Larrie D. Ferreiro

Historical Roots of the Theory of Hydrostatic Stability of Ships

The pohysical principles of hydrostatic stability for floating systems were first pronounced by ARCHIMEDES in antiquity, although his demonstration examples were limited to simple geometrical shapes. The assessment of stability properties of a ship of arbitrary shape at the design stage became practically feasible only about two millennia later after the advent of infinitesimal calculus and analysis. The modern theory of hydrostatic stability of ships was founded independently and almost simultaneously by Pierre BOUGUER (“Traite du Navire”, 1746) and Leonhard EULER (“Scientia Navalis”, 1749). They established initial hydrostatic stability criteria, BOUGUER’s well-known metacenter and EULER’s restoring moment for small angles of heel, and defined practical procedures for evaluating these criteria. Both dealt also with other aspects of stability theory. This paper will describe and reappraise the concepts and ideas leading to these historical landmarks, compare the approaches and discuss the earliest efforts leading to the practical acceptance of stability analysis in ship design and shipbuilding.

Cutwaters Before Rams: an experimental investigation into the origins and development of the waterline ram

Students at Stevens Institute of Technology (Hoboken, NJ, USA) investigated the reasons for an elongated projection at the bow of Mediterranean galleys. Using a 1:20 base model adapted from the Trireme Trusts Olympias fitted with: 1) an elongated projection; and 2) a control bow similar to excavated merchant ships, tow-tank tests were carried out at various speeds. Hydrodynamic resistance and power were calculated for each bow type. Above speeds corresponding to 6 knots, the cutwater bow significantly attenuated the models bow waves when compared to the control bow. These results were then compared to those of the ship with a ram-type bow from experiments conducted in 1985 at the National Technical University of Athens, which showed similar wave-attenuating characteristics.

Contested Waterlines: The Wave-Line Theory and Shipbuilding in the Nineteenth Century

Ship hydrodynamics in the nineteenth century was dominated by John Scott Russell’s wave-line theory. Russell, a prominent British shipbuilder and scientist, argued that wavemaking was the primary source of resistance for ships, and that by designing ships according to trigonometric curves and proportions (the wave line) this resistance could effectively be eliminated. From the 1840s to the 1880s, shipbuilders such as John Willis Griffiths, Donald McKay and George Steers designed their clipper ships (like Sea Witch and Flying Cloud) and yachts (America) with wave-line hulls, while authors like Jules Verne referenced Russell’s theory. The wave line slowly faded after William Froude developed his laws of ship resistance. The article examines how Russell’s theory became accepted by technical experts and the wider public to become the most widely known ship hydrodynamic theory of the 1800s—a reminder of how a persuasive idea can take hold of an entire profession, and even the public, for a long time.

SPIES VERSUS PRIZE: TECHNOLOGY TRANSFER BETWEEN NAVIES IN THE AGE OF TRAFALGAR

INTRODUCTION: NO SHIP IS AN ISLAND One of the lesser-known ironies of the Battle of Trafalgar is that the Spanish flagship, Santísma Trinidad, was designed by an erstwhile enemy, a British naval constructor (of Irish descent) named Matthew Mullan. He was not alone – over 80 constructors and dockyard workers left Britain in 1749–50 to work in Spanish arsenals, becoming the nucleus of the workforce that would rebuild the Spanish fleet between 1750 and 1793. A great deal of this rebuilding was actually done under the authority of French constructor Jean-François Gautier, who built five of the Spanish ships of the Combined Fleet. The Spanish ships at Trafalgar were not the only ones to have benefited from foreign influence; the French ships of the Combined Fleet were equipped with new technologies such as copper hull sheathing that they had scrupulously copied from the British navy. And finally, more than half of the British fleet consisted of the 74-gun ships that owed their design to a captured French warship. These examples show that ships which fought at Trafalgar were not wholly indigenous creations of each nation. The French, British and Spanish had long traditions of information exchange and technology transfer with other navies, albeit more often through unfriendly means than through cooperation. Through a complex series of spy missions, personnel exchanges and ship captures, advances in the science and technology of ship design and construction in one navy quickly found their way into other navies, adapted and often improved to suit that navy’s particular needs. This paper examines the mechanisms by which naval technology was shared between nations and addresses how they influenced the ships of Trafalgar. Each nation had its preferred method of obtaining this information: for France, it was industrial espionage; for Britain, capturing warships as prizes; and for Spain, a combination of exchanges and espionage.

Clippers, yachts, and the false promise of the wave line

John Scott Russell’s 19th-century theory of ship design promised speed and delivered elegance. But, ultimately, it didn’t hold water.

Pierre Bouguer and the solid of least resistance

Pierre Bouguer et le solide de moindre resistanceLa parution des Principia mathematica d’Isaac Newton en 1687 survint au sein d’une communaute qui ne l’attendait pas et qui n’y etait pas preparee, ainsi que le rappelle l’historien I. Bernard Cohen : que faire avec cet ouvrage et comment l’utiliser furent les deux questions posees pendant un certain temps. Un des premiers savants qui se servit des principes de Newton de facon pratique fut l’academicien Pierre Bouguer (1698-1758). Dans son Traite du navire (1746), la premiere grande synthese d’architecture navale, il adapta le scholium de la proposition XXXIV de la section VII du livre II, dont Newton disait qu’elle conduirait a la conception d’un corps solide, comme celui d’un bateau, presentant la moindre resistance dans un milieu resistant.L’etude de Bouguer sur le « solide de moindre resistance » de Newton, bien qu’elle s’averât finalement incorrecte, fut une des premieres investigations serieuses sur la nature fondamentale de l’hydrodynamique du navire, preparant la voie pour des recherches futures. Bouguer ne considerait que le « choc » de l’eau sur la proue (ou etrave) et ignorait completement les roles du reste de la carene et la resistance de friction. L’idee de la « theorie du choc » dans la conception des bateaux avait ete pressentie, apres Newton, par des auteurs anterieurs a Bouguer, mais elle ne devint utile que lorsque Bouguer produisit une methode systematique et pratique d’analyse, en particulier quand il travailla avec son collegue et ami Henri-Louis Duhamel du Monceau (1700-1782) a reduire cette analyse a un protocole de calculs facilement applicable a la conception du navire. Ces calculs devinrent partie integrante de l’ingenierie des vaisseaux francais pendant plusieurs decennies, jusqu’a ce que le poids theorique et l’evidence experimentale la rendent obsolete. Cependant, le legs du solide de moindre resistance perdura presque jusqu’a la fin du XIXe siecle, jusqu’a ce qu’une theorie applicable, utilisant des modeles soumis a l’essai en bassin, fut finalement concue.