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Bast, cording and sewing While the woodworking exercises were taking place, one group was studying the making of cords for sewing or lashing together the boat's parts. As previously mentioned, there was some uncertainty as to what material the sewing cords were made of. No traces of cord were found in the stitching, only impressions in the adhered sealing material. However, there was a bundle of cords at one end of the boat that had been interpreted as being made from lime bast. This material was already known to have been used for cordage production in the Stone Age.However, some wooden parts were found in a couple of sewing holes that could be interpreted as cords made from birch roots, for example. However, they could also have come from wooden sticks that were driven into the sewing holes after sewing to ensure that the cords remained tight, as seen on Maori boats in New Zealand.We had our doubts. We finally decided in favour of limewood, thinking that there should have been boats sewn together with cords of this material by now.One member had a son who was a forester on Zealand. He had a plantation of young lime trees that needed thinning. The member travelled to Zealand one day in June, when the trees are easiest to debark due to the sap rising. The trees, which had a diameter of 10-12 cm, were felled and cut into lengths of 1.5 metres. The bark was scratched with longitudinal scratches at a distance of 15 mm and peeled off. The strips of bark were then soaked in water for a month in vats. This allowed the glue (pectin) between the individual bark layers to rot away and the thin strips of bark could be peeled off. These were washed and hung to dry and finally bundled into 10 cm diameter bundles. The bast harvest totalled 13 kg. The bast strips were twisted into cords using a spinning reel that constantly rotated the finished cord piece.As the twisting progressed, new bast strips were added. The number of bast strips simultaneously present somewhere on the cord determines how strong the cord will be.The finished cords were then twisted together to form cord. This was done using a so-called shearing machine, a machine where three hooks rotated at the same speed and direction. The twisting of the cords into string was controlled by a top.The method used is no different from ordinary rope weaving. A method of spinning cords and twisting rope using only hands and fingers was tried. This method, which had probably been used in ancient times, gave the same good results, but it was significantly slower. The finished bast strips ready for cord making. Photo: H.P. Rasmussen. Twisting corded cord. Photo: H.P. Rasmussen. The find indicates that two-strand cord was used to sew the boards together. For the lashings of the ribs or wraps for the boards' cleats, we chose to use three-strand cord, as such cord was found in a bundle in the find. A total of 600 metres of cord was used to sew the boards and for the lashings.By moistening both the bast strips and the cords before tying, we achieved a much more beautiful and uniform result. A series of measurements were taken with two-stranded cord with a density of 6.8 g/m. After normalisation, where the cord was stretched, we found the following values: Shrinkage: from dry to wet: 1%. Coefficient of elasticity: 0.005 %/N. Breaking strength: 250-300 N (25-30 kg).We found that the breaking strength was on the lower side, which is why we increased the number of bast strips in the cords from 2-3 to 3-4. This increased the density of the two-stranded cords to 11 g/m, corresponding to a breaking strength of 40-50 kg, and it was with this cord that the boat was sewn together.Tests were also conducted on the strength of the sewing of the boards. Before we report on these tests, we need to look at the seal between the boards. According to Rosenberg, the find indicates that the seams on both the outside and inside were covered with an organic mass, which Rosenberg interpreted to be resin. Later research into the parts of the find revealed a lump of organic material that was analysed and found to contain animal fat and linseed oil.After discussions with the National Museum in Roskilde, we decided that the seal between the boards should consist of rolls of carded sheep wool dipped in a mixture of beef tallow and linseed oil. Some tests were carried out with different mixing ratios, and we found that an 80/20 mixture of ox tallow/linseed oil gave the best results in terms of sealing. The density of the saturated sheep's wool roll was 20 g/m.Two boards were now manufactured to represent tables. Over a length of 60 cm, these boards were sewn together with the sealing material in the gap between the boards. The final cord is wound (3-stranded). Photo: H.P. Rasmussen. Sewing together test pieces. The use of the ‘S-shaped’ tool is a hypothesis. It works, but is a bit cumbersome. Photo: Ib Stolberg-Rohr Notice the curved wooden tool used to tighten the stitching. It is a copy of a part from the find and is thus interpreted as a sewing tensioner. The stitching of the test piece was subjected to shear forces and we measured coherent values of shear force and mutual movement. The figure shows this correlation. Up to a force of 0.6 N/mm seam length, the pieces did not move relative to each other.0.6 N/mm corresponds to 36 kg force over the entire length or 60 kg force per metre of seam.At higher forces, we got a shear, but it was slow and hesitant, suggesting that the seal acts as a very viscous fluid. This displacement was permanent, i.e. it did not disappear when the force was removed.A stitch was sewn every 7.5 cm. Consistent with the finding, the stitch was double with a course that caused the knot to be self-locking, so that cutting a string would not cause the entire seam to unravel. Forskydningskraft og forskydning. Tegning: K.V. Valbjørn Self-locking double stitch. Photo: H.P. Rasmussen. Sources Hvad Haanden former er Aandens Spor. Language The text in this article has been translated from Danish to English using the free DeepL translation programme.
