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post #131 of 577 Old 02-24-2018
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Re: Multihull Popularity and Interesting Designs

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Originally Posted by outbound View Post
What upsets me about this thread and many threads on this forum is how some neglect a basic reality that underpins most cruisers mentality when thinking about boats. This reality extends across all classes be it monos,multis or motor.

There are good seaboats and those not so much.

Comparisons between classes of boats is foolish if not also accounting for if that specific craft is a good or bad seaboat. Grand Banks are wonderful, beautiful, comfortable great loop or coastal cruisers. Sea rays give great bang for the buck. Neither are designed to be or are expedition yachts.
You can blow big bucks and get an light ice Diesel Duck 492 for less than the glorious GB but only the first is the rtw boat. You can quadruple the purchase price and walk on a Seaton or Cape Scott and get the bling with the sea keeping ability to sail the Southern ocean.
The same occurs with monos or multis.

Looking at the title of this thread believe we should be looking at specific boats and critiqueing that specific design. Multis have several vulnerabilities as do monos or motor. This obsession about inverting limits this thread to one of many concerns so is much less informative than it could be.
Look at the various cats you see in Caribbean charter. These are like the Searays. Even in that relatively benign setting one sees:
They hobby horse. When motoring to windward( such as entering an anchorage) this is so extreme as to be dangerous to the occupants. Their beam to length ratio is moderate but capsize risk decreased by moderate rigs. They aim toward one level living with large expanses of glass. But a violent pooping may result in failure of the aft glass enclosure or its rim of support leading to down flooding. The steering is designed for the stresses of forward movement. Falling backwards after being stalled on the face of a wave may result in catastrophic steering failure. Interior living space is optimized for pleasant living at anchor with bridge deck forward of the mast and beam of hulls brought forward to allow a four berth set up. Beyond unpleasant burping the behavior in a seaway is compromised. They have low aspect fixed keels. Beyond decreasing ability to point increased possibilities of “tripping” on a large wave face is increased. Helm position is high and exposed. This is tiring to the helmsman and compromises ability to see the whole boat.

Now compare this to a boat designed as a seaboat. Perhaps the Rapido 60referred to above.
Single rudder. No linkage issues. Very fine hulls and very wide beam with much more force required to turn turtle. No significant structure beyond central hull before the mast. Daggerboard no fixed keel. Protected helm station. Walkways and rig designed to be worked in a seaway. No large glass expanses vulnerable in a pooping or from green water.

In short just like a Diesel Duck would seem to be a better seaboat than a Searay the R60 would seem to be a better seaboat than the charter cat.
I see you have read Chris White's Cruising in Multihulls book. It is a good start, but is pretty dated now, and only represents a single viewpoint among many different ones from very qualified designers and builders.

I have avoided responding to some of your posts in other threads because your information is just too twisted up and poorly presented to try and untangle and add context.

But I would like to point out here that your assumptions about, and categorizing/grouping of, production catamarans and their designs is just wrong on many, many levels. I could spend a page or two just unwinding this post. Like how a good sea boat should have a single rudder, and that single rudders do not have any linkages to fail and that a very wide beam is good. Good grief - that is a general lack of understanding of catamarans, steering systems, and dynamic stability.

Production cruising catamaran designers and engineers include Morelli and Melvin, Marc Van Peteghem and Vincent Lauriot-Prévost, Eric LeRouge, Jeff Schionning, Angelo Lavranos, Phil Southwell, Alex Simonis, Kurt Hughes, and many other extremely qualified people. Many of their designs and philosophy are in contrast to Chris White's, and they have a more extensive portfolio and experience.

I suggest you take your good start at understanding catamarans and their designs (his book is where I started), and allow yourself to push further into the topic with a more open mind. A lot has developed since 1990, when Chris White wrote his book.

BTW, do you realize that more Chris White catamarans have capsized than any other builder/model? That isn't even taking into account that there are 100 times fewer Chris White boats than other builders. While the total number of catamaran capsizes while not racing is extremely small, Chris White designs do hold that record.

FWIW, I like Chris White designs.

