Water has this annoying habit, like millions of tiny fingers, of dragging on any underwater surface it comes in contact with. Therefore, the greater the area of the boat’s hull exposed to the water, the slower it will be.
The best hull design is long, thin and as close to a circle underneath as possible. The problem with the circle is that it is harsh, as the boat crashes down after each wave and so a compromise towards the soft and forgiving V shape, which has a larger wetted area, is necessary.
It’s interesting how the Pacific islands and the west have approached the problem from different angles. Thinking western, one solution to the problem you can see below in the International Canoe – the use of a hiking plank or a trapeze, to shift weight outwards from the boat.
This, as you can see, is highly unstable though exhilarating in short bursts. The essential problem is that the wind is not even – it comes in bursts or ‘gusts’ and often changes direction, sometimes constantly. The result is sudden tipping over or ‘heeling’ moment and sudden crashes backwards.
The Pacific islanders said: simple – just put a log, an ‘ama’, of neutral buoyancy [i.e. one which can equally be pushed under or lifts into the air] at some distance from the main hull [vaka].
This is the solution which Gary Dierking chose in his Waapa below and it is quite workable in a small boat.
Where it comes unstuck is in larger, more extreme craft, such as the Hawaiian canoe below and you still have that sudden lift or crash problem. In the Pacific, where labour is plentiful and cheap, the answer is to load more bodies onboard and they run back and forth into certain positions to keep the boat balanced.
Added weight is the problem – the bane of sailcraft.
Going the other direction, the log can no longer be a log – it needs to be another thin hull with buoyancy and that is added weight.
One western solution is to have two equal outriggers either side, as you see below. Thus the trimaran was born although it is not specifically western – the west just adopted it in a big way.
The downside of the trimaran is that the weight is doubled and therefore you need much more sail, which tends to go upwards, cutting into the stability and creating serious fore and aft [front and back] stability problems.
With a western rig on board, the strain on the hulls is enormous and things can snap quite quickly. Tris have a nice motion through the water but the western variety are quite highly strung and temperamental.
The west tended to go the other way, traditionally. Widening the one and only hull, they put lead down below in a keel and this balanced the sail.
No matter which way the west tried to refine the design – space-age plastic materials, clever hull section design, variations on the keel, these boats were still tubs, slow due to their wetted area and inability to carry much sail. The west reacted against this inferiority by pumping in more power, more stress and a greater need for tougher materials, such as titanium and kevlar, at a hideously out of control cost.
Monohull sailors cite their safety record – that they’ve been plying the oceans for centuries. Yes they have – and they’ve been sinking too, especially when the lead keel falls off.
The only good things about a monohull is that if they are suddenly hit by a gust, they go over but then come back up again [something the multihull doesn’t] and they are good-looking. They really are beautiful to look at.
The west then looked at the Pacific for a solution and found it in the catamaran. Pound for pound, foot for foot, the cat gives the best and most stable performance and almost all the speed records at sea are held by cats or sailboards although this doesn’t include the outriggers, which might be faster, by a process of logic.
The downside of the catamaran is that it is not stable past a certain point. To illustrate this, put a plank on the floor, against a wall. Try pushing sideways with your fingers and it won’t budge but then, suddenly, with enough pressure, the edge of the plank suddenly shoots up and over.
That’s the catamaran.
The solution? Back to the trimaran. No other craft absorbs punishment as well and if you look at it it, it’s easy to see why. In a sudden ‘knockdown’ by the wind, no matter in which direction it’s going, the lee [or downwind] hull simply buries itself in the sea and when the gust dies, it comes back up again.
The trimaran is a very forgiving design, which is why it is preferred by so many these days for sea voyaging and island hopping. Yet if the outrigger is designed well [see below], then it can be excellent.
The best compromise of all – low wetted area, light weight, long, thin hull, comfort through the water, stability, both sideways and fore and aft, low stress on the rigging and on the boat, low cost of materials and the ability to be amateur built and repaired at sea, has to be a variation of the outrigger. It’s no accident that the Pacific islands have used them for centuries.
Of course, any yacht is only as good as its rig [sails] but that’s another topic. Looking only at hull design, if you can give the ama enough buoyancy and yet enough weight as well [a critical calculation], then on one tack [direction of travel], it will act as a trimaran and on the other – will be stable enough so as not to flip, providing you don’t build a huge deck across the akas [crossbeams], which the wind would use as a scoop.
Pound for pound, foot for foot, this enables a longer, thinner hull and that augurs well for comfort and safety at sea, along with speed - surely what one is aiming for.
Why won’t the west adopt this? For a start, it’s asymmetrical and the west loves symmetry. It is less comfortable, accommodation wise – most westerners prefer the floating home concept and then there is the evolution of sailcraft in the west. People tend to go with what is readily available, the accepted technology and its apparent superiority [though not borne out by test tank results] and innate conservatism, even for the lesser product – remember VCRs?
I can tell you – if I go to sea, I want to be in the best available craft and to hell with convention. A stable outrigger is most certainly the best all round performer and the best all round for safety.
But even more than that is the sheer joy of the motion for such a low cost - anyone can enjoy this without having to be a millionaire.