Complete Guide to Viking Ships

Viking boats and ships

Summary

Viking Expansion

Shipbuilding

The different types of Viking boats

Archaeological remains and replicas

Navigation

 The Dragon Harald Fairhair, a Viking ship of the 21st century

Viking Expansion

The Vikings sailed most of the North Atlantic Ocean, the Mediterranean and the Baltic Sea and occupied most of the river system of continental Europe as looters, traders, explorers, settlers and mercenaries. This phenomenon is referred to as Viking expansion.

Although renowned chiefs formed alliances to lead joint expeditions, the Vikings were interested, depending on whether they were Danish, Swedish or Norwegian, in distinct geographical areas.

• Vikings from Sweden went east, took control of trade routes along the Russian rivers to Constantinople, where they joined the ranks of the elite Varangian Guard and founded the Kiev Rus'.
• The Vikings of Denmark made their way south, through Friesland, southern England, France and the Mediterranean to North Africa.
• The VIkings of Norway headed west and north-west, north of England, Scotland, Ireland, the Orkney Islands, Shetland and the Faroe Islands, but also Iceland, Greenland and beyond to the New World.

Erik the Red, banished from Norway and then again in 982 from Iceland on murder charges, sets sail. A long voyage will end up leading him in 985 on an unknown shore. He baptizes it Greenland (Greenland), and founds a colony in Eystribyggð, between the cape Farewell and the polar circle. His sons Leif and Thovald, will push the adventure to the American continent, and arrive in the province of Newfoundland and Labrador, of which they will explore the coasts. Traces of a seasonal camp were discovered at Pointe Rosée and a settlement at L'Anse aux Meadows.

While the Vikings from Norway willingly faced the North Atlantic, others from Denmark were seduced by the lure of the South Seas. Throughout the 9th century, the men of the North, the Normans, launched raids, pulling their ships ashore when necessary, sometimes even over long distances. In France, they ransacked Rouen and Paris, harassed many other cities, even setting up camps to spend the winter, and gave no respite until they obtained from Charles the Simple the territory of Lower Seine, which would become Normandy and soon serve as a base for the invasion of England.

In 1066, William the Conqueror took command of a fleet of 3,000 ships, including 700 warships, bound for England. He met little resistance and occupied the island, as no one cared to continue the policy of Alfred the Great, whose powerful fleet had repelled a Viking landing attempt in 893. The sheer scale of these incursions and the relations established by the Normans paradoxically led to a boom in maritime trade.

If the Vikings dominated Europe between the 9th and 11th centuries, it was largely thanks to a technological revolution, their long and narrow sailing ships, the famous langskips, better known in France as drakkars.

The term drakkar, generally used to designate any Scandinavian boat from the time of the great Viking raids, is an invention of the romantic wave of the 19th century and has no historical reality.

A common idea is that drakkar comes from the old Norse dreki, certainly derived from the Latin term draco and used by association of ideas, as the prow of these warships was often decorated with a dragon's head. But it seems unlikely, even with the evolution of the language, that the word dreki became drakkar. The term drakkar may have been borrowed, in the 19th century, from Swedish drakar, plural of drake, whose primary meaning is "monstrous snake, dragon".

Until the 19th century, the term most used in various texts, and adopted very early by the Norman language, is the word esnèque or senèque. It comes from the old Icelandic word snekjur, plural of snekkja and applies to one of the types of warships common in the Viking Age, the snekkar.

Régis Boyer relates that Viking ships "took on board, on average, about forty men with their food, equipment and cargo. Add to that the few horses needed for shore reconnaissance and lightning raids." (The Vikings, 800-1050, "Everyday Life," Hachette Literature, p. 131)

Shipbuilding

6000 years of evolution

Viking Age ships are the result of 6,000 years of technical evolution.

In the Neolithic period, the inhabitants of the Danish coasts built pirogues (the oldest ones date back to about 5,000 years before our era) in soft and resistant wood to go fishing. Using flint tools, they carved logs of linden, a soft and resistant wood, to a regular thickness of 2 centimetres. These "monoxyl" pirogues, which were up to 10 metres long, apparently ventured out to sea, with paddles, for cod and whale fishing, as well as for small expeditions. Some were used as burial sites.

Then, about 3,000 years B.C.E., they began digging a row of holes along the upper edge of their canoes. Using ropes made of plant fibres, they fixed the lower edge of a plank in the upper part of the sides of the pirogue. These extra planks increased seaworthiness by raising the freeboard. Thus was born the clapboard technique, characteristic of Northern Europe.

