The Middle Ages Technological Revolution

If you are a history buff, it may surprise you to hear the words ''Middle Ages'' next to the words ''technological revolution.'' After all, the Middle Ages in Europe were times of social stagnation in many ways. People's lives did not change much from one generation to the next the son pursued the same craft as his father, and the vassal owed liege to his lord, down many generations. On land, indeed, life stumbled on unchanged by much in the way of technological advances during this period. At...

Breaking Waves

The equation for the speed, c, of a surface wave across the ocean is well known to physicists and is rather complicated. In deep water this equation reduces to a simple form that we have already encountered, c Vgm p. So, in deep water the speed of a wave depends on wavelength, l. This fact influences the hull speed of a ship, as we have seen. In shallow water, the complicated equation for c reduces to a different limit, c Vgh, where h is the water depth. So, in shallow water the wave speed does...

Lot of Torque

We construct lines from each vertex to the middle of the opposite side and look for the point of intersection. For two sails, as in fig. 5.2, the CE of each sail is found. The overall CE is somewhere along the line joining them, depending on the relative size of the sails. 2. For such a hull cross section, there is little restoring force (called the righting moment) because of the shifting center of buoyancy, discussed later in this chapter. Including hull righting moment would significantly...

The Story So

At this point I can briefly summarize the results of the analysis of sailing performance for square-rigged and Bermuda-rigged vessels heading downwind, across the wind, or upwind. If we compare the plots in figures Figure4.6. Creating wind If lift drag ratio L D is above the bold line for a given heading angle avw, Sparrowhawk creates her own wind and her initial acceleration increases. Otherwise she does not, and her initial acceleration slows down. The thin line applies for the sail trim...

Keel Appeal

In chapters 1 and 3 we encountered the structural keel the long structure that extended along most of the underside of a wooden boat and provided the foundation on which the boat was built. Here, we will examine the hydrodynamic keel the underwater foil (hydrofoil) introduced in modern sailing vessels to improve sailing performance, in ways that I will now discuss. The modern keel serves two or three separate functions that are not entirely compatible with each other. So, again, we are talking...

Sail Plans

The first school of oceanic navigation was established in Portugal in the early fifteenth century.* Clearly this action was part and parcel of a new view of the world with sharp eyes fixed on the horizon, the Portuguese sent out their little caravels to write the first chapter of the Age of Exploration. Madeira, the Azores, and the New World rounding the Cape of Good Hope and across the open ocean to India Southeast Asia, *This chapter covers the period from about 1550 to 1880, which spills...

Dutch Treats

From galleons to ships of the line I have taken you right through the mainstream of the evolution of Age of Sail warships. There were differences in design, and within a given category of ship, there were national variants. Thus, an English ship tended to carry more guns than her French counterpart (and enemy, usually, in the Age of Sail). So, the English vessel would sail deeper and may have been unable to open the lower gun ports in heavy weather. (For this reason the French would remove some...

Viking Longsh ips

I will take the justifiably famous Viking longship as the apogee of the northern European clinker-built strand of the Atlantic tradition. Of course there were other types of clinker-built ships, but discussing all of these would risk turning this chapter into an encyclopedia of nautical evolution. I will here utilize the Viking longship as a metaphorical clothesline on which to hang the showy outer garments of clinker-built technology should you be inclined to delve into the many and varied...

Sailing History

Anderson. A Short History of the Sailing Ship. New York Dover, 2003. Archibald, Roger. Six Ships That Shook the World.'' Invention and Technology 13, no. 2 (Fall 1997) 24-37. A detailed account of the American super-frigates, which include the USS Constitution. Bass, G. A History of Seafaring. London Thames and Hudson, 1972. Bedini, Silvio A., ed. Christopher Columbus and the Age of Exploration. New York Da Capo Press, 1998. An inexpensive paperback, this 800-page...

Flying through Water

There are capillary waves the tiny waves that you see often superimposed on regular water waves with wavelengths of maybe an inch. These guys are governed by the physics of surface tension, rather than gravity, and the formula for their speed is different. Also, the equation given for c applies strictly for waves in deep water. We will see in chapter 7 that wave speed in shallow water is different. 2. A vertical arrow in fig. 6.2 corresponds to the buoyancy force of the...

