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Old 05-08-2016, 11:08   #181
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Re: Catamarans in 50kt winds

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Originally Posted by softgoodsint View Post
Re Dulcesuenos comments. My question: while I understand hull speed limitation physics in mono's, but I'm unfamiliar with multi's, but it sounds like it's a planing hull (?) to hit 12kt on a 30' cat. I completely understand that when you're skimming on the water vs. in the water, that limitation disappears (e.g. windsurfing or foil designs, etc). But clearly, speed when it's not blowing F5+ is a major difference favoring multi's. I also know a larger factor than speed or even safety, is "wallet depth" eg. emptiness. In otherwords, the big difference multi vs mono discussion is the price tag differential. Especially in todays almost 'give away' market place for used, but still serviceable (another debate topic) craft. (what other era could you pick up a boat for less than a seasons' docking fees?)
Not a planing hull, a multi with fat side hulls and low aspect ratio keels. The leopard Cat we just crossed in weighed close to 17tons, we hit a top speed of 16.2 in a gust, no planing involved there. Cats have the ability to bleed of energy amazingly fast. Some even get weather helm in a severe gust if the main is up. What many fail to realize is that some of the cats at anchor or mooring that flipped, had a jib come unfurled , the ones that flip offshore carried too much sail and were mostly performance cats, ( excluding the ones caught in a cyclone)
Many monos that are knocked down can flood and go down if held there too long.
How about the 50 knot winds that rocked the dauphin island regatta last year?
3 alone were lost of a Cal 24, a smaller boat with a ballasted keel is I am not wrong. Also 3 others and dozens rescued.

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Old 05-08-2016, 11:09   #182
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Re: Catamarans in 50kt winds

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Originally Posted by Dockhead View Post
Another cat vs mono buying decision thread . . .


In my opinion, most of these statements are false. The key thing to making this comparison intelligently is to compare like for like. A 45' catamaran is not "like" a 45' monohull. It has two hulls, so it's more like a 55' monohull in terms of interior volume.

Once you compare like for like, everything looks different:

1. Cost is about the same.

2. Cat is not faster, and is probably slower if it's a loaded-down condo-cat. Cat has better fineness ratio, but a comparable mono will have a longer waterline.

3. Cats do NOT point worse than comparable monos. Condo cats don't point, but loaded down cruising monos ALSO don't point. High performance cats point very well.

4. Monos are NOT safer. Cats flip but monos sink. Statistically there is no difference between cats and monos in terms of safety.

5. What is more comfortable is a matter of taste. Cat has wonderful high and roomy salon but prison-cell like cabins. Mono worse view and light in salon but better cabins (as a gross generalization of course).

6. Lack of heeling a very profound advantage of cats, for long ocean passages. Less important for more typical cruising regime of short passages between long stays in port or at anchor, but still pleasant. Living on a heel sucks.


The biggest advantages of cats you did not mention:

1. Redundant propulsion, greatly enhancing reliability and maneuverability.

2. No ballast, so much more efficient motoring. Cats are totally superior motorboats, and this is important considering most cruisers motor more than 50% of the time.


Advantages of monos:

1. For some people, more pleasant motion at sea.

2. Easier to find berthing.

3. Better load carrying capacity.
If the mods made this a 'sticky' we could save a lot of bandwidth.
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Old 05-08-2016, 11:21   #183
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Re: Catamarans in 50kt winds

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Originally Posted by Cadence View Post
I have no dog in the fight but I disagree. It would be possible for wind to get under the bridge deck on a light cat.. Likelihood small. Knocking down a mono at anchor with 50kns isn't going to happen unless someone removed the ballast
Wrong, we were at key west bight marina on a 32' cat, the year Sandy was over the Bahamas. We had sustained 40+ knot winds across the beam for 2 days. A Benneteau42 or 43. D a 39' were right behind us. They spent those 2 days at the dock heeled at least 30 degrees and in the gusts even more so to he point of all let hitting the rigs on the boats across he dock a d perpendicular to them. I asked them each morning how they slept and was cussed out hehe. Do you realize how little effort it takes to pull over a 40' mono by a line tied to a halyard to the top of the mast and run out 150'? Huge keel boats have been lost when caught with their hatches open by a microburst .

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Old 05-08-2016, 11:29   #184
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Re: Catamarans in 50kt winds

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Originally Posted by Dulcesuenos View Post
Wrong, we were at key west bight marina on a 32' cat, the year Sandy was over the Bahamas. We had sustained 40+ knot winds across the beam for 2 days. A Benneteau42 or 43. D a 39' were right behind us. They spent those 2 days at the dock heeled at least 30 degrees and in the gusts even more so to he point of all let hitting the rigs on the boats across he dock a d perpendicular to them. I asked them each morning how they slept and was cussed out hehe. Do you realize how little effort it takes to pull over a 40' mono by a line tied to a halyard to the top of the mast and run out 150'? Huge keel boats have been lost when caught with their hatches open by a microburst .