Scandinavian ships evolved during the Bronze Age (2,000-500 BC), when the ends of the ship were raised and both bow and stern were decorated with spirals and animal figures. The figureheads represented snakes or dragons. But the ships are not yet able to face the high seas.

It wasn't until just before the Viking Age that northern carpenters finally created boats of extreme proportions and properties, adding tall masts and powerful keels. Offshore, the Vikings sailed most often, but used oars near the coast and to travel inland.

The dimensions and materials could vary depending on the place of construction, the seas they sailed and the tasks for which the different models of boats and ships were developed: transporting goods, travel, servitude, war...

Materials

• Oak wood, sometimes pine or ash for the planks, and willow for the gurnables (long wooden dowel, pin or dowel used for the assembly of wooden parts in shipbuilding).
• Iron for the rivets, anchor and some deck fittings.
• Tar, obtained by the pyrolysis of coniferous wood, to caulk and coat the hull. Associated with various colour pigments, this tar became a coating to colour the hull or sail.
• Vegetable and animal fibres were used in the composition of the various rigging ropes, such as horsehair for the sheets or bark fibre (lime tree) for the shrouds.
• Vadmal, a sheep's wool cloth for sailing. Vegetable tar and grease were added to the cloth to make the sails waterproof and windproof.

Features

Viking Age ships and boats are all designed according to the same plan.

• A one-piece keel, carved from a single straight tree trunk, with a T-section on which the hull is built.
• Couples resting freely on the keel, rather than fitting into notches made in the keel, as was the case in shipyards in the rest of Europe.
• Skeleton planking, green wooden planks cut in a star shape around the heart of the tree, about 2 centimetres thick, which form the outer hull by overlapping each other. The strakes of the dead works (i.e. the non-submerged part of the hull) were fixed to each other, and then to the couples, by iron rivets. On the other hand, the planking of the live-works, i.e. below the waterline, was fixed to the frames by gounables.
• A bow of a single piece of wood, usually carved in one piece.
• a single mast equipped with a sail
• a leather-tied rudder oar on the starboard aft side

Some ships were not decked, and even as they sailed along the coast, Viking Age sailors had their hands full with the rain and sea spray that had to be caught. The operation seems to have been so routine and essential that a saga tells the story of a crew where six men baited while seven others bailed.

Qualities

The design of Viking Age ships is critical to understanding the impact and role they played in Viking expansion".

• Flexible and light, boats are fast.
• Amphidromic, the boats can sail in both directions. Their quasi-symmetrical structure allows them to move forward and backward equally well.
• Able to travel on any waterway, whatever the depth, and to run aground directly on a beach, thanks to their flat bottom and shallow draft.
• Able to carry heavy loads.
• Easy to repair.

The different types of Viking boats

Viking boats were often referred to by the number of oars or benches each capable of accommodating 2 to 4 swimmers (the maritime term for "rowers"):

• sexoeringr: 6 oars
• tólfoeringr : 12 oars
• fimtánsessa: 15 swim benches
• tvitogsessa: 20 swim benches

There are 3 main families grouping the different models of boats, ships and vessels of the Viking Age, based on the tasks and activities they were used for.

Herskips

Herskips are warships, usually of large dimensions. They are equipped with a skjaldrim, a special planking where the rowers' shields are placed as protection against projectiles.

• Langskip: literally long ship, an old Icelandic word derived from the Latin navis longa and old English langscip.
• Snekkar: the most famous of the Viking warships.
• Skeid: very large ship. This word gave the Old English word scegd.

The snekkar is one of the largest types of buildings built by the Vikings from the 9th to the 12th century. It is one of the most admirable ships ever built. The aesthetic attractions of the ship also fulfilled technical functions, making the snekkar the most powerful boat ever.

Its shape was low (except at the bow, which was often dominated by a dragon's head), fairly elongated, but much less than the galleys of the Mediterranean. It was narrower than the knarr (length/width ratio of 7/1 - 4/1 for the knarr).

Designed for war and expeditions, it could measure more than 30 meters long. Although it had a mast to hoist a mainsail, oars were its main means of propulsion. The crew consisted of 60 to 80 men. It was possible to carry up to 160 more men (for boarding and pillaging). The sagas report that there were many larger ones, such as Olav Tryggvesson's Ormm lange (the Great Snake), which is said to have been over 40 metres long.

The mast of the snekkar was easily lowered, to decrease wind resistance and to obtain greater stability when the boat was rowed, or to avoid being spotted before a surprise attack. On the open sea, the Vikings usually used sails, but used the oars on rivers, bays or lakes. The combination of sail and oars gave them power and adaptability, both for river raids and for long-distance expeditions across the oceans. Modern replicas have shown that snekkars can exceed 10 knots in good conditions, and that they can travel an average of 200 kilometres in 24 hours over long distances.