Paper Games and the Coanda Effect

There is a well-known demonstration of the Bernoulli faction's viewpoint that lift is due to increased velocity in the streamlines. This demonstration is interesting for three reasons (1) it has nothing to do with increased velocity in the streamlines (2) a simple counterexample clearly shows that it has nothing to do with increased velocity in the streamlines and (3) it in fact supports the view of lift by the opposing momentum flux faction. Consider figure A.6. You hold a sheet of paper...

Momentum Flux Redux

We used a na ve version of the momentum flux approach in chapter 2 to explain how square-riggers derive drive from the wind. The most na ve version, as pointed out in chapter 2, simply supposes that the air particles impinge on the lower surface of an airfoil and transfer momentum to it the vertical component of this momentum is lift.* This approach is a very good approximation to the truth in regions of high speed and low air density, as when the space shuttle reenters the atmosphere, but for...

Glossary

A comprehensive glossary of sailing terms would double the length of this book. So I will limit entries to technical or historical terms and expressions. Thus, you will not find sail here I assume that anybody interested in this book would already have a pretty good idea what a sail is but you will find lateen. You will not find cannon, but you will find carronade. In short, I exclude everyday or well-known words. The resulting list is therefore to some degree arbitrary. The aim is to provide a...

The Incredible Hulk

The hulk originated in the Low Countries (modern Holland and Belgium) it is associated in particular with the Frisian Islands off the coast of Holland and northern Germany. While it was developed before the cog, it came to replace the cog only in the early fifteenth century.t The hulk had a larger, rounder hull than the cog and a much deeper, wedge-shaped cross section ending with a shallow, banana-shaped keel. Because of its deep draft, the hulk was more stable with better (i.e., less) leeway....

Egyptians and Phoenicians

You may wonder with some justification how I can possibly consider the ancient Egyptians and the Phoenicians to be part of European antiquity, given that these nation-states were located in North Africa and the Middle East. Well, I may be stretching a geographical point here, but in terms of maritime evolution the Egyptians and Phoenicians contributed to the Atlantic tradition, and not to any of the others, given that they sailed their ships in the Mediterranean Sea and in the Atlantic Ocean....

Tactics Ships of the Line

The tactics employed by navies during the period covered in this chapter (the late 1500s to the mid-1800s) were dictated primarily by these circumstances (1) ships were powered by the wind and (2) warships were * Marine archeologists have found sunken Spanish galleons with most of their ammunition still on board. armed to the teeth with increasingly devastating cannons.* Ships and cannons would evolve during these three centuries, but the wind remained constant or rather it didn't and the...

Analysis Square Rigged Ship Motion

From the sixteenth century (probably derived from luff, to turn the head of a ship toward the wind'') a boat of superior sailing capability that can stay upwind of other boats. Bosun Boatswain. From Old English bat or Old Norse beit (both meaning ''boat'') and Old Norse swain (''boy''). Doldrums Gloominess, stagnation. From Old English dol (''dull'') equatorial latitudes where low winds often becalmed sailing ships. Fathom A measure of six feet, or to gauge the...

Flettner and Magnus

Coanda Airflow

I add this section just for completeness. Flettner rotors and the Magnus effect have no direct bearing on sail lift. However, they are a part of fluid dynamics, and a couple of ships have been powered by the force of the wind in this way, so read on. Suppose, instead of considering the circulation of air about the airfoil, we consider airfoils that are circulating in the air. If this rather flippant way of introducing the bizarre Flettner rotor suggests that I am talking about two faces of the...

Enter the Vortex

At this point I have to yield to Feynman's dictum. I refuse to inflict upon you the mathematics of vortices they are an order of magnitude more complex than the mathematics used so far in this book and so I resort to a more heuristic explanation, and accept that it will not provide you with a full understanding. The consolation is that it is quite possible to provide a good intuitive feel for how vortices arise and act by using a few well-chosen diagrams. This is because the problem is...

