The Wind is Free: Sailing Ship Design, Part 1: Propulsion

An early seventeenth-century explorer, Captain David Pieterszoon De Vries, told the Duc de Guise, “My ambition is to travel and see the whole world in all its four quarters.” Three-fourths of the world is ocean, so it’s not surprising that he became a seafarer.

In his day, sailing ships were the sina qua non of world commerce. Sailing ships brought colonists and goods to the New World, and gold, silver, tobacco and sugar back to Europe. They competed with the caravans of the Silk Road for the spices of the Orient, and ferried grain and timber across the Baltic.

However, the seventeenth century was not the pinnacle of the Age of Sail. The art of sailing ship design continued to advance, and the tall ships of the nineteenth century were bigger, faster and safer than their seventeenth-century counterparts. While the twentieth century marginalized commercial sailing, it witnessed great advances in the sciences of aerodynamics and hydrodynamics, and this found practical application in the design of racing and pleasure yachts.

The question before us is what will be the impact of the Ring of Fire on the maritime world. Will sailing ship design be revolutionized, or will the Age of Sail be cut short by the new Age of Steam?

I don’t expect the immediate demise of the sailing ship thanks to steamship competition. Yes, the USE Navy began building steamships in 1633, and uses them quite effectively in the Baltic War of 1634. But steam won’t be competing with sail until the necessary steam engines and screw propellers are perfected. This will happen a lot faster than it did in the nineteenth century but it won’t be instantaneous, either. (You also need to have a cheap source of coal, and preferably iron as well; the lack of these resources was one of the reasons that Dutch shipbuilders were late converts to steam power.)

Even then, the steamship routes will be limited by the steamers’ coal capacity and by the distribution of coaling stations. Historically, steamships weren’t able to compete on the Europe-Asia route until the Suez Canal was built, avoiding the long, lonely arc around Africa. Thereafter, sailships were still able to compete on the southern route around Cape Horn, where they could avail themselves of the reliable, strong winds of the Roaring Forties. At least until the Panama Canal made the Cape Horn passage unnecessary for steamers (sailing ships couldn’t use the Panama Canal because of endemic calms).

I don’t think Murad the Mad is going to permit the digging of a canal between the Mediterranean and the Indian Ocean, and the Spanish are equally unlikely to want to make it easier for other Europeans to enter the Pacific Ocean. So I believe that there will be a demand for commercial sailing ships for at least several decades.

Sailing warships could remain at sea for as long as the fresh water, cooking fuel, and provisions lasted. A warship might carry two-and-a-half months of water and six months of food.

(Monceau 50). And a sailing ship didn’t carry any fuel. In contrast, HMS Warrior (1861), steaming at 11 knots, consumed 3.5 tons coal/hour, and only carried 853 tons. At 14.5 knots, it consumed 9 tons/hour. (Hill) It was, perforce, a sailing ship with auxiliary steam.

One must also remember that there isn’t a single book on shipbuilding history which fails to mention what is politely called the “innate conservatism” of sailors. And it is even alluded to in Flint, 1634: The Baltic War, Chap. 31: “The transition from sail or oar power to paddlewheel steamers had required greater mental flexibility than most up-timers would have expected, for a lot of reasons, and some people—whether up-timer or seventeenth-century—simply lacked that flexibility.”

For these reasons, it will be some years before steamships take over ocean shipping routes, even though it is clear from the up-time books that steamships are a viable long-term proposition.

Shipspeak

Ahoy, ye landlubbers! A “ship,” in the seventeenth century, was a large seagoing vessel. In the nineteenth century, a “ship” came to mean either a vessel with three masts, or, more particularly, a “ship-rigged” vessel (explained below). Even then, it retained the more generic sense used in maritime law. Nowadays, when three-masted sailing ships are rare, it usually means just any large vessel and that is how the term will be used here.

Wind is important for sailing ships, and so the direction the wind is blowing from is “windward,” and that it is blowing toward, “leeward.” A ship pushed unwilling in the latter direction is suffering “leeway,” and must fear the “lee shore.” If the ship is heading more or less downwind, it is “running,” if the wind is more or less over the beam, it is “reaching,” and if it is fighting its way upwind, it is “beating.” A beam reach is a course such that the wind is coming right over the beam, a close reach is a bit closer to the wind, and a broad reach a bit further from it. A wind which is coming from a direction in-between beam and stern is called a quartering wind.

The term “rigging” refers to the vessel’s entire sailing apparatus: sails, spars, and cordage. Ships may be classified according to their hull shape (flyboat, hoy, pink, zebec), rig (brig, ketch, schooner, sloop, snow), or a combination of the two (bark). (Svensson).

Spars are the relatively rigid vertical (masts) and horizontal (yards, gaffs, battens, booms, bowsprit) structures used to support the sails. On a three masted ship, the masts are (from bow to stern) the foremast, mainmast and mizzenmast.

The cordage, originally ropes, are the flexible lines which manipulate the sails and yards (the “running rigging”) or stabilize the spars (“standing rigging”). The latter are typically in a fixed position, and run mostly between the mast and the deck.

The larger seventeenth-century ships carry square-rigged sails, so called not because of their shape (actually trapezoidal, with a bottom arc called the “roach”), but because in their neutral position they are “square” (perpendicular) to the keel of the ship. They are carried on horizontal supports (yards) which cross the masts, and the yards can be “braced” (turned) so the sails better catch the wind. The modern yachting equivalent of the square sail is the spinnaker (Gougeon 96).

All ships carry one or more fore-and-aft rigged sails, so called because in their neutral position, they run fore-and-aft, that is, parallel to the keel of the ship. Square-rigged sails trap the wind whereas the fore-and-afts act as airfoils.

There is some variety in the shape of fore-and-aft sails; typically they are either triangular (lateen, Marconi), or a right-angled trapezoid (sprit, lug or gaff). If mounted on a yard from a mast, the yard may either cross the mast (lateen, lug) or end at it (gaff, Marconi). The sprit hangs from the bowsprit, rather than a mast, and triangular staysails from a stay, a rope supporting a mast. Staysails hung in front of the foremast, and running down to the bowsprit, are called headsails or jibs. (Headsails were a sixteenth-century Dutch innovation, so the square sails on the foremast wouldn’t shield them from a headwind, see Laing 46.)

A ship is referred to as square-rigged, full-rigged or ship-rigged if it has at least three masts and each of these masts bears at least one square-rigged sail. The fore-and-aft sails on a “square-rigged” ship will usually be staysails, or the lowest sail on the mizzenmast.

The Importance of Speed

In the seventeenth century, people were accustomed to taking a very long time to get anywhere. A round trip from Europe to Japan, with leisurely stopovers in Madagascar, India and Java, might take five years. The passage from Europe to America averaged two months, but no one was surprised if it took six instead. The twentieth-century preoccupation with speed is going to come as something of a surprise.

Big warships had big superstructures, carried lots of cannon, and tended to be on the slow side even when on their own. If in a fleet, they needed to maintain formation, and the bigger the fleet, the slower it traveled.

As for merchantmen, for most cargoes, getting to their destination and getting there with a lot of it, was more important than getting there fast. In time of war, most British merchant ships traveled in convoys and then speed was limited anyway by the speed of the slowest ship. (McCutchan 24; Laing 92).

The main reasons for speed were that the ship was carrying a perishable cargo (like slaves in the eighteenth century, or tea in the nineteenth) or that its cargo was contraband and it had to avoid the coast guard (and the cargo paid well enough so the shipowner could trade off cargo capacity for speed). Privateers also needed speed, so they could catch a merchant vessel when it showed them its stern.

While there was certainly smuggling and privateering in the seventeenth century, there wasn’t much emphasis on speed in ship design then. (Gougeon 24). In fact, even in the early nineteenth century, capacity was more important.

Wind Propulsion

A sailing ship, by definition, is propelled by the wind. Its force (and energy) are transferred to the sails, and thence to the spars and hull.

The simplest situation to visualize is the one which the ship has square-rigged sails and is running directly downwind. Such sails act like parachutes, obstructing air flow. The wind strikes the sails perpendicularly, the air piles up against the canvas, and it pushes against the windward side of the sail. A fresh breeze, perhaps 12 knots, creates a pressure of one pound per square foot (White 494), and the force is the pressure times the effective area. The force is transmitted by the rigging to the hull, and the ship moves forward. (Because the “center of effort” of the wind force, determined by the distribution of the sail area, is well above the ship’s center of gravity, the ship will also be rotated so as to dip its bow.)

