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Old 07-07-2009, 09:55   #1
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Hull and Rigging Design

Im fascinated by the evolution of boat design.

Ever since prehistoric man first sat on a floating log and realised he was in danger of getting his feet bitten off, boat hulls have evolved round the globe.

They are all the product of circumstantial adaptation to wind, current and useage, but does that mean a Dhow or Junk wont sail just as well on the other side of the world to that which it was originally designed?

What makes a Cornish crabber or a Bristol channel cutter, or a Devon Yawl, or Thames Lighter or Broads Wherry best suited to that particular piece of water?

Why did a Ketch rig need or evolve to a gaff rig to make it more suitable to another location or occupation?
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Old 08-07-2009, 00:19   #2
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theory

One theory I've read is that boats tend to evolve to suit their application first, and their environment second. So a local packet (mail) boat in south Florida is actually quite similar to one near Kiel: narrow, shallow, about 400 ft^2 of sail.

Generically speaking, rigs evolved as technology and materials evolved, only a bit more slowly. But again, the purpose of the vessel ruled. The most highly developed commercial sailing rig in Europe was still in commercial use in 1960 - the Thames Barge's sprit rig using leeboards instead of a deep keel. It could be run by a master and a boy on a 100' or more boat in any reasonable weather without a motor, which is a sight more efficient than most pleasure yachts today.

The lovely dhow is hugely efficient in beam winds, which it gets both up and down its regional waters. The gaffer improved the windward performance of the lugger, and both spread a lot of sail down low on their relatively shallow and low ballast ratio hulls, giving them the performance necessary to get along before motors were an option. The skimming dish racers of the north american east coast were dangerously over-powered racers whose skippers would do anything for advantage in a cash prize circuit, including throwing crew overboard during the race.

But much of what we see and know about these boats is hindsight. We see the intricate joinery and knotwork which held the traditional dhow's yard together and say it was ingenuity and designed to be repairable and extensible, when it was really a lack of spar lumber forcing builders to cobble together yards out of scraps and poor quality material. The heavy partners, complex wedges of a clipper-bowed schooner's rig were mostly due to an inevitably slack and inefficient rig and not some mythical 'work boat ethic'. The Scottish 'Dandies' were ironically named because the fishermen there were so conservative as to hold onto a rig that was more than a century behind the times.

One of the most common misconceptions in sailing today is that the Marconi rig is 'faster'. This belief evolved because racing rules limited sail area. But the rig is almost unheard of anywhere that money was made by being fastest and there was no limit on sail area. How many crew was often more limiting. Windjammers might sail with so few crew they couldn't load or unload the boat, but they could manage the low-stress rig one sail or one mast at a time. Gloucester fishermen, on the other hand, might have three or more times the crew, and set extreme racing canvas to beat the other boats to market. Sure a marconi rig is faster with limited sail area (although many of the fastest designs today have sails that look like high-aspect ratio gaffers, with a batten instead of a gaff holding an integral topsail), and the course is won going to windward and not going to leeward or beam, but that's a rather limiting pair of qualifiers.

Just a few thoughts on the development of rigs and boats.
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Old 08-07-2009, 00:52   #3
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Fascinating

Im a keen ameteur anthropolgist, totally in awe of natural selection and evolution of all aspects of life on our planet.

We always ask the old conundrum, ........chicken or egg, ..........cos its hard to see which came first.
In the case of natural history, critters, plants and insects didnt make a concious decision to grow or behave a certain way, it just happened over a long time that the ones which behave one way die and the others survive and breed.

A deliberate mechanical design is subject to a different process, yet still influenced by less obvious reasoning such as finance and shortage of materials.

You have a great blog Amgine
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Old 08-07-2009, 01:00   #4
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Boats normally do better where they are designed because they take advantage of conditions that predominate.
Boats on the Thames may go aground at low tide and may have keels to stand on. Junks reach out to the fishing grounds and reach back having little use for windward or leeward work.
Dhows have one sail that fills best on one tack for going in one direction say down a river. The sail would have to be rerigged on the other side of the mast to be as efficient going up the river.
Cat boats were nice because they were very easy to sail.
True sloops like the Friendships were great because they would heave-to so well.
Gaff rigs were replaced by jib headed mains or "Marconi" mains at first, because with the same amount of sail, you had more luff, which gave a boat more efficiency or drive to windward. Gaff Rigs were always faster off the wind but boats made their all-around reputation by going faster to windward and gaff rigs are more complex.
Schooners surpassed square rigs for the same reason and were in turn surpassed by ketches because the larger mast forward, made standing backstays possible and the larger forward mast allowed larger headsails, including spinnakers.
It goes on and on. Then there were Genoas.
By the way what ever made you think that ketch rigs evolved to Gaff Rigs. Ketches can have either Jib headed main and mizzen, Gaff headed main and mizzen or any combination. Today they are mostly jib headed, again because of a better ability to sail to windward, and being easier to manage than a gaff rig. They are popular among cruisers because they split a given sail area into more manageable sizes and make shortening sail easier and quicker.

Have fun & keep studying

Joe S
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Old 10-07-2009, 15:24   #5
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Well, the development of sailing rigs has shown that style, fashion, and non-survival conformities over-rule the strictly utilitarian in human-designed mechanical evolution.

Again, with no artificial limitations on sail size, the marconi rig tends to lose simply because efficiency does not overcome an extremity of sail area carried low. The UN's FAO did extensive engineering and social studies on sail rigs and determined the sprit was probably the best over-all for its low cost/low tech/highest over-all speed. The gaff placed higher in the studies than marconi, but no sail shape beat the crab-claw for over-all wind efficiency averaged over all points of sail.

Only racing boats "
made their all-around reputation by going faster to windward". Brixham trawlers and faering and clippers and skipjacks and on and on made their reputations by accomplishing a job, and not a one of them tried to go upwind at the cost of all other boating characteristics. Blue water boats then and now do everything they can to avoid going upwind, so windward ability is not the priority of their design, and every one of them can beat modern designs hollow off the wind by tonnage.

As for complexity, I assume you've forgotten to include the standing rigging of a marconi vessel in the equation when comparing it to the gaff. Consider only the fittings attaching the shrouds and stays to the mast and I'm sure you'll agree the gaff rig is of a lower order of engineering calculations.
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