In naval battles, the boats were tied together. Stones were thrown (they were in the hold to balance the boat), then arrows were fired before finally boarding.

It was customary for chiefs and notables to be buried in their most precious possession: their ship.

Kaupskips are merchant and transport ships.

• Knörr or Knarr: the main cargo ship of the Vikings, suitable for the open sea.
• Karv: used both for transporting goods, livestock or men and as a small warship.
• Eikja: kind of small cramming machine.
• Ferja: larger cramming boat.
• Byrdingr: wide and high, heavy and slow, carrying heavy cargo along the coast.

Knörr (or knaar or knarr - plural: knörrer ) was the generic name for Viking transport and trading vessels.

Usually made of oak, clapboarded, the knörr was a very common cargo ship in the Scandinavian region. It measured 15 to 21 metres long and 5 to 6 metres wide, and had a single mast with a square sail. Designed to hold a large cargo, it was heavier, wider and with a deeper hull than the langskips, the ships used for looting.

It was also less dependent on oars as a means of propulsion, as it had a fixed mast and was mainly propelled by sail. In light winds, or when approaching the shore, a few oars (measuring between 5.3 and 5.8 metres) placed at the stern and bow would supplement its propulsion power. Its crew could consist of 8 to 14 men. Its cargo capacity was quite limited: from 10 to 50 tons.

It had a speed of about 10 knots. Its construction gave it the ability to hug the wave and "bend" according to the strength of the wave, which earned the knörr the nickname "snake". The mast was 10 to 13 metres high and carried a rectangular sail. The bow and stern were symmetrical and a rudder oar was located aft on the starboard side.

The knörr was very reliable on the open sea and could be used for long voyages (although it was not very comfortable). Its flat bottom made it easy to sail up rivers and estuaries, and it could be easily beached. The knörr is undoubtedly the type of boat that settlers used to cross the North Atlantic to Iceland, Greenland and North America. For the transport of goods over short distances, the Vikings probably used smaller boats.

Utility Boats

• Karfi: local servitude boat.
• Skúta: cutter, small boat.
• Rodrarferja: rowing boat, small skiff for trips along the coast.
• Batr or eptirbátr: canoe, boat or rowing boat. 

Archaeological remains and replicas

The careful examination of Viking ships unearthed by archaeologists, such as those at Oseberg and Gokstad on display at the Viking Ship Museum in Oslo, has led to a better understanding of the supremacy of the Vikings as a seafaring people over well-established societies such as those in England, France and Ireland between the 8th and 11th centuries. Their superiority lay in their skill in shipbuilding.

Archaeological discoveries concerning grave ships are very rare, and even rarer are those of underwater wrecks. However, archaeology nowadays has new technological means at its disposal, such as georadar or ground-penetrating radar, which makes it possible to locate new burial sites housing a ship, and investigation methods enabling it to intervene on sites where conservation conditions are not optimal, such as in 2019 with the Gjellestad ship. Researchers are not to be outdone, in particular with the use of dendrochronological analyses which allow precise dating of the construction of the boats.

Utility Boats

• Karfi: local servitude boat.
• Skúta: cutter, small boat.
• Rodrarferja: rowing boat, small skiff for trips along the coast.
• Batr or eptirbátr: canoe, boat or rowing boat.

Archaeological remains and replicas

The careful examination of Viking ships unearthed by archaeologists, such as those at Oseberg and Gokstad on display at the Viking Ship Museum in Oslo, has led to a better understanding of the supremacy of the Vikings as a seafaring people over well-established societies such as those in England, France and Ireland between the 8th and 11th centuries. Their superiority lay in their skill in shipbuilding.

Archaeological discoveries concerning grave ships are very rare, and even rarer are those of underwater wrecks. However, archaeology nowadays has new technological means at its disposal, such as georadar or ground-penetrating radar, which makes it possible to locate new burial sites housing a ship, and investigation methods enabling it to intervene on sites where conservation conditions are not optimal, such as in 2019 with the Gjellestad ship. Researchers are not to be outdone, in particular with the use of dendrochronological analyses which allow precise dating of the construction of the boats.

Norway

Oseberg's boat

Grave boat from the 9th century, discovered in 1904, near the Oseberg farm in the Tønsberg area (Vestfold county). Preserved in the Viking Boat Museum in Oslo, the ship on display consists of about 90% of its original wood.