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Wood A possible stem piece. Photo: H.P. Rasmussen. Adaptation To carve the stems, you needed a short piece of whole log with a length of about 2 metres and a diameter of up to 1 metre. The Polish logs were of insufficient diameter, so we had to get local wood for these stems. One member donated a linden tree that was close to his house. This tree had a sufficient diameter and no large branches in the first 5 metres. This tree was a large-leaved lime (Tilia platyphyllos), while the rest of the boat was built from small-leaved lime (Tilia cordata)[1]. Rough adaptation of a possible stem piece. Photo: H.P. Rasmussen. An undecided design of the upper horns' connection to the stems caused a lot of discussion. There were three possibilities. The first possibility was that the upper horn was part of the stem and bent in heat after carving. The second possibility was that the upper horn had been contained in a branch from the trunk. And finally, the third possibility was that the horn was a separate part that had been mounted on the stem, as was the case with the lower horn.The possibility of a branch was first investigated, but neither of the first two bows we roughly carved could be used, as rot appeared in the gap between branch and trunk and in the core wood of the trunk.We decided to try to form the curved horn by steaming the horn that was carved as part of the log. A steam generator in the form of an oil-fired boiler was constructed by removing the overboiling fuse and we let the steam from the boiler flow into a hose from a tractor tyre that enveloped the horn. After a few hours in the ‘smoke and steam’, we began to curve the horn according to a doctrine that included the curved shape. It went well for a while, but then the horn broke at a crack. A dramatic attempt had failed. At this point we learnt that there had been heartwood in the middle of the bow as well as in the upper horn. This meant that either the upper horn was formed by a branch extending from the trunk containing the bow, or the upper horn was a loose part attached to the bow. We chose the latter solution.The actual carving of the bows was a lot of work, not least because of the above-mentioned experiments and because the bows had to be carved quite far before the quality of the wood could be ascertained.Two logs had to be discarded along the way. One finished log weighed 20 kg. An almost finished stem piece. Photo: H.P. Rasmussen. Sources 1. See the description of the wood species used in the production of Tilia here.Hvad Haanden former er Aandens Spor. Language The text in this article has been translated from Danish to English using the free DeepL translation programme.