The next possibility is that the wind isn’t quite directly downwind, but the sails are turned (“braced”) to face the wind. The wind still strikes the sails perpendicularly, but now the applied force is oblique to the direction that the bow points. One component of the applied force will drive the boat on the set course, but the other will drive it perpendicularly from that course. The resulting angular deviation is called “leeway.” (Leeway is resisted by a hydrodynamic force, the drag excited by attempting to push the ship sideways through the water. ) The leeway on Cook’s Endeavor was 11-17o (Phillips-Birt 249). Moreover, that leeward force component also tends to rotate the ship laterally, causing it to “heel.”

The third possibility is that the wind strikes the sails obliquely. Only part of the wind force is applied by collision to the sails, so the sail is less efficient in capturing the total wind force. However, the ratio of forward to lateral force is more favorable.

Obviously, the square sail is not suited to sailing upwind; the wind would strike the front side of the sail and try to push the ship backward. However, skippers sometimes took advantage of this weakness, deliberately positioning the square sails so that the ship was “taken aback.” The ship could be made to stand still, despite a wind blowing, or to turn on the proverbial dime. (Svensson 48).

The ideal position for a fore-and-aft sail is at about a forty-five degree angle (“of attack”) to the wind, and they work by presenting an airfoil. A “lift” force is generated in the forward direction, only the sail’s orientation to the wind is such that the lift is horizontal (rather than vertical as on an airplane wing), and at least partially in the direction that the ship wants to go. Thus, such sails can be used to claw upwind, because they can be angled so the ship is “sucked” forward, and the boom is freer to swing about. ( The sail also experiences a lateral force, creating leeway. Gougeon 91).

Eddies form behind a square-rigged sail, and, if the edge flutters, in front of it, too. This wastes wind energy. Fore-and-aft sails are more efficient than square-rigged sails of the same area because they form fewer eddies (93).

Nonetheless, square sails are more efficient than fore-and-aft sails when moving downwind, especially in light air. That is because when the wind is closer to the stern than forty-five degrees, fore-and-afts can’t maintain the ideal angle of attack, because the shrouds (lines) get in the way of the boom. (113). If the mast were free-standing (no shrouds), that wouldn’t be a problem, but a free-standing mast would have to be thick (adding weight) and require more ballast (more weight)(156).

Windage. When the winds are of gale or hurricane force, the ship can move even with bare poles (“scudding”), because of the force of the wind upon the parts of the ship above water level (“windage”). This is particularly true if the wind is on the beam of the ship. Svensson mentions that seventeenth-century ships had high stems, and therefore were susceptible even to quartering winds.

Upwind Travel. No conventional sailing ship can sail directly upwind. In general, fore-and-aft rigged ships can sail closer to the wind than square-rigged ones can. Typically, a fore-and-aft rigged ship can sail within four points (45o) of the wind, whereas a square-rigger is limited to six points (68o). (Laing 72; Phillips-Birt 228).

Both can nonetheless make progress directly upwind by tacking, that is, zigzagging diagonally so the wind comes alternately over the port bow (port tack) and over the starboard bow (starboard tack). This is of course quite slow, as not only do you have to sail constantly close-hauled, which is hard on both crew and rigging, you are taking an indirect path, which takes extra time, and you lose more time whenever you change tack.

A square-rigged ship usually changes tack by turning its stern through the eye of the wind (jibing, wearing ship)(Gougeon 11). It might make a mile long arc in the process, wasting time and perhaps being blown downwind to boot. (Mountford). The alternative maneuver (tacking, coming about, boxhauling) was used only when absolutely necessary (too close to a lee shore?), because it required a skilled crew and precise timing.

On the other hand, in a fore-and-aft-rigged ship, tacking was preferred. Jibing is slower than tacking (you are turning the long way around) and you are blown further to leeward in the process.

Apparent Wind. The force of the wind on the sails is what drives the ship forward, whether that be a drag force on the square-rigged sails or a lift force on the fore-and-aft rigged ones. We can consider the force to be proportional to the effective sail area (which depends on both the porosity of the sails and their angle with respect to the wind), and to the square of the speed of the wind.

The wind that the sail reacts to isn’t the true wind (what would be measured by a stationary observer). Rather, it is what ship designers call the “apparent wind,” the vector sum of the true wind and a “virtual wind” generated by the ship’s own motion. If you are sailing directly downwind, the apparent wind is simply the true wind minus the ship speed.

If the ship is initially at rest, the apparent wind has the same direction and speed as the true wind. If the ship is running with the wind aft of the beam, then, as the ship picks up speed, the speed of the apparent wind declines, and the wind strikes the sails at a less favorable angle as a result of pitching and heeling of the ship. Together, these dictate that the wind is less effective at driving the ship forward. At the same time, the resistance of the water to the movement of the ship increases as at least the square of the ship speed. Clearly, with the effective wind force declining, and water resistance increasing, the ship eventually reaches an equilibrium speed at which the wind force and water resistance are equal.

Points of Sailing. The maximum speed is reached on the ship’s best point of sailing. This usually isn’t running straight downwind. That’s partly because of the aft sails obstructing the foresails, but a more important point is that the wind felt by the sails is then at its weakest.

As the true wind shifts off your stern, the apparent wind increases and seems to come from a direction further forward of the true wind. Once the apparent wind is forward of the beam (i.e., you are effectively sailing upwind), it’s stronger than the true wind.

Unfortunately, a square-rigged ship isn’t efficient sailing upwind. Typically, a square-rigged ship sails best on a broad reach or a beam reach. The training ship Jean Bart made 40% of the true wind speed close-hauled (6 points off the wind, sails braced 32°), 60% on the beam reach (braced 45°), and 50% on a broad reach (2 points abaft; braced 22-30°). (White 512).

James Cook’s Endeavor (550 tonnes displacement, waterline length 101’5″, beam 29’2″, depth 11’4″, draft 11’10”, ship-rigged, sail area 10,000 square feet) sailed best with the wind a point or two abaft the beam, making seven or eight knots, and it made six knots in a “topsail gale” and five in a “topgallant gale.” (Phillips-Birt 248-9; ANMS).

With fore-and-aft sails, it can actually be faster to tack upwind then to run downwind, because the increase in apparent speed more than compensates for the zigzagging. In fact, iceboats can travel at speeds up to six times real wind speed! (Gougeon 157).

Speed Achievable. The Mayflower reportedly could do 7 knots in 24 hours, but its long-distance good speed was 4.5 knots. (Phillips-Birt 230?). He says that 10 knots was the fastest speed achieved prior to the nineteenth-century clipper (236), but other historians contradict this.

The fastest 24 hour runs ever reported for a commercial sailing ship were 465 miles (Champion of the Seas, 1854), 430 (Lightning, 1857), 421 (Donald MacKay, 1855), 420 (James Baines, 1855), 413 (Great Republic, 1856), and 411 (Sovereign of the Seas, 1853). (Villiers 388-9).

In Karen Bergstralh’s “Moonraker” (Grantville Gazette, Volume 9), De Roche believes that his ship will be able to sail from Europe to China in three months. In OTL, the record commercial run from England to China was 80 days, set by the 197′ composite tea clipper Ariel in 1866. The distance is about 16,000 miles by way of the Indian Ocean. The fastest return passage (1869) was the 89 days made by Sir Lancelot, returning the same way, despite an unfavorable monsoon. (Villiers 383). The record run on the New York to San Francisco run, a similar distance, was about the same (Shaw xxv).

Modern racing craft can do better; the record holder is the 125′ catamaran Orange II (24 hour run averaging 31.95 knots; trans-Atlantic, 28 knots; circumnavigated the world, 17.89 knots).(WSSRC).

The fundamental problem with the sailing ship was that it couldn’t keep to a timetable.. In 1885-86, Cutty Sark made the wool run (Australia to London) in 72 days, but 12 of its 26 competitors, all fast ships, took more than 100 days. (Villiers 59). The steel five-master Preussen (1902)’s ten passages from the Channel to 50°S averaged 59.5 days, but the range was 51.9-75.7. (394).

The maximum speed is, of course, dependent on the strength and direction of the prevailing winds. An early nineteenth-century man-o-war might expect to make 1-2 knots in a light breeze, 3-4 in a gentle breeze, and 5-6 in a moderate breeze (wind 13-17 knots). (Raper 133). The average speed for the Preussen (1902) in a favoring gale (Force 8, 34-40 knots) was 13.7 knots, but if it was sailing close hauled, only 8.2. A four-master might achieve 11 and 6.3; an iron three-master 10.1 and 6.1, and a wood three-master, 9.5 and 5. (Villiers 389).

