The purpose of this article is to give a cursory look at boat construction, not so that you would be able to build one, but to show some of the reasons why sailboats look as they do. Although there is a huge range of designs for boats they are basically the same whether they are a racing dinghy, a fishing smack, or an ocean racer or cruiser. They are as cars are -- the design changes only with the purpose of the machine, and after that for cosmetic effect.
So boats, generally, are sharp at the end that goes through the water first, they have varying degrees of width (beam) and they are blunt at the trailing end. They will have a mast, either tall or short, and they will have sails. Because they have sails, they must have a keel. If the boat is a fishing smack it will be slow, it will have a short mast, and it will be made of enormously strong timbers because it has to survive heavy weather, it has to carry a heavy catch, and it has to have great power to drag its nets.
If the boat is a racing dinghy, it will hold two, sometimes three people. It will be light enough to carry to the beach and trail home, and it will have a dish-shaped bottom and a centreboard. This is because it usually sails in sheltered waters, the weight of the crew keeps it upright, and it wants as little wetted surface as possible so that it can travel as fast as possible. An ocean racer won't have a doghouse (the bit of the cabin that sticks up above the deck), it will have a mast that seems ridiculously light for such a powerful vessel and it will have a wide range of sails to choose from.
The ocean cruiser will have a solid mast, often with steps up the side. It will have a big cockpit, and a big doghouse. The boat will tend to have more beam than the racer, although not necessarily so, and it will have sails that furl into the mast, or around themselves, with the controls running back to the cockpit. The point I am making is that, however the special purpose of a boat affects the design, it will still be within broad controlling factors.
Materials used to make hulls
In the same way that design can change for special purposes, so has it changed in the last few decades, especially because new materials have become available. In fact materials from which hulls are made have changed dramatically. Designers have moved from wood, fibreglass, aluminium and steel to specify foam and Kevlar sandwiches, end-grain balsa held by thin wooden skins inside and out, carbon fibre and other space-age materials. Also, instead of being constructed in a style which had not changed much since Biblical times, hulls are now moulded, and are even baked in giant ovens to cook the exotic materials into a lightweight shape that is lighter than alloy and stronger than steel.
Hull shapes
Hull shapes have changed, too. The fat, shallow, modern boat sails to windward far better than the traditional styles by utilising lift from the keel. And, because they are light, the modern boats run far faster. The only advantage the older, heavier boat has over the modern boat is that it is not thrown sideways as much in big, breaking seas.
But, however much shape and materials have altered, the skeleton of a boat is still much the same. To understand the structure of a hull is to understand the strain on it and to know when to take that strain off. It is outside the scope of this article to discuss design in the sense of which is the latest or which is the best. Every boat buyer decides that personal equation himself. We only want to understand enough about boat construction to see how the design and building absorb the stresses handed out by the sea.
Copyright 2008 Bevanda Pty Ltd
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