Wake Up

Energy Ship Wake

Everybody is familiar with the idea of a ship's wake. We generally cannot see a wake very clearly on the sea because much of it is masked by other waves, but we certainly feel it in a small boat when a large wake passes underneath. On calm lakes and slow rivers, we see wakes in all their glory, and some of us marvel at the complexity and consistency of the wake wave patterns.* Physicists are fascinated by this sort of thing, and the scientific explanation of wakes is complex and interesting....

Hull Speed

Hull speed is a phenomenon of displacement boats, and not of planing boats. Most sailing boats and all ships displace water move it aside as they plow through it. Planing craft, such as most motor boats, glide over the top like a surfboard. It takes more energy to push water aside than it does to slide over the top of it, and so displacement boats move at a more sedate pace than their lighter planing cousins. Some small sailing boats can be made to plane, but the general rule is that sailing...

Path Difference

A very common and wrong appeal to Bernoulli, when explaining lift, goes like this The air travels farther over the convex, upper side of an airfoil than it does over the concave side, and so the air speed is greater above the airfoil than below. From equation (A.1) we know that higher speed means lower pressure, and vice versa. So the pressure above an airfoil is reduced, and the pressure below is increased. Multiplying pressure by area gives vertical lift force. This explanation (illustrated...

Sailing Theory and Practice

The Physics of Sailing Explained. New York Sheridan House, 2003. A short technical book, good on induced drag. Chase, Carl. Introduction to Nautical Science. New York W. W. Norton, 1991. Practical advice, plus an excellent nonmathematical description of torque effects that influence boat handling. Garrett, Ross. The Symmetry of Sailing. New York Sheridan House, 1996. Gentry, Arvel. A Review of Modern Sail Theory.'' Proceedings of the Eleventh AIAA Symposium on the...

Beating to Windward with a Foreand Aft

When heading upwind, it is a different matter altogether. We know this from experience. Is the renowned superiority of fore-and-aft rigged boats vindicated by physics If not, there is something wrong with our *The official world record for iceboat speed was set back in 1938 by John D. Buck-staff on Lake Winnebago, Wisconsin. His craft Debutante glided over the ice at 147 mph. According to Encyclopaedia Britannica, iceboats can achieve speeds ''at least four times'' the wind speed when sailing...

One Sail Two Sails Foresails

Thus far I have restricted Sparrowhawk to deploying one sail. Most modern boats have at least one foresail (a.k.a. a headsail) a jib or a spinnaker. Here I will examine the physics underlying these extra sails and the benefits of a combination of two sails. First, though, an exercise in elementary geometry to provide one reason that triangular fore-and-aft sails are more effective than square sails of the same area. Consider figure 4.7 the square sail has the same Figure 4.7. Triangular sails...

The Medieval Contribution

We have now arrived at the start of the second millennium CE. The Roman Empire has come and gone but its dissolution provided a spur to sailing ship development. This is because the political turmoil that followed in the wake of Rome's demise resulted in more fluid borders and changing trade routes. The predictable year-in, year-out voyages of merchantmen between port cities of the Empire disappeared. Consequently, merchant ships needed to be able to tackle a wider variety of wind and sea...

Clippers Yankee and

Schooner Blackfish Lines Plan

In addition to the opening up of the South and East Asian market to competition, there were other incentives to American overseas commerce. The discovery of gold in California in 1848 stimulated trade from New York to San Francisco, around the Horn. This long journey was very profitable, and fast clippers could pay for their construction costs in just one trip. Gold discoveries in Australia in 1851 led to a similar ''demand for supplies.'' Concurrent with free trade incentives with the British...

South Pacific Tradition

Ancient Catamaran Boats

Catamarans have been around for at least three millennia. The traditional cats consisted of a double hull of logs connected by a rigid deck or platform. Westerners first learned of cats from an English adventurer in India, who wrote about them in the 1690s. The word catamaran is Tamil, and these vessels have long been associated with the state of Tamil Nadu in southern India cats have been recorded there since the fifth century CE. The cats that we know today more closely resemble those...

