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

Quote:
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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