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Text by Jørn Olav Løset, Norway.

Building a Viking ship or a boat of Norse design involves a traditional craftsmanship which is a refined art, delivered from master to apprentice, usually from father to son for generations. The skills vere passed on as tacit knowledge, mostly orally and by doing, usually without any detailed drawings or accurate diagrams. In additon, very often the crafter was himself an experienced seafarer, having participated in seasonal fisheries in the fjords and offshore from his early teens, giving him a first hand experience of what distinguished a good boat from a dangerous one. I have not yet built a wooden boat myself, but by visiting and knowing several boat builders I have a fair understanding of the main principles of how it has been and still is done in north-western Norway. This page is meant to explain some of the basic steps of norse wooden shipbuilding, and should not be regarded as a complete how-to guide as skill and experience is difficult to pass on in plain text.

Lapstrake - clinker boat building

The clinkered Viking ships stands in strong contast to the carvel method where strakes are fastened onto a skeleton of ribs. The Vikings did it quite opposite, following a shell-first sequence, laying the keel first, then adding strakes and fitting the internal timbers as the last stage. A Viking ship is much lighter and more flexible than a carvel built ship of the same size, giving the Viking ship both excellent seaworthyness and making it capable of crossing shallow waters as rivers and allowing the crew to pull it onshore in a hurry.
The steps mentioned here is for smaller tradition boats as I have seen it, but the Viking ship were built in the same manner. The larger ships are reinforced in the stem and the stern in comparison to the smaller boats and the scale is, of course, much larger. This following description is roughly how clinker built boats have been made traditionally in Scandinavia. The earliest boats were sewn with animal guts, but were soon replaced with rivets as soon as iron gradually became accessible for the boat builders some 1700 years ago. The iron rivets are still called 'saum' in Norwegian dialects, literally meaning 'stitch', revealing an unbroken tradition of lapstrake building that reaches beyond the Iron age.

The lapstrake boat hull. Copyright 2008 Jørn Løset.

The lapstrake hull in detail with english and the names of the parts in Old Norse language.
This is a basic Viking boat.

Færing of the oselvar type with the keel, stern, stem and the two first strakes in correct position. Crafter is Hallgeir Bjørnevik from Os in Norway. More about the oselvar >>

Arrangement for supporting the hull before the ribs are mounted. The boat is a færing from Sunnmøre during building. Crafter is Jakob S. Bjørkedal from Volda in Norway.

Every part of the hull have specific names, even each of the strakes.

This boat from Sunnmøre is unfinished for demonstration purpose.

Some of the hand tools used today in wooden boat building. A major difference from the viking age is the development of good saws and planes.

The Viking ship hull

Sea launch and rigging

Hopefully the illustrations will ease your confusion a bit. Click images to enlarge:

Splitting logs into strakes.
The point is to avoid the marrow.

Attaching the first strake to the keel

Keel support arrangement

Supporting the keel is absolutely essential to maintain symmetry in the keel when the strakes are added. Any errrors here can't be undone later. The diagram for splitting the logs into planks provides a challenge for boats builders who are forced to buy industrially sawn materials. Oak can be split radially, while pine permits tangentially split timbers, avoiding the pith in the center. Thus, it is possible to obtain wider planks of pine from a log of the same diameter.

Splitting or sawing the logs?

The shipbuilders in the Viking age (793 - 1066) used to split the logs by using axe and wedges along the centreline. The plank was then chopped into shape by using a broad adze, almost like it was a rough plane. This is illustrated in the Bayeux carpetry, and confirmed by investigating the strakes of archaelogical ship finds. From one log they usually only got two or four planks well suited for boat hull. This may look like a waist of resources to us, but the benefits are several:
In this way they achieved to get planks where the radial pores from the marrow (no: margstråle) where in parallell with the plank, instead of pentetrating the plank. The adze chopping and planing also compressed the cell structure in the surface and made the planks smoother and more water resistant. A third advantage was that the growth rings in the wood then got right-angled to the surface. Each strake then became stronger and more resistant to mechanical wear. The result was a stronger hull more resistant to leaks and wear.
A guess from my side is that it is possible that the root end of each strake was deliberately placed towards the front end ot the ship. Then the wood fibres in the strake and the surface chop marks would reject the water flow, instead of leading water into the wood cells. Adzing against the wood fibres is difficult, but along it is easy. This principle has been used in norse wooden skis for centuries and to some extent in wooden roof covering in Norway. It may very well have its parallell in norse shipbuilding. Much of this understanding of the mechanical properties in wood is lost with the introduction of modern saw mills.