Torque about Hull Stability

Torque applied about the longitudinal axis leads to heeling, and if the heeling angle is large enough, a boat may capsize. This is considered to be undesirable among all the boat owners I know, and so hull stability is taken to be a matter of some importance. Here, stability refers to the ability of a boat to right itself after having been heeled over by, say, a sudden gust of wind or a sudden change of course. We would like to know how much our boat can heel over before capsizing, and we would...

Time to Rock and Roll

Designing boat hull shapes for stability involves a number of trade-offs. Not least is the comfort of the crew and passengers. Not only must our Figure 5.8. The radius of gyration (dashed circles) about the center of gravity, CG (small circles), of a boat hull for different hull shapes. If the hull is a hollow cylinder (a), the radius of gyration is just the cylinder radius. For a solid cylinder (b) the radius of gyration is only 71 of the cylinder radius. For different boat hull cross sections...

East Indiamen and Others

Tall Ship Shrouds Seizing Labelled

In the seventeenth and eighteenth centuries several western European maritime trading nations established colonies or trading monopolies with peoples in South and East Asia. Luxury trade goods such as spices, silks, works of art, and, increasingly, tea were brought from India, China, Japan, and Indonesia to be sold in the markets of Europe. The Dutch, French, and British granted trading monopolies to their own East Indies companies, who operated very profitably though inefficiently as a...

Greeks and Romans

Mische Galeere

The speed of a boat in ancient times was determined by the number of oars that it carried or by the spread of canvas. Both the Greeks and the Romans made use of sailing vessels for commerce but used oar-powered galleys for maritime warfare. It is the slender and beautiful galleys that have come down to us as the maritime icons of European antiquity because they were much more impressive vessels than the slower, ungainly-looking trading ships. The rise of galleys is a testament to the weakness...

Planing and the Need for Speed

Surfers require waves in order to move, and windsurfers certainly will hitch a ride on one if they feel like it, but windsurfers can also achieve speed on flat water. The current speed record for any sail-powered craft on water is held by windsurfer Finian Maynard of the British Virgin Islands, who maintained an average speed of 48.7 knots (54 mph) over a 500-m course in April 2005. This achievement beat the previous record of 46.5 knots set by a catamaran in 1993. The nautical mile record is...

Wind Force Boat Force and Isaac Newton

Now let me give our boat a name and a sail. She will be christened Snoozing Goose, and her single mast has been square-rigged. So she is a small ship with square sails that can be trimmed to best advantage, permitting movement upwind (to some extent) as well as downwind, as we will see. I will treat Snoozing Gooses sail(s) as if they were a single flat sheet. Of course, this is not how real sails look, but it is a convenient approximation that permits us to readily specify sail orientation and...

Two Old Ladies

Hms Guerriere Plans

My goal is to tell you about the evolution and science of sailing ships in general, but I can't resist including this anecdotal aside about two particular sailing vessels because they carved for themselves such impressive histories and because both are still with us. These grand old dames one still sprightly and the other now infirm have many admirers who visit them each year and are both still very photogenic. If their stories don't stir your blood, then you are reading the wrong book. The...

The Slot Effect

The effect of sails in combination is not simply additive. Two sails can be twice as effective as one sail or less than twice as effective. The combination of jib and mainsail in a Bermuda sloop is very common because these two sails form a particularly beneficial symbiosis. The governing aerodynamics of this happy union goes by the name of the slot effect, about which much too much has been written over the years. By now the warning bells should already have rung in your head as soon as the...

Galleons

Model Galleon Plans

I have already mentioned one reason for the emergence of large, well-remembered galleons they housed large sixteenth-century cannons better than did the earlier carracks. More generally, the galleon was a response to the inefficiency of the carracks. The need for bigger ships also relegated the nippy little caravels to history enlarged caravels did not sail nearly so well. The galleon, a Spanish innovation that dominated European waters for two centuries, solved the problems of the times it...

East Asian Tradition

The name junk (from the Malay word djong, meaning boat) is applied to a wide variety of ocean-going sailing vessels from India and, in particular, from China. At their peak in the early fifteenth century, junks were by far the largest and the best sailing craft in the world. Junks maintained pole position until the nineteenth century, when ships from the Atlantic tradition eventually overhauled them in terms of performance and matched them in terms of size. The main characteristic of the junk...

