yachtbuilding

yachtbuilding. Yacht design was originally carried out by the shipwright or boatbuilder commissioned to build the yacht, and quite often to the shape agreed of a half model produced by the builder. A successful design would be copied and modified so that existing patterns could be used. In the late 19th century the advent of rating rules influenced the previous, more traditional shapes, so that more extreme types, such as the skimming dish, were developed to try and beat these rules.

The introduction of steam propulsion led to many large iron auxiliary and full-powered steam yachts being built. However, it was not until about 1870 that yacht design began as a separate profession, though most yacht designers retained strong links with building yards. Each developed his own style and yachts could be recognized as being from a particular designer.

In the 1930s the increase in ocean racing (see yachting: sail) and dinghy racing led to an increasing number of designers producing race-winning designs so that design offices expanded. After the Second World War (1939–45) yacht design was generally low key with small simple yachts, but by the 1950s the introduction of GRP provided a boost, and the spread of various forms of ocean racing provided battlegrounds for designers. Many of the successful ones from this period later became involved in the design of larger and larger yachts where a lot of the detail work again devolved upon the building yard.

Following modern shipbuilding practice, the modern yacht designer will work closely with a stylist and interior designer, as yachts become ever more sophisticated. However, he will still be responsible for the yacht's fitness for its purpose, and for performance, stability, structural integrity, and safety. To establish these he will first of all normally produce, for a sailing yacht, a preliminary general arrangement and a sail plan for the owner's approval and as a basis for a written specification with which to obtain building estimates. A lines plan is then produced, so that stability and performance checks can be made together with detailed weight estimates, and a construction plan, including decks and the scantling section. These, together with other structural drawings such as bulkheads, tanks, machinery seatings, stern gear, and rudder arrangements, may all need approval by a classification society. At this stage it is likely that the builder and the interior designer will become involved with the development of all the systems and the detail of the interior. Other specialists may also be brought in to design the spars, rigging, sails, and deck gear. There may be as many as 100 drawings for a 10-metre (32-ft) yacht or 400 for a 20-metre (65-ft) yacht.

Early Yachtbuilding.

From the inception of yachting, yachtbuilding followed the traditional methods used to build small commercial wooden vessels such as barges and smacks, with one of the main tools being the adze. The wood keel, of oak, elm, pitch pine, or other local timber, was laid on the slipway or on building blocks, and the wooden stem, sternpost, and stern frame bolted into place. The various frames (or ribs) were sawn to shape and erected in their respective positions along both sides of the keel from stem to stern, the lower ends of each pair being fastened to floor frames which were commonly oak crooks laid athwart the top of the keel. An inner keel, or keelson, was sometimes bolted on to the tops of the floor frames and running from the inside of the stem to the sternpost. Beam shelves, running from bow to stern and fastened to the inside of the head of every frame, carried the outboard ends of the deck beams which in turn were fastened to the shelves, often with a half-dovetail joint. Openings in the deck for hatches or skylights were joined by carlings to which the coamings were fastened. At all junctions beneath the deck where the racking strains of hard sailing in heavy seas were greatest, oak crooks or wrought iron knees were bolted to give more rigidity, hanging knees being vertical and lodging knees horizontal.

The planking of the hull was fastened to the frames and floors with galvanized iron spikes, bronze bolts, or, in smaller yachts, with copper square-sectioned nails riveted over copper collars (or roves) on the inside of every frame. The work of planking the vessels was started at the garboard strake on each side, and continued in sequence up to the turn of the bilge. Other planks were then fastened on from the sheer strake downwards, until the final gap between the two sets of planks could be filled in with an exactly fitting shutter strake. Deck planks, traditionally of white pine or teak, were laid fore and aft usually following the curve of the wide covering board at the yacht's side. The seams between the planks, cut in the form of a deep V, were caulked with cotton and payed with hot pitch. The seams of the hull planking were likewise caulked with cotton and finished smooth and flush with a patent stopping mixture which never set hard enough to crack when the seams worked in a seaway.

