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donradcliffe · 05-04-2008, 19:45

I'll try one last time with the physics you so love to misrepresent, then I'm through arguing with arm-chair sailors.

A cat has more initial righting moment, and is thus able to carry more sail, leading to higher performance. What my multihull friend does not realize is that once the heeling moment from the sails gets near the cat's maximum righting moment (evidenced by the windward hull's starting to lift), his safety margin to capsize is essentially zero. Any higher angle of heel will reduce the righting moment faster than the sail load, making the cat go all the way over unless he intervenes. This is not the case in a monohull until the boat heels more than 60 degrees, giving you plenty of warning that you are over-canvassed.

dcstrng · 05-04-2008, 20:59

<unable to differentiate between what happened when they raced a hobie back in the '70's to a modern cruising multihull…>

Very interesting thread – especially for those of us who are multi-hull curious but never having set foot on one except for adolescent Hobie rentals decades ago (perhaps only me). Although it may frustrate knowledgeable multi-hull sailors, it doesn’t bother me that some of the old fears (apparently long-ago conquered by veteran multi-hull aficionados) are dredged up, cuz they’re real enough fears, if no-longer necessarily real…

As I approach a time when I might seriously contemplate extended voyaging (again -- never got much of anywhere when the last opportunity was close...), I’ve once again begun reading whatever seems reasonably available on the multi-hull technical side (and hopefully theoretically rigorous rather than simply rabid…) and would be valuable for me at least if the discussion explored more in that direction… Boyhood family friends capsized a cruising tri in the pacific with catastrophic loss years ago (the Tinenenko saga) and that has colored my suspicions – however from what I’m now reading it appears the design of their craft was decidedly primitive by modern standards (buoyancy of amas, etc…).

My observation is that some the multi v mono debate occurs at a lower key within both camps… many mono sailors wouldn’t be caught dead in anything smaller than 40 feet, some think anything over 30-feet is a waste; just as there seems to be a bit of dividing line on length (and, perhaps, numbers of hulls) in the multi-hull camp… not a biggie… different comfort levels, different preferences, diverse set of esthetics, whatever – individual sailors just have their own penchants… have never capsized anything but dinghies and have no serious-weather offshore sailing experience, but have had mono’s deck in the water more than once in boats from 20-45 feet, so the concept of getting to 45-degrees of heel on a ballasted keel doesn’t bother me a whole lot… However, how the multi handles conditions as the ama gets near its limits is a topic I’d like to be more comfortable with… and the fact a multi makes a better life-raft I don’t find particularly comforting – would rather avoid the life-raft episodes altogether…

Most are well aware that in experienced hands, multis have handled almost any reasonable conditions on the globe, including serious high-latitude sailing, and blown the mono-hull speed records out of water in the process, but as was proffered -- for potential cruisers such as myself, we’re likely talking one modestly experienced (or maybe not very experienced) sailor accompanied by a lesser skilled mate -- what then…? Well-found monos have long enjoyed a reputation of being modestly self-tending in reasonably extreme conditions, but at least to those of us uninitiated to the multi-world, non-ballasted vessels enjoy no such status – although from my reading, it seems that the key is “well-found,” rather than number of hulls and/or percent of ballast…

Reassuring to me is the fact that many seemingly conservative sailors and their families cruise freely in multis, but for me I’d like to get comfortable with the science as well – some “science” other than just writing frightfully big checks… why are multis so horrifically expensive….? Boggles my mind… oh, well – different issue…

Few minor questions: (1) is there a length where tris (more appealing to my eye) are preferable to cats (or is that just an esthetic issue… and (2) for the backyard, do it yourselfer, are their current or past designers whose work passes muster under modern standards for multi-hull integrity (I like the look of the Constant Camber tris, but they seem to have been from an earlier era…), and (3) from a technical stand-point; what is the lower length limit for a multi other than load-carrying and general semblance of comfort (at least in monos, over several decades I’ve gravitated down to the less-is-more school; not altogether championed my many, but still my preference having had all the fun I care for with the maintenance on the larger, more generally accepted, boats..).

Thanks

44'cruisingcat · 05-04-2008, 21:47

Quote:

Originally Posted by donradcliffe

I'll try one last time with the physics you so love to misrepresent, then I'm through arguing with arm-chair sailors.