For most ship builders of today a viking ship project is a compromise between financial resources and to which extent one can follow the historic building techniques. In most projects the builder is restricted to selecting industrially sawed planks instead of splitting and adzing logs. This was the case for famous replicas like Saga Siglar and Gaia and others, even though the ship builders were well aware of the log splitting technique.
But despite shortage of time and money the above principles can still be used to some degree. One should try to select planks at the store which are sawn in a similar pattern along the core-line. Choose planks with dense growth rings and few knots. The weaker pith itself should be avoided and planed away, first by machine but preferably finished by hand planing.

Strake joints

Keel and stern joints

Plank steaming arrangement

The strakes and the keel joints are done by slanting the overlapping ends. The nails then penetrate both ends, forming a strong joint. Remember the direction of the water when the boat is in use so water is not forced into the hull by the movement the boat. Such joints should ideally be avoided or at least be spread evenly along the hull. Two joints in two successive strakes must never be placed at the same rib. This will substantially weaken the hull at this point.

Warning! The same goes for the keel if this is laminated. The Gokstad replica Ormen Friske built in 1949 had a laminated keel where the joints of each layer in the laminat were put way too close to the other joints, instead of being spread evenly along the keel. The result was a weak point in the keel close to the mast basis which turned out deadly when Ormen Friske hit a storm offshore in 1950. The ship broke apart and none of the 15 crewmen survived. The lesson is as simple as challenging: do not take any short cuts in the design and be critical when selecting the materials.

Stiff planks can easier be bent into shape after steaming. Steaming can be done easily by an arrangement of boiling water in an oil barrel, leading the steam through a pipe into a hollow profile of planks. If possible the hull should be built of "green" timber fresh from the saw mill or kept moist until builiding is done.
In some parts of western Norway the former boat builders used to soak the strakes or timer in salty water in the fjord. When sunk as deep as 200 m for a month or two the wood got penetrated by the salt in the cold water. When the wood later dried, the salt was left within as a natural proofing against rotting.

'Meginhufr' - 'the Strong Strake' in Viking ships

One of the strakes deserves to be mentioned in particular. Many of the excavated Viking ships feature a special design of the strake which is level with or just below the crossbeams, the so called 'meginhufr'. The name is Old Norse language, a compound of 'megin' and 'hufr', the first meaning 'large' or strong and the latter 'strake' or ship plank. Thus, the 'meginhufr' is the strong or sturdy strake, a construction element that absorbs and distribute the lateral forces from the waves and the crossbeams and at the same time makes up a longitudinal reinforcement that acts like a spring along the ship side, maintaining the flexibility of the hull. The meginhufr is thicker than the other strakes (about 50%), slightly narrower and often hewed into a rather intricate profile, like an L or an S with distinct edges. It is also made from a very long timber, 2 - 3 times longer, compared to standard strakes, as the ship builders have tried to make it as long as possible in one piece. The meginhufr is often seen in the early Viking ships, those with lashed ribs, and rarely in ships that dates to the 11th century or later. In later ships it has been replaced with stringers instead, that are attached to the inside of a more ordinary strake. Obviously a simpler solution for the crafter, requiring less specialized skills and saves some of the raw materials, but possibly also resulting in a weaker hull. The meginhufr is often found in one of the plank tier from 7 to 12 counted from the keel, depending on the size of the vessel. In the Oseberg ship the meginhufr is the 10th strake, running some 13 m long without joints. Anyone who replicates a Viking ship after an actual design that originally had this special strake (on both sides), should try to replicate it as good as possible as it is a significant element in the hull.

The rig and square sail

The rig of a viking knarr.
(Click to enlarge)

Phoenician merchant ship with similar rig, ca 1000 BC.
Image University of Texas, permission pending.

The Bayeux Tapestry

Nordfjord færing 19th century.