Towards the end of the 19th century sawn frames were replaced in the smaller yachts by steam-bent timbers, and this remained standard boat-building practice for wood-built yachts under about 14 metres (45 ft). In building a hull for steam-bent framing, the keel was laid first, and the stem and sternpost erected. Next, moulds, or patterns, were cut to the shape and measurements on the designer's plan. These were fitted inside the planking and spaced at their appropriate stations through the vessel. Then, on each side wooden battens called ribbands were temporarily screwed to the edges of the moulds, running from bow to stern and spaced roughly 15–23 centimetres (6–9 in.) apart. Each frame-timber was then made pliable by heating in a steam box, and while still boiling hot was smartly bent into shape on the inside of the ribbands, with its lower end fitting into a check slot already cut in the side of the keel. When all the timbers were in place and temporarily fastened to the ribbands, the ribbands were removed one by one as the planks of the hull were laid in place, being fastened to the timbers by copper nails and roves. Steam-bent timbering was suitable for either carvel or clinker planking.

Developments after the Second World War.

Design and building techniques, together with the introduction of many new materials, revolutionized yachtbuilding during the 1950s. Water-resistant marine plywood, introduced during the war, opened up the possibilities for amateur builders to construct their own boats, and numerous new designs were made available to plank in plywood from small dinghies up to cruising yachts of 12 metres (39 ft) in length.

Another popular material for the amateur boatbuilder which came into vogue at this time was ferrocement, or ferroconcrete. This method employed several layers of wire mesh, generally of the welded type, which were wired to the intersections of steel rods and tubes forming a close-knitted framework of the vessel's hull. When complete the whole fabric was rendered waterproof by an application, simultaneously from both inside the hull and outside, of a semi-liquid mortar mix, composed of cement and very fine sand. When cured and set over a period of a week or more, the resulting surface is smooth, hard, and resilient. Many barges and pontoons have also been made this way.

For yachts over 12 metres, the strength and durability of steel makes it favoured by those undertaking long ocean voyages and it is fairly easy to repair in any part of the world. Aluminium is also popular and, being lighter, is used to build racing yachts, but it has now been largely superseded by the composites mentioned below.

Modern Yachtbuilding by Jeremy Lines

By far the most popular material today for constructing yachts, both power and sailing, is glassfibre, or GRP, a revolution which occurred in the 1960s. After a female mould for the hull and deck has been made it is coated and polished to a high degree as this will be the finished surface of the actual yacht. This is then coated with a release agent which is followed by two gel coats before the first layer of glassfibre is laid. Resin is then rolled into this mat before the succeeding layers of reinforcement are laid and again impregnated with resin. The most usual resin is a polyester but other more expensive types such as vinylester and epoxy may be used for greater strength or less weight. A simple small hull such as a dinghy may have just a single laminate lay-up, but as size increases a cored laminate may be used to get more panel stiffness, and additional frames, stringers, and bulkheads may be fitted.

The unique property of a composite structure is that the designer can specify not only the thickness and size of the material but also the physical properties of the material itself by adjusting the type and orientation of the reinforcement and using different core materials and resins. Because the actual material is being made at the time of manufacture close control has to be maintained over the whole process as it cannot be remade.

Nowadays state-of-the-art racing yachts are built on the foam sandwich principle, the hull generally being formed over a male mould from two composite skins enclosing a central core of end-grain balsa wood, pvc foam, or other lightweight material. Some extremely light but stiff epoxy honeycomb materials are available today and, combined with an enormous range of reinforcement materials such as Kevlar and carbon fibre in woven, unidirectional, and combinations of the two, the hull structure can be built to the minimum weight in every part.

Using techniques adapted from the aerospace industry the reinforcements may be pre-impregnated with resin, thus ensuring the minimum resin weight, and then cured by controlled heating in an oven.

Resins are also used to seal and glue wood and this has helped to overcome many of the disadvantages—rot, high maintenance costs—of this type of construction and has led to a modest revival of wood in the yachtbuilding industry. Other methods such as cold-moulded wooden laminates glued with resin over a mould have produced many lightweight dinghies and racing yachts, but, worldwide, GRP production yachts now far outnumber other types of construction.

The introduction of GRP hulls and decks, and the standardization of yachts, led to batch production where the interiors were produced on jigs and then lifted in large sections into the hulls before the decks were bonded in. To reduce the cost still further, more and more of the interior is also now moulded in GRP so that the fitting-out time can be reduced to days instead of weeks. The decks may also be fitted out separately, both above and below, before being bonded to the hull. Most boat factories have the working area arranged at deck level with everything possible being prefabricated and tested before installation. Another great advantage of this type of construction, if done properly, is the close quality control that can be achieved. It also means easier maintenance, even if it means replacement rather than repair.

Bibliography

Watts, C. , Practical Yacht Construction, 3rd edn. (1970).