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October 2020

Remembering Arvel Gentry and John Letcher, Pioneers of Sailing Science

It was a quarter-century ago that Sailing World published "Fluid Dynamics: How Modern Science and Sailing Discovered Each Other." (You can read it here in PDF form.) The main players covered in it, Arvel Gentry and John Letcher, have gone to Fiddler's Green, Gentry in 2015 and Letcher in 2018. Both were geniuses and gentlemen of the sport.

Almost a quarter-century before that article appeared, Gentry had written a series of lessons in Sail magazine that debunked some of the popular concepts of how sails worked. "Gentry and company were weighing in with talk of stagnation streamlines, separation bubbles, starting vortices, Kutta Conditions. They were saying outright that much of what modern sailors had been taught about lift and drag on an airfoil was just rot. And they weren't appreciated."

They weren't appreciated because, as sailors and human beings, we tend to simplify concepts until our brains are comfortable with them. Well, as Einstein said, "Everything should be made as simple as possible, but not simpler." To this day, despite the prodigious advances in both the hardware and software that have made computational fluid dynamics (CFD) commonplace in the design of vessels, sails, and underwater appendages, there's still plenty of mystery in how these structures operate in the real world, and it's not for want of either brain power or computer power.

A CFD image of turbulence behind the space shuttle on re-entry. Source: Wikimedia Commons.

What aero-hydrodynamicists and computer engineers have been able to do with CFD is create an animation of dynamic events, and they can make pretty accurate predictions of how things will work given a particular set of imagined conditions. But of course fifteen degrees of heel angle are not always fifteen degrees. And real waves don't observe a constant height or frequency. Windspeed varies. Wind direction varies. The same goes for the set and drift of water current. Then add in the human factor: People steer differently, and trim sails differently, and move around the boat, changing everything all the time.

As the Fluid Dynamics article says, "The essential challenge... is in trying to make a vessel move nicely through two fluids simultaneously, part of it stuck down into thick, slow-moving water, and the other part stuck up into thin, fast-moving air. Add peripheral challenges like waves, local wind dynamics, geographical effects on both fluids, and the limitations of  boat design, and you've got an excellent puzzle to solve." Which is why people like Gentry and Letcher have always been drawn to the sport, and why sailmakers and Formula One engineers and aeronautical engineers enjoy talking to each other.

There's still mystery in sailing because the elements we sail in are always chaotic, slightly or greatly. It seems likely that there are some people who, by nature or practice or both, are better attuned to the what's coming through the chaos pipeline than the most powerful and sensitive computer program. Will that always be the case?

- DL 


The Gold-Rush Clippers

This is a slightly altered version of an article written for the May 1989 issue of Sailing World after Thursday's Child, skippered by Warren Luhrs, bettered the record of the clipper ship Flying Cloud on the New York to San Francisco run via Cape Horn. Flying Cloud's record had stood for 135 years. Reprinted by permission.


Picture of the world of 1848. The Industrial Revolution was almost complete. Scientists and inventors had changed the face of society with steam engines, electrical wonders, and the machines of mass production. Everywhere, it seemed, farmers were leaving their fields and joining the lines of factory workers. The modern rules of life were facing down the old ways, and there were full-blown political revolutions happening all over Europe. There was a new book out called The Communist Manifesto, whose authors were taking things a step farther, talking about the inevitable triumph of the industrial working classes.

FC - Wikimedia commons
Flying Cloud, designed by Donald McKay, held the New York to San Francisco record for 135 years. Image courtesy Wikimedia Commons

Victoria was queen. In three years there would be a Great Exhibition with a Crystal Palace and other wonders of the modern world. There would be a yacht race around the Isle of Wight, with a black schooner from America taking home the trophy that would bear her name.

The planet Neptune had recently been discovered. Big city doctors were beginning to use general anesthesia in surgery. Steam locomotives and short-run railroads were common; European mail could be delivered from Boston to New York in a matter of hours by train and steam packet (when it absolutely, positively had to get there overnight). It was almost incredible, but you could send a message at the speed of light: Morse’s telegraph lines were being strung up everywhere. Edison and Bell had arrived — they were in diapers, but they were here. In July, there was a big women's right convention in Seneca Falls.

