, most catamarans i am familiar with have two rudders, two steering linkages leaving one to steer with in the event of a failure.

Yes, I have used high end autopilots in big cats offshore.

The boat in the video was overpowered. The bows were stuffing. A few more knots and the bows could have buried, there could have been a rapid deceleration forward, the breaking waves at the stern would have had a 52 foot lever to push the stern around the bow broadside to the waves at 27 knots. I dont beleive an autopilot could have steered out of that. Autopilots are reactive by nature. A helmsman can see a breaking wave or a gust before it hits.

They were sailing that boat on the edge, having blind faith in your technology to get you out of problems in conditions like that is unwise in my opinion.
Depends on the steering system design and which part breaks. If the chain or associated sprocket or cable holders breaks, you lose all wheel control. If a cable breaks, you also lose wheel control. If a crossbar breaks, you may or may not have control of one rudder depending on if the system uses a single quadrant or splits between two. Ours is a pull-pull system, so a cable issue anywhere disconnects the wheel from the rudders. If a hydraulic system using independent drives on each rudder, then you have control of one rudder if one drive or cross link fails. If they are all integral, you lose it all if there is a hydraulic failure.

I would say at least 50% of catamarans will lose steerage from the wheel if any link breaks in the system. The number is probably higher than 50%. All single helm ones will lose it if the chain/sprocket system breaks.

I agree with being overpowered. However, I don't see a human getting out of a broach or stuff either. Particularly with that boat, which isn't the most responsive or light helm.

Modern autopilots are not purely reactive. Ours predicts. You can see this in action. 20-100 times per second it is getting pitch, roll, heave, heading, wind, SOW, and SOG data. A helmsman can see a breaking wave or wind gust on the water before an AP, but I'm not sure how much realistic space is there to do anything predictive in those conditions. You certainly aren't going to make large alterations in steering to prevent or adjust to that. Almost everyone in these conditions will have slowed the boat down so that breaking seas and wind gusts do not cause steering issues.

How good is a human in these conditions at night? Worse than a good AP IMO.

Those ocean racers are on AP constantly and they only have one rudder/steering system, where a break anywhere takes them down.

You may have experience with modern AP's in big catamarans offshore, but the only actual reference I have seen you give has been large commercial power vessels. These are apples and oranges to small recreational sail cats in both boat type and AP gear. Can you be more specific as to which recreational sailing catamarans and which AP's you have experience with?

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post #106 of 577 Old 02-24-2018
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Re: Multihull Popularity and Interesting Designs

So I have an honest question for you multi-guys, which I'll setup with a Disclaimer and my specific limited cat experiences:

DISCLAIMER:
Anyone who wants to sail anything, i'm on your side. To me, the argument over who's form of fun is better than they other guys fun for an absolutely unnecessary frivolous activity like sailing is, well, a debate for people who apparently aren't getting enough conflict in their lives. The real question is will anybody be left sailing anything 50 years from now, or will they all be sitting in their living rooms wearing VR googles and getting pizza delivery by drone, while arguing about what VR experience is better than another on social media .

So, with that disclaimer, I'll undo my own argument by stepping into the fray:

MY CAT EXPERIENCE:
Is my perception wrong about cruising cats? I've only chartered them twice, once in Belize and once in the BVI. I found that even when I was going 8 knots, I felt like I was sailing my dock. I had to look at the water rushing by or I'd think I was still tied up. It just didn't do it for me. That said, anchored up with my friends, it was a wicked good party platform and comfortable living. Not to mention, didn't even need to put my beer in a holder underway.

At the other end of the spectrum, I really enjoyed when I was younger getting out on the trapeze on a Hobie 16. What a blast. Yea, I read smack and others experienced pitch poles, and yea I did too. As a teen ager swinging up in the air when a hull went in was exciting. Gotta get your weight aft when a hull flies and it really goes.

THE QUESTION:
So the question is, are their cruising cats that aren't like sailing your dock? More like the Hobie, a bit more civilized, without turning into a barge with a mast on it? That might interest me. Anyplace I can charter one?
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Re: Multihull Popularity and Interesting Designs

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.....Every Cat we have been on requires a climb into the bunk. At first it may not seem so bad. May be fine if you are a twenty something but, it gets old (no pun intended) as you get older and have to answer natures call several times a night. I find myself at the end of a ten day charter looking forward to using a normal bed and appreciate the ease of getting in and out of the bunk on my own monohull. That's if you have no injuries like a pulled muscle which can make getting in and out of the bunk on the Cat extremely painful. We also have to make sure the layout of the bunk on our charter allows for each of us to worm out of it individually and not have to climb over each other. Which is not fun for either person.
Interesting, thank you, another post above left me with a different impression.

I totally agree about berth access, as the joints start passing their freshness date. When we're aboard a bareboat or maybe a friend's boat, with a traditional dog house quarter berth, I have to give myself a pep talk. You've done this many times, you can do it again!

Unrelated to a cat, I once got a charlie horse in my hamstring, while I was stuffed into a quarter berth. The only way to relieve such a thing is to stretch the muscle, until the spasm stops. However, the overhead in the berth was maybe 3 ft and I could not lift my leg high enough. I couldn't shimmy out either. Left a mental scar.

I prefer a berth I can comfortably exit from the side, which is admittedly a luxury.


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Re: Multihull Popularity and Interesting Designs

You are correct, commercial power cats only in this size range, but one was a high speed rig (3 years, faster than 27 knots) and of similar size to the one in the vid, 60 feet. Same rules apply surfing down waves whether recreational or not, except that power cats are easier to control because you can back off the power.

You are probably also correct that a helmsman could not have steered out of a serious broach at those speeds, but I definitely would have one standing by with the AP over ride in hand.

To be clear, I am not saying turn the AP off and steer by hand for the duration of the blow. I am saying it would be wise to have a real helmsman standing by with the ability to immediately over ride the AP if necessary, that is why I linked the pics of the portable controls. If you have the control with you and you see something going sideways, like say a telephone pole floating in the water, you just hit the jog button and over ride, then let AP take back over.
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Re: Multihull Popularity and Interesting Designs

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Y.....I am saying it would be wise to have a real helmsman standing by with the ability to immediately over ride the AP if necessary.......
Absolutely. +1000
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post #110 of 577 Old 02-24-2018
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Re: Multihull Popularity and Interesting Designs

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Yes, all an AP can do is drive the rudder position....but the basic algorithms are the same.

Mark
There is a diminishing return. My AP has steered 10s of thousands of miles... coastal, off shore. It's not perfect but it does better than I do and doesn't need rest or food. The course plots are damn good... But sure there is some wandering.

The AP does not have the full range of helm rotation.... it basically MOSTLY makes rather small course corrections based on whatever data it is using. If I wanted to turn hard over instantly.... AP can't do it. I can manually.

So for example when I approach the fuel dock in NPT... I approach heading south in the channel and make a tight as possible 180 even using reverse to kick the stern over. Not possible with the AP. Tight AP 180 won't work because there is not enough sea room... I use AP until I am ready to execute the turn. I doubt a new gen AP would do this.

I see little reason to "upspec".... but I would need to experience it to make the determination.

pay attention... someone's life depends on it

Last edited by SanderO; 02-24-2018 at 09:42 AM.
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