Hello Alexey! Bilingual report from the research project Support Vasa part I: Time dependent experiments

Guest blogger Alexey Vorobyev from Kazan, Russia, researcher on mechanical behaviour of archaeological wood in the Support Vasa project and PhD candidate in Applied Mechanics, Uppsala university, reports in his native language and English:

Эксперименты по ползучести археологической древесины в Музее Ваза.

Археологическая древесина корабля Ваза – материал со сложной внутренней структурой. Корабль пролежал на дне Стокгольмской гавани 333 года. После обнаружения и подъема корабля корпус Вазы был пропитан полиэтиленгликолем и высушен. Несомненно все эти модификации влияют на статическое поведение корпуса корабля.

The material Vasa is made of is very complex. Initially Vasa material was just oak and due to historical circumstances spent 333 years at the bottom of Stockholm harbour. After the ship was salvaged, Vasa was impregnated with polyethylene glycol and dried. All those modifications are undoubtedly affecting the mechanical response of the Vasa.

Археологическая древесина Ваза кубический образец. Vasa material cube sample.

Для прогнозирования деформаций и перемещений конструкции мы проводим эксперименты по ползучести древесины. Одна из особенностей этих экспериментов - это их зависимость от времени. В качестве образцов мы используем не только материал корабля, но и сухие образцы свежего дуба (Quercus Robur).

In order to predict deformations and displacements of the ship structure in the future, we are performing time dependent experiments with Vasa material. However it is not only archaeological material that is tested, we compare our results with reference material, which is a dried recent oak (Quercus Robur).

Весь эксперимент состоит из трех инсталяций. В первой мы замеряем изменение веса наших образцов в зависимости от времени и микроклимата в музее. Во второй мы замеряем ползучесть в планках из археологической древесины Ваза. Параметры прогиба, веса, толщины принимаются во внимание. Наконец в третьей инсталяции мы делаем упор на измерение ползучести под непосредственной нагрузкой в материале Ваза и свежего дуба для последующего сравнения. Нагрузка прикладывается на кубические образцы со стороной 25 мм в направлении древесных волокон.

Time dependent tests are consisting of three different installations. In the first we are measuring the change of weight of our samples with time, depending on museum climate. The second installation is measuring creep of planks. Here we are measuring parameters such as plank deflection, change in weight and in thickness with time and climate at the museum. The third installation is measuring deformation on Vasa wood and reference material. In detail, we are using cubic samples with a side of 25 mm and applying force in the longitudinal or axial direction.

Установка измерения ползучести в балках. Plank installation for measuring creep, with applied load.

 

Установка измерения ползучести в образцах обыкновенного дуба и материала Ваза. Rig for measuring creep in Vasa cubic samples under permanent load in axial direction. 

Результаты экспериментов предполагается использовать в качестве начальных параметров для общей статической модели поведения корпуса корабля под собственным весом. Мы надеемся, что текущая работа позволит нам понять, предсказать и избежать в будущем ненужных деформаций в корпусе корабля Ваза

The results of the experiments will be an input for a general mechanical model that will be used for prediction of the structural behavior of the ship.

We believe this will help us to predict, understand and avoid the unwanted deformations of the ship hull.

 Алексей Воробьев,

Казань, Российская Федерация

Докторант по направлению прикладная механика (Инженерная физика), Уппсальский Университет,

Специализация в области проектирования материалов и конструкций,

Тема проекта докторской диссертации: Исслелование статического и динамического поведения археологической древесины под действием нагрузки с течением времени (вязкоупругость, ползучесть).

Проект: ”Support Vasa”

                                                                                                                                                                                                                                       

Fotografering

Summer is kicking into high gear here in Stockholm, as evidenced by the lines stretching out and away down the sidewalk in front of the museum. Even from below in the magazines, through all the rebar and concrete of the excavation pontoon, there has been a noticable increase in the volume of foot traffic overhead. For the last few weeks, I've been keeping busy in the basement studio, photographing the tools. (And occasionally a few other fun things on request - see mystery object below)

 

Object photo of a small decorative animal

 

The goal is for the photos to look highly standardized; museum-style photographic documentation of artifacts requires a systematic and studied approach. For each object, we take six plan view shots (from all four sides, top and bottom - see example above) with a scaled ruler and the object number, two perspective views ("glamour shots" - see below) and finally any detail shots necessary. This adds up to a bare minimum of eight photographs in total per object, though usually more.

 

Perspective view of small animal figurine

Any guesses as to what sort of creature this may be? The missing face calls for some interpretation...


After processing, the objects float in clean white space, and the photos look straightforward and almost clinical. Simple, right?

