Why was Invincible so special?

Fifty years of naval supremacy had left Britain complacent. The 1744 fleet was large, but its ships would have been familiar to the captains of the 1680s. The Royal Navy’s motto might have been ‘if it floats, don’t fix it’.

On the other hand, the French were forced to go back to the drawing board – literally. They began to apply scientific principles to the design of a new generation of warships. The result was faster, more agile ships with more powerful guns.

Invincible’s secrets

The French built L’Invincible in 1744 as a warship with 74 guns on two decks. Just three years later a much larger British force captured her in battle. The Royal Navy quickly and carefully mapped every inch, revealing her design secrets.

She was wider in the bow (front) and narrower in the stern (back) than British ships, making her faster and more nimble. A narrow vertical rudder meant she could turn without slowing down, while a rudder position indicator helped the quartermaster and helmsmen steer more accurately. Her crew had more room to work because her longer hull allowed for more widely spaced guns. With a main gun deck six feet above the waterline, she could take on and defeat bigger ships whose lower gun ports would be submerged in rough seas.

The science of shipbuilding

By 1741, French naval constructeurs were trained for seven long years in the science and art of shipbuilding. Pierre Morineau, the constructeur who built L’Invincible, was one of the first to use scientific methods. He learned his craft before the national school of naval architecture was created, but he wrote at least two treatises in ship design.

The Royal Navy had seen little technical advance in over seventy years. Ships that rotted away were rebuilt to look exactly the same, and any new ships were built to rigidly laid-down dimensions. The shock of meeting this new type of fast, powerful and seaworthy French warship prompted some quick learning. The British absorbed the lessons of Invincible – and built on them.

‘It is said that the Invincible, taken lately from the French, is allow’d by them, and by all the English who have seen her, to be the best Ship ever built in France.’

Derby Mercury, 29 May 1747

Invincible’s design legacy

When Nelson defeated the French and Spanish fleets at Trafalgar in 1805, nearly two-thirds of his ships looked remarkably like a design seized from the French 58 years earlier: HMS Invincible.

After her capture she was repaired, refitted and brought into service under the Union Jack. Admiral Warren wrote,

‘The Invincible sails better in every way than any ship, and is in every shape a fine man-of-war.’

Admiral Warren

She’s quick, nimble and strong

On a run to Gibraltar and back in 1752 Captain Bentley logged a remarkable speed – thirteen knots (The best speed a comparable British ship could achieve was just 11 knots). But he did wreck a few sails on the way, so it may have been a case of ‘let’s see what she can do!’

Invincible was longer than British two-decker ships, and quicker and more agile too. The only Royal Navy ships that could match the power of Invincible’s guns were slower three-decker ships that couldn’t use their guns in poor weather.

Experiments with new guns

The Royal Navy used Invincible as a testing ground to try out some new, powerful guns. In 1755 her 18-pounder guns were swapped for bigger 24-pounders. These fired larger, slower shot, which crashed about inside the target instead of passing through, creating a lethal shower of sharp wooden splinters. She was also one of thirteen ships chosen to try out gunlocks – a new technology that used triggers to fire the guns. Firing was quicker quicker and the gunner could choose the right moment to shoot. In 1756 Invicible’s gun ports were enlarged, so gunners had more scope to aim their weapons from side to side.

Invincible’s legacy

The British were so impressed by the captured French ship that they copied her design and used it as a template to build new 74-gun ships. Experience showed that even Invincible was too short: there was too much weight in the front, and the bowsprit (the spar extending from the prow) stopped the forward guns working as well as they could. British ships also needed to be even stronger so they could cope with long blockade duties in any weather. These new improved ‘Seventy-Fours’ became the backbone of the Royal Navy –  the best sized and most high-tech general-purpose warship of their time.

In 1778, just twenty years after Invincible sank, the Royal Navy had 58 of Invincible’s descendants, the ‘Seventy-Fours’. By 1800 there were 70. Out of 27 ships in Nelson’s fleet at Trafalgar, 16 were copied from Invincible’s template.