Not far away from all this modern hubbub, along the Mississippi in places like Independence and Council Bluffs, the westbound traveler looked across the river and saw… well, Indians. What lay on the other side of the Big Muddy was about as different as you could get from the world of Queen Victoria and Karl Marx.

Out there, these were the days of Jim Bridger and Kit Carson, mountain men and isolated trappers.The great trails through the wilderness — the Santa Fe and the Oregon — had been traversed, but it was no cakewalk for settlers to get to California and Oregon. There were the Comanche, Blackfoot, Pawnee, Creek, Cherokee, Cheyenne, Kiowa, and Crow, and it wasn’t even close to the time of the last battles when they were driven off their land once and for all.  Cochise and Geronimo were peaceful young Apaches in 1848, and wouldn’t be heard from for another 20 years or so. Sitting Bull was a teenager. George Armstrong Custer was a 10-year-old schoolboy in Ohio.

In 1848 there was no question that the Native Americans ran the continent west of the Mississippi. Even if you were wise enough to enlist the services of an expert trail guide, it was by the good graces of the natives, or your own smarts, or luck, that you made it through without a fight.

Then there was the territory itself. The rivers carried names like Snake, Wind, and Cimarron. They were places called Hell's Canyon, Muddy Gap, Devil's Hole, Cripple Creek, Purgatoire, Death Valley. Winter was terrible in the mountains, and the desert was worse. If you strayed off the trail in a blizzard, or took the wrong cutoff, you were — not to put too fine a point on it —  doomed. There were grizzly bears, wolves, mountain lions, and rattlesnakes. And smallpox. Heading west was something to mull over carefully.

Rush to the Gold

Early in 1848, gold was discovered on John Sutter’s land in the Sacramento Valley. Word spread quickly, and everything changed. Danger? Hell — California here I come! By the end of the next year, 80,000 people had rushed to the Pacific. Emigrants of all nationalities flocked from every direction as fast as possible, by any means they could. For Easterners, one alternative to the risky wagon train was to ship themselves around Cape Horn. Most people booked passage on the scores of slower vessels, some decrepit, some sound, that were thrown suddenly into the California run. Others who could afford it demanded faster transport.

It wasn't only the Forty Niners who needed delivery to the coast; the goods to sustain them had to get there, too. Prices were astronomical in California, and there were huge profits to be made by getting the goods there quickly. For a few years, until the market was glutted and freight shipments lay wasted in the streets, ships bulled their way around the Horn laden with anything and everything their owners could throw on board. The faster the ship, the better the profits while the prices held high.

King philip

The Gold Rush didn’t create the clipper ship. Fast sailing ships had been called clippers for a long time, and they’d be known by that name well after their day in the spotlight. American sailors had developed a serious appetite for speed after the War of 1812, when it had made all the difference between a loss and a standoff with the world's greatest naval power. By mid-century Yankee ship design had reached a high stage of evolution, and sailing speed was a matter of interest not only to shipowners, to whom it meant good business, but to the public, excited by the idea that faraway exotic worlds were being pulled within reach. When R.H. Waterman brought the bark Natchez into New York after a 78-day run from Macau in 1845, he was lionized in the streets.

The early years of the Gold Rush did, however, make legendary a certain breed of clipper that sailed for about a decade between ‘49 and’ 59. These ships were unique in two inseparable ways: They were built strictly for speed at the expense of cargo-carrying ability, and they were driven by speed demons. Waterman was such a demon, famous for his China passages aboard Sea Witch and Natchez, and there were maybe a dozen others who became household names  in their time. Some, like Philip Dumaresq, commanded several ships; others were associated with a particular clipper, even if they sailed her for only one record-breaking passage: Ashbel Hubbard of the Flying Dutchman, Freeman Hatch of Northern Light, John Williams of the Andrew Jackson, Josiah Cressy of Flying Cloud, Asa Eldridge of Red Jacket, and J. N “Bully” Forbes of Lightning.

Of all the designers and builders who entered the fray, Donald McKay quickly rose to the top of the heap. Even before the decade of the California clipper, the speed records set by his ships had eclipsed many others. It wasn't just that McKay's ships were fast; they were outstandingly handsome, sturdy, and well-finished. These attributes helped them lure the best drivers, and success begat success. They became legends in their own time. McKay made his name with his first clipper, Stag Hound, launched at his East Boston yard in December of 1850. His second, built the next year, was Flying Cloud.

