Are trimarans safe?

[lyc]

Latest news in Route du Rhum is that British sailor Ross Hobson has been rescued, yesterday it was Steve Ravussin, Charlie Capelle overturned earlier.

Previous Route du Rhum was the same and in the Jaques Vabre many trimarans capsized. Why, is it worth it?

 

[BruceDanforth]

Well any boat is going to capsize or pitchpole if it is skippered beyond it's safe limits in a lunatic manner. It's not a problem with trimarans in particular.

 

[ChrisE]

Why is any endeavour 'worth it'?

Whilst there are people who want to push their machines and themselves to the limit then it is worth it.

However, I believe that there is now a case to be made for these races to have their own rescue facilities or at the very least insurance to cover the costs of the other vessels that have to rescue the skippers. Perhaps, the organisers already do this, does someone know?

 

[Benbow]

At a more mundane level, how do 'cruising' tris cope with simply plugging to windward (or as near as possible) in a blow ? A monohull will be uncomfortable for the crew but is an immensely strong structure and will just keep bobbing along.

It 'feels' to me however, that a tri will experience huge loads on fragile parts of its structure under these conditions. What happens when a wave completely breaks over one float ? Surely the boat will want to spin towards it and the float will want to rip off?

(this is a question based entirely on ignorance; I have never sailed a tri, but I like the look of the big dragonfly)

 

[Birdseye]

The big difference between a multi and a mono in a racing environment isnt that the multi is stable upside down (most racing monos are anyway) but that the point at which the boat changes from OK to "flip" is very sharp. So when you are sailing on the edge pushing hard you are sailing very close to this point and an error is quickly punished.

But if you want to get there fast and if a size limit prevents you achieveing this by going bigger, then a multi and in particular a tri is the only option.

Personally I dont see the problem - racing boat design is as relevant to what we do as F1 is to your road car.

 

[snowleopard]

The simple answer is that the structure of a multi has to be very strong with a degree of flexibility. Occasionally it's not strong enough, e.g. Team Phillips (though that was more to do with poor workmanship than design).

Monos have to have a lot of strength to but in different areas. Loss of a keel can completely spoil your day.

A big difference between racing and cruising multis is that cruisers always keep 2 hulls in the water (cat or tri) but racers are occasionally sailed with only one which is very fast but very dangerous.

 

[boatmike]

You have had a lot of answers around your question but no direct answer to it.

The answer I think is that when racing outright as these guys do you want the fastest machine there is. That's undoubtedly a trimaran. Unfortunately in big seas they are also the least "seaworthy" in many respects and only survive by avoiding the worst weather systems by getting the hell out of there ASAP which they of course can (most of the time) because of their awesome speed. When they screw up they can die. The risks associated with this ultimate form of racing are very high and it's only the bravest (some would say most foolhardy) that race these awesome machines at all. Is it worth it? Well not if you are a normal mortal it isn't no. But these guys are no more "normal" than mountain climbers, F1 car racers, or bungee jumpers. They are super heroes in my book and continually stretching the bounderies of human endeavour. If you (like me) are "normal" don't go there!

 

[boatmike]

Quick answer is there are very few true cruising tris because their only advantage over a cat is speed which is very low down the order of requirements for true cruising. Cats have more structural strength, loads more room on board and don't evacuate your bowels in a gale. The dragonfly is fun as an offshore day sailor but the novelty soon wears off as they are not actually very fast anyway as they have a very fat hull.

 

[bilbobaggins]

Re:\".....It\'s not the ships. It\'s the men in them.....\"

[ QUOTE ]
....this is a question based entirely on ignorance; I have never sailed a tri, but I like the look of the big dragonfly....

[/ QUOTE ]

Having sailed both big and small Dragonflys a fair lot of miles, they certainly do look good. The best guidance one can give in public would be to seek out and interrogate the past-owners of UK-based Dragonflys. Try the Royal Southampton YC.

And Mr Hobson's trimaran is no stranger to being upside down.....

The analogy with cars was put like this "Comparing a racing trimaran with a monomaran is like comparing a Porsche 911 Turbo with a Ford Mondeo. When driving the Ford too hard on a winding country road, there's plenty of warning that the car is being over-stressed, with body lean, squealing tyres, over-steer..... With the Porsche, you get lots of extra performance, but when it lets go, it goes completely.

You simply have to learn when to take the foot off the pedal. Otherwise, no-one but you will be surprised when you end up upside-down in a field....."

QED

As for Snowleopard's rather provocative - nay, contentious - point about 'poor workmanship', I was privileged to attend the Joseph Black Memorial Lecture one year at Bath University, where the eng graduates showcase their work and a prominent - sometimes controversial - industrial designer gives that year's keynote lecture to an assembly of the great and good from the world of eng design. One year, it was the turn of Adrian Thomson, designer of 'Philips Challenge', with a fascinating presentation on the challenges of his great design.

In the front row were the Heads of Design from the likes of BAe Sytems, Ove Arup, Airbus Industrie, etc., all of whom knew each other. For some reaon, I was in the second row, and able to earwig. "I wonder if he's thought of so-and-so..." one of the worthies in front of me remarked. "He doesn't seem to be aware of YYY", said another. "There's no sign of ZZZ considerations", said a third.

No-one wanted the thing to fail, but one of those world-class structural engineers summed up the feeling over tea - "If he's got it right, all the rest of us have got it wrong."

Nonetheless, it was a remarkable leap - whether of faith or engineering, time will tell.

 

[dulcibella]

Re:\".....It\'s not the ships. It\'s the men in them.....\"

"Comparing a racing trimaran with a monomaran is like comparing a Porsche 911 Turbo with a Ford Mondeo. When driving the Ford too hard on a winding country road, there's plenty of warning that the car is being over-stressed, with body lean, squealing tyres, over-steer..... With the Porsche, you get lots of extra performance, but when it lets go, it goes completely.

