The Seaworthiness of the merchant vessel

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With respect to the danger involved in loading the ship too heavily, both the ancient Grågås Law (1169) and the Gulating Law (13th century) contain clear directions: "A vessel is adjudged seaworthy according to the Farmanna Law (the Merchants' Law), when it is so loaded that two fifths of the ship's side are above water amidships", says Grågås

Sailing techniques and seamanship

With the wind behind or abeam, the large, almost square sail was effective and high speeds could be obtained. Magnus Andersen mentioned 11 knots for the Gokstad-replica Viking and trial-runs with the knar-replica Saga Siglar both before and during the circumnavigation yielded top speeds of 13 knots! Even though such speeds are not achieved every day, there were many good nautical days with distances covered of almost 200 nautical miles; an excellent distance covered in 24 hours even for the ocean-going sailing-ships of later centuries.

As far as 24-hour distances were concerned, the Vikings would seem to have had their own system of measurement. The source of information about this is the medieval manuscript RIM II from about 1275 but the information contained in this is considered to be much older. The system is based on the old Scandinavian nautical mile known as viku. This is 11 km long or 6 present-day nautical miles. Six vikur are considered to make 1 dagsroning (day's rowing). Twelve vikur siøs could also be called 1 tylft (dozen) or 1 halvdøgr (occasionally 1 døgr). Twenty-four vikur equals 1 døgr, which is to say that a day's sailing is reckoned at 144 nautical miles, a distance which a seagoing merchant vessel would have been easily able to cover in normally favourable circumstances, at least to judge from our experience with Saga Siglar. It is important to note that døgrsigling is not a measurement of time but of distance. When it says in a saga, for example, that a ship sailed for four døgr, this means that it covered a distance of approximately 580 nautical miles, which could well have taken more than four days with unfavourable wind and weather!

There are indications that a smaller viku was employed in Iceland. This is 9.25 km or 5 modern nautical miles. Twenty-four hours sailing would then be 120 nautical miles. A tylft would be 60 nautical miles which is the equivalent of a modern degree of latitude.

The ship sailed quickly with wind behind or abeam or obliquely ahead but it was an altogether slower task to sail the merchant ship directly into the wind. There are still many who believe that the Vikings rowed their ships in a headwind. This is true enough of the warships. They had large crews and oars all along the sides of the ship, as can be seen, for example, on the small warship in the Viking Ship Museum. The merchant vessels only had a few oars (Saga Siglar, for example, only 4) and they were therefore too heavy and clumsy to make it worthwhile trying to row. The oars were only for manoeuvering or rowing over short distances in calm weather.

In a head wind it was necessary for the merchant vessel to beat to windward. That the Viking ships could tack with their square sails has, for example, been demonstrated by trials with full-scale replicas carried out by the Viking Ship Museum. Trials with Saga Siglar have shown that this knar can beat 60° off the wind with a leeway of between 5° and 10°, i.e. a course made good of 65°-70°. […]

In a head wind, however, the classic sailing-ships were slow. If we look at the theoretical speed into the eye of the wind, the so-called VMG (velocity made good) for Saga Siglar with 67° off the wind and a speed made good of 4.1 knots is 1.6 knots on smooth water without waves and in a wind-speed of 9 metres per second (approx. 17 knots). In less favourable conditions on the open sea with a strong swell, the VMG would certainly not be better and with a speed of less than 2 knots, there is a long way from Norway to America. It must have been very rare to set out, if the wind was ahead. It was a much better strategy to wait close to home for a favourable wind or lie at the ready in the lee of an island out in the skerries. The saga texts contain many examples of ships' waiting for several weeks before setting out.[…]