Flying Cloud is a good focus for a clipper ship discussion for two reasons. First, her record run from New York to San Francisco was not bettered for 135 years, until 1989, and then only by a high-tech, high-performance sloop that could skim the water with no cargo aboard. Second, she truly represented the state of the art. Samuel Eliot Morison, in his Maritime history of Massachusetts, summed her up this way: “McKay built faster clippers, but for perfection and beauty of design, weatherliness, and consistent speed under every condition, neither he nor anyone else surpassed Flying Cloud. She was the fastest vessel on long voyages that ever sailed under the American flag.”

She was 229’ long on deck, 235’ from knightheads to taffrail. Her maximum beam was 40’8”, and she drew 21’6”. She registered at 1782 tons. Her rig is described in Howe and Mathews’s American Clipper Ships 1833-1858: “[L]ength of foremast, 82 feet; topmast 46; top-gallant, 25; royal, 17; and skysail mast, 13. On the main — 88, 51, 28, 19, and 14 ½. On the mizzen — 78, 40, 22, 14 and 10. [Length of] yards; on the foremast: 70, 55, 44 ½, 32 and 22. On the main — cross-jack, 56, topsail, 45; topgallant, 33; royal, 25; skysail, 20. The foremast was 35 inches in diameter, the main, 36, and the mizzen, 26. Diameter of the foreyard, 20 inches; main yard, 22; and cross-jack, 16 inches. The bowsprit was 28 inches in diameter, 20 feet outboard. The jib-boom was divided at 16 feet and again at 29 feet, with a five-foot end. The spanker boom was 55 feet long; gaff, 40 feet; and the main spencer gaff, 24 feet. The masts all raked alike, 1 1/4 inches to the foot.”

The terminology doesn’t come naturally to the modern sailor, but once you’ve located all these parts in your mind’s eye, you begin to see an awesome picture. What the particulars make obvious, even in an age of hollow aluminum extrusions, plastic, and carbon fiber, is that this ship was gigantically sparred for her size. Like other “extreme” clippers she was meant to spread many thousand square yards of sail and keep most of it up in heavy winds and seas. That was the way to speed records and profits.

On Flying Cloud’s maiden voyage in 1851, Josiah Cressy took her out of New York, around the Horn, and to San Francisco, in 89 days, 21 hours, anchor-to-anchor— an astoundingly fast passage. On her fourth voyage, begun on January 21, 1854, she bested her own time, arriving at anchor in San Francisco 89 days, 8 hours out. This was the record that stood until 1989. (There has been a longstanding debate over whether the record should have been credited to the Andrew Jackson, a clipper that made the run in the winter of ‘59-’60 to the pilot grounds inside the Farallon Islands in 89 days, 4 hours, but was then becalmed and couldn’t make port until the next day. A tempest in a teapot, you say? The most rabid fans of Red Sox and Yankees could not have been at greater loggerheads.)

The clippers of the 1850s represented a great leap forward in naval architecture. They had sharp entrance lines with radical concave bows, moderate or low deadrise with flattish bottoms and shallow, clean runs aft for minimum drag. With their enormous sail areas they were radically fast by any standard. Compare them to what came before: The original American naval frigates like Constitution, Philadelphia, and Constellation, which outsailed the British men-of-war in 1812, were occasionally capable of 12-knot speeds. Early merchant clippers like Sea Witch and the famous Baltimore ships like Ann McKim could do a knot or two better. Flying Cloud had her best day’s run during her sixth and last voyage around the Horn in ‘56 — 402 miles at an average of 16.75 knots. In 1854, the McKay-built Champion of the Seas made 465 miles noon-to-noon on December 11-12 in the Roaring Forties — an average of almost 20 knots. It would be 40 years before a steamship could equal that. In Southern Ocean conditions it’s still a good day’s run for a 21st-century warship.

The thoroughbred clippers weren’t just temperamental to sail, they were downright frightening. In order to set records they had to be sailed at the far edge of sanity. Riggers would often be sweating over the last of their work as the ships were being towed out of harbor on their maiden voyages. Everyone understood that the hemp would stretch, and that if sails weren’t reefed at the right time, and sheets and yards weren’t tended properly, and if the helm wasn't handled perfectly, gigantic objects would start breaking.