The ship was built in the year 820, in oak with sides composed of 12 planks. It was used in its original function for several years before being used as a burial place. Even though it can sail, the ship remains quite frail and was only to be used for coastal voyages.

Oseberg's boat is 21.34 metres long and 5 metres wide. It had 30 oars at its disposal. Its sail area was estimated at approximately 90m², propelling it at a maximum speed of 10 knots.

Did you know that? The total weight of the ship, evaluated thanks to the weighing system set up by the Viking Boat Museum, is 4219 kg. In addition, the carvings that adorn the stern and bow of the ship gave the name Oseberg to a style of Viking art.

The Gokstad boat

Grave boat from the 9th century, discovered in 1880 under a burial mound near the Gokstad farm in the Sandefjord area, (Vestfold county). It is currently preserved and exhibited at the Viking Ship Museum in Oslo.

Dendrochronological analysis suggests that the Gokstad boat was built from logs felled around the year 890. It was built of oak, with sides consisting of sixteen planks. Heavier and sturdier than the famous Oseberg boat, it belongs to the category of langskips designed to sail on the high seas.

The Gokstad boat is 23.30 metres long and 5.25 metres wide. It had 32 oars. Its sail area was estimated at approximately 120m², propelling it at a maximum speed of 12 knots against 5 knots per oar.

Grave boat from the 9th century, discovered in 1880 under a burial mound near the Gokstad farm in the Sandefjord area, (Vestfold county). It is currently preserved and exhibited at the Viking Ship Museum in Oslo.

Dendrochronological analysis suggests that the Gokstad boat was built from logs felled around the year 890. It was built of oak, with sides consisting of sixteen planks. Heavier and sturdier than the famous Oseberg boat, it belongs to the category of langskips designed to sail on the high seas.

The Gokstad boat is 23.30 metres long and 5.25 metres wide. It had 32 oars. Its sail area was estimated at approximately 120m², propelling it at a maximum speed of 12 knots against 5 knots per oar.

Grave boat from the 9th century, discovered in 1880 under a burial mound near the Gokstad farm in the Sandefjord area, (Vestfold county). It is currently preserved and exhibited at the Viking Ship Museum in Oslo.

Dendrochronological analysis suggests that the Gokstad boat was built from logs felled around the year 890. It was built of oak, with sides consisting of sixteen planks. Heavier and sturdier than the famous Oseberg boat, it belongs to the category of langskips designed to sail on the high seas.

The Gokstad boat is 23.30 metres long and 5.25 metres wide. It had 32 oars. Its sail area was estimated at approximately 120m², propelling it at a maximum speed of 12 knots against 5 knots per oar.

Grave boat from the 9th century, discovered in 1880 under a burial mound near the Gokstad farm in the Sandefjord area, (Vestfold county). It is currently preserved and exhibited at the Viking Ship Museum in Oslo.

Dendrochronological analysis suggests that the Gokstad boat was built from logs felled around the year 890. It was built of oak, with sides consisting of sixteen planks. Heavier and sturdier than the famous Oseberg boat, it belongs to the category of langskips designed to sail on the high seas.

The Gokstad boat is 23.30 metres long and 5.25 metres wide. It had 32 oars. Its sail area was estimated at approximately 120m², propelling it at a maximum speed of 12 knots against 5 knots per oar.

• 6 replicas of the Gokstad boat: Gungnir (2001) - France, Dreknor (2008) - France, Íslendingur (1996) - Iceland, Gaïa (1990) - Norway, Hugin (1949) - Denmark, Viking Landfinger (1893) - Norway.
• Virtual visit to the Viking Boat Museum in Oslo: The Gokstad Boat

Tune's boat

9th century gravestone ship, discovered in 1867 under the Båthaugen mound near Haugen farm in Østfold county. It is a karv-type ship, currently kept in the Viking Boat Museum in Oslo.

Tune's boat was built around the year 900 and is made of oak.

Tune's ship is 18.67 to 20 meters long and 4.35 meters wide. It had 22 to 24 oars.

No replica was made.

The myklebust - Photo: Sagastad.no
The ship of Myklebust

Grave boat discovered in 1874 under the Rundehåjen mound near the Myklebust farm in the Nordfjordeid region of Norway. The ship was burnt down at the funeral and only its footprint left by the ashes, rivets and shield umbos. It is the largest Viking ship found in Norway. It is probably a skeid type warship.

Historians believe that King Audbjørn of the Fjords was cremated in the ship of Myklebust, a typical funeral custom of the 8th and 9th centuries. According to the Snorri saga, he died at the Battle of Solskjel in 876.