The captain will attempt to choose courses which let the ship take advantage of strong, reliable winds such as the trade winds, the monsoons, and the westerlies. Of course, there can be too much of a good thing; if a gale is encountered, the sails have to be reduced to avoid losing sails or even getting dismasted. According to nineteenth-century data, the average wind speed in the trade wind region of the Atlantic is about 5 meters/second (9.7 knots, Force 3), but in the Atlantic and Indian Oceans below 40°S, it is perhaps three times as fast, Force 7 (White 205; cp. CMS). Brouwer discovered the Roaring Forties in 1610.

Rig Power. A standard measure of the sailing power of a ship when winds are light or moderate is the dimensionless ratio (“SADR”) of the sail area (square feet) to the two-thirds power of the ship’s displacement (cubic feet). The displacement is the volume of water displaced as a result of the weight of the ship (35 ft3/long ton) and the “two-thirds power” makes it a surrogate for the wetted surface area. The frictional resistance, the dominant resistance at low speeds, is proportional to that area.

The extreme clipper Lightning (1854) had a sail area of about 56,000 ft2 (Lubbock 76), and displacement about 57,000 ft3 (ChapelleSSUS 421), so the SADR was 37.8. An English “74” (1832) might have 22,325 ft2 sail (Fincham 271) and displacement 106,505 ft3, for a 9.9 SADR. A nineteenth-century merchantman would probably be 6.5-10. (Fincham 499). For modern yachts, cruisers are 10-15, racers above 20, and high performance racers above 24.(USSailing). The Orange II is 92! (Staff).

If the winds strengthen, stability becomes an issue, especially if the wind is on the beam. The wind may cause the ship to heel over so much that it must reduce sail rather than capsize. This is particularly a problem for ships carrying excessive sail (“overhatted”); it has an advantage in light air, but its crew must respond rapidly to a change in the weather. (ChapelleBC 104). Stability is dependent on hull breadth, depth, and shape, and weight magnitude and distribution, as will be discussed in part 2. However, for nineteenth-century ships of similar form, the wind speed at which the ship must reduce sail was roughly proportional to the square root of the breadth.

If stability isn’t a problem, the resistance created by the waves made by the ship will still increase dramatically as the winds propel the ship faster, and the maximum practical speed will be proportional to the square root of the waterline length of the hull. Indeed, the usually limiting speed in knots (“hull speed”) is ~1.34 times that value: 22.2 for Lightning. It probably never reached hull speed for any significant length of time.

Rigging

Rigging Classification. A variety of rigs existed in the seventeenth century. However, back then ships were named on the basis of their hull shape, and function, not their rigging. The following is a typical nineteenth-century English classification of rigs:

Masts

At least one square-rigged sail on . . .

1

2

3+

all masts

Nordland; Humber keel

brig

brigantine (fore-and-aft mainsail)

ship

all but aftmost mast

bark

foremost mast only

hermaphodite brig; topsail schooner (only upper sails)

barkentine

mainmast only

“mainmast barkentine”

none

cutter; sloop

schooner; yawl; ketch

schooner

All ships required fore-and-aft sails for upwind performance. But all regular warships also needed some square-rigged sails for stopping and backing, and for increased speed (ChapellHASS 47). For eighteenth-century privateers, the topsail schooner was popular. The schooner rig made it weatherly and the square topsail on the foremast gave it a bit of extra drive. (132).

Each rig is most suitable for a particular range of ship lengths: sloop (14-50′), brig or brigantine (70-120′), two-masted schooner (36-130′), three-masted schooner (70-150′), and ship or bark (90-200′ or more). (ChapelleYDP 118).

A fore-and-aft rigged ship needs just half (Rogers 132) or even a quarter (Gougeon 28) the crew of a square-rigged vessel, in part because it can sail closer to the wind and thus is less frequently required to change tack. Also, when it changes tack, only the headsails need to be handled. Baker (142) estimates that the necessary crew is one man for every 4-6 tons burden for a square-rigger and for every 13 tons for a fore-and-after.

However, fore-and-aft rigged sails can be difficult to hoist, lower and reef (Gougeon 11). They also don’t scale up well, and the large ones are more vulnerable than their square counterparts to damage in vigorous wind and sea conditions. (28).

For the large ships which went on long voyages, square-rigging tended to dominate, since the skipper could pick a route to minimize upwind travel, but there was more likelihood of encountering unavoidable heavy weather. (Philips-Birt 129).

Seventeenth-Century Rigging. Prior to the seventeenth century, large ships had as many as four masts, with the two aft masts carrying single lateen sails. In the 1620s, the fourth mast (bonaventure) disappeared, and a square topsail was added above the fore-and-aft sail on the third (mizzen) mast, creating the classic three-masted, predominantly square-rigged “ship rig” (“full rig”). (Svensson 21; AndersonRS 8). In addition, the large ships added a headsail, in the form of a small square sail (the “spritsail topsail”) hanging from a spar lashed to the bowsprit. Despite its shape, it was a fore-and-aft sail (Phillips-Birt 158).

The presence of a spritsail topsail screams “seventeenth century” to a naval historian, but the seventeenth-century designers are mute when it comes to explaining why they bothered with one. Phillips-Birt (185) said that it balanced the mizzen sail. Or perhaps it balanced the effect of wind on the high stern when the latter was no longer balanced by a forecastle (Anderson 141). Or it reduced leeway created by the high side of the ship when it received a quartering wind (Svensson, 22). (I believe its purpose was to irritate naval historians.)

Staysails were first used on small craft, well before the Ring of Fire (Anderson 147). Staysails gradually appeared on large ships, beginning in the mid-seventeenth century. My sources conflict as to the order of appearance of the fore, main, foretop, maintop and mizzen staysails but I would guess they were all present by the end of the century, and the main staysail was used as a storm sail. Triangular headsails appeared in the late seventeenth century and largely replaced the spritsail by the early eighteenth. (Svensson 29; Phillips-Birt 225).

Spar Materials. The wood for masts must be straight, cylindrical, and free of knots. It also should be strong yet flexible and light. That meant the royal forester wanted conifers, preferably from a region with a short growing season. And only trees of a great length were suitable for making the main masts of the larger ships.

At the time of the Ring of Fire, the seventeenth-century European navies obtained most of their masts from Scotland, Norway and the Baltic (Williams 176). For example, “Amsterdammers are known to have exported Russian masts to Portugal in 1615.” (Kotilaine 252). There was just a trickle of timber from North America to England. (Davies 194)

The traditional European mast-timber was Pinus silvestris (Scotch Pine; Riga Fir, Dantzic Fir, Red Deal), but the Pinus abies (Spruce; White Deal) and Pinus larix (Larch) were also available. The pines of the Eastern seaboard, notably Pinus strobus (Eastern White Pine; Weymouth Pine) and Pinus palustris (Virginia Pine), were first exported to England a few decades before the Ring of Fire. (Murray 157; Schlich 580). Pseudotsuga menziesii (Douglas Fir, Oregon Pine) was first encountered in western North America, and therefore didn’t come into shipbuilding use until the nineteenth century.

Mast Assembly. The heels of the lower masts are “stepped” onto the keelson, a longitudinal timber above the keel, or occasionally onto a lower deck. Yes, that means that a considerable part (“howsing”) of the length of the lower mast is actually out of sight.

Wooden masts could be reinforced. Prior to 1800, they were “woolded”; wrapped with a rope nailed down on each turn. Later, iron bands were driven on while hot. (Longridge 164).

“Divided” masts are “doubled”; the heel of the mast above overlaps the head of the mast below. Originally the two were just lashed together. As the upper masts grew, a stronger scheme was needed. The mast below, at the “hounds,” has side projections (cheeks) on which the butt end of the mast above rests. Also above there is the “fid,” which is a bar which passes through the heel of the mast above and interlocks with the trestle trees and cross trees which support the “top” (a platform). And then above that is the cap, which has holes for both the mast above and the mast below. The body of the mast runs from the “partners” (at deck level) to the hounds, and the masthead is the part above the hounds.

A “pole mast” is one made from a single tree, whereas a “made mast” (“built” mast) is composed of several pieces of timber joined together, to increase the effective length or diameter of the mast. (While that definition would seemingly apply to a divided mast, whose sections collectively increase the length, the term “made” mast is most often used when the pieces are joined in parallel, to increase the girth.) It was not unusual for the lower topmast to be a “made” mast and the topmast and topgallant mast to be pole masts. “Made” yards were also known.