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As mentioned earlier, the four large lime logs arrived at the end of January 1994. The three logs were transported to Dyvig and lowered there using pieces of iron to keep them fresh, while the largest of the logs, which seemed best suited for the production of the bottom plank, was towed into the hall at the Linde shipyard. Splitting The trunk had a length of 18 metres, a diameter at the root end of 90 cm and an age of 170 years. It was orientated so that the largest crack was vertical and the trunk was supported with wooden wedges.The splitting was done by driving steel wedges into this crack from the root end of the trunk. As a crack appeared on the upper side of the trunk where the bark had been removed, this crack was opened by driving wedges vertically into the crack. Initially, steel wedges were used, but as the crack grew larger, beech wedges were used, which did not hurt the soft linden wood as badly as the steel wedges. Linden wood does not split as readily as oak or beech, and there were always ‘runners’ from one half of the trunk to the other. These were cut with hatchets.The splitting took about three hours. The first stem is almost completely split. Photo: H.P. Rasmussen. Shaping We now had to decide how to orientate the bottom board in one half of the trunk.After roughly levelling the split side and removing the bark and sapwood from the entire trunk, we realised that the maximum width of the bottom board over the middle 6 m could not be contained within the trunk. It was decided to cut a hole in the log and then stretch or open it to a wider and flatter shape using boiling water. While the chopping was going on, two 1 metre long, half-round vessels were made from lime wood, open at the ends and with a wall thickness of 3 cm. They were to be used for stretching experiments, as the plan was to boil them in water before stretching. According to the rule of thumb, a plank that needs to bend strongly should be boiled for one hour per inch of thickness. After boiling sample 1 for two hours, it stretched and cracked lengthwise in several places. Test piece 2, which was boiled for a further hour, also cracked. We now realised that heating with boiling water was not a viable method. After an unsuccessful attempt to open the hollow trunk, we had to cut it flat and glue planks to increase the width.Drawing: K.V. Valbjørn However, the traditional method in ancient times was to heat boat shells to be stretched by heating the wood over a fire. It is claimed that the wood needs to reach a temperature of 140 degrees to become suitably plastic. To achieve this temperature, the boat shell was filled with tar, which was brought to a boil by heating it in the fire. We had to abandon this method, partly because we had no experience and partly because we realised that the already fairly hewn keel line would result in an excessively curved keel line when the boat shell was opened amidships, causing the ends to lift. We realised that our predecessors had not used this method for the same reason. They must have had a large enough trunk so that they could cut the bottom plank into shape without stretching.As we had already started cutting the plank, we had to increase the plank width by gluing. We found a glue commonly used in wooden shipbuilding (an epoxy from System West) and a carpenter experienced in using this glue was contacted.Some experiments with gluing planks together and subsequent loading resulted in no difference in strength or elasticity, whether the planks were whole or glued together. The hollowed-out plank was chopped almost flat over the middle 6 metres, creating 10 cm wide glue surfaces. As the glue could hardly withstand more than 0.7 mm thick glue joints, these surfaces had to be planed very flat. 13 boards, 8 cm thick, were carved from the other half of the log. The boards were moulded with flat gluing surfaces. The actual gluing was carried out by ship carpenter Arne Wahl, Fåborg. As the boards were placed, the joints were clamped together with grease-lubricated screws that could be removed after the glue had hardened. The gluing process is described in detail in the member folder in section 4.5.After curing and removing the screws, the plank with the glued boards was ready for further processing. Smaller planks are adapted before gluing. Photo: H.P. Rasmussen. The processing The plank was turned over so that the outside could be worked down to its final shape. After the final operation that left the surface smooth (without using sandpaper), the plank was turned over and the inside was carved and cut out. A particular challenge was the carving of the cleats and the through hole through each of them. This hole was found to be square with an edge length of 10 mm.Some U-shaped chisels were made, the handles of which were shaped so that they could pass over the neighbouring cleat. The square holes in the cleats were carved with a U-shaped chisel. Photo: H.P. Rasmussen. The edge of the bottom plank was left raw so that it could be adapted to the side plank during assembly. The ends of the bottom plank contained the tongue-and-groove joint between the bottom plank and the lower horn, also a wood carving job of dimensions.After completing the bottom plank, we realised that the wood present largely determines the workflow.The weight of the finished bottom plank was 96 kg. The bottom plank is finished. Photo: H.P. Rasmussen. Sources Hvad Haanden Former Language The text in this article has been translated from Danish to English using the free DeepL translation programme.