 

Perspective view of small animal figurine

 

In reality, the process requires a fair amount of fussing and creative thinking, because there is so much variation in the objects themselves. It involves a lot of very careful object handling, some very delicate and considered supporting and propping up with slivers and wedges of white gum eraser, and lots of balancing off ladders and holding-of-breath to get clear shots with the least amount of lens distortion possible. Also plenty of cajoling and trickery to convince the lighting set up and external flashes to cooperate (it's somewhat advanced in years). I'm about two thirds of the way through photographing the roughly 230 or so charges in my care.

 

Taking photos of taking photos

A rare glimpse of the photographer in her natural habitat- shot of shooting shots above, courtesy of Irene!


As with all of this fiddly work though, time seems to pass quickly, and I enjoy the attention to detail it requires. I'm starting to see further connections between objects as I go through them one by one for a second time. It's heartening to follow along with catalog records and drawings done six months ago and realize how much I have learned about the collection since then in the process. 

Dammsugning

The time has come again to clean ship! I brought a real camera with me this time because I was working from the overhead crane with our head conservation tech, Ove, vacuuming the rig. It's an unusual vantage point from which to see the ship, so I wanted to share a few shots with you:

The overhead crane basket

The basket, pre-launch. It kind of feels like being in a hot air balloon.

 

Shot of the rig, looking up

View of where we're headed from just above weatherdeck level. Not for the faint of heart, or those disinclined towards working at some height.

 

View down onto deck from the overhead crane

Looking down on the deck; to give a sense of the height, remember that the ships longboat down there is a little over 11m/36ft long...

 

Armed with dust masks, brushes and vacuums, we attack the tops

The mizzen top.

 

View looking aft from the main top

& the view looking aft from the main top at our freshly vacuumed mizzen top. Hurrah! [Edit: I was asked recently how far we are from the ground level in this shot, and it's about 30m/100ft]

...

Meanwhile, conservator Emma  works on the transom sculptures from the after platform crane:

Conservator Emma Hocker vacuums transom

 

The view from here is also rather stunning:

View of after platform looking down towards rudder

Another great few evenings! Dusty hard work, but always a privilege to have a chance to investigate the ship so closely. Iit's very satisfying to clean on this scale; my experience in art conservation labs to date has more often involved cotton swabs and microscopes than giant feather dusters and skylifts. Definitely more fun than vacuuming the average living room. 

Bärgning

One of the things I especially love about working in storage is doing research in "Rum 149: Fotoatelj." It's the very last room at the end of the magazine, a bit chillier than all the rest, and it contains the bulk of the documentation produced during Vasa's active conservation. Here you can find excavation maps, negatives from salvage, drawers of test tubes full of tiny plugs of wood (core samples), hundreds of leftover excavation tags strung together on wire loops, and two tall filing cabinets full of grey archival-box-style binders.

Photograph of the binders containing original excavation records

Seven shelves, fifteen binders per shelf, three hundred sheets of paper per binder:

A stack of original find records

These are the original find records from excavation. One for every object brought up from the bottom, mud rinsed off, stored in bathtubs on the pier while awaiting tagging and preservation. Each sheet briefly identifies the object, its find location within the ship including deck level and side, the date it was excavated, and the initials of the archaeologist responsible for filling out records on that particular day. There are also rough sketches and measurements in many cases.

Photograph of find location and record number

In looking through these records, from 00001 (Vasa herself in the database, but an individual plank on paper) to 35534 (a piece of sail, one of the last things to be painstakingly unfolded and conserved), one can sense the transition from outdoor excavation and the pressure of oncoming winters, to the urgency of clearing the ship of mud and contents once she broke the surface (the engineers were quite concerned about the ship supporting her own weight before a permanent cradle could be built around her), to the slight breath of relief with the transition to a lab as reconstruction and conservation proceeded. 

 Original find record sketch Original find record sketch

The drawings, when present, appear in varying degrees of detail and sophistication (see above, left and right, for example). Again, one can feel the pressure of an excavation season's end approaching in the roughness of some. And more than a few still wear a layer of Stockholm harbor mud over top. There are hand prints and finger prints, and I have become as familiar with our archaeologists' handwriting as I am with the tools themselves.

Harbor mud on find records

If you spend enough time flipping through the records, you start to see glimpses of personality through the paperwork. An accession sheet for a diver's cap, a ham-handed sketch out of keeping with that particular archaeologist's style, a few pages of fat charcoal pencil or pen instead of the usual no.2 weight lead lines. It's a delicate distinction between the acknowledgement of the inherently human nature of archaeological practice (humans studying humans), and romanticization. Still, it's important to remember the people that collectively account for the history, interpretation and continued life of Vasa. This includes the king and government administrators who first conceived of her construction, the shipwrights who laid the keel and the sailors on her maiden voyage, but also extends to those involved in attempted salvages in the 17th and 18th centuries, the archaeologists and conservators of the 20th century, and our researchers, guides, curators and visitors today.

Modern catalog record