Catamaran on open seas

the thing is I am represending a person that wants to buy a boat and reconstruct it to live and work in it. He wants to buy a catamaran
and I have serious worrys about its stability on open seas. Does any of you
fellow bloggers have any information about where I can find information
about Catamaran ships and there performance on sea.
thanks in advance.
daniel (scurvy buccaneer)

 

It totally depends on the boat's design, size, materials, condition and the expertise of the operator. Is it a sailboat or powerboat?

I have been on the open seas in 16+ meter catamarans and they are quite comfortable and relatively spacious. In big storms they might be more risky than monohulls because they can be fliipped with no chance of being righted. I personally don't want to be on open seas in small boats like that. But many people love the exhilaration of being right up against those huge natural forces. So do I, but I'd rather be on a 250 meter ship while doing it!

 

I understand Jonathan
they actually have found this 32m passanger ferry. With max 2 day
fuel capasity and it is build 1992 in norway I think.... Thay are music people
and onboard they want to build a music studio for online working.
This boat will be crusing from Iceland to the USA and south America and where ever the weather suits there clothes. The fueltank arrangement has to
be modified to this usage and I doubt it can be done on this vessel without
doing total recalculation on the stability.
I must get som data on this boat before asking Ques like this, I have a photo somewhere or a link to track it down.
thanks anyway Jonathan.
daniel

 

This has the sound of the Ethan Allen all over again. Count me out.

 

Actually, the catamaran is arguably the most seaworthy of hull forms. The probability of wave-induced capsize depends on the wave size relative to the beam, and the catamaran's wide beam means it is more resistant to this form of capsize than is a monohull of comparable length.

See Barry Deakins' paper on multihull capsize.

For design criteria you might use to pick an appropriate boat for your purpose, see John Shuttleworth's paper on multihull seaworthiness.

 

With one fatal flaw

 

For reading it might be interesting to go to the NASA or NOAA site and review Rogue Waves , which seem to be far more common (75ft high) than previously thought.

Cats CAPSIZE , its just a matter of when.

FAST FRED

 

My neighbor said anything smaller than 600 foot long was to small for him,i have heard storys of navy men having waves come up on deck of destroyers and such,i used to have a subscription to multihull magazine.It had many happy people cruising all over the world who loved their catamaran.And many of these were around forty foot.I admit to never being out on the ocean and wonder about what it would be like in different types of ships.When i was younger i liked the trawler type ship with its deep keel,now i think of the rolling it would do.Must be something to sleep in!Fast fred what kind of ship do u have?and have u been on a catamaran on the ocean?

 

A 32m Norwegian passenger catamaran...
It's probably built to be fast and not very fuel efficient.
Not an ideal boat for long distance cruising, unless the musicians sell a lot of records

 

hi there Ragnar
well there is some selling of records but still as you say it probably
won't cover the fuelcost. It is a fast boat two engines and you can
ofcorse run it economically. I took a breef look at some info I got erlier
on this topic here above and what I had some worrys about was the stability
of this kind of a vessels, and I have no experiance of sailing a catamerean
ship beeing a marine engineer myself, and I must confess that I had some
prejudice for multihull ships. But on the cotreary these ships seem to be
quite stable.
daniel
(sorry about my english)

 

Stable upside down, too. Many monohulls will right themselves if capsized. Also the course you are talking about is partly the North Atlantic. I have been on a 320 meter long ship in the North Atlantic when the waves were towering over the 25 meters of the ship that was above the waterline. 32 meter boat of any kind gets capsized in these waves. But the monohull can be designed to right itself. Not so for the catamaran. Unless........ you install a mast with ballast on the bottom underneath the deck. The mast must be quite strong (carbon fiber?) and have parallel sides. The mast would need to have gear teeth built into the side. Then a hand crank is used to raise the mast on the capsized multihull. Now the ballast that was on the bottom of the mast is raised and by raising the center of gravity the boat capsizes once again and you are upright. You can call the ship the Rube Goldberg.

 

Do you have even a single study to back that up?

What percentage monohulls remain afloat after being rolled? The study you cite on rogue waves would indicated that every boat will be capsized, not just multihulls.

Have you ever heard of a multihull sinking? I thought not. Monohulls sink on a regular basis - we even had one sink this year in Puget Sound when a not particularly bad squall line came through a racing fleet.

If you'd like to read some genuine information about multihull safety, instead of ignorance and predjudice, check out
http://www.f-boat.com/safety/index.html
http://www.f-boat.com/pdf/F-41SafetyOptions.pdf

 

I feel compelled to offer a corollary to Freds statement, since monohulls of any size usually have a rather substantial counterweight: Monohulls SINK, it's just a question of when.

Yoke.

 

There are storms in the North Atlantic in which every second wave is a rogue wave. Only big ships reliably survive this kind of weather.

That is a really informative article about trimarans, Tom. Catamarans may be more susceptible to breakage because of the span between hulls. Remember we are talking about trans-Atlantic travel in a 32 meter power cat meant to be a ferry boat. Still if it is really solid construction it might make it 980 times out of 1000 attempts. Not bad odds. But I'd still rather take a cruise ship. or an airplane!

 

"What percentage monohulls remain afloat after being rolled? The study you cite on rogue waves would indicated that every boat will be capsized, not just multihulls. "

Every boat would be overwhelmed by the wave , but not necessarily capsized.

If properly built most monohull offshore cruisers should take a simple knock down or rollover.
Sure the modern lightly rigged redundancy free "cruiser" will lose the rig , but a monohull that floats upright with the ability to set a jury rig is preferable to living in a capsized Cat.

While many multihulls have done an OK job of offshore cruising it is with lots of special effort .

I started with a Hedly Nichol Voyager 45ft custom cold moulded in Belize in the mid 60's.
She suffered as most tris then from having both amas imersed , and rigging
lead all the way outboard.
The result was high wetted area to sail area and no way to run a really large headsail for light airs.

Cats share those flaws , but with many added problems.

First Cats and most multihulls (cruisers) have a very hard time with the tons of gear needed offshore for the --4 men for 60 days --usually needed to cross the larger stretches with a bit of reserve,over 60 or 75 ft , no sweat on loading, but might have bigger crew.

The Multihull Problem of having to set only enough sail set for the Puffs , means that 3/4 of the time the boat is undercanvassed , to assure non capsize.
The lead sleds will be set up for sailing with the lulls , and merly accept the puffs as a bit of heel. This is esp true when on self steering gear , cruising.

Weather a Roge Wave can be avioded by sailing in season is a gamble,
but HEAVY WEATHER can never be avoided completly.

That is the biggest hassle with multihulls , the weight and scantlings are kept down for a bit of performance , and load carring , yet the vessel WILL be swept by the sea in really heavy weather.
Most multihulls are NOT designed for a series of waves breaking over the boat. The hatches , doors,deck structure , and windows are far from strong enough for sea service.

YES those stories of waves 75 ft up on the carrier deck are TRUE, as are the photos of Destroyers beind swept by large waves , for days on end.

The DREAM of poping up over the waves is exactly that , a DREAM not born out by actual offshore sailing.

Cats for costal , tris (or lead sleds) for trans ocean was the motto in the 60's when I got started , and seems the ocean hasn't changed much since then.

Multiihulls are a delight in a rolly anchorage , as they pop up & down rather than roll the decks awash.
And there a delight in fair weather costal cruising , if heat is not required and only a weeks worth of food , water & fuel need burden the boat.
The shallow draft lets them into crowded harbors where lead sleds are gathered outside .

But for offshore the downside is far bigger than any upside , for those that can't breathe water.

FAST FRED