Why do Some Boats Have More Than One Hull?
All boats have a hull, from a dinghy to a super-yacht they all have at least one, some are tiny – size of tea tray (Hydrofoils) whereas others are vast. Since man hollowed out a tree trunk in order to paddle to where he wished to go boats have sat in the water with a hull containing their equipment, weapons, families and catches.
Modern day boats mostly have fibre glass (or high spec alternatives) hulls although there are many wooden built hulls in service and many are beautiful to look at as well as being built to last a lifetime – or two. The purists among us may only want to sail a clinker-built wooden boat that has been lovingly crafted by people using their hands and woodworking tools. We can understand the appeal of wood that has been worked, sanded to silky smoothness and yacht varnished to produce a glorious patina. So long as the timbers are sound such a boat should last longer than its builder. By the way in the days of sail, ships were, eventually, covered with copper sheet below the waterline to stop sea worm, a rather nasty phenomenon that could weaken the hull of a ship if not treated causing the bottom to collapse, not good!
For many years alternatives to wooden hulls have been developed including concrete, metal, and with the rapid development of ‘plastics’ far lighter and easier to handle materials have been employed.
Dinghy’s, yachts, and power boats have become faster, easier to handle – onto and off a trailer for example, sleeker and far more efficient in the water. Racing boats of all sizes and classes are hugely popular, thanks to their high-tech hulls.
With super efficiency at its heart the boat building industry has embraced computer modelling and amazing creations have been launched. Twin hulled Catamarans are multi-hulled boats with two parallel hulls of equal size. It is a geometry-stabilized craft, deriving its stability from its wide beam, rather than from a ballasted keel that would be found in a single hull boat. Catamaran is from a Tamil word “Kattumaram” which means logs tied together, cultures across the world have also used outriggers for stability and twin hulls can provide much the same stability for modern boats. Catamarans typically have less hull volume, higher displacement, and shallower draught than monohulls of comparable length allowing them to be used in shallower water. The two hulls combined also often have a smaller hydrodynamic resistance than comparable monohulls, requiring less propulsive power from either sails or power units, making them faster when racing. The catamaran’s wider profile on the water can reduce both heeling and wave-induced motion, as compared with a monohull.
Love them or hate them Catamarans are stunning to look at and great fun to sail.
Author: Roger Langley