Spec Tech: Dreaming of Windships
I have been daydreaming recently of windjammers, the last of the great merchant sailing ships. I’ve looked back at the sailing ships of the recent past and imagined the future windjammers that may yet be.
Is there a future for commercial sailing ships? I wouldn’t rule it out. The ageless winds still blow, girdling the globe in great bands of usable and ready energy. The wind is not, and never has been, free but it may be attractive once again when the day comes that fossil fuels become significantly more expensive, as assuredly one day they must. But before we look at the windjammers of the future, we should take a quick look at the windjammers of the not so distant past. As Faulkner noted, the past isn’t dead. It isn’t even past.
Windjammers began to disappear less than a hundred years ago. At the turn of the 20th century there were still close to 5,000 of these grand sailing ships hanging on against competition from the steamers. The last commercial voyage by a merchant windjammer was in 1957. More than a dozen of these mighty ships still exist as museums, restaurants or tourist venues. A few are still even out sailing the world’s oceans.
The reason that the windjammers held on so long was because they sailed where the steamers couldn’t or wouldn’t go – on the long windy passages through the Southern Ocean, south of the Cape of Good Hope and Cape Horn. They carried the lower value bulk cargoes – wool, coal, iron, and nitrates. In their day, the windjammers were among the largest bulk carriers sailing the oceans.
The windjammers of our recent past were dramatically different from the famous clipper ships of the mid-19th century. The graceful clippers were built of wood with hemp rigging. The windjammers were much larger ships, often two to three times larger than the typical clipper ship. They had a iron or steel hulls. Most of the yards and masts were also steel, and their rigging was steel cable, rather than hemp. They were beautiful brutes of ships which sailed with often less than half the number of sailors employed on the old clippers, despite being much bigger ships themselves.
It is often said that the two major canals, the Suez and Panama, killed the windships. As soon ships could take the short cut through the canals there was no longer a need to round the treacherous and windy capes. Any commercial advantage that a sailing ship may have had was gone. Then around the 1970s, something changed. Bigger and bigger bulk carriers where built which no longer fit through the canals. These became known as capesize bulk carriers because, like the windjammers, they sailed south of Cape Horn and the Cape of Good Hope.
So why not just slap some masts and sails on the cape sized bulkers? Not a bad idea, really, except that the the world of ships has changed. Ships are now bigger – much, much bigger. At the turn of the twentieth century, windjammers were among the largest bulk carriers and could carry around 4,000 – 6,000 tons of cargo. Today, the largest bulk carrier in service, the Vale Brasil, can carry 400,000 tons of cargo , an increase of almost one hundred fold.
We do have clues as to what a modern windship would look like, nevertheless. Back in the 1960s a German naval architect, William Prölss, developed a design for a modern mechanized sailing ship which he called a Dynaship. His design featured square sails on rotating masts. The sails were set and furled mechanically, rolling up up inside the freestanding masts. Gone was the aerodynamic drag from the miles and miles of running and standing rigging on conventional sailing rigs. And gone was the need for crew to climb the ratlines to set and furl sails.
With the Dynaship, the day of the modern sailing ship was again at hand. And then, for over thirty years, nothing whatsoever happened. Only one full-sized Dynaship has been built, not as a commercial cargo ship, but as a rich man’s yacht. In 2007, the Maltese Falcon was delivered, a 288 foot long yacht with 25,791 square feet of sail area. That is seventy feet longer than the famous clipper Cutty Sark and, in proportion to the overall size of the ship, the Maltese Falcon carries more sail. If nothing else the Maltese Falcon demonstrates that a modern sailing rig would work on a ship of about the size of a windjammer of the early 20th century. How well would a Dynaship or similar rig work on a modern capesize bulk carrier one hundred times larger by mass that the Maltese Falcon?
With proper engineering, it could work reasonably well. The modern windjammer wouldn’t have to to carry proportionately as much sail as early 20th century counterparts because they would still have an engine tucked away in the engine room. The old ships, without engines, needed lofty light air rigs to help them cross the doldrums near the equator where there was often no or very little wind. A modern sailing bulk carrier could motor through these windless patches back into the steadier trade winds. With modern weather routing and course planning a sailing bulk carrier could spend most of its time in the windier waters with the wind abaft the beam, probably out-sailing the clipper ships of old.
To try to get a reality check on the praccticality of a modern day windjammer, I ran a few simple numbers. Naval architects and yacht designers use a non-dimensional coefficient, Sail Area to Displacement ratio, to compare sailing rigs on vessels of different sizes. (For anyone interested, the ratio is Sail Area(sq ft)/Displacement (Long tons)^2/3.)
Looking at seven sailing ships from the 19th and early 20th centuries, the SA/D ratios averaged around 14. Interestingly, two modern sailing ships, the Maltese Falcon and the Stadt Amsterdam, have SA/D ratios over 21, not untypical for a modern racing yacht. Unlike the older ships the Maltese Falcon and the Stadt Amsterdam were not designed to carry cargo, which is reflected in their smaller displacements while still lofty rigs.
Applying these ratios to a capesize bulk carrier with a displacement of 200,000 tons, the figures get very large but are still manageable, especially if one adjusts the sail area downward due to using the engine in light airs. Accordingly I’ve assumed a SA/D ratio of 8 rather than 14 of the older ships. The sail area resulting is still almost four times larger than that of even the five masted Pruessen. Even so, spreading the sails over six rather than three, four or five masts, the mast height would not be much taller than that of the Maltese Falcon.
Will there be a new generation of wind ships? The answer is probably yes, while the harder question is when?
And what does this have to do with speculative fiction? Nothing and everything. Wind is no doubt a universal form of solar power regardless of what planet one may be on. “Wind-punk” may have as much potential as “steam-punk” in the hands of the right writer. Any post apocalyptic tale near the ocean should include sailing ships.
If windjammers are too oceanic, you also might consider sailing off on the solar wind.