Investigation 3

A personal account – Paul Constantine (PCon)


Before building a ship it might be a good idea to talk to people who already have experience of such an undertaking to find out what they think and listen to any advice that they can offer.


The centre for historic reconstructions in Denmark is Roskilde (pronounced Roskiller).

Visiting from England. Peter Clay, Malcolm Hodd, Peter Bradbeer, Paul Constantine.

In Roskilde we met Vibeke Bischoff and Sǿren Nielsen.


Later we also visited the recent Danish reconstruction of the Nydam (pronounced Nudam) ship.

Peter Bradbeer and Paul Constantine also visited the original Nydam ship in Schleswig-Holstein and the Hjorstspring ship.

These notes are mainly an understanding of what Vibeke & Sǿren said, with some added observations. It is not necessarily in the chronological order of the conversations, but in places has been re-ordered to produce unified topics.


The Anglo-Saxon ship should be built in Britain.

Define what are you trying to achieve.

You need to have a clear picture of your intentions e.g.

In one historic reconstruction that we have seen, the builders began to

mix their modern and ‘historically-authentic’ tools. They used modern caulking.

In another project, they reconstructed what was found in the ground, not the craft.

What will the allied research plan be seeking to achieve?

Decide on the afterlife of your boat early.                                                                           Vibeke Bischoff                 

Academic expertise

Initially we didn’t use PhD people.

They didn’t know what to write down. We gathered our own information. One young man used our results to gain his PhD. We had to tell him/them what to do … to make the job clear to him/them.

Record: How many hours? How much wood?

We preferred craftsman not academics. No PhD students working, only boat builders.

The PhD people were happy with investigating.

Most academics we took in didn’t know what questions to ask the boat builders. The most successful was an ethnologist who had studied people.

To work alongside academic people there has to be cooperation between them and the skilled crafts people. We have seen 3 different ways to do it.

1. Use educated skilled boat builders.

2. 1 master craftsperson and then the community who wanted to do it as accurately as possible. Their volunteers own their boat. They will love it for the rest of their lives.

3. Mainly academics. Using volunteer archaeologists, not skilled boat builders.

Whatever the method, the key is cooperation.

Volunteers. Don’t get too many. One person must have the experience.

Computer modelling.

Roskilde use Rhino. Use 2D but not 3D as you can break the laws of physics in a computer. Some frames are recorded digitally, but usually model in cardboard.

A Danish firm with sophisticated equipment printed some drawings for Roskilde ‘for fun’.

A 3D model of Harald Fairhair for tank testing had cost £10k. Tank testing is limited in what can learned. It cannot test flexibility or handling. Reality is better than theory. It is the questions you ask that are important. There was a description of a real experiment undertaken to test the ideas of vortex generation and the vacuum between the rudder and the ship, using bare feet to sense the plank distortion and wedges to control the shape of the underside of the ship.



Set up the building environment.

Use a small group. Review all the components several times, before going to the forest.

Work from the drawing, but when the theory doesn’t fit, change the drawing. What is discovered is more important than the drawing. The plan was only a guide that could be changed. Make your own decisions about things. Build as correctly as possible. Decisions have to be made about how to iron out irregularities.


Time and Money. If there are no limits on money everything can be done authentic, but this might not be the best approach for ‘everything’. With floor timbers half were made with axes and half with a chainsaw. The chainsaw took 5% of the time taken with axes. We decided how and when to use the saw to save some time. Should we shorten a plank with an axe? Fit the time to the money.

Do not to keep it secret, explain it.

We are asked: Why do you not wear Viking clothes?

We are asked questions about navigation, toilet paper and food …

We say: We are not Vikings.


Dangerous undertaking.

Martin Carver was on the Oseberg ship that sank. He used the capsize pictures. They were rescued, but they were cold and could not rescue themselves. There were only 7 to be rescued with no lifejackets. Sea Stallion carried 60-65. The ship with them had a crane with a net to drop in the water. The people could be rescued about 15 at a time in the net, lift them aboard and then drop the net again.

When the rudder broke on Sea Stallion the ship laid broadside to the wave doing 4 knots downwind in a Force 9. It took in water. It only has a draft of 88cms.