A cat has more initial righting moment, and is thus able to carry more sail, leading to higher performance. What my multihull friend does not realize is that once the heeling moment from the sails gets near the cat's maximum righting moment (evidenced by the windward hull's starting to lift), his safety margin to capsize is essentially zero. Any higher angle of heel will reduce the righting moment faster than the sail load, making the cat go all the way over unless he intervenes. This is not the case in a monohull until the boat heels more than 60 degrees, giving you plenty of warning that you are over-canvassed.

Confusing racing boats with cruising boats again. A cat may be ABLE to carry more sail, but does it? Racing boats do, but not cruising boats. Because they are lighter than mono's, they can perform better with LESS sail area, which, combined with the huge righting moment, makes capsize very, very unlikely. For instance, the boat I'm building is 44 feet, weighs 5 1/2 tonnes, and has only 80 sq metres of sails (main & jib)

A fast cruising monohull of similar length I was considering building weighs 8 1/2 tonnes, and carries 105 sq metres of sail. Even with 25% more sail area the mono won't perform as well as the cat.

It's also worth pointing out, that by the time the cat has reached the point you mention, where righting moment is close to equalling heeling moment, the monohull would have long been knocked flat - with less righting moment, AND a bigger sailplan, it would have all been over for it long before.

Really, if multihulls were anywhere near as unpredictable and dangerous as you make out, nobody would be sailing them. I've been on a cat in 40 knots of wind, with 2 reefs and part furled jib, and thoroughly enjoyed it. The boat was as solid as a rock.

44'cruisingcat · 05-04-2008, 22:04

Quote:

Originally Posted by dcstrng

Most are well aware that in experienced hands, multis have handled almost any reasonable conditions on the globe, including serious high-latitude sailing, and blown the mono-hull speed records out of water in the process, but as was proffered -- for potential cruisers such as myself, we’re likely talking one modestly experienced (or maybe not very experienced) sailor accompanied by a lesser skilled mate -- what then…? Well-found monos have long enjoyed a reputation of being modestly self-tending in reasonably extreme conditions, but at least to those of us uninitiated to the multi-world, non-ballasted vessels enjoy no such status – although from my reading, it seems that the key is “well-found,” rather than number of hulls and/or percent of ballast…

Reassuring to me is the fact that many seemingly conservative sailors and their families cruise freely in multis, but for me I’d like to get comfortable with the science as well – some “science” other than just writing frightfully big checks… why are multis so horrifically expensive….? Boggles my mind… oh, well – different issue…

Few minor questions: (1) is there a length where tris (more appealing to my eye) are preferable to cats (or is that just an esthetic issue… and (2) for the backyard, do it yourselfer, are their current or past designers whose work passes muster under modern standards for multi-hull integrity (I like the look of the Constant Camber tris, but they seem to have been from an earlier era…), and (3) from a technical stand-point; what is the lower length limit for a multi other than load-carrying and general semblance of comfort (at least in monos, over several decades I’ve gravitated down to the less-is-more school; not altogether championed my many, but still my preference having had all the fun I care for with the maintenance on the larger, more generally accepted, boats..).

Thanks

Do you think that every one of the hundreds of multihulls that have circumnavigated had highly experienced crew? Try googling "Bumfuzzle" And I'm sure there were many many others.

There are instances where cats have been abandoned, and have survived severe storms with no assistance from crewmembers whatsoever.

To answer your other questions - most seem to feel that under around 35 feet a tri will have more useable room, over that number (more or less) cats become roomier.

There are many designers who'se boats can be built in a backyard to commercial survey standards if that's what is wanted.

A lower length limit would depend on the individual, but IMHO longer is better for a given amount of accomodation. There are a lot of designers who say this, but not many who actually seem to stick to it. Bob Oram is one - his boats are generally "small" and light for their length.

**Steve Rust** · 05-04-2008, 22:57

Quote:

Originally Posted by donradcliffe

What my multihull friend does not realize is that once the heeling moment from the sails gets near the cat's maximum righting moment (evidenced by the windward hull's starting to lift), his safety margin to capsize is essentially zero.

Yes, we all sail along in blissful ignorance not knowing the warning signs that our multihulls are over canvassed until we flip over. My tri will tell me when it's time to slow down and this is way before any threat of capsize. Any owner who understands his/her boat will have a feeling for the warning signs well before trouble develops.
It is true that a cat has reached it's maximum righting moment when the windward hull lifts but it does not then all of a sudden drop to zero. It tapers off until at about 45 degrees it is the same as the monohull, after this it has less.