Traditional “made” masts are dovetailed, bolted, cemented (with resin), banded, and roped together to form a durable solid structure. Better glues will of course make it possible to make stronger “made” masts. (Kingston 87).

Even if there was large enough tree available to make a pole mast, its “made” mast equivalent had the advantage that one could use just the strongest parts of several trees. The disadvantage, of course, was that it required greater skill to make a “made” mast so it would resist the wind as if it were a single tree. (Douglas 140).

If the purpose were to build up the diameter, perhaps for a lower mainmast, there would be a central spindle, surrounded by side pieces, without any significant gaps. However, hollow “made” masts (or yards) are also possible.

Hollow spars. In a compressed cylinder, most of the resistance to buckling comes from the outer layers. So why not leave out the inner layers and reduce the weight? Hollow wooden spars (first yards, then masts) were introduced in the early 1800s. The first were made by carving troughs into two boards, gluing them together, and then rounding off. In the late 1800s, Herreshoff glued six staves, with trapezoidal cross-sections, to make a hexagonal cross-section. Another approach is the “box” spar, with four staves glued together. (Gougeon 65).

However, the advantage of hollow spars over natural (hence solid) spars is not as pronounced as a simple-minded application of “Euler buckling” theory would suggest. After all, trees are subject to winds, yet they don’t blow down all that often. The reason is that a tree grows so that its wood is “pre-stressed”; that is, when no wind is blowing, the outside is in tension (and the core in compression). The result is that if the wind builds up, the tree experiences greater tension on the windward side, but less compression on the leeward side, than if the wood hadn’t been pre-stressed. And wood can resist tension much better than compression. (Gordon 278-83).

The nineteenth century also witnessed the introduction of hollow metal spars. The Seaforth (1863) is reportedly the first ship with steel (as opposed to wrought iron) spars. (Anderson 194). The Thomas W Lawson (1902) had steel lower (135′) and pine upper (58′) masts (Rogers 137). Because of the effect of weight aloft on stability, twentieth-century yachts may use hollow aluminum or carbon fiber spars. Unfortunately, both are going to be a scarce material for some years after the Ring of Fire. Metal spars weren’t without their disadvantages; they couldn’t be repaired at sea (Phillips-Birt 204).

Placement of Masts. In the 1630s, the mainmast was generally midships or slightly further aft. And there was greater distance between mainmast and foremast, than mainmast and mizzenmast. (AndersonRS 5-9). On Chapman’s eighteenth-century ships, the relative positions of the masts along the waterline length are about 14%, 58% and 85%, respectively. (Creuze 41).

On most ships, the masts are single file. However, there have been exceptions. Philips-Birt (129) describes a junk with two side-by-side foremasts, and the Grangesberg (1903) had seven pairs. More recently, there has been interest in catamarans with twin masts, one per hull)(WO2003/101822).

Spar dimensions. It appears that each seventeenth-century shipwright had a rule of thumb for sizing the masts and yards, based on the keel length, maximum breadth (B) and depth of the ship. For English ships, Manwaring (1623) said that the mainmast length should be 2.4B (measured outside planking), and Miller (1655) held out for 2.5B. It is also worth looking at the 1600 and 1640 “establishments” for British warships of various sizes. Spanish and Dutch ships appeared to have somewhat longer masts, perhaps 2.67B (inside planking). (AndersonRS 15). The other masts were sized relative to the mainmast. For example, the main topmast was then about half the length of the mainmast.

The mainyard was sized with respect to the keel length, but the length/beam ratio was such that this usually worked out as 85-100% the length of the mainmast (52). The other yards were sized relative to the mainyard. The 100-gun Sovereign of the Seas (1637), 137’KL and 46.5’B, has a 113′ mainmast and a mainyard of equal size. (Lees 192). The diameters of masts and yards is proportionate to their lengths, and they are tapered.

There is much nineteenth-century data in Fincham, On Masting Ships and Mast Making (1829). Fincham’s schooner tables are reproduced by ChapelleBC (179-85) and thus are very likely to be available in Grantville.

According to a very extensive 1832 comparison of the English and French navies, an English 74 (176’LOD, 48’B) had a mainmast of 108′, foremast 98.5′, mizzenmast 73′, mainyard 96′, and main topmast 64′. Its French equivalent (183’L, 49’B) had mainmast 112′, foremast 103.4′, mizzenmast 77.8′, mainyard 98′, and main topmast 69.3′. In general, for a given warship class, the French favored longer masts than did the British. (Fincham 267ff).

Raking. When the mast is inclined slightly backward, it is said to be “raked aft.” It is rather difficult to be sure how common raked masts were in the early seventeenth century. AndersonRS (13) says that in HMS Sovereign of the Seas (1637), the foremast is vertical, the mainmast raked slightly, and the mizzenmast raked somewhat more.

One reason for raking is so that the force of the wind, acting well above the center of gravity of the ship, doesn’t cause the ship to pitch forward as much. Another is that it reduces the strain on the backstays. Unfortunately, while the rake makes the ship look faster (a bit like swept wings on a jet fighter), it actually reduces the driving force. (Alston, 67; ChapelleBC 169).

Mast and Sail Co-Evolution. In theory, each mast could bear one gigantic sail. In practice, that doesn’t work out well. It is easier to handle several small sails rather than one large one (Svensson 47), and, by dividing the sail area into multiple sails, it becomes possible to better adjust the sail area to the wind level (see below). If a sail is damaged, whether by the wind or a cannonball, it will tear, and it is better that one small sail be lost, with others left intact.

The square sails are named according to the mast on which they are hoisted, and their position on the mast. From bottom to top, they are course, topsail, topgallant, royal, sky, and moon.

Originally, each mast was once a single tree trunk (“whole mast”). As mast heights were increased (to carry additional sail) and forests were depleted of the tallest trees, it became difficult to find trees of adequate straightness, length, diameter and strength. Hence, “divided masts” were introduced in the fifteenth century. Initially, this was a two section mast, with lower mast and topmast lashed “permanently” together, and each section carrying one sail. Later it was made possible to lower the topmast for increased stability in stormy weather.

Of course, the demand for more sail and more mast length didn’t stop there. A large seventeenth-century ship’s “mainmast” might actually be three sections (the lower mainmast, the main topmast, and the main topgallant mast), each carrying a single square sail. There were as yet no sails above the topgallant.

The royal was added in the eighteenth century; OED’s first citation was from 1769 (but the sail itself is older). For the skysail, OED has an 1829 entry, and for the moonsail, 1841. Gordon (227) calls the two “an affectation of the clipper era.”

The upper sails have always substantially smaller than the lower ones, but the proportions have changed over the years. “In a sail plan of about 1600, . . . the area of the main topsail is not much more than half that of the mainsail [course], and the main topgallant sail is only about one-sixth of the topsail.” By the nineteenth century, the upper sails were more prominent. “In 1832 the main topsail was about one-tenth bigger than the mainsail, and the topgallant was more than one-third of the topsail.” (Anderson 194).

When the royal sail was introduced, in the early eighteenth century, it hung from an upper yard on the topgallant mast. By the mid-eighteenth century, the royal sail was large enough (at least on first-raters) that a royal mast was added atop the topgallant mast, resulting in a four section mast.

Beginning in the mid-nineteenth century, a new pattern emerged. Previously, it was the topmost sail which was divided, and then the mast was divided so the upper division could be made even larger. But the new pattern was to divide the course and the topsail even though there were sails above them. This was to have the benefit of increased speed while minimizing crew requirements. (Lardas). The corresponding mast was not divided.

Initially, a light spar was attached to the middle of the new divided topsail; the upper part could be released so it would be double over the spar, which would hold up the lower part. Forbes (1841) and Howes (1853) developed two different systems for hoisting and lowering the divided topsails (Svensson 48).

In the late nineteenth century, there was a new trend; mast heights were reduced, but sails were made broader, and the ships were made longer to accommodate additional masts. The extreme example of mast proliferation was probably the Grangesberg (1903), 440 feet long, with seven pairs of masts. (Rogers, 152).

Sail materials. The ideal sail material would be inexpensive, light, impermeable to air, smooth, and resistant to strong winds, enemy fire, ultraviolet radiation and rot.

In the seventeenth century, the traditional sailcloth is linen, made from flax. Unfortunately, linen is stretchy (which impairs the aerodynamic performance of fore-and-aft sails) and leaky (Gougeon 31, 94). That leakage was especially problematic when the wind was weak, and the sailors would dampen the sails so they would shrink and tighten.