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We established a close co-operation with the National Museum in Copenhagen and Roskilde, and established a ‘scientific network’ of people with special knowledge of interest to the Guild.These people can be: archaeologists, historians, museum staff, specialists in the crafts related to the Hjortspring Boat, etc.Most of these people have been contacted at the beginning of our project, however, employees from the National Museum and its departments in Roskilde and Brede have been involved several times, most recently in connection with the testing of Tilia.The descriptions below are from the beginning of the project, so the data for each individual is not current here in 2020, unfortunately some are no longer with us. Flemming Rieck Master's degree in prehistoric archaeology from Aarhus University 1977. Born 7 April 1950, grew up in Svenstrup on Als - close to where the Hjortspring boat was found.Excavation manager at Haderslev Museum 1973 - 84.Museum curator at NMU 1984.Head of NMU from 1993 - 2003.Coordinated 10 years of investigations and excavations in Nydam Mose.From September 2008 director of Køge Museum. P. Terndrup Pedersen Professor at DTU Mechanical Engineering. Preben Terndrup Pedersen is the person who, over the past 30 years, has had the greatest impact on education and research in Denmark within the maritime field. His efforts have had a major impact on the Blue Denmark being recognised as an innovative maritime cluster for the benefit of the Danish economy and society.From a mention on DTU's website at the presentation of the Maritime Prize to PTP. Søren Vadstrup Trained as an architect at the Royal Danish Academy of Fine Arts School of Architecture in Copenhagen, Department of Building Restoration. Research project on Viking Age shipbuilding tools, shipbuilding methods and wood technology.As part of this, Søren Vadstrup has studied finds and sources and carried out practical archaeological experiments. Among other things, Søren Vadstrup has been interested in wet wood technology as a special Nordic/Baltic phenomenon. Flemming Kaul Danish archaeologist; curator at the National Museum of Denmark since 1986. Born on 5 March 1955.Kaul has specialised in Bronze Age research with an emphasis on the religious aspects. In 2006 he was awarded a dr.phil. D. in 2006 for his thesis Bronze Age Religion. Studies of the iconography of the Nordic Bronze Age. Using imagery from rock carvings and artefacts from the period, Kaul has attempted to recreate the myths of Bronze Age religion. Kaul is a committed communicator and has written several books on archaeological subjects, including Rock Carvings: Images from Bornholm's Bronze Age (2005) and Europas dysser og jættestuer (1998).In 2007, Kaul was awarded the Erik Westerby Prize for his extensive research efforts, which have gained international recognition.2010: Knight's Cross of the Order of the Dannebrog. Harm Paulsen Professor, experimental archaeologist Making fire, bow and arrow, Ötzi, ...Schleswig-Holsteinisches Landesmuseum, Schloss Gottorf. Jens Risom Esben Kannegaard Cand. phil. curator at the Museum of Syddjurs with responsibility for the archaeological tasks Early Stone Age burials and settlement finds.Experiments with Stone Age technology. Replica of the canoe from Tybrind Vig. Ole Magnus Rope layer, consultant for NMU Hans-Ole Hansen Author Manager of experimental centre Lejre (now: Sagnlandet Lejre).From 1986-19, manager of the Dybøl Banke Visitor Centre. Orla Madsen MA in Archaeology from Aarhus University. Director of Museum Sønderjylland Jørgen Lund Moesgaard Museum Klavs Randsborg Professor of Global Archaeology, University of Copenhagen. Language The text in this article has been translated from Danish to English using the free DeepL translation programme.
