On my way to work, I usually listen to podcasts. The current favorite is “The infinite monkey cage”, hosted by physicist Brian Cox and comedian Robin Ince. It´s hilariously funny, but once and again some really serious and complicated science crops up.
Take gravity for example, one of the fundamental forces that somehow keeps the universe together (or is it expanding?). Tricky stuff anyway. It also works on boats; the center of gravity pulls the boat down into the water. Luckily, there is also the center of buoyancy, so the water pushes back against the boat and keeps it afloat.
When you’re out sailing all sorts of forces are working on you and on the boat, so you will probably not be too concerned about gravity, unless you are sinking of course. But you will subconsciously take in the force of the wind and adjust your sails accordingly, make sure that hatches and other openings are secured so the boat doesn´t fill with water if it gets rough, try to figure out what the weather is doing and so on. There are hundreds of forces to reckon with, which is partly why sailing is so exciting. (There is also the scenery and nice places to visit).
Forces of nature.
When Vasa sank, something obviously went wrong with gravity and buoyancy. Well, the gravity was still there, but buoyancy went haywire as the water started to fill the hull through the open gun ports.
So, where am I going with this? And how does it relate to Vasa?
Well, Vasa is no longer afloat or at the bottom of the sea. Standing inside our lovely museum she is basically floating in a sea of air. The density of air is small compared to that of water, so the buoyant force is not great. This means that Vasa is depending a lot on her support cradle to remain upright and intact. To complicate things further, Vasa´s wood is also degraded and has far less strength than new oak (or recent oak as our scientists at Uppsala call it). To come to terms with this degradation, or weakening, Vasa has also been chemically modified with polyethylene glycol in the conservation process. This has of course helped to make the wood more stable, but we now know that there are ongoing chemical reactions inside the wood. One thing that seems to slow down these disturbing reactions is the stable climate inside the museum building. So, there are a lot of interacting and also conflicting forces inside and around Vasa, and she is more or less in the hands of an elaborate life support system for survival.
Does this sound really worrying? Perhaps it is, but the thing is that Vasa, despite all her ailments, is fairly stable. We know this because part of the life support system is a really neat geodetic system for measuring movements in the ship. This system is not so easy to explain, but basically we are using an surveying instrument called a “total station” which we direct to a large number of measurement points on the ship. The measurements are then transformed into the actual movements within the ship´s structure.
So why is Vasa moving at all when she is standing in a cradle inside a climate controlled building? Could it be gravity, or is something the matter with the support cradle? A bit of both probably.
When I lift my own boat ashore for the winter and put her in her cradle, things happen. Although she is a fairly modern and strongly built fiberglass yacht, lockers will suddenly stick, doors will be more difficult to open and hatches tend to jam. Gravity at work, because Signe (that´s her name, after my wife´s grandmother) is no longer buoyant, and her winter cradle does not give the same support as water when she´s afloat.
So in a way it´s quite amazing that Vasa is as stable as she is, considering her age and what she has been through. Obviously, we can´t do much about gravity, but we can (among a lot of other things) work with the support cradle.
This is why our latest research project “Support Vasa” is so important, as the results are totally vital for designing and building a state of the art future support system for Vasa. One part (just started) of this project is building a full scale section of Vasa´s hull for testing the strength in joints and various components of the ship. To accomplish this, our shipwrights have just ordered about ten tons of oak, but more about this later…
So who knows where science can take us? Perhaps Vasa really could be floating in a sea of air in the future, or something very like it. What do you think, dear reader?
Floating on a sea of glass. SS Great Britain, Bristol, UK.
This past week, I had the privilege of visiting Repslagarmuseet in Älvängen, just north of Göteborg, where the ropewalk still runs. I was there to take photographs of the rope making process on behalf of Vasamuseet, as one of our forthcoming publications deals with the rigging of Vasa and we need a few illustrations. While the machinery at Repslagarmuseet is from a later period (18th century), the basic elements of the production process are still very much the same. It was quite a privilege to observe the process; there will definitely be more reflections (and photos, and sketches, in all likelihood) coming soon.
In the meantime, here are a few fun sloppy pencil sketches of our girl-
This summer, we (my wife and I and some boating friends), are planning to sail to Poland, Lithuania and Latvia by way of Bornholm. For a holiday cruise, the total distance that we will sail is fairly long. It´s about 900 nautical miles, which is roughly 1600 kilometers.
