25 July 2015

Viking Ship Museum - Roskilde, Denmark

This week, I feature a visit to the a truly fascinating museum and shipyard in Denmark. I selected the construction of the Gislinge Boat to show you. There are many other projects to view on the museum site should you have an interest.

My wife and I have visited this museum in Roskilde, Denmark, where you can watch men actually build everything from small boats to ships using age old tools and methods of construction from the medieval Vikings.

There are numerous links on the site to the museum's many building projects.

I am a huge fan of the Viking Ship Museum and I hope you enjoy your visit. 

We begin with an excerpt from my third novel on the Greenland Vikings, Assimilation, An Axe of Iron Novel. I thought you might enjoy a scene from my historical fiction novel that covers ship construction at Halfdansfjord before going to the Viking Ship Museum where you will be treated to the real experts in the field of Norse ship building. Shameless self-promotion you say? You betcha'! (Ed.)
Timber to build the two ships had been accumulated over the past summer, selected by all the same men that were now building the ships, and skidded to the landing beach building site with teams of horses. The same hot water rivulet that ran through Thorvard’s tanning pond ran into the bay next to the shipyard. Easily dammed, the rivulet became a pond large enough to keep all the timber save the masts and yards from drying out.
All the hull pieces assembled were of green timbers – live trees – and they must be kept green until use during the winter; the pond accomplished this end. Hardwoods and even soft woods like pine and fir were easier to work while green. Oak and ash became so hard and dense when cured that they defied the sharpest blade.
Standing, live trees were picked for their natural shapes. Naturally shaped timbers were much stronger than cut timbers, and finishing them to their final shape took less effort. Straight, curved, forked, and almost every other shape likely to be required to shape the desired structural members were selected. Oak, ash, and birch hardwoods for the keel, mast fish, gunwale planks, and stems of the hull, as well as the ribs, knees, thwarts and other internal structural members had already been roughly shaped while green, before being put in the pond in the fall. The workmen retrieved them from the pond as they were needed.
Four straight-grained fir logs, two long thick ones for the ships and two short thin ones for the boats, were cradled side by side while men wielded axes and adzes to shape and smooth them. The sail yards, to which the wadmal sails would be attached, received the same treatment. Like most of the other parts for the ships these timbers had been selected and cut during the summer, skidded to the building site, and barked to facilitate curing until they could be finished later. Unlike all the other structural members, the masts and yards were allowed to cure until dry.
The ships’ planking, a mix of curved or straight knot-free pine and fir logs had also been harvested over the summer, and kept green in the pond. Workmen staked the logs so they would not roll and began splitting each lengthwise along the grain into thin, wedge shaped planks. Other workers propped and wedged these planks into small tree forks that had been tamped tightly into holes during the summer and now stood solidly upright in the frozen ground. With the thin edge up, each plank was wedged into place in the fork, smoothed, and cut to the desired thickness with a short-handled, T-shaped side axe with a long thin blade designed for that purpose. The resulting shaped plank, thicker at the top than the bottom was stacked in the shallows of the steaming hot water pond to keep them pliable until their eventual use by the crews planking the two ships. Had the hot water pond not been available, each wet plank would have had to be laboriously heated over the coals of a long fire pit until the wood was hot enough to be pulled and bent into position along the sides of the ship.
The thickest of the planks were those that ran from the keel upward to the waterline. From the waterline to the gunwale plank at the top of the hull the planks were progressively thinner in each run until about half the thickness of those from the keel to the waterline. The gunwale plank, at the top of the hull, and the plank in the area of the oar locks were of ash. When dry, ash was one of the hardest and toughest woods available, fully capable of withstanding the stress and wear at those two sites of the ship’s hull.
Wood scraps and chips from these efforts were fed into a fire that kept a cauldron of pine pitch suspended from a tripod bubbling. This aromatic mixture would be reduced by boiling until it became the black pine tar necessary to seal all the various hull members as they were joined together. A pile of pine pitch blocks, collected and cast while pine sap still freely flowed were handily piled nearby. They would be added to the cauldron as necessary to ensure sufficient pine pitch for the work at hand. The fire also provided a place for the men to thaw out from time-to-time.