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The Hjortspring boat Copies of the original drawings (scale 1:10) were obtained from Oldskriftsselskabet.Copies of Fr. Johannesen's sketches for the drawings were obtained from the University of Oslo, Department of Archaeology, Art History and Numismatics.From the National Museum of Denmark's Marine Archaeological Investigations (NMU) in Roskilde, we received measurements that had been the basis for the reinstallation of the Hjortspring boat at the National Museum in 1988.These drawings were sufficiently accurate for us to start exercises in making elements of the boat and prepare actual construction drawings on our CAD system (AutoCad).Translated with DeepL.com (free version) The Hjortspring boat as designed by Fr. Johannessen in 1936. The Hjortspring find, PLANCHE II. The image is composed of four sub-images; therefore there are - faint - border lines in the image, they are not part of the drawing. Construction It was our intention to produce a replica of the boat with respect for the latest interpretations. However, the overall starting point, which these latest assessments also had, was Johannessen's drawings. These drawings, which were in 1:10 scale, were loaded into an AutoCad programme on the guild's computer. Transverse hull profiles. AutoCad drawing: Hans Lumbye-Hansen. The longest plank in the boat was the bottom plank, which measured 15.4 metres from bow to stern. At both ends, it was finished with the tongue part of a tongue-and-groove joint for attaching the keel horn. In addition, the ends of the bottom plank had a rabbet that guided the stem pieces. Drawing of the end structure of the bottom plank. AutoCad drawing: Hans Lumbye-Hansen. These details were not immediately clear from Johannessen's drawing. Therefore, a 1:1 polystyrene model was made of the end of the bottom plank and the bow. By looking at this model, the most likely design of the joint could be chosen. A key objective was to define the transverse profiles of the boards. These profiles were to be used to produce a series of gauges that would be used to control the carving of the boards. The numbers refer to the frame systems, as there is 1 metre between the frames and frame no. 1 is the rearmost frame. A is 1 metre aft for frame 1 and F is 1 metre forward for frame 10. You can see that there is a slight deviation in the shape of the boat between bow and stern. Profiles of the bottom plank. AutoCad drawing: Hans Lumbye-Hansen. Frame model in 1:10 scale. Model: H. Lumbye-Hansen. Photo: Ib Stolberg-Rohr. To study the edge shapes of the side and railing planks in the flat state, a 1:10 scale frame model was made in which the frame plates, sawn from computer drawings, were glued to a beam.The edges of the bottom board were marked on the frame plates. After modelling the planks in thin wood, they could be held against the frame plates. You could see that the side plank was straight on its bottom edge. Its top edge should have a convex arch with an arrow height of 20 cm.The bottom edge of the railing plank should therefore have a similar curve, but concave.Its upper edge, the railing, should describe an arch with an arrow height of 35 cm in the unfolded state, i.e. before assembly, to achieve the relatively weak sheer that Johannessen's boat had. Sketch of unfolded railing plank. Drawing: K.V. Valbjørn. The mechanism can be understood as follows. When the plank attached amidships is bent inwards, a straight railing will describe a straight line perpendicular to the plane of the plank and land high up on the bow. Such a small sheer, as indicated by Johannessen, would therefore require a strong curvature of the railing when unfolded. The design team felt that it was unlikely that the timber group, let alone our predecessors, could obtain a tree of such dimensions (or with such a curvature) that a railing plank with a convex curvature of the railing of 35 cm and a concave curvature of the lower edge of 20 cm could be contained within it.Consequently, preparations were made to allow the railing to curve by only 12 cm, which would give the ship a sheer that was a good 20 cm larger than Johannessen's estimate. Effect of rail curvature on sheer. Drawing: K.V. Valbjørn. The reason we've paid so much attention to this sheer is because the sheer is crucial to the boat's sailing performance, indirectly at least, as a large sheer pulls the keel line up, giving the boat a more curved keel line. Finally, the plank thickness and cleat dimensions were chosen.While the design group studied the shape of the boat, a member of the construction group had made a 1:10 scale model of the boat. This model also emphasised the problem of sheer as a function of the curvature of the rail. Plank and cleat dimensions. Drawing: K.V. Valbjørn. Computer data is discussed (O. Møller-Olsen and H. Lumbye-Hansen). Photo: H.P. Rasmussen. Model 1:10. Model: Dan Feldfos. Photo: H.P. Rasmussen. Sources Hjortspringfundet.Hvad Haanden former er Aandens Spor. Language The text in this article has been translated from Danish to English using the free DeepL translation programme.
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