On August 10th, 1628 this was the most powerful weapon in the world.
20 minutes later it was at the bottom of Stockholm harbour.
There aren’t any visible signs of damage; the wood hasn’t been set ablaze, ripped
apart by a reef or blown apart with cannons.
So why did this warship never see war?
Who sank the Vasa?
Lets relive the fateful day of the sinking.
After being dragged along the eastern shorefront from the Skeppsgaden shipyard the Vasa was
ready to take sail.
Named for his family, the Vasa Dynasty, King Gustavus Adolphus of Sweden was anxious for
her to join him fighting in the 30 Years War.
Onboard are sailors and their families, while along the shore thousands waited to see the
flagship of the Swedish navy take to the seas.
All the gun ports along both the lower and upper decks are opened; ready to fire a salute
as the ship leaves Stockholm.
After unfurling her sails she made her way steadily through the port.
Just as she rounds Beck-holen island a strong gust of wind made the ship bank heavily to
port, in fact so far did it lean that the lower gun ports become submerged.
As water rushes in the fate of the ship is sealed and she sinks in a matter of minutes.
Since they hadn’t gone very far, most of the passengers and crew make it safely to
shore where the captain is immediately arrested.
Sofring Hansson swears that everything had been tied down properly and that his crew
was sober.
So if the sailors weren’t to blame, why did she sink?
All ocean vessels operate under the influence of two key forces.
Weight and buoyancy.
To see how these interact I've created this demonstration.
The top tank is filled with water.
If any of it gets displaced its going to spill out and into the larger container.
We’ll be able to measure the weight of the displaced water using a set of scales.
This is an analogue for the Vasa ship.
It weighs in at precisely 37 grams.
When we place it into the tank some of the water spills out.
How much water?
37 grams of it.
We’re now adding in some cargo; about 65 grams of it.
The extra weight pushes the boat down further, but it doesn’t sink.
At the same time more water spills out.
How much this time?
About 65 grams.
As you can see; the mass of water displaced is always the same as the mass of the object.
That’s because displaced water generates buoyancy which is opposed by the object's mass which generates weight.
In the end the boat sinks just far enough to exactly counter the extra mass.
It was 1625 and King Gustavus had a problem.
Up until the 17th century the Swedish navy had focussed on smaller, faster vessels, well
suited for the boarding rather than outright sinking of ships.
However, as cannon technology advanced, he saw an opportunity for a new type of warfare.
When, during the height of the Thirty Years War, 10 of his ships sank during a storm,
Gustavus informed his shipwrights that they would be building a new flagship, using the
latest in technology.
The Vasa was equipped with 64 cannons across two gundecks, including 48 of these 24-pounders.
At the time this was the Baltic’s largest concentration of artillery on a single vessel.
But flagships aren’t just about firepower, they are also political statements.
You can see in this 1/10th scale replica the brightly coloured ornamentation of the Vasa.
Scenes from Roman and Greek antiquity are intertwined with figures from the Old testament
and ancient Egypt.
All of this propaganda and extra canons puts a lot of extra mass high up in the ship.
Just having equal forces isn’t enough, they’ve also got to be balanced.
In its initial configuration, our boat is really stable.
That’s because the cargo makes the weight force act through a point lower than the buoyant
force.
If we tilt it to the side these forces generate a restorative torque back to the centre.
On the other hand, if we were to increase the height of the cargo, then it’s a lot
less stable.
Buoyancy acts through the same point, but now the weight force is much higher up.
If the ship tips even a little then this tilt gets magnified.
We can prevent tipping in two ways.
Lower the centre of mass by adding in more weight lower down, or by making the base wider
so it must lean further before falling over.
When Gustavus ordered the Vasa to be built, the shipwrights had already started construction
on a smaller vessel.
Rather than wasting the resources, they instead just extended the already-formed keel by 8
metres, bringing total ship length up to 70.
In order to compensate for this instability, they added as much ballast as possible, however
the narrower profile of the ship made it much less effective.
After 120 tonnes were added the ship was sailing too low in the water.
Any more mass and the water would start to spill through the gunports.
Before the Vasa could launch it had to pass a lurch test.
This involves having 30 men run side-to-side along the deck.
Making the ship rock back and forth.
By doing so we can infer the relative positioning of weight and buoyancy forces.
In Pirates of the Caribbean they use an especially exaggerated form of this test to flip the
Black Pearl.
After just 3 traversals is was decided that the Vasa was lurching way too far and the
test was abandoned.
For comparison, it took Jack Sparrow and his crew more than 10 times that amount before
their ship would sink.
At this stage, someone should probably have told the engineers, or even the king, that
the ship was unseaworthy.
However, it appears the message never got through, and with Gustavus at war and anxious
for the Vasa to join him the launch date was set for August 10th.
The rest, as they say, is history.
So, at the end of the day, who sank the Vasa?
The official inquest found that no one was to blame, the captain was just sailing a ship
that had indeed passed a test and was built to specifications outlined by the king himself.
Were the court going really going to accuse the most powerful man in Sweden of sinking
his own warship?
Probably not.