Some people are going to risk their lives. You have a responsibility.


An issue for consideration. Keel rocker

The first Oseberg ship reconstruction was the wrong shape. The keel was too straight and the cross section in the bow not right.

Sea Stallion of Glendalough. It can be seen that the ends of the ship are not on the ground - the keel has 'rocker' which means it is curved upwards

Comment (PCon)

Vibeke Bischoff is very sure that all the craft should have a rockered keel. It may not be a huge amount, probably about 150mm. She has applied this rocker to the Ladby ship and the Oseberg ship. She believes that the centre of the ship is supported by the water and the ends have less support. Over time the unsupported ends will gradually drop making the keel straight and then possibly they will drop further, producing a hogged keel. When we eventually visited the Hjortspring boat it had a permanent line rigged the full length of the craft (hogging truss) that was tensioned with a Spanish windlass attached to specially shaped blocks at stem and stern to keep the ends of the boat permanently lifted. This was used in the original craft. Part of the reason for this form is to push the midship gunwales outwards and to make the vessel more manoeuvrable.

Everyone we asked about this feature was convinced that it was correct, based on their experience.

Both Vibeke and Sǿren thought that we should apply rocker to the Sutton Hoo ship. They wondered if photographs of the excavation might show that it had a rocker, but it is difficult to imagine how such information could be derived from photographs and how conclusive it might be. The ship may have dropped its ends in its working life before burial and the process of burial might also have further distorted the hull.

It is a decision that will have to be made prior to the build. At this time no decision has been made but the evidence for applying rocker should be considered.

Hojortspring ship 325BC reconstruction

The twisted rope running the length of the ship is the hogging truss


Nydam visit.

The meeting was with the Nydam ship build group lead by Vincent Jessen (who has since died) and Ole Brixen Sondergaard.

The most relevant information for the Sutton ship related to building in green timber.

1. It did not appear to be a problem from the viewpoint of drying and splitting the wood. Their craft took about 5 years to build.

2. The shrinkage must be allowed for, if there is a final defined shape to be achieved. Their ship cross section drawings and formers defined a location point on the upper, inner corner of each plank. This then made allowance for each plank to shrink to become the correct dimension. A figure of 10% shrinkage was mentioned.

 Woodbridge visitors with the Nydam team 


A box of tools was found on their original ship (dated approx. 325AD). Spokeshaves and simple planes were part of the equipment. Different axes and shallow (slow) gouges were the main tools. They agreed with the Roskilde idea of fitting the time to the money. They had used saws, but then reworked the timber surface with their hand gouges to make it appear authentic.                              


They used a finely woven woollen cloth about 45mm wide. (The width of the lands of the planks.) They impregnated this with a mixture of beeswax and tallow. The tallow was about 5% when used in the lower ship (harder) and about 10% (softer) higher in the ship to change the consistency.


The rivets are iron without carbon added. This allows the rivets to be soft. The iron came from Sweden as round bars. After heating they beat the iron down to size and drove it into shaping tools. A small hole was used for the point and a larger hole for the rest of the rivet. They were about 5-6mm diam. To form the head of the rivet about 45mm of the bar is needed for flattening. A batch of about 20-25 rivets is made, taking two people about 3 hours. The rivets are then heated to cherry red and allowed to cool to black when they are submerged in Stockholm tar which sticks to them and blackens them acting like a galvanising coating.

It is important that the rivets are soft so they are malleable and flex with the wood. If they were harder they would wear holes in the wood. The textures of wood and metal are in tune with each other. Modern rivets and roves are usually made of copper which is soft. The iron roves are cut from an iron strap with a chisel. Holes are made with a spike over a hole in the anvil. They cut first and formed the hole afterwards. (I would do the opposite, but experience will tell. PCon)



All green oak was used at Nydam. Trenails are willow. They had trouble sourcing wood for their frames which are grown and intricately shaped. The wood all came from Denmark, sometimes sourced from the large 'Bride Oaks' that resulted from Napoleonic era conflict. I am indebted to Ole Brixen Søndergaard for the following explanation:

The British Royal Navy either destroyed or took away Danish ships in 1807 following an engagement off Copenhagen when the city was destroyed with great loss of Danish lives. Losing the fleet meant that there was a need for 90,000 oaks to rebuild the Danish Fleet. The Danish fleet authority confiscated all usable oak in the country and the king issued a command that oak for the navy had to be planted all over Denmark. To get permission to marry, any bridegroom had to plant a defined number of oak trees. Some of these Bride Oaks still survive to be found in the forests. The royal command to plant was never withdraw. As late as 2007 one manor sent a letter to the navy authority: 'Our navy oaks are ready for delivery.' This is the reason that many well-grown, 200-year-old, Navy Oaks are still found in Denmark in a usable condition, for the reconstruction of historic ships. Nydan Tveir is one of them. 


The Hjortspring boat needed lime trees and they were found near Warsaw in Poland. The geographical circumstances of locating timber (One Roskilde ship was built in Ireland) allows the Sutton ship timber to be sourced from where it is available.

Nydam planks are very different from Sutton Hoo ship planks due to the upstanding cleats used to secure their tied frames. Their planks begin at 150mm (6ins) thick and are carved away from the solid. For this reason they need not be quartered. If the inner tree rings are placed to the outside of the ship the plank will bend as it shrinks with its curvature facing outwards. As they used only 5 planks per side this natural curvature assists in making a more rounded hull form and re-aligns the plank edge to ease the cutting of the land-bevels.

We were told that a lot of the East European timber comes with a generous amount of shrapnel embedded.


Tholes and Oars

Tholes are not all the same as each other; neither are oars. Each one is an individual. They theorised that each person made their own, but the natural differences in the timber would tend to make them different anyway. In modern times we are accustomed to the uniformity produced by machines, but this was not possible at that time. Having said this, one thole, the nearest to the starboard bow was markedly different in design and construction.

The tholes are tied in place. In use it has been found that the ties stretch and become too loose to be useful. To correct this they decided to attach the tholes with hidden pegs. This is a very good example of them changing the construction to make it work. To some extent it would offer the option to do the same with other aspects of construction if it was found necessary.



In Roskilde rope had been made from a variety of fibres. Seal skin rope is very stiff and was being used for standing rigging. Wool rope is quite soft and was being used for running rigging. In Nydam and Hjortspring they used Lime bast rope made from the inner layer of the bark, which after a lengthy soaking in water separates into strands that can be twisted into stiffish, yet strong rope almost like thick string. This rope was used to sew the Hjortspring boat together. To pull it tight it was wrapped around a specially-shaped stick that was then used to lever it.


Some conclusions.

Peter Bradbeer.

It was clear from the tone of the conversation that funding & academic approval were not in the forefront of their thinking, but just part of the project. The projects were driven by a desire to build the ships not by finance or scientific considerations which are just treated as intrinsic parts of the projects. This is especially true of the amateur projects.

The Glendalough project (Sea Stallion) had the academic write-up almost as an afterthought and this project was still not complete.

The use of Guilds to operate and maintain the ships after construction which start to coalesce during the construction phase is an important precedent that should be heeded.

Salient features:

State your aims clearly and concisely at the outset.

Involvement of National institutions provided the Danes with protection from criticism.

Build in the UK with local craftsmen. It can be done.

  • Modifying building methods is possible providing explanations are given and don’t damage the integrity of the construction.
  • Decide on certain construction issues e.g. the decking (which we may now have the answer to)? (He is referring to the system used in the Nydam ship. PCon.)
  • It is far more complex than it appears at first sight, but the Sutton ship construction is simpler than Nydam.
  • Safety; people’s lives are at risk.
  • We are not Saxons.
  • The Rocker. This requires careful research as does rudder development.
  • The mixing of green wood and seasoned wood does not appear to cause difficulty. Drawing up plans from a seasoned wood specification requires an adjustment for shrinkage.

What Next?

The next waypoint is to produce a set of construction drawings following the above points. This will mean making decisions on everything that is presently missing. Remain open minded if the facts change later. Plans can be changed to accommodate.