Posted by razzbuffnik on September 1st, 2011
My wife (Engogirl) is an engineer who works as a senior consultant in computational analysis. Engogirl tends to take photos of things that stimulate her thoughts rather than eye candy like me. Below is is an e-mail that Engogirl sent to her co-wokers in Sydney.
Today’s safety moment comes to you from the Vasamuseet in Stockholm, Sweden. This museum houses the 69m long warship ‘Vasa’, which was built for King Gustav II Adolf from 1626 to 1628, and was one of the most heavily armed warships of its time.
The attached photos show the actual warship viewed from the front port side,
and a 1:10 scale model viewed from the stern.
Ten minutes into the Vasa’s maiden voyage in 1628, a light breeze blew as the ship emerged from the lee of the city. The sails filled, and the ship heeled suddenly to its port side, leaning so far over that water entered the open gun ports. This caused the ship to further destabilise, and it quickly sank to the bottom of the harbour in 32m of water, with only the tops of the masts left showing. There it stayed until 1961, when it was salvaged and found to be almost entirely intact. The ship is now housed in the Vasamuseet. Of the estimated 150 people on board when it sank, at least 30 are thought to have perished.
So why did the ship sink? Basically it was top-heavy. When the ship heeled, the centre of gravity was so high that the result was an unstable load condition. The heavy guns were too high above the waterline, too far from the ship centreline, and there was too little ballast in the hold below the waterline to lower the centre of gravity and provide a restoring moment. This was further exacerbated by the gun ports being left open on the maiden voyage – contrary to usual practice.
What lessons can be learned?
1. Letting the client dictate the design as well as the function
The King had ordered the ship to be constructed with specific dimensions, and two gun decks with 48 heavy 24 pound cannons. He ordered and approved the designs, but was not a shipbuilder.
2. Loss of key personnel
In the 1600s ships were built without any drawings. The shipwrights used various rules of thumb to determine the measurements. The Dutch shipwright Henrik Hybertsson was commissioned to build the warship, but he fell ill one year into the job, and died in the spring of 1627. The ship was completed by his assistant, Henrik Jacobsson. During the inquest following the sinking, Jacobsson claimed he just followed the instructions of Hybertsson.
3. Ignoring the results of preliminary testing
The ship’s captain ordered some heeling tests to be carried out before the ship was completed. The hull was floated and thirty men ran back and forth across the upper deck to start the ship rolling, and it was found to be so unstable that the test was stopped early for fear that the ship would capsize. Despite this result, the construction continued as it was behind schedule and the King was applying extreme pressure for the ship to be completed.
4. Relying on God to save you
Following the heeling tests, the captain apparently commented that he would trust in God to keep the ship afloat. Unfortunately, such trust was apparently misplaced.
The good news is that the high levels of pollution in Stockholm harbour resulted in excellent preservation of the timbers, ropes and even the sails, and the Vasa now offers a fascinating insight into naval techniques of 17th century Sweden.