It’s hard for modern-day sailors to picture the mayhem when things did break. On her maiden voyage, Sovereign of the Seas, built by Donald McKay and commanded by his brother Laughlan, lost her main topmast, mizzen topgallant mast, and foretopsail yard over the side in a gale off Cape Horn. With a record to set, there was no option of cutting the rigging away and heading into Valparaiso for repairs. McKay re-rigged her then and there. “Theoretically, it was impossible in the heavy weather that existed to save the massive spars,” said Carl Cutler in his authoritative Greyhounds of the Sea. “...It required herculean efforts merely to prevent the spars from pounding the ship full of holes, let alone getting the ponderous weight of the spars and the backstays on board again…

“Within 24 hours the fore and main topmasts and mizzen topgallant mast, with all the yards, sails, and gear attached, were back on board and the work of re-rigging was underway. It was a task that involved everyone engaged in it in the utmost danger. The main topsail yard alone was a stick that must have weighed considerably more than three tons without the hamper attached to it, and the work of disengaging such a spar from the snarl of rigging in the heavy seaway that prevailed was a thing to tax the courage of the bravest and most active sailors afloat.”

Within 30 hours they were making 12 knots. For the record, the main topsail yard on Sovereign of the Seas was 19.5 inches in diameter and 70 feet long, about twice the size of a typical utility pole, and much heavier. To be put back in service it had to be hoisted about nine stories into the air with hemp rope and wooden blocks in a violent rolling sea, by men in soggy and inadequate clothing being whipped by a cold wind.

On the other hand, imagine the thrill of a fast passage. On February 12, 1853, Laughlan McKay took Sovereign of the Seas out of Honolulu, bound for New York with 8,000 barrels of whale oil. They were extremely shorthanded, with only 34 crew in addition to the officers. McKay closely followed sailing directions given to him by Lieutenant Matthew Fontaine Maury, then director of the U.S. Naval Observatory. Maury would soon publish his Physical Geography of the Sea, which would set the standard for all modern oceanographers. For now he was pleased with McKay’s confirmation of his theories: Sovereign made New York in 82 days, obliterating all previous records. She averaged 378 miles a day for four days straight, and 330 miles a day for another eleven-day period. In mid-March she recorded a 24-hour run of 430 miles (later analyzed and reduced by the Navy to 410.7 miles in 23:18, or about 421 miles in 24 hours). A letter from one of the ship’s officers to a friend in Boston is quoted by Howe and Matthews:

“The day we ran 430 miles she had the wind on the larboard quarter and carried all drawing sail from the topsail down, but had the topmast been sound she could have borne the topmast studding sail also. The sea was high and broken, the weather alternately clear and cloudy, with heavy showers, and at night we had occasional glimpses of moonlight. She ran about as fast as the sea and when struck by a squall would send the spray masthead high. Now and then she would fly up a point and heeling over skim along between the deep valleys of the waves, and then, brought to her course again, righten with majestic ease and as if taking a fresh start would seem to bound from wave to wave.”

On Sovereign’s earlier, maiden voyage, the re-rigging triumph would probably have been impossible if it weren’t for the fact that Laughlan McKay was a master carpenter, having served as such aboard the frigate Constellation, and had brought with him a mostly hand-picked crew of 105 — a huge crew to ship aboard a clipper. Most clipper captains were unable to attract decent crews, either in numbers or expertise, and sailed shorthanded, as McKay did in his Honolulu-New York run. Those who did ship out were generally miserable about it, and were treated miserably as well. They were paid a few dollars a month to endure unheard-of hardship and danger with no time off, bad food, and bad company. “Americans would not willingly accept such wages for such work,” said Morison. “Coasting vessels, paying $18 a month, absorbed the Yankee boys with a craving for the sea. The shipowners could have obtained American crews had they been willing to pay for them, but they were not. Like the factory owners, they preferred cheap foreign labor.”

The crew problem, the rise of steam power, and the cost of operating fast, low-capacity ships in pursuit of markets no longer frenzied — these were the main factors that brought about the demise of the Gold Rush clippers. But the 1850s, a decade of often painful social and technological transition that foreshadowed the American Civil War, were golden years for some of the most exotic ships ever to sail.