You simply have to learn when to take the foot off the pedal. Otherwise, no-one but you will be surprised when you end up upside-down in a field....."

Monomaran?? I've never heard of a bimaran either.

 

[bilbobaggins]

Re:\".....It\'s not the ships. It\'s the men in them.....\"

[ QUOTE ]
Monomaran?? I've never heard of a bimaran either.

[/ QUOTE ]

You simply must get out more.....


aka 'leadmines'



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[StellaGirl]

Re:\".....It\'s not the ships. It\'s the men in them.....\"

all interesting and fair comments but with reference to this particular incident it was an autohelm failure that caused him to capsize!

 

[jimi]

Re:\".....It\'s not the ships. It\'s the men in them.....\"

Another big difference is that a capsize with a mono is never due to wind alone, its is due to a big bad wave or the keel falling off. The multi on the other hand can be inverted by wind alone.

 

[snowleopard]

Re:\".....It\'s not the ships. It\'s the men in them.....\"

My comments about workmanship were a result of direct observation. I was speaking only a couple of weeks ago to someone who saw the boat in build and said the quality of laminating was the worst he had ever seen. That was backed up by reports that the cause of the bows breaking off was lack of bonding between the skins and the core. A fault like that occurred while I was building my cat (a result of premature resin set on a hot day) - I scrapped the panels and started again but it looks as though they let that sort of thing go.

A properly made sandwich is immensely strong but if the skins aren't bonded to the core it's not much stronger than a cardboard box. I still believe that if properly built, TP would have been strong enough.

At the time of the breakage, someone on this forum said "Any fool could see that a long unsupported structure like that would fail". I presume he only flew in biplanes!

 

[snowleopard]

Re:\".....It\'s not the ships. It\'s the men in them.....\"

[ QUOTE ]
Another big difference is that a capsize with a mono is never due to wind alone, its is due to a big bad wave or the keel falling off. The multi on the other hand can be inverted by wind alone.

[/ QUOTE ]

But how relevant is that? Certainly my cat could be turned over by wind action alone. To do it I would have to take it out under full sail in flat water in a F9, pin the sheets in and turn beam on to the wind.

BTW - no multi ever capsized as a result of the keel falling off!

 

[bilbobaggins]

Re:\".....It\'s not the ships. It\'s the men in them.....\"

[ QUOTE ]
it was an autohelm failure that caused him to capsize!

[/ QUOTE ]

The worthy tooth-fairy from Newcastle is IMHO perfectly entitled to go to sleep, with autopilot in command, and with enough sail set that a system failure puts the vessel in 'inverted mode'. That's what SH racers do, and it's their gamble....

As for gambling, we all - well, most of us - know that if one keeps going back to the table, sooner or later one loses one's shirt, or worse, to the Casino.

Again IMHO, a system should be set-up so that a single unattended failure should not cause the loss of the vessel. That's an eng design consideration, and I'd like to hear from sailing eng designers on how this state of affairs might be averted in the future.

I.e. Can we learn - and progress - from this?

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[jimi]

Re:\".....It\'s not the ships. It\'s the men in them.....\"

Jings, there's a challenge;-)

Seriously though if you were sailing along in a F7ish beam reach with too much sail up would'nt you risk inversion if the combination of a wave and gust at the same time picked a hull up and allowed the wind to get under it?

 

[snowleopard]

Re:\".....It\'s not the ships. It\'s the men in them.....\"

The point I was making is that cruising sailors normally sail so far within the safety limits as to make risk of capsize negligible. If one normally reefs at 20% of the limit, a sudden doubling of wind force still leaves you safe. A racer might push to 70% leaving himself vulnerable to a big gust.

 

[bilbobaggins]

Re:\".....It\'s not the ships. It\'s the men in them.....\"

[ QUOTE ]
if you were sailing along in a F7ish beam reach with too much sail up would'nt you risk inversion ?

[/ QUOTE ]

Absolutely. And it happens.

Much work was done some years ago in the attempt to provide useful guidance to owners, sparked off by the stability requirements of the Recreational Craft Directive. One can quite readily calculate the force required to lift a catamaran hull clear, after which the Righting Moment is decreasing. That can be translated, in respect of various 'sails sets', into critical wind speeds. Assuming those to be 50% gusts ( not unheard of ), then lower 'sustained' wind speeds can easily be derived, at which a skipper should/may consider reefing.

Trouble was, many owners take an emphatic view that 'I know my boat. Nobody tells me when to reef....' Several designers, sensing a notional 'disadvantage' when/if comparisons were made with others' designs, refused to play.....

'Stability Information Cards - for the guidance of wise men, and the adherence of fools'.

The worst problem is, of course, that such calculations referred only to Static Stability. No-one has yet found a way to calculate for Dynamic Stability and the problems of a 'rough and tumble' sea, suddenly-increased gustiness, and the effects of fatigue on decision-making.

Except, 'when in non-standard conditions, reef early and reef deep.'

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[lyc]

Re:\".....It\'s not the ships. It\'s the men in them.....\"

Don't think it was autohelm failure this time Stella Girl.
[ QUOTE ]
BYM News: Both skippers of the other two tris that capsized blamed an autopilot fault. Do you think that was a factor in your case?

I was on autopilot, because I was forward, but I don’t think it was a factor. If there was a fault it was mine, for not being quick enough at getting rid of the jib. I was tieing down the main, then I was going to go back to the cockpit and get the jib down, to run under bare poles; I just never made it.


[/ QUOTE ]
Further interviews with Ross Hobson here and here