Multihull Mythologies (Part 3)

#3: It has to be 40ft to do blue water

One of the greatest furphies (for our international readers a Furphy is a unsubstantiated comment) I have heard over the years is “If you are going blue water you need 40ft”. I am at a loss to know where this idea originated. I have heard it in monohull as well as multihull circles.

At the outset let me say that longer is always better, all other things being equal. Again, all other things being equal then longer is quicker, you can carry more gear and the motion is usually more gentle and predictable. That is not a mythology, that’s just the laws of physics at play. The question is however, is there some magic in the 40ft mark? And obviously the first question at play here is that I didn’t know that Poseidon or Neptune used imperial measurements. I mean its all a bit silly to say that you need 12.192 metres! So I have occasionally heard reference to 12m, which of course is 39ft and 4ins.multihull-mythologies-part-3-seawind-luxury-catamaran


I suppose what I am trying to demonstrate here is the silly arbitrariness of these sorts of truisms.

What is far more important than a couple of foot here or there is, not surprisingly, the standard fundamentals of multihull design. So let us consider them for a moment:

• BEAM: A beam of at least half the length is preferable though not absolutely mandatory.

• HULL SHAPE: A lengthy conversation could be held on this topic for our purposes here let me summarise by saying that slim easily driven hulls are important but so is reserve buoyancy, the ability of stems to resist burying the bows particularly when surfing big swells.

• MASS and its DISTRIBUTION: It is very very important in blue water boats to keep the ends light, to allow the boat to rise to the swells and following seas, I would rather be in a boat that was 11m with light stem and stern than a 15m with all its weight in ends. Equally I would rather be in a lighter 11m boat than a stupidly heavy 15m boat. Excess weight on a multi is bad at so many levels. It inhibits performance, it reduces the ability of the boat to react to the elements, it increases load on components and it certainly affects performance in a negative way.

• ENGINES and their placementThis could be and probably will be the subject of an entire discussion on various engine related mythologies. But for the moment what is critically important is that the engines are placed as far forward as possible, for weight distribution issues and that access does not involve opening hatches that can allow following seas to enter the engine compartment, because once that happens its all over. The reality is that no cat will have enough fuel to do really long blue water passages so we should be using boats that sail well, but when we do use the motors we need to know that if there is an issue we can access the motors in a manner that is safe to the boat and the sailor. More than one instance has occurred of boats being rendered unpowerable as a result of having to open hatches at sea that are near the ocean. It appears that many people are prepared to trade off seaworthiness for the perceived convenience of external access to engines, not saying that all external access is bad, just those which have hatches too close to following seas.

• BRIDGEDECK CLEARANCE: Of course this is very important – not only does to low a bridgedeck clearance result in uncomfortable and slow pounding it places enormous stress on the structure and on the rig.

• BERTH PLACEMENT: Sleep at sea is important, keeps a sailor more alert and thus safer. It is important to have a berth that is around the centre of the boat to reduce motion and noise and also at least one that is for and aft to ensure that in violent conditions the sleeping sailor does not have their head smacked against a bulkhead. That doesn’t mean all berths need to be for and aft indeed centrally located island type berths are a great boon at anchor or in protected waters.

• VISIBILITY: the absolute key to safety is to be able to see what you might hit, reduced visibility leads to reduced situational awareness and increased risk, its a no brainer, as they say.




Annaliese is a 30ft Oceanic sailing cat. In the early 70’s Rosie Swaile and her family sailed it round the world including round Cape Horn (for a great read see her book Children of Cape Horn). That is 30ft folks, and they seemed to survive, indeed the boat survives now, I saw it at Boatworks on the Gold Coast recently.

The Prout Snow Goose 37/11.2m was one of the most successful and widely cruised boats ever designed. About 500 were built and sailed the world. Again this was when modern sailing catamarans were somewhat in the formative years, if an 11.3m boat could do it then, with modern construction, rigs, sails etc it should be safer by many degrees of magnitude.

Piver Lodestars 35’s, have a background of successful transoceanic sailing, and whilst on trimarans, the Jim Brown Searunner is a massively successful 34-37 footer that has cruised the world.

Seawind 1000’s (10m) have many many blue water passages under their belt as do the Seawind 1160’s.

People have sailed beach cats across the Atlantic, one mad Frenchman is sailing one around the world as we speak. The Louisiane 37 launched into the market in 1983 was a highly successful oceanic cruiser. Innumerable Wharrams from 26-35ft have circumnavigated. Multis have to be 40ft to go bluewater? I don’t think so. Seems like 40 years of history have disproved that myth. Surely it is far more important that a boat be designed and built well and with due deference to the laws of physics rather than it be some arbitrary imperially measured length.

See more: Multihull Mythologies (part 1) >>

See more: Multihull Mythologies (part 2) >>


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