You can take your ball and go home now.

Robertcateran · 06-04-2008, 01:46

One of the big advantages of a multihull is the shoal draft. One of the most hazardous parts of cruising is getting your dinghy to shore and back when parked a long way out If you hit the bottom as you are crossing a bar, it is not much fun, and if you end up on a lee shore, if you can float right to the beach, there is a much better chance of survival.
By far the most comfortable commercial fishing boats I have been on have been cats- working in an extra 5-10 knots
Robert

Tropic Cat · 06-04-2008, 07:32

Quote:

Originally Posted by Whimsical

I just had a look and there is an area for the monohullers. Fancy that I never noticed before.

Now that can't be true... who in their right mind would go to sea with lead weights attached to their keel? That's just crazy.

Tropic Cat · 06-04-2008, 07:53

Quote:

Originally Posted by donradcliffe

I'll try one last time with the physics you so love to misrepresent, then I'm through arguing with arm-chair sailors. .

Well I suppose this post is close to being correct as my helm seat is pretty much an arm chair. Come to think about it, with two hulls and two diesel engines I feel as safe in my helm seat as I do in my arm chair at home.

Although you seem to love to argue this point, I will just say this. The manufacturer of my boat posted a reward for any owner demonstrating he could get his windward hull out of the water. 600 boats and 20 years later, it has never been paid.

Please don't confuse cruising catamarans with a Hobie 16 which seems to be a common mistake for arm chair mono guys.

You buy a boat, you learn to sail her and that is pretty much the end of it.

dcstrng · 06-04-2008, 08:06

<Bob Oram[‘s] … are generally "small" and light for their length…>

Appreciate it – I’ve looked at his quite a bit, actually… noting that he advocates cats generally above 38ft, but I was intrigued by his 29… nonetheless, his designs remind me of the ULDB designs (down-wind sleds of another era) that rather revolutionized thinking in offshore monos… I’ve nothing against long-waterlines as long as they aren’t attached to a condominium complex, which unfortunately store-bought vessels of both genres seem to be, more often than not…

As for the observation about 35ft being the rough dividing between tris and cats -- that was my guesstimate after reading about the Net over recent months, so thanks for the insight…

The veiled annoyance from the mult-hullers when queried by us mono guys is palatable – absolutely no offense intended… I run into this all the time on forums catering to my other vices – openwheel Indy-style racers don’t like associating with us dirt-track and stock-car guys, crotchrocket speedsters won’t give the time of day to us long-pavement riders, etc., etc… always baffles me, but generally just read along in stealth mode…

Therapy · 06-04-2008, 08:44

Quote:

Originally Posted by dcstrng

… always baffles me, but generally just read along in stealth mode…

Just human nature. Unknown is fear and to be condemned. Natural.

I started reading about cats in the early 80s.

I was convinced then.

I read this site in "stealth mode" for a long time.

Some will never trust a cat. I don't care.

More room at the beach or dock for me.

Southern Star · 06-04-2008, 08:45

Donrad the Almighty has spoken!!!!! The rest of us are armchair sailors who 'misquote' physics (although no contrary stability curves are cited as there are none). Good riddance to such aggressive arrogance and ignorance.

And Larry, this isn't 'veiled' annoyance, it is also not a multi versus mono thing. It is the real frustration of having to counter fictions that are expressed, not as opinion, but as 'inarguable facts'.

Brad

smj · 06-04-2008, 08:45

When we first started looking at cruising cat's in the early 90's we went to the insurance companies for their opinions. Lloyd's of London considered cruising cat's a better risk than the mono's. That convinced us we were making a good decision.
A.J.

Southern Star · 06-04-2008, 08:52

Yes smj ,but what does Lloyd's of London know about assessing risk? What do they know about sailing vessels? I mean, where does some upstart company with no marine history get off making that assessment? Donrad the almighty has spoken and it is an inarguable fact that cats are at much greater risk of capsize (and because they cannot be righted, loss) than monos.

Brad

smj · 06-04-2008, 09:11

Brad, We only seem to manage to capsize our cat ounce a year. The positive note being what a great time to clean the bottom, and when righted it forces us to do our spring cleaning!