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Old 05-08-2016, 12:12   #185
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Re: Catamarans in 50kt winds

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Originally Posted by Juho View Post

- In high latitudes people tend to use monohulls. This is partly because of the rough weather, but also because it is simply easier to keep the monohulls warm.
I believe high latitude is more a function of mono's being less weight sensitive.

The boats pushed for high latitude work tend to be steel or massively thick fiberglass hulls with the theory being they will shrug off a minor impact with ice.
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Old 05-08-2016, 12:18   #186
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Re: Catamarans in 50kt winds

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Originally Posted by Souther Wombat View Post
It's not even sensible to suggest any normal ballasted monohull sailboat could be rolled in sheltered water from wind heeling moment alone. It takes a breaking wave to do that.
If we are talking about a gust that builds over 10-15 seconds, I agree...of course, if I'm at the helm of a cat, I'm probably releasing the main sheet or taking other action to mitigate the potential issue (remember we are talking about sheltered water where you would expect to be at the helm.

The gust that goes from 5kts to 50kts in a couple of seconds (yeah, freak gust combined with coming out from behind a headland) that could flip a cat will induce a roll moment to the mono, so even though it spills the wind, the mono will still be rotating after the wind starts spilling and could meet the definition of knock down. Even if it doesn't meet the definition of knock down, a quick roll to 60degrees could clear everyone violently out of the cockpit with the boat popping back up and sailing off on it's own. Not really a better outcome unless you own the boat and it was stolen by someone you don't like.
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Old 05-08-2016, 12:33   #187
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Re: Catamarans in 50kt winds

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Originally Posted by valhalla360 View Post
I believe high latitude is more a function of mono's being less weight sensitive.

The boats pushed for high latitude work tend to be steel or massively thick fiberglass hulls with the theory being they will shrug off a minor impact with ice.
Really? I didn't know that........
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Old 05-08-2016, 14:05   #188
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Re: Catamarans in 50kt winds

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Originally Posted by softgoodsint View Post
Re Dulcesuenos comments. My question: while I understand hull speed limitation physics in mono's, but I'm unfamiliar with multi's, but it sounds like it's a planing hull (?) to hit 12kt on a 30' cat. I completely understand that when you're skimming on the water vs. in the water, that limitation disappears (e.g. windsurfing or foil designs, etc). But clearly, speed when it's not blowing F5+ is a major difference favoring multi's. I also know a larger factor than speed or even safety, is "wallet depth" eg. emptiness. In otherwords, the big difference multi vs mono discussion is the price tag differential. Especially in todays almost 'give away' market place for used, but still serviceable (another debate topic) craft. (what other era could you pick up a boat for less than a seasons' docking fees?)
Hulls with a LWL:BWL ratio of more than about 8:1 don't generate such a big bow wave as to create a "hull speed" limitation. Long skinny hulls can go much faster then theoretical hull speed without planing.

For a good example of this, watch the Olympic rowers.
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Old 05-08-2016, 14:10   #189
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Re: Catamarans in 50kt winds

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Originally Posted by donradcliffe View Post
Now, lets hit a mono with a big gust of wind in sheltered water. The boat heels over, and several things happen:

1. The righting moment increases, typically up to a maximum at 75 degrees or so, and does not go to zero until the angle of vanishing stability--say 120 degrees, when the mast is well into the water.
2. The forces on the sails decrease, going to zero at about 90 degrees, or before the mast hits the water.

3. The boat develops severe weather helm, which rounds it into the wind, further decreasing the pressure on the sails.


All of this happens without human intervention, and the boat finds another stable point (with a bunch of flapping from the sails and an increased heel level. The reality is that a mono can't get into a whole bunch of trouble without wave action (unless you are a gung-ho racer with a spinnaker up, which is another chapter).

Now lets look at a catamaran in a similar situation. When the gust hits the boat starts to heel, and several things happen:

1. Instead of increasing like the mono, the cat righting moment starts to drop after one hull lifts out of the water, or at about 10 degrees of heel.

2. The pressure on the sails drops like the mono, except that once the hull starts to lift, the wind pressure on the wide structure on the boat starts to make an increasing contribution to tipping it over.

3. The cat hull shape does not produce much weather helm as heel increases, which means that the boat will not round up as severely as the mono, and an autopilot may be able to keep course.

Once you start to fly a hull, the catamaran is in an unstable situation. Unless there is intervention in the form of releasing at least the mainsheet (a sharp turn downwind may help, but is not as effective), the next stable position for the cat will be inverted. Even releasing the sheets does not work once the heel angle exceeds 50-60 degrees, because the wind pressure on the hull and bridgedeck is enough to push the boat over.

