San Juan Nepomuceno

Posted by F.F. on Saturday 30th of November 2024 17:11

Spanish ships in the time of the ships of the line were built according to the following principles:
• Until the end of the War of the Spanish Succession, principles inherited from the time of Emperor Charles V; thus galleons (sometimes three-deckers, and in size more or less like the St Michael) were then the largest Spanish ships.
• From the end of that war until the middle of the century, they were built according to the principles drawn out by engineer Antonio de Gaztañeta e Iturribalzaga («sistema español»). The result was large and fine ships. La Princesa (1733) inspired the British shipwrighter who drawn the hull of the Royal George of 1756, and Slade for his Victory of 1765, both men-of-war being regarded as fine sailers; and el Fénix of 1749 became in the British Navy the famous Gibraltar ship of 80 guns.
• From a bit after the middle of the century to around 1765, they were built according to principles drawn out by mathematician Jorge Juan, after his 1749-1750 spying mission in England. Ships of to this «sistema inglés» weren't regarded usually as good sailers but had staunch hulls.
• From then to around 1782-1784, ships launched for the Real Armada were built according to principles made out by a French engineer (who had drawn previously two ships of 64): François Gautier. Sailing qualities were improved: el San Miguel was the best sailer in the Spanish line of battle, and the frigate la Santa Margarita, taken by the British Navy, was regarded as a very good one. But in the same time English dockyards launched ships, from Slade's and Bateleys drawings, vastly better than those of the middle of the century, and cooper sheathing added to their advantage.
• From then to the end of the century, two new systems applied: that of José Joaquín Romero de Landa, and that of Julián Martín de Retamosa.

Jorge Juan wrote a book, Examen maritimo (1771), pleading for his own «sistema», and depicting ships built according to Gautier's system as having non durable hulls because of their light carcasses. He said that a ship of 70 built according to the English system had a displacement of 2801ｔ (SI), and that a ship of 70 built according to the French system had a displacement of 2620ｔ (SI).

Whereas the question was what was to be prefered between thick sides (protecting against shots) and heavy carcasses (making ships more durable), many modern readers have conclude that hulls of Gautier's system were light ones, and that hulls built in France were also too light ones. Some have even conclude that French ships bore less food and less water than the other ones.

When comparing what Spanish sources state about one of Gautier's 74s (el San Juan Nepomuceno), two of Romero de Landa's class of 74s (el San Ildefonso), and the Retamosa's 74 (el Montañés), who all where at Trafalgar, and which displacements and deadweights are known (partly from the «estado general del día 19 de Octubre de 1805»), I found that hull weight was:
— 45.6% or 46.3% (according to sources) of the displacement (≈ 2740ｔ), with a deadweight of 1600 or 1630 toneladas ≈ 1472 or 1500ｔ (SI), for Gautier's el San Juan Nepomuceno.
— 41.7 or 44.1% of the displacement (which for the eponym ship herself is given as uncommonly low in the estado general, ≈ 2590ｔ instead of ≈ 2700ｔ everywhere else) for the two Romero de Landa's ships of the San Ildefonso class, with a deadweight of 1640 toneladas ≈ 1509ｔ (SI).
— 45.6% of the displacement (≈ 2530ｔ) for Martín de Retamosa's el Montañés, with a deadweight of 1499 toneladas ≈ 1369 ｔ (SI).

Burthen, as measured in England, was 1740 tons for el San Juan Nepomuceno, 1752 tons for el San Ildefonso, and would have been some 1680 tons for el Montañés. As measured in Spain, burthen (arqueo, currently used in Europe only when measuring merchant ships) would have been 1858 toneladas for el San Juan Nepomuceno, 1829 toneladas for el San Ildefonso, 1828 toneladas for el Montañés. So in size they were comparable, and Gautier's hull were at least as heavy than those built according to other systems.

French ships of 74 of Sané's le Téméraire class had a hull weight decreasing from 51.4% in the 1780s to 49.5% near 1800, and to 46.5% around 1810-1815 (carcasses becoming lighter and deadweights increasing, total displacements remaining what they had been), so in fact French hulls were proportionally heavier than Spanish ones.

And it is to be noted that, when Spanish ships one the line had food and water for three months, English ones had food for six months and water for three; and French ones had food for seven months and water for four.