Landnámabók (S.20) says that Ávangr settled in Botn and built an ocean-going ship from the woods in the forest there. Svarfdæla saga (ch.12) says that a large oak was cut above Svarfaðardalur in north Iceland and floated down the creek to where it was used for the keel of an ocean-going ship built at Tunga. There are no oaks in that area today (left).
Ships were built using simple tools. Long shafted axes were used to fell the trees. Tree trunks were split into planks using wedges driven by hammers. Planks were trimmed using short shafted T-shaped broad axes, as illustrated on the Bayeux tapestry, shown left. Saws, although known, were not used.
Planes were not needed to smooth the planks; ship builders could make the surfaces of the planks sufficiently smooth using only their axes. However, the overlapping edges of the strakes were smoothed with a plane in order to obtain a tight fit.
Where the strakes overlapped, a groove was cut with a mold scraper. Tarred woolen yarn or animal hair was forced into the groove to make the joint between strakes as watertight as possible. The mold scraper was also used to carve decorative patterns on the planks. Holes were made using a spoon-shaped bore pressed against the wooden surface by the builder's breastbone.
Each strake was different, shaped to fit into the curved three-dimensional space required to form the shape of the hull. A strake and the pine plank from which it was cut is shown schematically to the right for one of the strakes of a Skuldelev ship. The plank had to be much wider than the finished strake, due to the curved shape of the strake, resulting in a lot of waste.
The keel, stem, and sternpost were by far the most critical components of the ship. Errors in the design or construction of these components resulted in a ship with poor sailing characteristics.
It's not known what, if any, measurement instruments were used. It's certain that ship-builders had a very clear mental picture of the completed ship during the construction process. In this illustration from the Bayeux tapestry, William gives instructions for the construction of his invasion fleet to his ship-builder, who holds a T-shaped broad axe in his hand.
Chapter 88 of Óláfs saga Trygvassonar tells of the construction of the Ormr inn langi, the Long Serpent. Þorbergr skaffhögg made the stem and stern, but was obliged to leave before the ship was completed. When he returned, he apparently was not pleased with what he saw. Secretly at night, he cut crossing diagonal incisions into the upper strakes on one side, ruining the ship. The next morning, King Óláfr, in a rage, vowed death to the man who had done the damage. Þorbergr freely admitted to it, and the king ordered him to repair the ship so that it was just as fine as before. Þorbergr didn't replace the damaged strakes, but rather, took yet more material off with his adze, until the damage disappeared. Everyone agreed the ship now looked better than before, and King Óláfr asked him to do the same to the other side of the ship. The Ormr inn langi was considered to be the best ship ever built in Norway.
There is little doubt that ship builders used plumb-lines together with staves and strings to lay out the ship. It's been suggested that a measuring stick called a boat ell was used to measure the angles between the runs of the strakes, and that master ship builders recorded the details of their designs with marks cut into this stick. Ship designs are based on segments of circles with different diameters based on the length of the keel. (The photo to the left shows the stem of the Íslendingur.)
As with other Norse objects, ships were highly decorated. The intricate carving on the stern of the Oseberg ship is shown to the left, and a weathervane from a Norse ship is shown to the right (above).
Dragon heads may have decorated the prows (and occasionally, the sterns) of ships. The dragon head decoration of the Íslendingur is shown to the right (below). Early Icelandic laws (as stated in Landnámabók H.268) prohibited ships with dragon head prows from entering harbor, lest the frightening appearance of the ship threaten the tranquility of the landvættir (land spirits).
A ship's sail was a very precious item. It's quite possible that the sail cost as much to make as the hull. Typically, the sail was made from the finest grade of homespun wool, woven on the same vertical loom (right) in the home that was used for clothing. It has been suggested that it took several women several years to make the fabric needed for a single sail.
On the other hand, chapter 68 of Egils saga says that while Egill stayed with Arinbjörn one winter in Norway, he had an elaborate sail made for Arinbjörn as a gift.
The sail for the Skuldelev 1 knörr was probably on the order of 90 sq m (950 sq ft). When completed, the sail was coated with animal fats and oils to protect it from the elements. Literary sources say that sails were often striped.
Sails were square and had a low aspect ratio. The sail for the Skuldelev 1 knörr had a height of approximately 5.5m (18ft) and a length of approximately 16.5m (55ft), resulting in an aspect ratio of 0.33.
The mast was stepped into a socket in the keelson, a longitudinal timber on top of the keel. The keelson rested on the keel, but was not fastened to the keel. Instead, it connected to multiple ribs on both sides.