Hand-woven cotton sails were first used in the early nineteenth century. While they were less stretchy and leaky than linen, they were expensive. The economics changed when the power loom was introduced in the 1830s, and there was also the bonus that machine-woven cloth was tighter.

Canvas sails are perhaps 20% permeable. (GEC). Beginning in the early 1900s, sails were singed or varnished to reduce their resistance to airflow. (Gougeon 98). Twentieth-century sail fibers, which offer greater strength, and less weight and permeability, include polyester (Dacron®), nylon, aramids (Kevlar®), polyethylenes (Spectra®), and carbon fiber.

Sail Construction. Sails aren’t made of a single cloth. In the late seventeenth century, William Penn (of Pennsylvania fame) and William Bolton persuaded the British Admiralty that it was better to use narrow cloths, and hence many seams, to minimize stretch. (Phillips-Birt 267).

The sails actually varied in weight; you used a heavy sail in a storm and a light sail when the air was barely moving. The Admiralty #4 canvas, which would be used for topgallant sails (Kipping 68), weighed 36 pounds per bolt (2′ x 117′) (EB11/Sailcloth).

Look closely at sailcloth and you see that it is a grid, with the warp threads being those which originally ran with the roll, and the weft threads crossing them perpendicularly. It resists a pull parallel to the warp or weft threads, but yields when the pull is on the diagonal.

Unfortunately, prior to the nineteenth century, sails were constructed so that the sails were pulled obliquely to the grid, and therefore stretched . . . reducing their crosswind and upwind performance because they couldn’t be given the right shape. (Gordon 251-5).

“Ripstops”—reinforcement threads, arranged in a cross-hatch pattern spaced 5-8 mm apart—came into common use in World War II, in nylon parachutes. The ripstop concept can be applied to other fabrics, including cotton.

Fore-and-Aft Sail Shape. Much ingenuity has been devoted in this century to improving and maintaining the airfoil shape. You want the sail to bulge near the leading edge, and flatten at the trailing edge. Short horizontal battens running inward from the trailing edge can be used to stiffen the latter, making it stay flatter. Or you can use full-length battens, which vary in thickness so that, when compressed at the ends, they form a good airfoil shape. (Gougeon 97).

Just to complicate matters, for smooth airflow, you want a deep airfoil at low wind speed and a shallow one at high speed. So you want to regulate the curvature of the sail. On yachts, the lower part of the sail can be flattened by an “outhaul” and the upper part by a bending mast (112-9).

Square Sail Shape. Seventeenth-century sails were “baggy,” so the wind must be at least three compass points (34°) behind the sail for it to fill properly. The efficiency of the “flat cut” sail wasn’t generally appreciated until the America‘s 1851 triumph. (Harland 60).

Sail Area. There are great differences in sail area among ships, from small craft, like the 30-ton pinnace Virginia (1607) with 1130 ft2 canvas (BakerCV 60), to the 11000-ton Preussen‘s 60,000 (Villiers 1) and the ill-fated megaclipper Great Republic‘s initial 144,000 (Rogers 124). A post-Napoleonic “first rate” warship would probably carry about 30,000 ft2 (Fincham 251, 267ff).

The greater the sail area, the greater the amount of wind energy which can be captured and used to propel the ship. There are really only three ways to increase sail area:

—vertically, make the masts taller and have them carry either taller sails or more sails

—horizontally, make the yards and thus the sails wider, or stick additional sails out on booms

—longitudinally, add more masts, each carrying sails.

Vertical expansion had certain advantages. Because of wind shear, wind speed increases with height; at 100 feet it is likely to be about 40% stronger than at ten feet (Raskin). A French 120-gun warship (1832) had a mainmast 130′ long (Fincham 267ff).

Unfortunately, the vertical expansion of sail area is limited by the strength of the available spars. It’s also more difficult to handle (that is, raise, trim, reduce or lower) a sail that’s 100 feet above the deck than one closer to the surface. It takes time to ascend to the sail’s level, and the ship’s pitch and roll will be more disturbing. Of course, machinery could alleviate this problem, but it would increase weight aloft.

Moreover, lengthening the masts delivers a triple punch to ship stability. First, the “center of effort” of the sails is higher, which means the wind is acting at the end of a longer lever arm, and increasing the tendency of the ship to pitch and heel in response. Typically, for a ship- or bark-rig, the height of the “center of effort” of the sails above the water was 1.5-2 times the vessel’s breadth. (White77, 495). For the 110-gun Queen (1839), 59′ breadth, the COE was 91′ above the waves (Fincham 251).

Second, if the yards are unchanged, the sail area is presumably greater than if the mast were kept short.

Third, the more weight there is aloft, and the higher up it is located, the higher is the center of gravity of the ship, and the less the stability. If you add ballast to neutralize the effect on stability, then you have further increased the mass of the ship, and will probably also need to increase its displacement to compensate. The net result could be a lower maximum speed. Concerned with stability, Bougier (1746) urged that the mast be shortened “prodigiously,” while making the yards longer to compensate. (Monceau Supplement 26).

Horizontal expansion is limited by the strength of the yards. Moreover, wide yards cause more “blanketing” of sails further forward, and are harder to turn quickly if the wind shifts.

The longitudinal expansion is limited by the same factors which limit the length of the hull (see part 2). In additional, for a given length of hull, there are limits to how many masts you can squeeze on without the yards fouling each other (Longridge 156), the aft sails shadowing those ahead, the hull hogging under the concentrated weight of the masts, etc.

In general, I believe that in the new time line, horizontal and longitudinal expansion (facilitated by iron) will be favored over vertical expansion.

The types of sail carried also affected the sail area available. Chappelle comments, “no rig of the fore-and-aft variety could be made to stand if it contained the same area of sail as the square rig.” (ChapelleHASS 47).

Adjusting Sail. When in light air, the crew will hoist every scrap of canvas that might catch some wind. A peculiar seventeenth-century practice for increasing sail was bonneting. This was lacing an extra piece of canvas (the bonnet) to the foot of an existing sail, usually the fore and maincourses, the mizzen, and perhaps the spritsail. The bonnet was usually one third the area of the main body of the sail. A large ship might have another piece, a drabbler, lashed below the bonnet of the courses, and one third the bonnet’s area. (BakerNM 114).

It was also possible to rig a spar onto an existing yard, to hang a sail over the side of the ship. These “studding sails” were introduced in the sixteenth century (Phillips-Birt 201), but weren’t really common until the nineteenth. (Svensson 29, 43).

When winds increase in force it becomes dangerous to maintain full sail. The sail may be ripped or blown away, and the mast can be carried along with it. If the sails remain intact, the force of the wind could also force the ship to pitch or roll to a dangerous degree. Hence, it is necessary to be able to reduce sail quickly and efficiently.

Your basic choices were to take down the sail, furl the sail (roll or gather it up on its yard) or to reduce its area in some way.

In the early seventeenth century, you would first furl the topsails, which were considered light sails, then remove the drabblers and bonnets from the lower sails, and finally proceed under just the forecourse.

Reefing was another method of reducing the area of the sail. A square sail would carry one or more horizontal reef bands, essentially a strong strips of canvas sewn on both sides of the sail proper. Each reef band bore a row of reef points (cords) and corresponding eyelets. The reef points passed through the sail and were knotted so one end hung ahead and the other behind the sail. If a sail was to be reefed, the appropriate reef band was pulled up close to the yard, and the ends of each reef point were crossed over it, and knotted. There were a number of variations on the theme (Harland 139).

The history of reefing is a minor nautical mystery. We know that reef-points were in use from the thirteenth century to the beginning of the sixteenth century, but that they vanished for a century, reappearing around 1660. First topsails, and by the end of the seventeenth century, also the courses, could be reefed. (Anderson 146). Thereafter the bonnet fell into disuse (it being faster to tie reefs than to untie bonnets). (Id.). The 1631 Ring of Fire occurred during the Reefless Interregnum. However, in my story “Stretching Out, Part 4: Beyond the Line,” reefing is installed on a ship which leaves Hamburg in December 1633. So the up-timers have already had an impact on sailing ship design.

Once reefing was rediscovered, it became customary to first furl the lower sails, then reef the topsails. (BakerNM 114; Phillips-Birt 227). The number of rows of reef points in the topsails increased from one (1650s) to two (1680s) and then to four (eighteenth century). When the divided topsail was introduced, the number of rows dropped down to one or two again. (Mondfeld 260).