This does perhaps not sound like a huge distance and it isn´t. But you have to take into account that an average sailing yacht built for cruising is not very fast; the average speed might be around 5-6 knots. That´s 5 nautical miles, or about 10 kilometers per hour. So, literally walking pace.
Another thing is that sailing boats cannot always go in a straight line from A to B, if there are changes in wind direction and weather conditions. So, to get around these obstacles, a sailor will have to do a passage plan and also figure out how best to navigate within it.
A passage plan is an overall idea based on what you know about the places that you want to visit, prevailing wind and weather conditions for the area, any known hazards etc.
Navigation these days is pretty straightforward, as most boats going offshore will have a chart plotter (a bit like the sat nav in a car), an echo sounder to figure out how deep the water is, an electronic speedometer (log), a compass and probably an array of instruments to measure wind speeds and angles, water temperature, the position of other ships and boats and so on.
So, as long as all the electronics are working and talking to each other, you will know exactly where you are, in what direction you’re heading, how fast you are going, what the weather is doing and when you are likely to arrive at your destination. If not, you are back to paper charts (maps), pencil, compass and dead reckoning (look it up on the internet, dear reader), which is why the prudent sailor will always have these means as a backup.
All this planning for future sailing is great fun and helps winter moving towards spring, but it also got me thinking about sailing Vasa. The more I thought, the more curious I got, mainly because I realized I didn´t know much about sailing or navigation in the 17th century. So I talked to Dr Fred Hocker over lunch to find out more. Fred is the research director at the Vasa museum, and of course knew all about it.
One thing I do know; a sailing boat cannot sail straight against the wind! A modern yacht can point perhaps 30 – 40 degrees from where the wind is blowing, and Vasa could perhaps manage 70 degrees at best. So in order to get there if the wind is against you, you have to sail a zigzag course, if you follow me.
Sailing to windward.
To make matters worse, there is also leeway. Especially when sailing to windward, the pressure on the sails and also the force from waves will push the boat sideways to a certain extent. The amount of leeway depends on how deep the boat´s keel is, and how much it will hinder this sideway motion, but also on the wind strength and the amount of heavy seas. Vasa has a shallow keel and a lot of surface area above the waterline, so leeway would have been significant.
So, what did the Vasa sailors do? Well, they probably avoided sailing to windward, waited for better conditions if possible, and tried to lay a course with the wind on the quarter. This means that they would have the wind 45 degrees or less from behind. According to Fred, this would be Vasa´s best point of sailing.
All this is fine in theory, but you can´t always choose your winds or your destination. Talking to Fred, I learned that Vasa had three options, had she reached “Älvsnabben” (about 30 nautical miles south of Stockholm) which was the goal on her unhappy maiden voyage. Vasa was in the “reserve fleet”, so she could either have gone on to Copenhagen in Denmark, to Stralsund in northern Germany or to Gdansk Bay in Poland.
Gdansk Bay would probably have been the easiest option, and the distance from “Älvsnabben” is also the shortest, about 280 nautical miles as the crow flies. Stralsund would be about 340, and Copenhagen 370. A nautical mile is roughly 1.85 kilometers.
But distance is just one element, the position of your destination in relation to where you start could be more important. Now, Copenhagen is to the south-south west of “Älvsnabben”, and pretty much to the west as you round the southern tip of Sweden. Stalsund is roughly to the south, but Gdansk Bay is a bit to the south-south east.
The prevailing winds in the Baltic during summertime are south-westerly to westerly. You could also have sea-breezes blowing from south-east to south. This doesn´t mean that it will blow like this all the time, but it´s the general pattern anyway.
Given a fair wind, preferably a westerly or even better a north-westerly wind, Vasa could have sailed to Gdansk Bay in more less a straight line, though she would have to round the island of Gotland, which is bang in the middle of the course for Gdansk. Fred estimates that it would normally take Vasa three days to get to Gdansk Bay, which means an average speed of 3.9 knots. Not bad at all.
Messing about in 17th century boats.
Sailing straight to the goal, navigation would have been pretty straightforward. As I understand from Fred, there were no proper charts (maps) of the Baltic available, but Vasa would have had at least two pilots, sailors with expert knowledge of the area, onboard. She would also have carried a compass, and also lead-lines to sound the depth and take samples of what the bottom of the sea was like. The latter is not unimportant, because a sample of mud, sand or what have you can tell a lot, as the seabed differs depending on where you are.