Sailing the merchant vessel in bad weather

If the wind in the North Atlantic increased so that there was a danger of capsizing or putting the hull or rigging to too much strain as a result of too great a speed in the high waves, the speed and the wind-pressure could be reduced by reefing the sail. This is done quite simply by lowering the sail some way down the mast. As soon as this is done, the worst of the pressure has already been removed. Now it simply remains to roll the lowest "surplus" section of the sail into a sausage and lash this with the short lanyards known as sveptingar, which are fixed to the sail for that very purpose. Finally, the sail is stretched up again with the halyard (dragrebet) and the whole manoeuvre can be completed within 3-4 minutes by a well-trained crew. […] If a real storm arose, all thoughts of sailing by the wind had to be abandoned. The ship would turn its stern to the waves and run before the wind -sigla unna. It was not possible for the open merchant vessel to turn its stem obliquely into the wind and heave to with reduced sail, as was done by later sailing-ships with full decks. This was because it would ship too much water.[…]

High speed, however, could in itself be dangerous. Flateyarbók, the manuscript which contains the "Saga of the Greenlanders" among many others, employs the expression: sigla lausum kili, to sail oneself keel-loose, for the situation in which the ship planes so swiftly on the surface of the water that the ship and hence the rudder lose their grip on the water. Then the very worst can happen. The ship can plunge sideways from a wavetop down into the valley in front and then be filled with water by the wave from which it has fallen. […]

If conditions grew still worse, the sail had to be taken right in and the ship would continue on its way with the mast bare. On a voyage between Greenland and Newfoundland in 1984, Saga Siglar, the knar-replica, survived a hurricane-force storm in this way. With a wind-speed of 35 m/s (70 knots) and waves 12-14 metres high, the merchant vessel scudded for ten hours without making more water than the crew could manage to pump out again. "I wouldn't have missed this experience for the world", said Ragnar Thorseth afterwards, "but I hope never to have to go through it again".

Incidentally, pumps were not used in the Viking period. The Vikings used bailers (storause). In the large vessels it was necessary to have two men to each bailer because of the great height from the bottom of the ship to the gunwale. One man stood in the bottom of the ship and bailed, and then gave the bailer to his partner higher up, who could easily empty the water out where it belonged.[…]

While running for the bare pole, Saga Siglar's average speed was about 8.4 knots, corresponding to about 200 nautical miles in 24 hours. […] If the bad weather continues for several days, it is not to be expected that the ship's crew will know where they are when the storm finally abates. The situation is familiar from the sagas, where it is referred to as hafvilla, not knowing where one is on the sea. It was as a result of an extreme case of hafvilla that America was discovered by Bjarni Herjólfsson in 986!

The most dangerous situation of all, however, arose when a ship was storm-driven towards land so wide it could not be avoided by unnasigling. In this case, there was one last desperate remedy: the steersman would select what seemed to him to be the least dangerous part of the coast and then deliberately beach the ship at full speed so that it would be carried as far up on land as possible. […]

[…]that most of the vessels employed by the Vikings for their expeditions in the seas around Greenland and North America were much bigger than Saga Siglar. The Saga of the Greenlanders and the Saga of Erik the Red mention ships with crews of 30 men or more, with provisions, clothing and weapons. In addition there would be a smaller number of women with their belongings, as well as livestock for food and breeding. If one also reckons with space for all the extra sailcloth, rope and tools that were recommended by the father in The King's Mirror, and many other practical necessities, it will be understood that the knar for sailing the Greenland seas must have been much bigger than the small, although very seaworthy, knar in the Viking Ship Museum. […]

During the construction of the new SAS hotel near Tyskerbryggen in Bergen's old harbour, the remains were found in 1962 of a huge ship built according to the Viking period shipbuilding tradition. The find does not survive in its entirety but the ship would seem to have been about 36 metres long, 11 metres across the beam and drawing about 4.5 metres. (It would have been necessary with more than two men to the bailer on that ship!). The mast was 55 cm thick at the base and is assumed to have been getting on for 30 metres high. In that case it would have carried a single square sail of approximately 400 square metres. The cargo capacity must have been almost 200 tons. This huge ship was dated to 1250-1300 [now dendrochronologically dated to the winter 1187/88], a period when communications with Greenland were at their height and incidentally had Bergen as their starting point. So this may be one of the legendary Greenland knörrir. […]