Beaufort proposed, not only a wind scale, but a matching policy for adjusting sail: carrying full sail (including royals) in a fresh breeze (force 5, 16 knots), single-reefed topsails and topgallant sails in a strong breeze (force 6, 22 knots), double-reefed topsails in a moderate gale (force 7, 28 knots), triple-reefed topsails in a fresh gale (force 8, 34 knots), close-reefed topsails and courses in a strong gale (force 9, 41 knots), close-reefed maintopsail and reefed foresail in a whole gale (force 10, 48 knots), storm-staysails in a storm (force 11, 56 knots), and no canvas at all in a hurricane (force 12, 64 knots). These guidelines were adopted by the Admiralty in 1838. (Raper 133).

Ships also reduced sail before going into battle, as most of the crew was needed to serve the guns. Typically, the courses would be clewed up (lower corners raised), and the principal “fighting sails” were the topsails and jib (Coggins 731). Smith’s Seaman’s Grammar (1627) refers to a chase stripping himself to “fighting sails.”

The divided topsails of Forbes and Howes could be shortened quickly; in Howes’ system, the upper sail fell in front of the lower sail when the halyards were released. In the nineteenth century, mechanical reefing and furling systems were developed. In Cunningham’s roller reefing (1850), the yard rotated to wrap up (and thus shorten) the sail.

Sail Blanketing. One sail can prevent the wind from reaching another. Sail interference will be at its worst when the ship is running with the wind, and when reaching, it can be reduced by bracing more directly. But it’s quite evident from the discussion of spar dimensions and mast placement that the masts are so close together, and the lower yards so wide, that the main course is surely going to “shadow” (block wind from) the fore course no matter what the brace angle, and that there will be a lesser degree of shadowing of other foresails by mainsails, and mainsails by mizzensails.

The shadow isn’t absolute; the aft sails will let some air through, and the air can swirl around one sail and nudge against another. But the overall effect of permeability and shadowing is probably to reduce overall sail efficiency to something like 50% of the nominal sail area. (Lindmark).

Metal hulls will allow building longer ships, and thus increasing separation between masts.

Just to complicate matters, the interaction between two sails can be favorable; wind funneled in the “slot” between the sails and increasing lift.

Cordage. The cordage was hemp until the 1850s and 1860s, when it was gradually replaced with wire-rope (Anderson 193-4; Phillips-Birt 269). The problem with hemp was that it stretched, creating an unsteady rig. Phillips-Birt asserts that wire rigging was critical to the performance of the nineteenth-century tea clippers. Corrosion-resistant stainless steel wire was introduced in the early 1900s. Nelson’s flagship, HMS Victory, had 26 miles of cordage. (Victory).

Rigging Strength. The wind presses on the sails, thereby applying a force to the yards and masts. Masts are tall and thin, and it wouldn’t take a lot of wind to knock the masts over, or bend them to the breaking point, if they weren’t stabilized by the standing rigging. The latter causes the sideward wind force to be redirected down the mast; masts are made to resist such compression.

Masts usually fail by buckling. The center of a mast does not contribute much to buckling resistance so you may want to replace solid masts with hollow ones. You can either use larger diameter hollow masts of the same weight (for more resistance) or the same diameter hollow masts (for less weight aloft). (Gougeon 63).

On a square-rigged mast, all the stays run behind, so they can pull to counter the forward push of the wind. If the wind swings about to strike the front of the sail, then an aerodynamic jujitsu ensues; the stays help the wind knock down the mast.

Standing Rigging. The purpose of standing rigging is to relieve the stress on the masts and yards created by wind force. The mast is stabilized by stays: forestays in front, backstays behind, and “shrouds” on either side. For a mast bearing square-rigged sails, the backstays are of particular importance, because the wind tries to bend the mast forward. Each mast bears at least one pair of backstays; these run aft and to the sides of the ship. The forestays run directly forward.

An unstayed mast will bend in response to the wind. When that happens, it compresses on the leeward side and stretches on the windward. Wood is weak in compression and hence an unstayed wooden mast must be pretty thick or it will rupture. (Doubling the diameter increases the maximum load eightfold. Carbon fiber is about 27 times stronger than Douglas Fir, so an unstayed carbon fiber mast can be one-third the diameter of a fir one.)

If stays are attached to the mast, then instead of the mast bending, the stay is stretched, and the mast is axially compressed. In effect, instead of the mast bearing the entire force of the wind, some is now borne by the stays.

The stays, ideally, are made of material with a high tensile strength (stretch resistance). The same tensile load can be withstood by, say, a 6 mm wire, a 14 mm modern rope, or a 40 mm natural rope. (Classic Marine)

You also try to have as a big a “staying angle” (the angle between the stay and the mast) as possible, because that minimizes the tension on the stay. For forestays and backstays on a large ship, that isn’t hard (the bowsprit in front and the bumpkin in back help). However, it is harder to attach the shrouds so as to achieve a favorable staying angle, especially on a narrow-beamed ship. The trick was to attach the lower end of the shrouds to projections (chainwales, channels) hanging outside the ship’s hull. They are mentioned in John Smith’s 1627 Sea Grammar (228). Modern yachts use spreaders.

A stayed mast, being axially compressed, tends to fail by buckling. Double the length of a column and the load required to buckle it is only one-quarter. So, even with stays, there is still incentive to reduce the length of masts.

The buckling load also depends on the “fixity” of the ends—that is, are the ends restrained from moving and from rotating. In the seventeenth century, it was customary to fix masts at both deck and keel, which creates a fixed end and increased the allowable buckling load. (The catch is that if the clamping is out of alignment, the mast is bent and the allowable load is reduced.)(Gordon 286-90).

For fore-and-aft sails, the standing rigging used to be attached to the top of the mast, because the sails were attached to loose-fitting hoops that slid up and down the mast. By 1910, yachts were using “sail track.” The sails were equipped with slides that could engage a rail fastened to the aft side of the mast (or a groove integral to the mast). Sail track made it possible to attach stays to lower points on the mast, or to spreaders (crossarms) on the mast, and thereby distribute the wind load. And that meant that masts could be made lighter. (Gougeon 60-1; Lehar).

The introduction of metal spars will make possible a reversion to the pole mast. This could be combined with sail track so that some sails could be raised and lowered from the deck.

Running Rigging. This controls the shape, orientation, and size of the sails. The ropes used actually vary depending on the type of sail. Generally speaking, halyards (“haul yards”) and downhauls are used to hoist up or lower the yards. Slings and trusses attach them to the mast. Braces turn the yards and lifts tilt them. The head (upper edge) of the sail is “bent” (hung) on a jackstay which runs along the top of the yard. Sheets attach the lower corners (clews) of the upper square sails to the yard below. Clewlines, leechlines and buntlines are used to pull the sail back up to the yard, preparatory to furling it. Bowlines hold tight the windward edge of the sail when the ship is sailing close-hauled.

Bear in mind that considerable force might be needed to manipulate the yards. The 82′ long, 22″ diameter main yard of the clipper Flying Cloud, when carrying sail, weighed over two tons. (Shaw 35, 180).

Machines could be used to assist with the arduous task of operating the running rigging. The capstan (vertical barrel) or windlass (horizontal barrel) was the principal machine on the ship. The HMS Victory could put a hundred men on the capstan bars, and pretty much lift anything that way (Longridge 63). The sailors pushed on the capstan bars (levers), and this drew a rope or chain wrapped around the barrel. The ship also had several winches, used for smaller jobs. A winch is really a windlass equipped with a crank in place of a bar.

In the nineteenth century, steam winches were introduced; the Great Republic (1853) had a fifteen-horsepower steam engine to hoist sails, etc. (McCutchan 38; Rogers 137).

Weight of Rigging. The thirty gun French frigate Renommee (1744) carried 40,000 pounds of masts; 6,444, of blocks; 24,444, of cables and hawsers; 7,998, of sails and cases; and 17,282, of cordage, totaling about 89,000 pounds rigging, including spares. In contrast, its hull weighed 701,388 pounds, and the load displacement was 1,571,556 pounds. (Monceau 50). An English “74” (1832) bore 260 tons rigging; its load displacement was 3043 tons. (Fincham 267, 272). So rigging is 5-10% displacement on warships.