Mark

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post #132 of 577 Old 02-24-2018
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Re: Multihull Popularity and Interesting Designs

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In conditions like that it really is a good idea to slow the boat down.
I think we are all in violent agreement on this point.
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post #133 of 577 Old 02-24-2018
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Re: Multihull Popularity and Interesting Designs

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How are you 2 saying I am stuck on APs. Somebody posted a vid of a big cruising cat surfing at 27 knots and I made one post basically saying I thought it would be foolish to leave that boat doing those speeds with an auto pilot in complete control of the boat. Then you two responded with pages of posts trying to prove me wrong, and it isnt working. I still think its foolish.

I disagree that a big cat wont broach. There are physics at play here and those physics dont necessarily point to a 60 000 lb boat doing a stern over bow somersault down a wave front. When the bow stuffs it stops, the inertia in the 60000 lb boat wants to keep going, gavity wants the stern to stay down so that inertia could result in a horizontal rotation instead of a vertical rotation, thus resulting in a broach.

I know this isnt painting a very pretty picture of some of the challenges that can be faced by some boats in heavy weather, but its how it is. In conditions like that it really is a good idea to slow the boat down. Failing slowing the boat down, at least try to keep her under control, you do that in part by steering, not all, but some broaches can be recovered from, but not generally by an autopilot.
I never posted anything trying to prove you wrong that the boat was out of control and the autopilot was handling it perfectly. I can't count the posts now where I've stated in several ways that I thought the people on that boat were foolish to be operating it that way.

I just posted a bit about modern AP's being different than older ones - more predictive and faster responses. I never stated that putting the boat in danger and then relinquishing the helm to an unsupervised AP was reasonable. You have been making that argument, not me.

I stand by what I say about broaching in a catamaran being rarer than in a mono, and pitchpoling being a greater worry. There is a huge geometry and design different between a mono and catamaran in terms of underwater appendages, control surfaces, prismatic coefficients, overall beam, and several other considerations. The reality is that a "broach" on a catamaran, if it occurs, will be gentler and more controlled than on a monohull. It will be more like a slide on a slippery driveway than falling over a cliff like a mono. Pitchpole, on the other hand, is where the catamaran design and geometry work against it.

You are also guessing that not all broaches can be prevented or recovered from under AP, and that they can under human hands. I don't subscribe to this, and doubt you have any statistics or even empirical evidence.

But again, this is completely silly because it is a stupid stunt and doesn't represent catamaran sailing at all. Not any more than a stupid stunt on a monohull represents all of mono sailing. Nor do either represent limitations of either types of boats.

The AP has nothing at all to do with anything about this. It seems like you are intentionally being argumentative.

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Re: Multihull Popularity and Interesting Designs

I continue to be amazed at the level of comfort on a cat while underway. Here is a Lagoon 400 sailing across the Indian Ocean from Cocos Keeling to Chagos...


Now, though I think Delos had better overall weather on this same passage judging by the videos - compare the level of fatigue/sickness of the crew to the above family, and keep in mind that there are 7 young and fit crew on Delos for watches, etc. - and just the mom and dad and kids on the Lagoon...


Good comparison I think. I would take the Lagoon over the Amel any day. Though I have to say, these videos make it obvious that multhull sailors can't make a good video to save their lives. I'll have to fix that.

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post #135 of 577 Old 02-24-2018
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Re: Multihull Popularity and Interesting Designs

I was not talking hurricanes but tornadoes. Why do you bring up hurricanes?

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On the other hand, it can be impossible to avoid [tornadoes] in JUST the right circumstance - like getting hit by lightning...especially if you're relatively close to land where thunderstorms can be far more powerful (like your example which I would equate to sailing in Galveston Bay like we used to do - but I wouldn't call that cruising).
You wouldn't call it cruising if you are 'relatively close to land'? When you are cruising you never get within the sight of land? Don't be ridiculous.

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Now, just like lightning, had this thing been coming right at us I don't think we could have avoided it. And had we gotten a direct hit - who knows what could have happened. And, to the point I think you and others are trying to make, it would have potentially been more dangerous in a cat simply because air can get under the central platform and make the boat fly (though that's impossible to say for sure). This is what I assume happened to that other boat shown in the Florida video that was hit by the tornado - and maybe even that Prout that Noelex mentioned.
That is EXACTLY the point I was making.

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But, I personally don't buy boats for their tornado or hurricane performance. I have no interest in that. I buy them to cruise. Our Hunter did very well on the hard in a direct strike from Category 2 Irma - and we were safe at home. But there were also a few cats in the same yard that did just as well. So, again, I'm not sure what that has to do with cruising.
Let me repeat what I said: it is IMPOSSIBLE to entirely avoid tornadoes while you are cruising, except if you are doing polar expeditions or something. Taking into account how a boat deals with potentially dangerous situations is, in my book, an essential part of good seamanship.