The keelson transferred all of the forces of propulsion generated by the sail to the hull of the ship, and so it was a very substantial piece of oak.
In order to avoid having to lift the full weight of the mast to get the boot of the mast in and out of the keelson socket when stepping or unstepping the mast, the socket was rounded in the forward direction. As a result the boot of the mast slipped in and out without having to lift the entire mast up over a lip.
The mast partner (sometimes called a mastfish because its shape is reminiscent of that of a fish) is the portion of the mast support that is visible in the photo to the left. Some ships did not use a mast partner. However, when used, the mast partner spread out the forces transmitted from the sail to the hull, greatly relieving the stress on the socket in the keelson.
A cross section of the mast support for the Gokstad ship is shown to the right (forward to the left, and aft to the right). The keelson rested on the keel, attached to four ribs. The mastfish rested on four crossbraces, and on a raised portion of the keelson. A wedge in the mastfish helped hold the mast in place, but could be removed when the mast was to be unstepped.
The Gokstad mast did not survive intact, but is estimated to have been 12m (40ft) high. The mastfish was the most substantial piece of wood on the ship. The Gokstad mastfish was a single piece of oak 5m (16ft) long, 1m (40in) wide, and 50cm (20in) thick.
Upright stanchions (described in more detail later) held the sail and yard when not in use. On the Gokstad ship, one of the uprights was mounted on the mastfish. No such uprights were used on the Íslendingur, seen in the photograph above.
The details of the ship's rigging are obscure. Evidence indicates that a forestay was used, as well as shrouds from the mast to the sides of the ship aft. There is no evidence for a backstay, and probably none was needed because of the strong seating of the mast.
In some cases, the cleats for the shrouds were outboard, with the shroud attached to a willow ring fastened to the cleat to prevent rubbing.
Some sources claim that ropes were made of hemp, or from walrus or seal skin. These skin ropes were highly prized, and were an important trade item. They were probably made by cutting the hide in a spiral around the body of the creature.
However, Crumlin-Pedersen claims that there is little evidence of hemp or animal skin ropes being used for nautical applications and suggests that bast fiber from oak, elm, or other trees was used for ropes.
One piece of evidence for animal skin ropes from after the Viking age comes from chapter 161 of Íslendinga saga, which describes a journey from Norway to Iceland in the 13th century. The ship was wrecked, and four men survived thirteen days by eating the walrus-hide tackle with butter, the only part of the cargo that was salvaged.
Chapter 18 of Króka-Refs saga says that Refur was welcome when he arrived in Denmark because he brought with him walrus-hide ropes from Greenland, which were hard to obtain in Denmark.
The carvings of ships under sail made during the Viking age (left) show an interlace at the foot of the sail. It has been suggested that this was used to fine tune the curve of the sail to get the best speed possible as close to the wind as possible.
Another explanation is that the interlace was used to reef the sail in high winds. Pulling on the bottom of the interlace caused the sail to pucker, reducing its effectiveness.
The carvings also show a cross-hatch pattern on the sail whose purpose is unknown. It has long been thought simply to be artistic license. Recently, it's been suggested that the cross-hatch was actually walrus-hide (or other leather) reinforcements. The homespun wool used for sails was probably not strong enough to hold its shape. As a result, the wind would blow the sail out of shape in time. Walrus-hide reinforcements created a more stable sail that set well. As far as I can tell, this idea is pure speculation, without any evidence to back it up.
The stories talk about a beiti-áss (cruising pole), a spar used to hold one corner of the sail further forward, allowing the ship to sail closer to the wind. Nothing has been found in any of the Viking ship wrecks that can be identified as a beiti-áss, but some ships have notched timbers that are thought to have held one end of the beiti-áss when it was set. Chapter 46 of Ynglinga saga says that King Eysteinn sat at the rudder of his ship when another ship sailed close by. There were some swells, and the beiti-áss of the other ship knocked the king overboard, and that was his death.
The ability to sail upwind was prized. While in Norway, King Haraldr gave Ingimundr a ship called Stígandi (stepping), as told in chapter 16 of Vatnsdæla saga. Though small, the king said that in sailing, the ship "bit" better (i.e., sailed upwind better) than any other ship and thus was fastest in a voyage. Ingimundr soon discovered what a fast ship Stígandi was as she stepped through the waves.
