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Old 04-01-2008
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Multi-Hull stability?

Ok, I'm new but I thought multi-hulls were supposed to be more stable than monohulls. I also realize that when racing they push design and abilities to the limits but reading the article it says 20+ knots of wind with lumpy seas, that doesn't sound too bad but the results seem pretty catastrophic.

See the March 29 entry.

Southwest by South Sailing News
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Old 04-01-2008
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You might want to re-read the story. The boat didn't capsize, it pitchpoled. The bows of two of the three hulls dug in and the sucker pitched forward--stern over bow.

Quote:
Ed Baird, who was onboard, provides some insight into what happened: "As we were bearing away, always the highest risk situation on a multi-hull, both the leeward and the central hull dug into the water and the rudders came out. From then it was out of our hands and we capsized forwards. As the mast hit the water, it broke, followed by the rear beam." He continues: "The crew reacted very quickly in getting everyone back on board, doing a head count and checking injuries before calling for help and beginning to secure the boat."
This type of accident is fairly typical of racing multihulls, which generally have less buoyancy in their hulls than cruising designs do. They were probably also a bit overcanvassed for the conditions.
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Old 04-01-2008
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Ok, I'm new but I thought multi-hulls were supposed to be more stable than monohulls.
They're stable alright. There's no way that little baby is turning right side up.
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Old 04-01-2008
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As some of you know, we have some very good friends that sail a Farrier 25C doublehanded most of the time. This is no doubt a powered up hiperformance multi, and can be quite a handful for the two of them in a breeze. By the time the wind is up to 10 knots they are flying, beyond 18 or so nearly all their efforts go into keeping the speed down to avoid just the kind of incident above.

They are justifiably petrified of digging in an ama into the back of a wave at the wrong moment.

This boat is a wild ride, wet, unbelievably fun when things go well... (reaching at 18 knots boat speed in 12 true) but ........
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Multihulls have more initial stabiliy, since they're so much wider than monohulls. But if you ever get past the angle of vanishing stability on either one, that multihull is staying upside-down, while the monohull (assuming hull integrity intact) has a chance of re-righting, either through regaining positive stability, or from wave action, or (though this is not ultimately a real good thing) by losing the rig.

Monohulls, at least when the keel stay intact, generally reright themselves. Multihulls generally don't.

But for ordinary daysailing, yes multihulls are more stable. Just don't try to tack in one, unless you've set aside some extra time...
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Old 04-01-2008
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My son has been interested in cruising cats so I have been doing some research on them and I have to admit I had some preconcieved ideas about them that were based in ignorance. There are a large number of cats (and tri's) that have circumnavigated and an even larger number(increasing rapidly) out cruising throughout the world. There is a huge difference between the "Hobie" type cats and a bluewater cat. They are very impressive downwind and do pretty well upwind. Most are extemely stable and the number of cases of capsize or pitchpling are few and far between. They have redundant systems and lot's of storage. They are expensive to buy and can be expensive to moor in places. I've never loved the looks of them compared to a nice mono, but to each his own. I think my son has decided on a Hallberg Rasmus ketch, mostly because of location and finances (nice boat).

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Old 04-02-2008
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Originally Posted by jrd22 View Post
My son has been interested in cruising cats so....... I think my son has decided on a Hallberg Rasmus ketch, mostly because of location and finances (nice boat).

John
John, don't you love it that our kids are interested in carrying on with boating, even after it becomes their own choice?

We must have done something right!
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Old 04-02-2008
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Quote:
Originally Posted by Faster View Post
This is no doubt a powered up hiperformance multi, and can be quite a handful for the two of them in a breeze. By the time the wind is up to 10 knots they are flying, beyond 18 or so nearly all their efforts go into keeping the speed down to avoid just the kind of incident above.

They are justifiably petrified of digging in an ama into the back of a wave at the wrong moment.

This boat is a wild ride, wet, unbelievably fun when things go well... (reaching at 18 knots boat speed in 12 true) but ........
I didn't realize multi-hulls could get so much speed compared to mono's. So it would seem that the multi-hull speed has a much different dynamic when it comes to top speed. I've read that the mono hull length is the limiting factor for hull speed, the longer the boat the faster it can go.

As for righting it, that would scare the hell out of me knowing if it went turtle there's no way of getting back up, when time and again you read about a mono pitchpoling then righting itself. Gives me a new respect for those that sail multi-hulls, it would seem you need a greater awareness of the wind and weather to manage your sail plan as it changes, where a mono-hull is more forgiving in that you can get knocked down and not have much worry other than having to clean up below.
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Old 04-02-2008
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Faster- It does appear that I passed on the boating chromasomes. He is getting married in June and hopes to sail away from the wedding (with the new wife) at Blakely Island for a trip around Vancouver Island. Of course he is hoping to have his own boat, but if not, he'll take the Northsea. Then the plan is a 2 year trip around the Pacific if he can sell some property. Envious? You bet I am.

John
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Old 04-02-2008
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I saw a Stilletto 23 pitchpole on lake Hefner in Oklahoma City. There was a motor launch there in just a few minutes and they were able to right the boat quickly. The captain however, was taken away by ambulance. Every pitchpole I have ever been involved in has been quick and violent,but there is nothing that can compare to being double-trapped all the way to the sterns just trying to keep the tips of the bows out of the water, going like a bullet.
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