The burial mound was 30 metres in diameter and 4 metres high, with a wide trench around it filled in the 19th century.

A replica of the Myklebust ship was built. It is 30 metres long and 6.5 metres wide. The ship is able to reach the waters of the fjord for navigation from its exhibition site in Sagastad.

Denmark
The Ladby Ship - Photo: Ladby Viking Museum
Ladby's boat

A 10th century tomb-ship, discovered in 1934 at a burial site on the island of Fionia, Denmark. It is currently preserved and exhibited at the Ladby Viking Museum in Kerteminde, built above the mound that covered the ship.

Built around 925, it was originally intended to be used only for coastal journeys.

The Ladby boat is 21.5 metres long and 3 metres wide. All that remains of it in the grave is its footprint with nearly 2000 rivets, the rings for rigging the mast, and at the bow the anchor with its original chain. The bow is decorated with a mane figured by iron buckles.

2 replicas of Ladby's boat: Ladbydragen (2014) - Denmark, Imme Gram (1963) - Denmark. This was the oldest replica of a Viking ship, before it was shipwrecked on July 26, 2009 near Lyø Island.

Roskilde's boats

The five 11th century ships were discovered in 1962 in a waterway between Peberrenden and Skuldelev on the Roskilde fjord, 20 kilometres north of the town of Roskilde in Denmark. They are preserved and exhibited in the Viking Ship Museum in Roskilde.

They were used as storm and invasion barrier ships.



The Skuldelev 1

The wreckage is 60% preserved. The ship was built around 1030 in the Sognefjorden region (western Norway) from thick pine planks, but has been repaired several times with oak and linden wood in the Oslo fjord and eastern Denmark. It is a sturdy knarr-type freighter that is believed to have sailed in the Baltic Sea, North Sea and North Atlantic Ocean.

Skuldelev 1 is 16 metres long and 4.80 metres wide, with a draught of 1 metre. She had only 2 or 4 oars for a crew of 6 to 8 men. Her sail area is estimated at 90m² and propelled her at a maximum speed of 13 knots.

1 replica of Skuldelev 1: Ottar af Roskilde (2000) - Denmark


The Skuldelev 2

The wreckage is 25% preserved. The vessel was built in oak around 1042, in the Dublin region of Ireland. It is a skeid type warship.

The Skuldelev 2 is 30 metres long and 3.80 metres wide, with a draught of 1 metre. She had only 60 oars for a crew of 70 to 80 men. Her sail area was estimated at 112m² and propelled her at a maximum speed of 15 knots.

1 replica of the Skuldelev 2: Havhingsten fra Glendalough (or Sea Stallion of Glendalough, 2004) - Denmark


The Skuldelev 3

The wreckage is 75% preserved. The ship was built in oak around 1040, in Denmark. It is a byrdingr cargo ship, suitable for shorter voyages in Danish waters and the Baltic Sea.

The Skuldelev 3 is 14 metres long and 3.30 metres wide, with a cargo capacity of 4 to 5 tonnes and a draught of 0.90 metres. She had 4 to 6 oars for a crew of 5 to 8 men. Her sail, with an estimated surface area of 45m², propelled her at a maximum speed of 10 knots.

1 replica of Skuldelev 3: Roar Ege (1984) - Denmark

The Skuldelev 4

The ships were numbered at the time of their discovery with the numbers 1 to 6, because archaeologists thought they had found the remains belonging to six different ships. When they were preserved, it turned out that Skuldelev 4 was part of Skuldelev 2.

Skuldelev 5

The wreckage is 50% preserved. The vessel was built in different types of wood (oak, pine, birch and alder), around 1030, in the Roskilde region of Denmark. It is a snekkar-type warship, suitable for navigation in the Danish shallow waters of the Baltic Sea.

The Skuldelev 5 is 17.30 metres long and 2.50 metres wide, with a draught of 0.60 metres. She had 26 oars for a crew of 30 men. Its sail area was estimated at 46 m² and propelled it at a maximum speed of 15 knots. The freeboard boards are equipped with holes for the shield straps.

2 replicas of Skuldelev 5: Helge Ask (1991) - Denmark, Sebbe Als (1969) - Denmark

The Skuldelev 6

The wreckage is 70% preserved. The boat was built in pine, around 1030, in the region of Sognefjorden (Western Norway) for whaling in the fjords. Later, its sides were raised to make it a coastal freighter, of the ferja type, capable of carrying a larger load.

Skuldelev 6 is 11.20 metres long and 2.50 metres wide, with a draught of 0.50 metres. It had 14 oars for a crew of 5 to 15 men. Its sail area was estimated at 26.5 m² and propelled it at a maximum speed of 12 knots.

