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-   -   Heavy weather sailing in a catamaran (http://www.sailnet.com/forums/seamanship-navigation/65450-heavy-weather-sailing-catamaran.html)

seashine 06-10-2010 04:48 AM

Heavy weather sailing in a catamaran
 
I have about 6000nm blue water experience in a traditional long keeled (36') monohull and about 2500nm coastal hopping and blue water sailing in a (43') catamaran. We experienced Force 10 in the mono but I have never experienced anything over 30kn in a cat. While I am aware of the need to reef earlier and risk of pitchpoling when surfing large waves, there seems to be little information out there on how to sail a cat in heavy weather, or indeed if a cat would be a suitable vessel for cruising over to the Eastern Pacific from Australia then on around the planet. I do hope the experienced sailors on this forum can help :) One reason I am seriously considering a cat is the fact it enables us to poke in up inlets/between reefs and generally explore more of the "bits around the edge".

sailingdog 06-11-2010 05:11 PM

I would highly recommend Mike McMullen's book, Multihull Seamanship, which is available at Alibris.com even though it has been out of print for quite some time.

I'd also point out that the Polynesian islanders explored and settled an area of the Southern Pacific ocean larger than most continents using small multihulled sailing craft. Many of the Wharram designs are evolved from the craft used by the Polynesians.

One of the tactics that many multihulls, especially those with retractable boards, use is lying ahull. This isn't generally a good or acceptable practice for monohulls, but a multihull with the boards up will generally move with the water and not capsize or trip. Another common storm tactic with a multihull is lying to a jordan series drogue.

TropicCat 06-13-2010 05:03 AM

I think we should look to The Queen's birthday storm for guidance. The Two catamarans caught in that storm both lay ahull through out the storm. Regardless of the wave size, both boats survived without injuries or serious damage. Almost all the monohulls caught in the storm were rolled and dismasted, and lives were lost.

seashine 06-13-2010 05:34 AM

Hi TropicCat, forgive us down here in Oz but which storm and when? Is lying ahull achievable/possible in a cat with mini-keels?
And thankyou SailingDog for the reference to McMullen's book, I'll see if it's available locally. I am aware of the use of drogues and sea anchors and the importance of strong points to attach them to, but have been disappointed in a lot of cats I've looked at in terms of heavy weather preparedness. I cannot fathom why anyone would risk no inner forestay and no permanent backstay on a cat. It would seem that for production boats (and this means mono- as well as multi-hulls) the trade-off between lightness and seaworthiness leans heavily in favour of the lighter boat. Unfortunately cats are often the lightest of the light, hence their poor reputation in serious weather. I know this is not a foregone conclusion, it's a matter of design. Any pointers on seaworthy catamaran designs (the Wharrams are definitely seaworthy but the accomodation is somewhat uncomfortable) would be most welcome:-)

sailingdog 06-13-2010 09:51 AM

Things that can make a cat less seaworthy:

High windage—look for boats with lower cabin profiles, etc.
Deeper keels—if the boat has fixed keels, they should be as shallow as possible to minimize the risk of tripping the boat in heavy seas. The better designs will have a retractable board—either a centerboard or daggerboard to give decent windward performance without sacrificing shallow water capabilities.
A full bridgedeck—the better boats generally have less weight forward and an open partial bridgedeck with netting forward, rather than a solid bridgedeck.
Good reserve buoyancy in the hulls forward—this can help prevent the bows from burying themselves, which is often the triggering event to the boat pitchpoling. For the same reason, it is generally a good idea to leave a catamaran or trimaran a bit heavy aft, especially if the boat is overloaded.

One reason the Wharram Polynesian-derived catamarans tend to be very seaworthy is that they have very low windage, since they tend to have a very spartan bridgedeck. They also have netting between the hulls for a good portion of the foreward part of the bridgedeck. However, they do give up considerable living space in doing so.

Be aware that the scantlings for multihulls are quite different from those of monohulls, as they do not have to support the weight of a massive keel. This means that the hulls are often lighter in design and materials than a similar LOA monohull.

The better multihulls IMHO will have cored hulls and decks. Airex is an excellent choice for hulls and end-grain balsa or divinylcell is a good choice for the deck, cabin top and topsides. The use of kevlar in the hull laminates can make for a very damage resistant laminate that can resist holing in even severe impact situations. The better multihulls will actually be buoyant and effectively unsinkable, even if severely holed, since the materials they are made of are overall lighter than water.


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