At the opposite and more optimistic end of the scale is the purchase of a new ship. This is as complex a matter as any other multi-million deals and may be more complicated than many. Unlike, say, an office building where the precise number of square meters of floor space will be known before the first spadeful of earth is turned, a ship goes through several design stages before finally being ready for sea. Even today, with the aid of the most sophisticated computers, it is quite possible for the precise dead-weight cargo capacity of a ship not to be known until the ship is almost completed. Of course there will be no wild discrepancy but it must be remembered that, unlike a building on land, a ship has to contend simultaneously with two sciences, architecture and hydrodynamics (the science of forces exerted by liquids).
There are various stages at which a contract to purchase a new ship may be signed. The parties may agree to a contract based on a very general specification with clauses to take into consideration variations, which come about as the detailed drawings are produced. Often the builders undertake to make wax models of the hull and test them in mile-long tanks. After such tests, quite appreciable changes may be agreed. For example the tank test may prove that the ship will perform even better if she is made longer than originally contemplated; a bonus for the buyer if length is not critical because of the extra cargo that can be carried. In some cases, the buyers may employ their own naval architect to produce detailed drawings of the desired ship and then ‘do the rounds’ of the builders in order to seek the best deal. Some yards offer standard designs; this was a very popular trend towards the end of the1950s when owners were looking for a general-purpose ship to replace the World War Two ‘Liberties’. Such vessels as ‘Freedom’ types and the very successful SD14 (Standard design 14 knot 14,000 tonner) built in the Sunderland yard of Austin & Pickersgill.
Today there are no standard designs with a ‘brand’ name but several yards have ‘off-the-shelf’ designs for such things as ‘Panamax’ bulk carriers. The obvious advantage of a standard design, or indeed accepting the design of a ship built for another owner, is not only the saving of a great proportion of design costs but also the fact that many of the ‘bugs’ will have been eliminated the first time around. Naval architecture is a highly developed art but the problems of the forces of sea and weather cannot entirely be simulated in the laboratory. Some ship scientists now argue that the economy of scale in ship sizes has reached its limit. They consider that any further increase in size will require so much additional reinforcement to cope with the stresses that the cost per dead-weight ton will increase rather than decrease.