2 replicas of the Skuldelev 6: Kraka Fyr (1998) - Denmark, Skoldungen (2010) - Denmark, with a different interpretation in the bow and stern design.

 Sweden
Äskekärr's boat - Photo: Göteborg City Museum
Äskekärr's ship

Wreck from the 10th century, discovered in 1933 during archaeological excavations about 50 metres from the bed of the Göta älv River, not far from the village of Äskekärr in Västra Götaland County. It is currently preserved and exhibited in the Göteborg Municipal Museum.

The Äskekärr boat was built around the year 930, out of oak. It is a knarr type boat. It is 13 metres long and has the special feature that at the base of the mast there are rune engravings, such as "Fehu", belonging to the old futhark still in use at the very beginning of the Viking Age. The boat must have been in use for many years because it shows many signs of wear and minor repairs, including a spare part 70 years younger than the rest.

1 replica of Äskekärr's boat: Vidfamne (1994) - Sweden


Viksbåten - Photo: Erikskulle Museum
The Viksbåten

Wreck from the 11th century, discovered in 1898 during canal draining in the municipality of Norrtälje in Stockholm County. It is currently preserved and exhibited in the Erikskulle museum in Norrtälje.

The boat, a karv type, was built around 1050, out of oak.

The Viksbåten is 9.6 metres long and 2.2 metres wide, with a draught of 0.54 metres. It had 12 oars. The trace of a mast foot indicates that she had a sail.

1 replica of the Viksbåten: Tälja (1998) - Sweden

Valsgärde's boats

Of the sixty or so graves discovered in 1920 in Valsgärde, a farm near the river Fyris 3 kilometres north of Gamla Uppsala, 15 are boat graves and 5 are particularly noteworthy for their rich burial furnishings (graves 5, 6, 7, 8 and 13). Grave boat 13 is 9.8 metres long and dates from the 8th century. The oldest of the site dates from the 6th century and the last from the 11th century.

Germany
The Haithabu 1 Viking Museum in Haithabu, Germany - Photo: Kai-Erik Ballak
Haithabu's ship, or Haithabu 1.

Wreck of an 11th century ship, discovered in 1979 in the port of Hedeby in Germany, formerly known as Haithabu, a Viking trading post established in Denmark until 1864. It is currently preserved and exhibited in the Viking Museum of Haithabu in Germany.

It was burned and sunk when the town of Haithabu fell in 1050, at the end of the Viking Age. The ship had been filled with straw or brushwood and then set on fire to set the enemy buildings ablaze.

Dendrochronological analysis suggests that the Haithabu ship was built from oak trunks felled around the year 985 in the Schleswig region.

The Haithabu 1 is 26 to 32 metres long and 2.7 metres wide, with a draught of 1.5 metres. It had 24 to 26 oars at its disposal.

No replica of this ship has been made.
France
Reconstruction of the Cruguel mound for an exhibition at the Port-Musée in 2013 - Photo Henri Moreau
Cruguel's boat

A ship-bomb from the second half of the 10th century, discovered in 1906 under the Cruguel mound, already partially destroyed by marine erosion, on the island of Groix in Morbihan. The burial results from a transport of the remains of a cremation on the Pointe de Cruguel.

The boat, built mainly in oak and to a lesser extent in pine, measured, according to the number of iron rivets found, a little more than 10 metres long and 2.50 metres wide. 

Navigation
Great navigators, the Vikings crossed the seas long before the compass or magnetic compass was invented.

"You didn't have to be a magician, but you had to rely on a lot of observations," says Johan Christian Keller, an archaeologist at the University of Oslo who specializes in the northern expansion of the North Atlantic about Viking Age sailors. These observations included the location and morphology of the coastline, the flight of birds, the migratory routes taken by marine mammals such as whales, the clouds forming over land and, of course, the position of the sun and stars in the sky.

However, navigation poses many problems, especially in the far north. Fog and bad weather frequently set in, and when the sun was sometimes veiled, it must have been extremely difficult to find your way around. In summer, the sun does not disappear completely, making navigation by starlight impossible. Finally, the compass was not introduced in Europe until well after the end of the Viking Age. So how did they manage to navigate so well and so far with so few technical means at their disposal?

Sundials and compasses

The Greenland Gnomon

Fragment of the wooden sundial discovered in Greenland and engraved with hyperbolic curves - Illustration Gábor HorváthIn 1948, the Danish archaeologist Christian Leif Verbaek discovered a wooden disc with a central hole and multiple regular indentations on the circumference, showing straight and hyperbolic engravings, on the site of an ancient 11th century Benedictine monastery in Uunartoq, South West Greenland, near Cape Farewell. The object was sent to the Danish National Museum for expert appraisal, but researchers were unable to determine its use.