Prior to the storm, the long keels had both been set across short log blocks and braced securely in place. Stem and stern posts carved out of properly shaped curved timbers by the stem master were now securely nailed in position at each end of the keels, and propped upright at the desired angle. Both the bow stem post and stern stem post were incised at the proper angle to accept the ends of each plank of the ship.
Beginning at the very bottom of the bow stem post, where it joins the long keel, the garboard plank, the first plank attached to the keel on both sides, was carefully nailed into position along its bottom edge. The angle established by this plank, outward from the keel on each side, determined the final shape of the ship as each succeeding run of planks were riveted in place to the preceding run. The garboard plank’s placement was vital to ensure the ship’s sides in cross section were identical and that she was watertight.
Equally spaced holes had been augered along the bottom edge of the thin planks before they were positioned along the keel to accept the long iron spikes that would be driven through and into the keel. In positions where the long iron spikes could not be safely driven in without splitting the keel, hardwood pegs, or treenails, slightly thicker than the hole they were driven into were used. These pegs would later swell as they soaked up water, making an even tighter bond.
When each garboard plank was in position on the keel, the graceful outward flow of the hull was established by the shape of the keel itself. In cross section the keel was cut in the shape of a T with the ends of the crosspiece at the top angled upward about thirty degrees from level. The keel shape created a shelf on which to mount the first plank. The bottom, vertical portion of the T-shaped keel, became the bearing surface of the completed hull when the ship would later be beached. The keel also facilitated the ships ability, in company with the huge steerboard, to hold the desired course without sideslip in the water from the pressure of the wind on the sail. The keel‘s shape created the outflowing curve of the bottom planks and relatively flat bottom of the completed ship.
Each of the several planks on each side of the ship was of differing lengths. An adjustable gauge, with an inset iron scribe point, gouged a channel an equal distance from the bottom edge of each plank. Spaced equidistant just above this channel, and marked at the same time the channel was cut and by the same gauge, holes were augered. These holes became a guide to auger holes through the top of the preceding plank run to which the new plank would be joined with iron rivets and roves. The channel would receive the tarred caulking twine. The edges of each plank were beveled so as to flow onto the plank to which it was joined. Each plank was clamped in place to the outside of the plank it was joining with long, hinged wooden clamps that were placed over the two planks being joined. Then a wedge was driven between the upper jaws of the clamp, firmly gripping the joined edges of the two planks together for riveting.
The ends, where they joined the preceding plank on the same level were carefully scarfed before mounting, creating a beveled scarf joint that was tarred, caulked, and riveted together, creating a continuous plank run from end-to-end along each side of the ship. As planks joined the preceding run along the bottom, the two bearing surfaces received liberal daubs of pine tar from the bubbling cauldron; twisted wadmal caulking twine was pressed into the channel, making the joints watertight when riveted.
After holes had been augered through the joined planks, men working in teams – one outside the hull, and one inside – riveted the edges tightly together with iron nails and roves provided by the smithies. These essential iron parts were actually a pointed square nail with a large head, tapered along its length to the point, long enough for the job at hand, and a flat washer with a center hole punched large enough to accommodate the nail. The nails were used by themselves whenever attachment of a structural member did not completely pierce through the two being joined. When the nail tip went all the way through the wood, as it did on the scarf and edge joints of the planks, a rove was added on the inside of the plank to protect the wood from the clinched nail point. The two together, nail and rove were called a rivet.
The nails were driven through the predrilled holes along the edge of the plank being mounted from the outside, and the man inside placed the rove over the nail’s point and clinched it over with his hammerhead. The man on the outside of the hull held the head of his hammer against the nail head as resistance against the tendency of the clinching forces to push the nail back out of the hole. This force from both directions during the clinch pulled the plank edges tightly together against the pine tar and caulking twine, effectively sealing the joint.

 Excerpt, Assimilation, An Axe of Iron Novel
J. A. Hunsinger, © 2015, All Rights Reserved

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Viking Ship Museum Roskilde, Denmark

The hull takes shape




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