So, in favorable weather conditions, with the basic tools for navigation and a couple of good pilots onboard, sailing to Gdansk is all in a day´s work. In hard weather, against the wind, or in bad visibility it would take all the seamanship you could find in the 17th century. But it is still about messing about in boats.
When I tell people that the bulk of the time I spend on cataloging is taken up by the production of measured drawings, executed by hand, they are often surprised. "By hand? Really? In this day and age?" "Why bother with such an old fashioned practice?" "Why not just photograph, why not laser scan, why not use lidar? What about structured light? I saw that in your exhibition about conserving Vasa! Don't you have all that equipment at the museum?" or, "But you've had all this practice with photogrammetry! It must be so time consuming! Isn't some poor intern just going to have to scan these twenty years down the road?"
These are all excellent questions. And the answer is yes, we do have many of these resources available to us at Vasamuseet, and we use them often. We will eventually use some of them on the same tools that I'm presently drawing one by one. But in this case, we still prefer to start with a mechanical pencil and measured drawings. There are a few reasons for this. Part of it is a question simply of logistics: most of the objects I'm dealing with are quite small. Tools, after all, are meant for hands. Much of the scanning equipment we have for taking measurments digitally is designed to record larger objects- like the ships hull, for example. It would be a very silly thing to try to make a miniature topographic map of an awl handle with a lidar setup, which is designed for large scale surveying. It would also be more time consuming (not to mention frightfully expensive) to scan my two hunderd or so objects with a laser scanner, and then go through all the necessary processing and data curation (i.e. throwing out 99% of the information taken in by the machine) to achieve the same end: a fairly simple line drawing.
"Ok, fair," you might say, "but why not just photograph everything and be done with the cataloging in a week?" That's a better question. Of course, we will also do that. But we're missing a fundamental thing here: the point of research is not to be done with it all tomorrow. As researchers, it is instead our task to spend enough time with one data set or collection that we can see the patterns and relationships, start to gain some fluency in the topic. The final drawing, though an extremely useful tool for publication, reproduction, and the general conveyance of information, is actually an artifact of a process that in itself is as important as the product.
In taking the time to draw and measure by hand, we are engaging in extremely close observation. When you first start out with a project like this, you're not always so sure what you're looking for. Your statements feel a little wobbly, you sort of wonder at the legitimacy of the things you note. There are a lot of question marks on the cataloging sheet. "Awl handle? Turned? Has been conserved- evidence of glue (?)" You second guess yourself: is that a crack I'm seeing, or some glue? That is disgusting, did someone sneeze all over this or can PEG residue really look like that? Is that a replica, or has it been conserved differently than what I've already seen? Is that hole evidence of turning, or is it a hole from an old artifact tag fastener...? Shooting a photograph and putting something back in a drawer doesn't give rise to the same sort of questioning as having to make decisions about which details to present in a drawing. Deciding which lines are important, what is modern, what wear or use was contemporary, what measurements would be key in building a replica - though on a very small scale, these are all curatorial decisions.
The more time you spend drawing, measuring, turning these things over, checking them out under the microscope, adjusting the light and the angle, feeling the weight, and the more that pass through your hands, the more literate you become. "Literacy" in the context of 17th century tool marks or the physical evidence of 1950s conservation practice sounds a little weird, but I can't think of a better way to put it. And then, maybe all the way through cataloging the braces and mallets and halfway through all the awls, you start to make connections you wouldn't have considered before. Carved "bomärke" - ownership symbols used by the illiterate (see photo above) - all of a sudden declare themselves as if highlighted in neon. You revisit some of the things you worked with early on, and you start to notice new details. You've developed a system, a list of points to check and re-check, you have an inherent understanding of what falls in line and what stands out. It's almost connoisseurship, in a funny way.
This is why we still draw, with pencils, on paper, when we catalog at Vasamuseet. Boatbuilding, archaeology, drafting, these are all fundamentally human and physical practices. Each of the tools I am studying was both made and used by one or maybe a small handful of individuals. There is character in these objects in much the same way that there is individuality in handwriting. We can use the most sophisticated technology in the world to augment our work, and we will use those tools when it makes sense. But the practice of close and discerning observation and the human mind's ability to draw connections and curate across a collection is hard to replicate with a computer program. Thoughts like these help us cultural heritage proponents, registrars, curators, conservators, educators, et. al., rest easy at night. You know. Job security.