In 1953, Christian Leif Verbaek presented his discovery in a British magazine. On reading this article, Carl Solvaer, a former Danish captain, quickly had the intuition that this disc fragment was probably a fragment of a bearing dial and that the notches must have corresponded to the rays of a primitive sun compass. But the idea was controversial.

It was not until 1983 that Søren Thirslund, former captain at the time in charge of the Maritime Museum in Kronborg, Denmark, made several reproductions of a sun compass based on the one imagined from the fragment found in Greenland. His aim was to experiment with them by entrusting them to navigators such as the Norwegian Ragnar Thorseth, who used them on board the Saga Siglar, a replica of a large knarr, during a crossing between Reykjavik and Greenland in 1991. Afterwards, many experienced sailors agreed to test the solar compass and proved that this instrument, reconstructed on the basis of an intuition, fulfilled its function perfectly: to locate the geographical north along latitude 61° N from May to August, even on the high seas... but only if the sun shines. This navigational instrument has since been known as the "Viking solar compass".

The sundial on the island of Groix

Assembly of the Groix navigation instrument and proposals for its use in horizontal and vertical position - Illustration: Bulletin de l'A.M.A.R.A.I. n°19Loïc Langouët, doctor in History at the University of Rennes, reports and comments in the Bulletin de l'A.M.A.R.A.I. n°19, on the excavations carried out in 1906 on the site of the 10th century Viking ship-tomb on the island of Groix. Paul du Châtellier and Louis Le Pontois had unearthed a series of flat elements, made of superimposed iron sheets, which they could not interpret individually.

It is finally the reconstitution of the object that allowed the researchers to distinguish in certain points, holes of fixing. Jean Renaud suggested that it might be a stern ornament or a possible navigational instrument. This last hypothesis was developed and argued by the climatologist Pall Bergthorsson.

The whole would have been fixed on a circular wooden bottom with a diameter of approximately 45 cm, having included an orthogonal needle in its center. Another needle mounted on a support completed the instrument. By placing the instrument horizontally, the navigator could determine the direction of north, at sunrise or sunset, by noting the shadow cast by the vertical needle. The horizontal pointer was used to indicate north or the route.

By arranging the same instrument vertically, it became possible to measure the height of the sun at noon (the largest shadow of the needle for a horizontal arrangement of the instrument). At the winter solstice, the shadow of the stylus fell in the middle of one of the two upper circles (22+1°), the height of the sun corresponding fairly well to the latitude of the area of the island of Groix (48°) at noon. But, during the summer solstice (68+1°), the stylus shadow fell in the middle of one of the two lower circles.

According to Bergthorsson, this suspended and well oriented set could allow to locate the height of the sun and thus to locate in time, which was necessary to locate the north when the instrument was placed in horizontal position. Although at the same time, the peoples of the Mediterranean used a more refined instrument, the astrolabe, to measure the height of the sun, the instrument on Groix's ship-gunboat would prove to be particularly well suited to navigation in the region.

Sunstone and Icelandic spath

Since the Viking sundial can only be used when the sun is shining, the question arises as to how the Vikings navigated when the sun was hidden by clouds or fog, a situation that can last for days when crossing the North Atlantic.

Perhaps the beginning of the answer can be found in an intriguing passage from the Hrafn Sveinbjarnarson saga, where it says: "The weather was overcast and stormy.... The king looked around him and saw only blue sky... Then the king took the sun stone and holding it above him, saw from where the sun shone". But what is the nature of this sun stone ("sólarsteinn")?

In 1967 a Danish archaeologist, Torkild Ramskou, proposed an ingenious theory. According to him, the Vikings could have been like other living species that, like the monarch butterfly, exploit the polarization of sunlight to find their way. To do this, the Vikings would have taken advantage of the optical properties of certain crystals.

Birefringence of the sunstone observable with green fluorite behind the Icelandic spath - Photo: Futura sciencesThe Icelandic spath, an optical calcite whose birefringence is precisely a consequence of the phenomenon of polarisation of light, has long been considered a serious area of research. It so happens that the human eye perceives the polarisation of light in certain situations.