When the sail was furled, the sail and yard were stored on uprights located fore and aft. The photo right shows the yard and sail on the Viking Saga, a passenger carrying replica of a Skuldelev knörr at L'Anse aux Meadows in Newfoundland. If the mast needed to be unstepped, it, too, could be stored cradled in the uprights. It's possible that oars were stored here, as well.
Anchors were usually made from stone lashed into a wooden frame (left). The anchor shown to the right (from Denmark) is made entirely of iron and is about 1.5m (5ft) in the long dimension. Some of the more elaborate anchors that have been found use an iron bound wooden shank and have iron rings to accommodate the cable.
The value of the anchor can be seen in an incident related in chapter 28 of Ljósvetninga saga. After waiting a long time for favorable weather, a cold wind from the northwest finally sprung up, so Þorvarður had the anchor raised on his ship. But as his crew pulled, the cable broke. Þorvarður asked for a volunteer to make a repair. Only Hallur stepped forward. Taking off his shirt, he dove into the cold water with the cable in his hand. He reattached it to the anchor so it could be raised. The anchor was too valuable to the ship for the skipper to allow it to be left behind.
The tiller and a side rudder were located on the starboard side. The rudder was held away from the side of the ship by a "nipple", to which it attached by a knotted rope. The rudder has been pulled away from the hull in the photo to the right.
The side rudder is not very effective for large course changes, but it is easily handled because of its balance.
I have read in several sources that the side rudder makes the ship slow to respond. I consider myself a novice sailor, but my brief time at the helm of the Viking ship Vésteinn suggests those published sources are incorrect. My sense was that the ship answered the helm with alacrity.
The tiller and rudder of the Vésteinn are shown to the right. I was surprised by the strength required to work the rudder. That shouldn't have surprised me, given the limited mechanical advantage offered by the rudder.
Some rudders have multiple tiller holes which suggest the it was used in a "half-up" position to control the course of the ship even at the last minute before beaching, which was the normal method of loading, unloading, or stopping for the night.
The skipper of the Viking Saga told me that the ship can easily capsize when the wind is from abeam. That explains how, on one hand, Viking-era ships can be described as performing well in adverse conditions, and how, on the other hand, the sagas describe ships being blown far off their intended course under adverse wind conditions. In stiff winds, a Viking ship would have to be steered in a direction to keep the wind off the beam.
The skipper also commented that the Viking ship sails very differently from a modern sailing vessels of similar size. He said some practice was needed to become familiar with the ship's idiosyncrasies, but once mastered, "the ship sails herself".
Estimates of the capabilities of Norse-era ships vary from one article to the next, and even amongst organizations operating modern replicas. Estimates of top speeds under ideal conditions are in the 20-25 knot range. It's unlikely, though, that speeds greater than 15 knots were common. A modern replica similar to one of the knörr found at Skuldelev is capable of 12.5 knots under sail using a conservative seagoing rig. At that speed, England was only a day and a night away from Denmark. However, "effective" speeds were certainly less, perhaps more like 3-6 knots. Because of the minimal freeboard, the maximum heel of these ships was on the order of 15 degrees. So for the Gokstad ship in a 16 knot (8.6m/s) wind at her most efficient, the ship had to traverse 3 miles in order to sail 1 mile to windward, implying a speed made good to windward of only 2 knots.
It's still unclear how Norse ships can be so efficient under sail. One theory is that a "sausage" of air is trapped between the keel and the upper strakes, which reduces resistance to forward motion, and increases stability by decreasing the tendency of the ship to lean.
It's unlikely that the Norse used any navigational instruments. The sun-compass and the sun-stone sometimes mentioned are most likely modern fabrications.
The sólarsteinn (sun stone) is not mentioned in the Sagas of Icelanders, although the term appears in the contemporary sagas, which take place well after the end of the Viking age. There are no descriptions of its use for navigation in the stories. Even if the sun-stone were a polarizing stone, as some believe, the device would have only limited navigational use in northern latitudes.
The wooden fragment found at the site of a Norse Benedictine monastery in Greenland has been interpreted as a sun-compass, but that interpretation seems fanciful (right). The artifact is too small to make a useful navigational tool.
Some believe that portable sundials existed in the period, corrected by month, that allowed a navigator to determine time of day or latitude based on differences in the length of a shadow. Others doubt the existence of even this simple navigational tool.
Typical Norse voyages were along the coast, at a safe distance offshore. Dead reckoning between known points was used to determine distance run. Sailing at night was avoided. Ships were beached at the end of the day, avoiding navigational hazards difficult to see at night, and allowing a cooking fire to be safely kindled.