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Traditional Methods of Boat Design

Copyright 1990 - 2011 Michael Kasten

Then...

First, there would have been a need. Usually for survival, whether for defense, or for commerce. These are the needs which shaped the boats of the past. There have always been limits: those that materials imposed on both the structurally possible size, and the economically reasonable size. As we humans have become more capable boat builders; as we have begun to employ metal for structure; and as wealth has been gleaned from ever wider areas, we have gradually built bigger ships.

Boats have always been the product of slow evolution. In the not so distant past, boats were usually crafted by first finding an example that was serving its purpose well, then making just enough of a change to both try a new idea, and to assure success by virtue of similarity to the prior vessel. Analytic methods were not applied... they were not well developed, nor were they especially needed. The attrition of the unsuccessful was accepted as part of the evolutionary process. The rules were simple: if you created a bad boat, you would probably die in it or someone else would. Thus the conservative approach taken by builders when asked to make an innovation.

Using fishing vessels as an example, the process of design would have involved first seeing the need for an improvement, or a changed capability, then involving a builder to make it so. A simple sketch might be the only guide, or even just a conversation. A half-model, carved by either the owner or the builder might have been a further step in defining the new vessel. There would have been no designer, per se, except for the builder and the owner. The involvement of a "boat designer" is a more recent thing.

In England, it was Sir Anthony Deane in the 1670's who began to outline a methodology for ship design. His approach consisted of defining critical dimensions, such as length, draft, and beam, then defining certain ways to "fair" the curves. Deane mostly used radii, both for the longitudinal and the sectional shapes.

A bit earlier, in 1628 during sea trials the Swedish ship Vasa rolled over and sank in Stockholm harbor. By 1659, King Carl X Gustaf noticed that the English ships were better sailors, and sent for qualified English shipbuilders. In 1757, after three generations of English influence, the stage was set for the Swedish shipbuilder Frederik Henrik af Chapman to become assistant Shipwright to the Royal Swedish Navy.

In 1768, af Chapman published his Achitectura Navalis Mercatoria, a collection of 64 engraved plates illustrating the lines of ships and boats of all sizes and types. His objective was to show a synthesis of the most successful results achieved by shipbuilders of different lands by traditional means. These vessels represented the best of an era before the use of mathematics and physics to determine a ship's properties. In most of the plates af Chapman drew two separate concentric circles near the mid-section of the ships to indicate the center of gravity and the metacenter - the basic data from which stability is calculated.

By 1796, copies of af Chapman's drawings had been stolen by Napoleon, by the Danish, and by the Russian Navy. Prior to that, in 1775 af Chapman published a text to accompany the engravings, the Treatise on Shipbuilding. This was translated into French in 1799, and shortly afterward into English.

In 1793, when af Chapman retired, he was given the duty to create a Corps of Naval Constructors. He introduced a new uniform for the Corps which included a button that carried the formula for calculating a vessel's Metacentric Height:

Metacentric Height Formula

This is just the mathematic notation for:

Metacentric Height Formula

Between 1768 and 1806, af Chapman presented papers to the Royal Academy of Sciences in Stockholm on displacement, center of gravity, stability, resistance, center of effort, and appropriate ship proportions.

Between these two men, Sir Anthony Deane and Frederik Henrik af Chapman, we were given the early roots of what has become the formal "boat design" science, Naval Architecture.

Interestingly, the ships and the small boats of the past always managed to carry with them some element of the craftsmen who built them. This is not peculiar to wood as a boatbuilding material, as can be observed during the 1800's. For example, at the Jefferson County Museum in Port Townsend there is an exhibit entitled "Port Townsend Area Wooden Boat Tradition: 250 Years." However, on looking closely at the exhibit, and in fact even at the museum's poster for that exhibit, we see the Balmoral Castle, which is actually built of iron...! In fact, some 50% of the entire exhibit are photographs of iron ships.

The point here being only that the material of construction seems to have had little effect on the aesthetic presentation made by the builders.
 

Now:

Many changes have come in the 20th century. We have begun to use the "design" stage almost exclusively whilst creating a new vessel, unless of the smallest size. We now use fuel rather than wind and oars to drive our ships, and living conditions at sea have dramatically improved.

Manufacturing trends have led us to mass produce most everything. We have developed refinements of materials, giving us new possibilities. We have developed communication and electronic technologies which hold the promise of linking us more intimately together. However, for larger ships it is still the case that the limits are both economic and technical.

Interestingly, some ingredient or combination of factors during the 20th century has caused the aesthetic presentation we make with the majority of our ships and boats to be one that is seriously lacking. It often seems as though current day ships are fashioned as though squeezed out of a tube, then merely cut off where needed.

Until the current age there was an element of the aesthetically fine - even the ornate - in nearly every boat, unless perhaps only the rude raft used for an expedient crossing.

When did this change? What caused it?

Why did we so avidly abandon the aesthetic excellence offered by tradition...?

Michael Kasten

Metal Boat Quarterly #18 - Spring 1999 Editorial - Updated 2009

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