The catamaran is blessed with significantly greater initial stability than the mono, which provides for the possibility of improved performance by carrying more sail. However, that increased performance comes with a downside risk. If you increase the sail area to displacement on a cat, it lowers the gust required to capsize it.
However, because the cat isn't dragging around several tonnes of lead, it actually has LESS sail area, not more. And usually gusts which produce a round up knock down in a mono, just cause an increase in speed in a cat.
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Old 05-08-2016, 14:20   #190
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Re: Catamarans in 50kt winds

To the OP.


As has been said, statistically, in terms of sinking vs capsizes of CRUISING boats, there little to no difference in the safety of either mono's or cat's.


There's a much bigger difference in MOB risk though.


"
A 1983-1987 study conducted by the US Coast Guard that reported that 80% of all reported deaths (36 fatalities in total) within U.S. waters on single-hulled auxiliary-powered sailboats were a result of the person falling overboard. During the same period there were no reported multihull fatalities in U.S. waters."

Read more at Multi-hull Mythbusters - Australian Yachting November/December 2010 - MySailing.com.au


But if you'd feel safer in a mono, buy a mono. I feel safer in a cat, but you shouldn't let other people's opinions make your decisions for you.
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Old 05-08-2016, 14:37   #191
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Re: Catamarans in 50kt winds

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Originally Posted by 44'cruisingcat View Post
To the OP.


As has been said, statistically, in terms of sinking vs capsizes of CRUISING boats, there little to no difference in the safety of either mono's or cat's.


There's a much bigger difference in MOB risk though.


"
A 1983-1987 study conducted by the US Coast Guard that reported that 80% of all reported deaths (36 fatalities in total) within U.S. waters on single-hulled auxiliary-powered sailboats were a result of the person falling overboard. During the same period there were no reported multihull fatalities in U.S. waters."

Read more at Multi-hull Mythbusters - Australian Yachting November/December 2010 - MySailing.com.au


But if you'd feel safer in a mono, buy a mono. I feel safer in a cat, but you shouldn't let other people's opinions make your decisions for you.
I'm afraid almost 30 yr. old data is not that good? Very few cats then.
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Old 05-08-2016, 14:41   #192
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Re: Catamarans in 50kt winds

Sure. Feel free to provide more recent info.
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Old 05-08-2016, 14:44   #193
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Re: Catamarans in 50kt winds

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Originally Posted by valhalla360 View Post
I believe high latitude is more a function of mono's being less weight sensitive.

The boats pushed for high latitude work tend to be steel or massively thick fiberglass hulls with the theory being they will shrug off a minor impact with ice.
Yes, also that can be one factor. I guess nobody uses sailboats as ice breakers, but steel hulls may tolerate occasional hits well. Some catamarans can carry quite a lot of weight, but steel is not often used in catamarans. Some steel monohulls can survive in frozen sea (in protected waters, with not too much ice pressure). I'm not aware of any such catamarans.
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Old 05-08-2016, 16:22   #194
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Re: Catamarans in 50kt winds

Catamaran not so good in ice. Can jam up between the hulls.
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Old 05-08-2016, 16:47   #195
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Re: Catamarans in 50kt winds

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Originally Posted by Souther Wombat View Post
I made a mistake before in the link. This is the link I actually wanted to paste. It's worth reading and absorbing.

SailNet Community - View Single Post - How do you feel about catamarans?

As I said add the recent total loss again of all crew in the Leopard cat that inverted recently.

You can confuse the issue with statistics and there's a lot of issues to survival, not just what sunk but who survived.

A sinking monohull still lets you launch and access boats, life rafts grab bags and Epirbs. It's almost impossible in most multihulls as they are designed and you have to try and dive into the flooded hull for anything. The upturned hull is death trap in the same weather that casues it to overturn.

An inverted cat is an immediate disaster with no warning and no time to do anything. The death toll as a total loss of crew is alarming because designers don't allow access into an inverted cat or access to emergency gear.

When fit able bodied crews all die it begs the question of what happens to young children or as I am getting, the older and more infirm.

Chris White is not impartial he even says on his site or did until recently that no cat has ever flipped without sails up. That's not true.
An inverted cat is very uncommon for cruising cats. And usually the crew survives. The death toll is minimal compared with keel boats. Keel boats sinking without trace happens all the time. Several each year in the South Pacific.
Having rode to a sea anchor in both a 45ft steel keelboat and a small cat, in similar weather, the comfort levels are about the same. I felt safe in either. Note that keel yachts returning from the islands were sinking, and being rescued, North of New Zealand both those times.
Keel race boats are not seaworthy.
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