Boat building

Boat building is the design and construction of boats and their systems. This includes at a minimum a hull, with propulsion, mechanical, navigation, safety and other systems as a craft requires. Wood is the traditional boat building material used for hull and spar construction. It is buoyant, widely available and easily worked. It is a popular material for small boats (of e.g. length; such as dinghies and sailboats). Its abrasion resistance varies according to the hardness and density of the wood and it can deteriorate if fresh water or marine organisms are allowed to penetrate the wood. Woods such as Teak, Totara and some cedars have natural chemicals which prevent rot whereas other woods, such as Pinus radiata, will rot very quickly. The hull of a wooden boat usually consists of planking fastened to frames and a keel. Keel and frames are traditionally made of hardwoods such as oak while planking can be oak but is more often softwood such as pine, larch or cedar. Plywood is especially popular for amateur construction but only marine ply using waterproof glues and even laminates should be used. Cheap construction plywood often has voids in the interior layers and is not suitable to boat building as the voids trap moisture and accelerate rot as well as physically weaken the plywood. No plywood is rot resistant and should be coated with epoxy resin and/or a good paint system. Varnish and Linseed oil should not be used on the exterior of a hull for waterproofing. Varnish has about 60% of the water resistance of a good paint system. Only boiled linseed oil should be used on a boat and only in the interior as it has very little water resistance but it is very easy to apply and has a pleasant smell. Note that used linseed rags should not be left in a pile as they can catch fire. A valuable 200-year-old waka (Maori canoe) caught fire in New Zealand in June 2014 when restorers left rags piled overnight. Raw linseed oil is not suited to boats as it stays damp and oily for a long time.