Bracing. Bracing is turning a yard to more directly face the wind. Because of the standing rigging, the yards bearing the courses couldn’t be turned closer to broadside than about 27-30° (White 509). Harlan says three points (34°); together with the three points needed to fill the sail, that explains why the square-rigged ship couldn’t be sailed closer than six points of the wind.) The spread of the rigging for the upper sails was less, and hence they could be turned more sharply, each perhaps half a point more than the sail below it. A fore-and-aft rigged sail could brace its yard more sharply (White says 13-17°, Harland one point) of the keel line, and hence a fore-and-aft rigged ship could sail as close as four points to the wind.

It is possible to alter how the standing rigging is arranged in order to make sharper bracing possible. A ship in the “Experimental Squadron” (1827) could brace to 19°, and there is a modern “mainmast barkentine” (Pelican) which achieved a similar result by leading the backstays further aft, and lowering the attachment point of the main forestay. (Goode).

The bracing angle is actually a compromise between maximizing the force on the sail and minimizing leeway. “Modern” practice is that if you are sailing close-hauled, you brace as sharply as possible, but otherwise the yard is positioned so as to bisect the angle between the wind and the bow. Thus, for a beam wind, the yards would be braced to 45°. (Harland 62).

Bipod and Tripod Masts. The demand for standing rigging can be reduced by strengthening the mast. Simply increasing the diameter of the mast is one approach. However, the ancient Egyptians used an “A-frame” style bipod mast, which of course increased the lateral stability of the mast, without the need for shrouds (Philips-Birt 25). Of course, it also increased the weight aloft. A carbon fiber bipod mast has been used recently on a catamaran to support a fore-and-aft crab claw sail. (Seluga). An advantage of the bipod support is that the effect of the mast on wind flow over the sail is reduced.

Tripod masts are also ancient (41), and may well have been used by Asian seafarers in the seventeenth century. What is certain is that in the early nineteenth century the Samal of Mindanao (Philippines) had oared gunboats (garays) with a single unstayed tripod mast carrying a large quadrilateral sail. These could sail much closer to the wind than a conventional square-rigger. (Francis 245-7). The paduakans of Indonesia were small merchant ships (up to fifty tons) with a tripod mast and a lateen sail. (St. John 184).

The British Navy equipped the ill-fated HMS Captain (1869) with revolving turrets, and since the ship carried 50,000 square feet of sail, it had three tripod masts. These minimized standing rigging, and thus maximized the arcs of fire. Unfortunately, they also would have increased the weight aloft, and this (and the large sail area) probably contributed to its capsize in 1870. (Gordon 228-9; Wikipedia).

Junk (slatted lug) sails. The Chinese had a unique solution to the problems of dividing the sail area for easy handling, and of reducing sail. The junk sail was somewhat like a giant Venetian blind with rectangular fabric panels, connected along their long edges by wooden, slightly inclined slats (battens). Stays, if present at all, run only from the top, so they didn’t interfere with the movement of the slats (The sail may therefore be turned almost ninety degrees). The sail was positioned across the mast (like a Western lug sail), with about one-quarter of the sail area forward of the mast, three-quarters behind.

The Chinese sails could be hung on stayless masts because the Chinese are willing to tolerate the bulging of the sail cloth between the battens when the wind is strong. Indeed, they may deliberately relax the canvas so that the mast isn’t blown down. (Gordon 123-6). The mast is flexible.

On junk sails, the battens (which are functionally equivalent to Western yards) are made of bamboo. Western yachtsmen who have experimented with junk sails have tried fiberglass and ABS pipe. (Kasten).

The junksail could easily be shortened or even hauled in much like an upside-down Venetian blind, without sending topmen aloft. It is also self-tacking and self-jibing (the running rigging doesn’t need to be adjusted). Thus, it is a very labor-efficient rig.

The junk has good performance in light air, and also has a high factor of safety in heavy weather because of the lack of stressed stays. It runs and reaches well. The junk’s main disadvantage is that it’s not as efficient as a modern Bermuda rig when clawing to windward. (Frankel 216).

Gougeon provocatively says, “one wonders if a clipper hull, had it been fitted with junk-type sails, could have been even faster. It almost certainly could have been manned by about a third of the crew required for the Western-type rig.” (19).

Tops. The tops, which were just above the “hounds” of the lower masts, had three purpose; they were useful workplaces for the sailors aloft; they made it possible to increase the “staying angle” for the shrouds; and they were firing platforms for marine snipers. Tops existed in the seventeenth century; they are mentioned by John Smith.

The tops are surprisingly big. In the early nineteenth century, the main top’s width was one third the length of the main topmast, and its length was three-quarters its width. For the HMS Victory, that worked out as 23’6″ by 17’6″. The fore top was almost as large, and the mizzen top about 70% the size of the main top. (Longridge 171).

Mast shape. In small fore-and-aft-rigged ships, the aerodynamic characteristics of the mast are important; a mast with a gaff sail is the leading edge of the airfoil. It is now customary for the masts to be streamlined. (Gougeon 66), and it is even possible on some ships to rotate the mast so the “teardrop” remains aligned with the sail. If the mast is elongated fore-and-aft, you get a “wing mast,” which on some yachts is as much as 40% of the “sail” area. (98-9, 106).

Hard Sails

Periodically, alternatives to the traditional soft sail have been considered. Here, we will take a look at wing, kite and windmill sails.

Wing Sails. The classic fore-and-aft sail is flexible, and its shape is a function of how it is attached to the spars, and the speed and direction of the wind. It is possible to construct a sail which is rigid, so it has a fixed airfoil shape. Imagine an airplane wing stuck on deck so its tip points upward and the front of the wing faces forward. What would become vertical lift on an airplane wing is forward “lift” on a wing sail. The sail is rotatable to get the best angle of attack on the wind, and will also have a trailing flap which can be adjusted to produce more lift. The wing sail can be seen as the extreme development of the wing mast, in which the “cloth” sail is dispensed with.

Since tacking can put the wind on either side of the sail, either the wing sail must have a symmetrical profile (unlike an aircraft), or there must be a means, such as a movable batten structure (USP4624203), for reversing the profile after a tack.

The effective “airfoil thickness” of a classical sail is its “billow,” and is small but variable. A thick wing sail gives more lift than a classical thin sail if the “Reynolds number” for the sail is higher than 60-120,000. The longer the sail (parallel to the wind), and the faster the wind, the higher the Reynolds number, and it’s 140,000 for a 1 meter sail in a 2 meter/second wind. It’s fairly typical for wing sails to have double the lift of a thin sail. (Raskin).

You wouldn’t use a solid sail anymore than you would a solid mast; the interior doesn’t have an aerodynamic effect and its contribution to bending resistance is small. But even if the wing sail were hollow, it would have a high ratio of weight to area if the surface were completely made of wood or metal. So, we have two choices. We can wait until glass- or carbon fiber-reinforced plastics are available, or we can compromise and stretch a fabric across a scaffolding which approximates the desired shape.

Most ships with wing sails are small racers; indeed, they dominate the international C-class catamaran (300sf sail area) championships (Killing). However, there have been a couple of recent commercial vessels built to test the concept: the 1980 Shin Aitoku Maru (236 foot tanker; 1600 deadweight tonnes; 40 by 26 foot sails; 12 knot maximum speed) (Time) and the 1985 Usuki Pioneer (26,000 deadweight tonnes). The latter actually has a hybrid sail; a rigid sail with a soft sail attached by a boom (Fujiwara). Despite lower fuel consumption, freight costs actually were higher than for a conventional powered ship, so these commercial wing sails didn’t catch on (Cavendish 2013; O’Rourke).

Kite sails A kite sail is attached by cables to the ship, and pulls it along, most likely from the bow. The principal advantages of the kite sail over a conventional sail are 1) masts are eliminated, 2) heeling movement (the force acting to tilt the ship laterally) is reduced (because the kite is tethered at deck level), 3) the wind speed at kite altitude (150m) is significantly greater (~25%) and more stable than at ship level (10m), 4) interference of the kite control lines with cargo handling, or cannon fire, is minimal compared to the effect of a conventional sailing ship’s rigging.

Chinese kites were brought to Europe in the late sixteenth century, and our buddy Athanasius Kircher showed some interest in them (Needham 281). There was a brief flurry of experimentation with kite sails by an early nineteenth-century preacher, George Pocock. He used kites to tow a carriage (1828), making a speed of 25 mph, and even a yacht in Bristol Channel. (Weldgren).

Kite sails are still quite experimental, but in 2008 the M/V Beluga Skysails made a 12,000 mile round trip using a computer-controlled 160 square meter towing kite, deployed at an altitude of 100-300 meters, to save about 10-15% in fuel cost. Its kite sail is supposed to operate at winds of Beaufort Force 3-8, and it can tow the ship as close as 50 degrees to the upwind direction. (Skysails).