The Last Days of Sail

Hermaphrodite Brig

With hindsight we can see that, even without rough seas, unfavorable economics, and civil wars, steam engines alone would have killed off the clippers. James Watt made his major breakthrough in steam engine design the same year that HMS Victory was built the age of steam locomotives coincided with the clipper revolution, and it was only a matter of time before steam engines replaced sails to drive ships. At the beginning of the nineteenth century, ships were made of wood and powered by wind by...

The Venturi Nozzle

Before leaving our discussion of the approach of the Bernoulli faction, we should look at the approach of an offshoot the Venturi school who offer a simpler explanation of lift. The simplicity of this explanation is seductive, but again, the price to be paid is bad physics. There is certainly a Venturi nozzle effect, as shown in figure A.5 the problem is that it is misapplied when utilized to explain lift. Venturi nozzles are used to determine the airspeed of a plane by Named after Giovanni...

Sailboards

The equipment is called a sailboard the action is better described as windsurfing. Some of you may argue that sailboards are not boats and so don't belong in this book. To forestall such mutinous mutterings, I note first that a sailboard is a hi-tech raft, that it is equipped with a fore-and-aft sail, and that windsurfing is hugely popular. Second, windsurfing brings out a few interesting aspects of hydrodynamics and the physics of sailing that are not apparent in sailing with boats....

Equilibrium Speed

The first and most significant conclusion that we can draw from this analysis concerns the maximum speed that the wind force can impart to our boat. Here we are ignoring the water wave phenomenon that gives rise to hull speed, discussed in a later chapter, and concentrating simply on the speed that Snoozing Goose can extract from the wind. By setting her sails appropriately, she can catch the wind and make forward progress in any direction except straight upwind. The math analysis of equation...

The Age of Exploration Carrack and Caravel

Carrack Ship Design

In the early fifteenth century the pace of ship development in the Atlantic tradition began to pick up this was the period with the most intense development of sailing ships. I hinted earlier about the potential for ship growth in size and development should the northern clinker and the Mediterranean carvel designs fuse. Such a mixing began with the Crusades. Many northern knights headed for the Holy Land in their double-ended clinker-built ships, taking them into Mediterranean ports en route....

Momentum Flux and Effective Sail Area

High Aspect Gaff

I need to nail my colors to the mast before proceeding further and tell you a little more about momentum flux. The most na ve application of Newton's laws envisages the wind force on a sail as illustrated in figure 2.4a. Here the wind is viewed as a myriad collection of atoms and molecules, little ball bearings that collide and bounce off each other and off the sail. Between collisions they are considered to be quite independent of one another, and so move in straight lines. A sail in the wind...

Pumping and the Katzmayr Effect

Pumping is the action of fanning the sail back and forth in such a way as to increase forward momentum. You may have observed windsurfers energetically wafting their sails and wondered how this action generates thrust as an aeronautical engineer would call it, though some sailors call it ''negative drag'' for their rigs. A simple explanation follows. Pumping represents another difference between yachts and sailboards, at least in races, because for yachts pumping is controversially illegal...

Carvel versus Clinker

The front-cover difference between clinker-built hulls and carvel-built hulls is illustrated in figure 1.5. The front cover does not represent the whole book, however, but like hull planks, or strakes, is what you see on the outside. Carvel-building probably came firstt and originated in the The reason for this behavior is discussed in chapter 5. tCarvel-built vessels were standard for the first millennium BCE in the Mediterra- eastern Mediterranean region. It was a natural extension of the...

Stop Torquing

I have touched on several aspects of torque as it applies to sailing boats. We have seen how torque can change heading direction, unintentionally for example, while the boat is heeling and intentionally when the helmsman adjusts sail trim . Another torque, perpendicular to the heading torque, applies to heel the boat and to cause it to roll we have seen how the basic physics works here. As I have emphasized repeatedly, the details are much more complicated than I have portrayed with my...