Preindustrial ship building question

How much thought went into designing a transcontinental sailing ship–let’s say ca. 1500s. Did they simply know that “wood floats” and get to work building something that would more or less stay together and not take on too much water? Or did they actually recognize buoyancy can be calculated by figuring the volume of the hull’s geometry and comparing that to the weight of an equal amount of water, etc. and come up with some reasonably accurate expectations of how the boat will sit in the water, how much cargo you could put on it, and how the thing will handle with varying amounts of weight and where to distribute it—all before starting construction? Or did they just build the new ship sort of like the last one that worked pretty well, maybe with a few adjustments, and figure out the individual ship’s own peculiarities through experience?

My understanding is that it was mostly tradition and improvisation with very little science. There’s the old story about the Romans wanted a fleet to fight the Carthaginians but knowing nothing about ship building. So they captured one Carthaginian ship and disassembled it down to the individual pieces of wood. They then used these pieces of wood to make duplicate pieces and reassembled all of the pieces into a fleet of ships that were all identical to the model.

Surprisingly, that kind of thing continued right through the sailing age. The Venetian fleet of the sixteenth century was made up of ships that were mass produced on an assembly line. England in the Napoleonic era, despite its seafaring history, was surprisingly bad at ship building so the Royal Navy would often disassemble captured foreign ships and build duplicates of them.

As a bit of possibly interesting information, the San Diego Maritime Museum is currently building a replica of Cabrillo’s galleon, The San Salvador. They’ve laid the keel and the stern plate (?) and are starting to install ribs. Very impressive project…

There weren’t any plans! They did as much research as they could, but, to some degree, they have to fake it. They sent representatives to Spain and Portugal, to study all the old paintings of ships that they could find, hoping to derive ship-building details!

San Diego Maritime Museum San Salvador information page

Another thing no one knows is: how did they sail these things? We have some pretty detailed information on 17th, 18th, and 19th century sailing operations, but a lot less on how to operate a galleon! I guess they’ll have to generalize…or discover it all anew by trial and error!

It’s almost like something from the Society for Creative Anachronisms!


This man is often called the first naval architect:


There were lines drawings before him, but he got himself a mathematician as a teacher, when he wanted to use them. I have a vague memory of one of the Bernoullis having been involved with theoretical buoyancy calcs.

So 16th century is right out and I suspect in the 18th it’s still only the most expensive big ship of the line.

There was something on the history channel about a french naval attache who was performing a study to calculate how many trees of whatever kind of wood they used for ships at the time it would take to make a ship-of-the-line. I personally though the level of forethought was fascinating even though in his time the answer was obvious; I guess he was trying to think/find something other naval archetects had not.

I kind of wonder if they did miniature models like they do these days to get a rough idea of how a ship of a given shape would handle. But like others have said, they probably stuck with what works because building a ship in the 1500s must have been such an investment in money and manpower you wouldn’t want to risk having an innovative design end up in the bottom of the ocean.

You mean like the Mary Rose?

Here’s a link to a scanned book on rigging, rope, mast making and naval tacticsfrom 1794. Steel was one of the first to create such a detailed and useful book on the subject. There is no math IIRC but a lot of drawings and cross-sections along with tables of costs for various rigging components.

It was in the early Napoleonic period that scientists began state-supported attempts to engineer ships. Towing-tank tests were invented in France and a lot mathematics was circulating amongst Europe’s scientists. Most of the theories were wrong (like that water resistance could be calculated as the effect of the impacts of water molecules on the hull) but they were trying.

… or the Vasa.

There was a prevalent belief that wood needed to be “seasoned”. Not just dried out from its green state as in the modern definition of the term - seasoning used to mean cutting wood into planks and then leaving them outdoors for a year or two of exposure to the elements. Apparently it was felt that this toughened up the wood or something. What it actually did in most cases was start the wood rotting.

So you’re saying that ships were routinely built from partially rotten wood?

Ship builders did various things to save money. Bolts that were supposed to be several feet long and, well, bolt things together were replaced by inch long bolts inserted into short holes.

One of the National Geo books, Men Ships and the Sea, tells the story of building a replica Mayflower, and discovering–on the way–how she handled during a Storm. Thor Heyerdahl’s The Ra Expiditions also describes OJT with an ancient vessel.