What does it have to do with this discussion that your Hunter was not destroyed in a hurricane while it was sitting on the hard?
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post #136 of 577 Old 02-24-2018
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Re: Multihull Popularity and Interesting Designs

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I'm not sure many would want to use their AP to go to a fuel dock. We use ours for almost everything, but will dock the boat by hand. Also not sure how many would require their AP to go hard over instantly.

On the other hand, our AP has full range stop-to-stop control of the helm, and a 5 second hard over time. With a push of a single button it goes into manual mode, where holding down the buttons moves it about as fast as I can. If we had the other controller, it has a knob for steering like this.

I believe I could dock it using just the AP, but it is much easier to use the wheel based on the motion efficiency alone. Underway, if we need to dodge something, the AP can turn the boat 90* in 2-3 seconds. Our AP can auto tack and has adjustable tack times. Ours is set for 6 seconds, and it does go through tacks that fast. It could go faster, but catamarans don't tack that fast.

Mark
2-3 seconds is not fast enough in an emergency...
I don't dock with an AP... and the way I dock using reverse to kick the stern over is not possible either.
AP provides course corrections and they are very tiny in a sea way... It can tack but not hard over as the AP does not turn stop to stop...
I adapt to its limitations

pay attention... someone's life depends on it
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Re: Multihull Popularity and Interesting Designs

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I stand by what I say about broaching in a catamaran being rarer than in a mono, and pitchpoling being a greater worry. There is a huge geometry and design different between a mono and catamaran in terms of underwater appendages, control surfaces, prismatic coefficients, overall beam, and several other considerations. The reality is that a "broach" on a catamaran, if it occurs, will be gentler and more controlled than on a monohull. It will be more like a slide on a slippery driveway than falling over a cliff like a mono. Pitchpole, on the other hand, is where the catamaran design and geometry work against it.

You are also guessing that not all broaches can be prevented or recovered from under AP, and that they can under human hands. I don't subscribe to this, and doubt you have any statistics or even empirical evidence.
I am not guessing at anything here. Catamarans can and do broach and I have been there when it happens. I said a human may be better able to steer out of a broach I didnt say an auto pilot would never steer out of a broach. If I am not using absolute statements, then my meaning is not absolute. There is no need to look for hidden meanings in my posts, I am saying exactly what I am thinking.

Yes, I recognise that pitch poles are bad, I am not saying they aren't.

If you want statistical evidence on everything I post, please support everything you say with statistical information. This is a discussion forum, I am offering my opinion, if I wasnt, this would be a pretty one sided conversation.
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Re: Multihull Popularity and Interesting Designs

Okay Mast.

I'm in this thread to talk about cruising cats. That's all. A couple of the capsize examples above are from hurricanes which is why I mentioned it. To be clear, I don't hold that multis are great boats for hurricanes or tornadoes regardless of where the boat is in proximity to land.

Apart from that, I'm not interested in arguing. I'm trying to get info from multi sailors about multis.

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Re: Multihull Popularity and Interesting Designs

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2-3 seconds is not fast enough in an emergency...
It is about as fast as I can turn our 46" wheel through 2 revolutions

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Re: Multihull Popularity and Interesting Designs

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I've spent enough time on multi's.

Tell us, how do you handle this, on a multi, at night, with a short crew inside and sheets cleated off? Anna, Leopard and Fujin come to mind.

We're talking good and bad right?

https://www.youtube.com/watch?v=valA6iqyzzk
You do exactly what he did. You ease the sheets (though he sure waited a long time to do that). But more importantly, you pay closer attention to the weather and prep your sails accordingly. The helmsman wasn't doing that. There are a million multi videos out there that show how it should be done.

The only correlation to Anna, Leopard and Fujin I see here is that these people were over-canvassed and reacted way too late. It sounds like that's what happened with Anna and, perhaps, Fujin since it was racing. The G4 capsize was definitely due to the same issue of not blowing the sheet at the right time. Leapoard got hit by a tornadic burst - a completely different bucket of monkeys.

Last edited by smackdaddy; 02-24-2018 at 02:12 PM.
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