How a ship can be sunk on the slipway
A vessel's stability rests on a simple relationship: where its weight is and where the water's buoyant force acts. The lower its center of gravity, the more readily a ship rights itself after heeling. The Vasa's weight was raised upward: 2 gun decks instead of 1, more than 60 cannons, and a tall stern with hundreds of carved figures. Below, they put in as much ballast as would fit in the narrow hold: no more stone could fit.
This didn't happen out of stupidity. Sweden was at war, the king wanted the most powerful ship in the Baltic, and its dimensions were changed as construction went along. Plans in the modern sense didn't exist: the hull was built from experience and proportions, and the shipyard had no experience with a 2-deck ship. The master shipwright Henrik Hybertsson died a year before the ship put to sea - the Vasa was completed by someone else using another man's estimates.
The test they stopped
The ship was tested after all. Vice Admiral Klas Fleming put 30 men on deck and ordered them to run from side to side: they rocked the vessel this way to see how quickly it righted itself. With each run, the Vasa responded by heeling more and more.
30 men on deck. The only stability test available in the 17th century: there was no way to calculate it.
Run from side to side. Rock the ship by hand and see whether it readily returns upright.
Stop after the third run. The swing was growing too quickly. The test was stopped - but the launch wasn't canceled and no ballast was added.
There was hardly anyone who could cancel it: the king was waiting for the ship and pressing for it in letters from the war in Prussia, while adding more ballast would have lowered the lower gunports right to the water. On the day of departure, the wind was light: beyond the headland, a gust came down from the hills onto the Vasa, the ship heeled, and water rushed through the gunports left open for a salute. Within minutes, it was on the bottom. About 30 people died; the investigation found no one at fault.
Why you can touch this mistake today
The Baltic is only slightly salty, and shipworm, which eats wood in warm seas, does not live there. The Vasa lay on the seabed for 333 years and was raised in 1961 almost intact - the only completely preserved 17th-century ship.
of the ship in the museum is authentic 17th-century wood
Once ashore, the hull was measured and found to be asymmetrical: the left side was thicker than the right. Among the recovered tools were rulers of different lengths - the Swedish foot was divided into 12 inches, the Amsterdam foot into 11. The carpenters worked side by side, each using their own measure, and no one reconciled them.
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Sources
- The Vasa Museum in Stockholm and hull measurements by its researchers: asymmetrical sides and rulers using different feet. The sinking - August 10, 1628
- the recovery - 1961
- the death toll is estimated at about 30 people