To make use of kite sails, we would need to develop a kite, a tether, and means for launch, control and recovery. It’s critical to minimize the weight per unit sail area and tether length. The lower that weight, the lighter the wind the kite can stay aloft in.

The parafoil kite (invented 1963) is a soft kite made of a strong, light, stiff material (e.g., nylon) and inflated into an airfoil shape by the wind. Unit weight for modern parafoils is 0.01 psf, so they can make do with 2 knots wind.

The semi-rigid kite is “fabric” (fiber-reinforced polyester film) stretched over ribs, and is inflated with a buoyant gas. In the old time line that was compressed helium, but in the 1632 universe it is more likely to be hydrogen. Unit weight is 0.1 psf and the necessary wind is 5 knots.

The rigid kite has a continuous hard surface similar to the wings of an unmanned aerial vehicle, like the Predator; the Golden Hawk UAV uses carbon composite. Unit weight is 1 psf; 15 knots wind is needed. However, the rigid kite offers the best lift-to-drag ratio.(Roesler).

I can also imagine balloon-kite combinations, in which a kite is suspended from a helium or hydrogen balloon, allowing the kite to be launched even when there is no ground wind.

We also have to worry about the weight of the tether and control lines, per unit length, and their tensile strength. Modern kite sails are tethered and controlled by lines made of high tech material such as KEVLAR aramid or SPECTRA ultra high molecular weight polyethylene fiber. These have tensile strengths perhaps ten times that of steel, and less than one-fifth the weight.

Of course, those materials won’t be available for a long time. Silk is available, and compares respectably with steel, but it’s a luxury fiber. It is possible that within a few years we could use copper or steel wire; we want steel wire for standing rigging anyway. Nylon is something our chemists are making progress toward. Some sort of crude carbon fiber is also possible.

In modern kite sail systems, deployment, control and retrieval are automated. The power developed by the kite can be increased (perhaps doubled) by “flying patterns,” such as figure-8s, under the command of an autopilot. In the 1632 universe, we would probably have to make do with manual control. But of course conventional sailing ships need to adjust their sails in a variety of ways.

Windmill Ships. Why would you put a windmill on a ship? The general idea, at least initially, was so that the ship could sail directly upwind. The windmill (more precisely, wind turbine) would face the wind, the wind would cause the blades to rotate about the hub, and through gearing, this would turn a propeller.

The idea is a fairly old one; I found an issue of The Mechanic’s Magazine ridiculing an 1836 British patent as a “mere transposition of a common wind-mill from land to ship-board, and the substitution of paddle-wheels for millstones.” It added that it was “not the first by some score, of such plans . . . .” Of course, the modern wind turbine is quite a bit more efficient than even an early nineteenth-century windmill.

The upwind sailing advantage is perhaps not very important. While a sailing ship can’t sail directly against the wind, one zigzagging at 45 degree tacks off the wind is still probably going to make better speed to windward than a windmill ship. At least, that’s been the experience with the few prototypes; Bose’s Falcon (1986) made five knots in a fifteen knot wind; and Bates’ Te Waka (1980) did seven in a fourteen knotter. (Sinclair).

The theoretical power developed by a wind turbine is proportional to the area swept out by the blades (not merely the total blade area) and the cube of the wind speed. The maximum efficiency is 59% (Betz’ law). This is further reduced by friction at the hub, or in the transmission system, to 40-50% for a modern rotor.

There are several design parameters for the wind turbine: the number, length, width and shape of the blades, the pitch of the blades relative to the swept area, the angle of the blade axis relative to the hub mast, the angle of the hub mast relative to the deck, and the distance of the hub from the base along the mast. A two-bladed turbine is a bad idea as the forces vary sharply as the blades turn, so I would say that at least three blades is desirable. The main reason to increase the number of blades further is so that the turbine can catch a light wind, but the problem is that the maximum thrust will be reduced.

Twentieth-century materials technology (aluminum; glass or carbon fiber reinforced composites) has made possible longer, thinner and lighter blades, with less drag, but of course the 1632 universe options will initially be more limited.

It has been argued that the equivalent of reefing (taking in sail) in a wind turbine ship is easier and faster than on a conventional sailship; you can change the pitch of the blades. That presumes having some electromechanical linkage to accomplish this.

It’s important to recognize that those seeking to exploit kite and windmill sail technologies in the 1632 universe will not have the usual advantage of knowing, at least in broad terms, what works and what doesn’t. And they will have the usual disadvantage of a more primitive infrastructure; you can’t just order a delivery of carbon fiber to your door. But a story could have these technologies touted by a crackpot or a con artist, and, who knows, perhaps some author will know how to make them work.

Hybrid Propulsion

From time to time, sailing ships have been equipped with an auxiliary propulsion system so they could make way even in a calm. In the sixteenth-century Mediterranean, there were “brigantines” with two masts and 30-34 oars, and “frigates” with single mast, and a smaller number of oars (Maxwell, 92). Oarsmen could be placed on the upper deck, above the gun deck, or on the gundeck in-between the cannon. The standard sail was the lateen.

The oar-sail hybrids survived longest in the Mediterranean, the Black Sea, and the Baltic. Peter the Great built them in 1694 to use against the Turks, and in 1703 to attack the Swedes. The Swedes returned the favor. Throughout the eighteenth century, both the Russians and the Swedes found them useful in shallow, heavily shoaled waters off the coast of Finland. (Anderson 175).

Unfortunately, oar power requires a large crew, and is short on stamina. A more modern form of auxiliary propulsion is the steam engine. The auxiliary steam engine could also be harnessed for purposes other than propulsion, i.e., operating rigging or moving cargo.

Of course, the engine and fuel add to construction and operating costs, they take up space which otherwise might be devoted to cargo or armament (although coal acts as a form of armor), they also add to the weight of the ship (and therefore reduce its acceleration), and they alter the sailing qualities of the ship. In the latter regard, the screw propeller was usually deemed better than a paddle wheel.

At the other extreme we have steamships (or motorships) with auxiliary sail, such as the kite sails discussed above. There, the purpose of the sail is to reduce fuel consumption, wind power being free. Of course, the rigging has to be carried the whole voyage, whether used or not, and this has an energy cost. And if it couldn’t be put in the hold during steam operations, then it would be increasing windage when heading upwind, and reducing stability (by virtue of the weight aloft) that a pure steamship could avoid.

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I close this part with some suggestions as to when various innovations in rigging might be introduced. Please don’t make the mistake of putting them all on one ship!

Proposed Rigging Timeline

Prototype Introduction

Category

Innovations

1633-35

Uses Traditional Rigging Materials in New Way

—staysails on large ships

—reefing sails

—dividing sails (two yards on same mast unit)

—royals

—narrower sailcloths, better orientation

—ripstops in sails

—hollow wooden spars

—unstayed tripod masts (maybe)

—aerodynamically shaped spars

—Chinese lug sails (see below)

1634-37

Requires Cheaper/More Abundant Supply of Down-Time Material; Consistent with 19c Practice

—machine-woven cotton sails

—-hollow wrought iron or steel spars

—longer ships (iron or composite) with five or more relatively short masts

—wire rope standing rigging

—steam winches

—steam/sail hybrids

—sail handling mechanisms (roller reefing, sail track, etc.)

—wing sails (fabric over wood scaffold) (within 19c capabilities)

late 1630s and beyond

Requires 20c Material

—artificial fabric sails (need organic chemical industry)

—aluminum spars (need bauxite, cryolite, electricity)

—carbon fiber spars

—wing sails (GRP)

???

Speculative Tech

—windmill sails

—kite sails

May the wind take you where you wish to go.

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About Iver P. Cooper

Iver P. Cooper, an intellectual property law attorney, lives in Arlington, Virginia with his wife and two children. Two cats and a chinchilla rule the household with iron paws. Iver has received legal writing awards from the American Patent Law Association, the U.S. Trademark Association, and the American Society of Composers, Authors and Publishers, and is the sole author of Biotechnology and the Law, now in its twenty-something edition. He has frequently contributed both fiction and nonfiction to The Grantville Gazette.

 

When not writing (or trying to get an “orange blob” off his chair so he can start writing), he has been known to teach swing dancing and folk dancing, or to compete in local photo club competitions. Iver adds, “I can’t get my wife to read my fiction, but she has no trouble cashing the checks.”

Iver’s story “The Chase” is in Ring of Fire II