A spectacular effect of birefringence is the double refraction by which a light ray entering the crystal is split in two. The atmosphere similarly splits sunlight into concentric circles. If one looks at the sky through an optical calcite, it appears alternately bright or dark - depending on the position of the crystal, the light is either transmitted or blocked. When the light entering the crystal is polarized in the same way as in the atmosphere, the crystal appears brighter and points towards the sun. By checking the polarization at two different locations in the sky, mariners would have been able to determine the position of the sun, even on overcast days. All they would have to do is place a light source in the direction indicated by the crystal to cast a shadow on the sundial.

However, Ramskou's theory remained controversial, with some claiming that the sun stone was not able to give reliable indications in bad weather, when too little light could penetrate the water layer.

Polarimetric navigation

Gábor Horváth, a biophysicist at the University of Eötvös in Budapest, and his colleagues set out to study the phenomena of light polarization under cloudy and foggy skies in Hungary, Finland and the Arctic Circle. From 2001 to 2007, Horváth's team carried out 5 scientific experiments to test the sunstone theory.

To begin with, the researchers took photographs of overcast skies with a fisheye lens and asked subjects to define the position of the sun. The subjects were 99% wrong, which confirmed to the researchers that Viking sailors must have needed help to navigate on the open sea in such weather.

Horváth and his team then tested the function of the sunstone under different climatic conditions during expeditions to Tunisia, Hungary and the Arctic Ocean. Instead of calcite, they used a polarimeter (a device that measures polarization). The results they published online on the Royal Society website in 2011 show that polarimetric navigation works in cloudy and foggy conditions. However, the method is not totally reliable under very cloudy skies, concludes the physicist, because the refractive index is not unique, it depends on the direction of polarization of the light wave.

Proof by science

In practice, there is still uncertainty about the ability of the Vikings to actually navigate using optical calcite at Arctic latitudes, given the actual polarization of light.

Two French physicists, Guy Ropars and Albert Le Floch, have published an article in which they use Leif Karlsen's work on the subject as a starting point. They show, by calculation and experience, that Icelandic spath can indeed be used to locate the sun in the sky even when it is overcast. This requires using the crystal as a depolarizer. If one looks at the sky through an Icelandic spath, its birefringence properties make it possible to obtain two different images. An incoming beam of light emerges as two beams, one of which has lost its polarization. Their intensities are usually different, but when you turn the crystal, the two intensities end up being the same, which then allows you to locate the Sun in the sky. According to Guy Ropars and Albert Le Floch, an accuracy of a few degrees can be achieved, even in twilight conditions.

The much later discovery of a crystal of spath in a 16th century British shipwreck off the Channel Islands of Alderney has brought water to the researchers' mill. The latter pointed out that the metallic mass of the guns of this ship could alter by induction the magnetic field measured locally to such an extent that significant navigational errors could result. The use of an optical compass based on calcite could therefore be a necessity and this would explain its presence on board the ship.

In the absence of direct written records or clear archaeological evidence that the Vikings did use such an optical compass, physics has now at least proved that it was a possibility.

The Dragon Harald Fairhair, a Viking ship of the 21st century
The Dragon Harald Fairhair, or Draken Harald Hårfagre in Norwegian, is the largest ship built today.

It is not a replica of a ship from the Viking Age discovered by archaeology, but was built in the Norwegian shipbuilding tradition from the Viking tradition, with historical sources to support it. The yard, financed by Sigurd Aase of Viking Kings AS, started in March 2010 in Haugesund Municipality, Norway. The ship, named after King Harald I of Norway (850-933), nicknamed Harald with the Beautiful Hair, was launched on 5 June 2012.

The Dragon Harald Fairhair is 35 metres long. It is equipped with 50 oars, each requiring 2 oarsmen. Propelled by its 260 m² sail, the crew can be reduced to 30 people.

In May 2016, the ship left its home port of Haugesund to make the mythical Atlantic crossing of Leif Erikson more than a thousand years ago, passing through the historic former Viking colonies in Shetland, the Faroe Islands, Iceland and Greenland.

Sources

• Régis Boyer, The Vikings, 800-1050, "Everyday Life", Hachette Littérature
• The Viking Boat Museum in Roskilde (Denmark)
• The Viking Boat Museum in Oslo (Norway)
• Le Port-Musée (France)
• The Viking burial by boat on the island of Groix
• The Scandinavian burial by boat on the island of GroixThe Scandinavian burial by boat on the island of Groix (108.88 Ko)
• List of Viking shipwrecks
• The Viking sun compass
• The sun stone of the Viking navigators is not a myth...
• On the trail of Vikings with polarized skylight: experimental study of the atmospheric optical prerequisites allowing polarimetric navigation by Viking seafarers
• A depolarizer as a possible precise sunstone for Viking navigation by polarized skylight