One mast and a square sail

The viking ship had only one mast which could be taken down. The sail was square attached to a cross beam in top. In addtion the mast was supported by ropes from the top down to the stern and stem and to several places along the gunwhale. The crossbeam could pivot around the mast so that the ship could be sailed with wind from behind and from both sides. The main problem was to sail against the wind. It was possible to some degree, but could not sail as sharp as with a modern rig.
The sail was made of woven wool or linen. The ropes were usually tar-proofed hemp. In more rare cases ropes were made from horse tails or even from walrus hide.

Phoenician inspired rig?

I believe that the scandinavians were strongly influenced by mediterranean rig designs when they started to put mast and sail on their ships. The transition from pure rowing ships to sailing ships probably took place in the 7th and 8th century.
The phoenicians used rig designs with one mast and a sqare sail some 2000 years earlier. Although the phoenicians eventually disappeared, their rig design survived in greek and roman ship designs. Somehow the ideas of such rigs must have travelled to northern Europe. Eg. the romans used sailing crafts when they expanded the Roman empire to include parts of England. Roman coins have also been found as far north as Herjolfsey in Iceland, which may indicated that the romans undertook long voages deep into Scandinavia long before the Viking age. But the scandinavian ships remained rowing ships until the keel was strong enough to carry the strain from a sail in the 7th century. Perhaps the keel was developed in direct response to just meet these demands? The further development of the keel, mast base and rig then must have followed hand in hand.

Carved picture stones from the 8th century from Gotland in Sweden shows several varieties of ships with rig. The height-width ratio of the sail should probably not be regarded as accurate in these images as they are very rough in design and limitated to the shape of the stone. But they all confirm the sqare shape of the sail. Some of these images also picture a lower yard in the bottom of the sail.
The ships in the Bayeux tapestry do not have these lower yards. Instead they show problems with the sail collapsing in its lower part. These ships were built in Normandie by William the Conquerer, and may not be good examples of a viking rig design or the embroidery may be inaccurate in displaying correct rigs.
This indicates that several rig designs existed side by side. Most (or all?) modern viking ship replicas have left out a lower yard, but sometimes include a lower beam for keeping the sail wide at the foremost lower corner while tacking or sailing downwind in modest winds.

The rig of the Gokstad ship

A major problem for maritime researchers and historians is that a viking ship with a complete rig has never been found. Some remains of ropes and parts of a sail was found in the Gokstad ship. The mast was cut or broken and some wooden beams belonging to the rig was found. But still the rig was incomplete, so one is left to some guessing to get the entire picture. The size of the sail and heigth of the mast is widely discussed ever since the Gokstad ship was excavated.
The 1892 replica Viking had a sqare sail, but this was probably too tall. Later replicas have been equipped with a lower and broader sail. An old norwegian rule of thumb says that one should be able to lower the mast within the stern of the ship. In the case of the Gokstad ship this limits the height to about 12 m.
Later wooden boats from western and northern Norway are direct descendants of the viking ships, and are likely to have rigs and sails very much like the vikings used.
The sail and rig designs were usually slightly different in each geographich area and of course in size according to the size of the boat. But the square forms (quadratic, trapezioid or rectangular) were dominant into the latter part of the 19th century. Boats from western Norway usually had lower sails than in northern Norway, and some with trapeziod sails.From about 1880 triangular sails took over as the main design. This also changed the way the norse wooden boats could be sailed, and in many ways the sailing tradition of the vikings was broken.

These are the key elements in norse shipbuilding as I see them. Before you eventually go ahead building a boat, seek as much information as you can. Study finished boats in detail and listen to people who have done this before you (thus.. not me!). Take care selecting only good materials. Oak is what the vikings preferred, but pine is also fine. In northern parts of Norway spruce was used, as the climate there is to cold for growing pine in suitable dimensions. The sail can be sewn from Duradon if you are building on a budget, as most bulders do. A sail of woven wool is historically much more correct, but will also rise the cost of a project by one half or even more.

For further inspiration, see the rest of this site.

Regards from Jørn Olav Løset

The workshop of Jakob Helset in Bjørkedalen, Volda, Norway. This boat was later named 'Tylft' and has five pairs of oars. Overall length is 10.5 m.

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Copyright 2004 Jørn Olav Løset. Last update 12.04.13. E-mail: joeolavl @ online.no