Hasholme Logboat

Hasholme logboat is a late Iron Age boat (750-390 BC) discovered at Hasholme, an area of civil parish of Holme-on-Spalding-Moor in the East Riding of the English county of Yorkshire.

The boat was located and excavated at Hasholme, on the north bank of the River Foulness in the broad river channel. The boat was situated in mostly waterlogged clay (silty-clay, silt, and sand) deposits, which greatly helped the preservation of timbers. Apart from the boat itself, the excavations did not produce any major associated artifacts, with the exception of a single pottery shard. For dating purposes two techniques, tree-ring dating and radiocarbon C14/ thermo-luminescence, were employed. Both methods gave rather comparable results some time between 750 – 390 BC, which approximately correlates with later European Iron Age. Based on reconstruction of the landscape around the site, we know that it was dominated by mixed oak, birch, and alder woodland, some meadows and marshes, as well as many river tributaries and oxbow lakes.

"Parent log" of the boat's hull

The hull of Hasholme Logboat was made of an oak ("Quercus" sp.). After all the measurements of the hull were taken, it was estimated that the parent log (oak log the boat was made of) had to be approximately 14 m long with at least 5.4 m circumference. Thus the theoretical weight of this log must have been around 28.5 tons but because of the presence of the “heart root” (natural process of rotting of the interior of the log) these estimates are exaggerated. Based on the size of the oak and other dendro measurements, it was also suggested that this kind of tree was between 810 and 880 years old on felling. Oaks of such advanced age and size must have developed a rot known as “brittle heart,” which originates at the bottom and spreads upward. In the case of Hasholme, this rot spread almost to the very top of the trunk. This meant that even though the hollowing was much easier, the openings on both ends had to be closed and watertight. It was not an accident to select a tree with an extensive rot along its entire length and thus save tremendous amount of time.

Shape

Hasholme boat is made of one whole log, rather than two, and is generally log-shaped. It has flat bottom outboard and also inboard. With the bottom horizontal, the top edge of the sheer-line generally slopes down towards the bow. However, when the boat is afloat the sheer-line becomes horizontal and the bottom gradually slopes upward. Near the bow, the bottom becomes even more rounded and distinctly angled. At the other end, at the stern, the thickness of the bottom gradually increases to provide sufficient timber to support transom. The forward upper edges on both sides of the hull are curved in sections and rabbets to support extensions in the form of washstrake. The overall length of the Hasholme logboat is 12.87 m, 1.4 m in maximum beam, and 1.25 m in maximum height.

Bow

The bow section of Hasholme logboat has very original design. It is made of two parts, lower and upper bow timbers, which together formed a front enclosure to the log. The lower bow piece is 60 cm long and 2 cm thick. On both sides of this timber there are symmetrical rabbets which match similar rabbets on the main hull as well as series of cleats with transverse holes through which the second and third transverse timbers passed. Those transverse timbers, three total, not only fastening the lower bow timber to both sides of the hull, but were also strengthening and linking the bow section. Forward of the groove for the foremost timber, there were three large vertical holes. The upper bow piece is also around 60 cm long and has rather complex shape. Bottom section of the upper bow timber has a transverse lip to envelope the leading edge of the lower bow timber, and series of longitudinal grooves on both sides to fit over the forward ends of the washstrakes of the upper part of the hull. This upper timber was fastened to the lower timber by three vertical tree-nails through corresponding holes in the lower bow. Those tree-nails were approximately 35 cm long and 0.6 cm thick.

Stern

In general, stern is at the right angle to the rest of the boat. Approximately 25cm forward of the stern, a transverse groove was cut into the bottom and sides to support the transom piece. Forward of the transom several grooves were cut to support transverse shelves, with the most aft shelf covering the transom. Such fitted transoms, which enclose the end of the log, have been relatively common in prehistoric logboats. In case of Hasholme boat, the rotted heart prevented a construction of integrated bow and stern therefore both sections had to be precisely fitted and watertight. The transom itself is 1 m high and 1.08 m in breadth, with rounded lower profile and upper corners cut away. The thickness varies from 25 mm to 90 mm. At the top portion of the transom there are two horizontal holes without any visible wear. Since the original transom weighted between 60 to 75 kg those holes were necessary to place it inside the grooves. Those grooves were later caulked with some mixture of mosses and twigs to make the whole structure watertight. The upper corner of the starboard was cut away and long tree-nail drove through both sides of the hull tightening the transom in place. The second function of this tree-nail was to form a tie between both sides of the hull, with similar beam-ties in the bow section of the boat.Fitted transoms are relatively common in pre-historic logboats since it is much easier to make a transom and watertight it, than to hollow the entire healthy log.

Beam-ties

Beam-ties are transverse timbers fitted athwartship near the stern and their function was to tie the two sides of hull together. This becomes especially important for logboats without integral ends, that is fitted transom and bow. At the bow section, transverse timbers were fitted and functioned as beam-ties.

Thickness gauges

At seven points along the bottom of the boat, thickness gauges have been cut. Those holes were bored from outside of the log after the outside of the boat was formed. The depth of the holes equaled to required thickness of the boat bottom. In Hasholme logboat, however, the thickness gauges were bored not at the bottom but at the turn of the bilge, and later corked by oak tree-nails.

Holes near the sheer

There are eleven equally spaced holes (60 mm in diameter) near the top edge of the sheer line. Closes analysis of those holes showed no signs of any intensive wear or fitting marks inside them so there purpose is still a mystery?!?Possible functions of the holes:
* Expansion of the hull: unlikely with Hasholme because it was made of thick oak, which does not expand. The thickness of the sides would not allow expansion.
* Holes as lashings during the construction phase.
* Cross-beams/ Ribs; also discounted because there is not evidence of any pressure or attachment, nor need for any.
* Caring-handles: poles could have been passed through those eleven pairs of holes to carry the boat. However, the great weight of the boat would require some 44 men. Nobody knows either if such thin poles would support the weight.
* Fastening holes for hides: Holes could be used as some sort of fastening points for hides to keep cargo or men dry during longer expeditions.

Washstrakes

Both sides of the front-upper hull consisted of washstrakes fastened to the hull by series of tree-nails and rabbet grooves. Giving the limitations of the log, the washstrakes were probably fitted to the hull to increase the height of the sides near the bow section. They were directly attached to both sides of the hull and fitted inside special grooves in the upper bow timber.

Repairs

It appeared that there was a repair done on the portside hull. To patch it, a larger portion of the hull was worked away and a rabbet was cut around the edges. Then, a repair patch, some 1.25 m long, was manufactured with similar rabbets so both parts would perfectly match. In both parts, the corresponding holes were cut and tree-nails used to fasten them from outside. The other repair, which was done to the starboard inner face of the hull at the stern, was patched by an insertion of a pre-shaped block and fastened by a tree-nail. Based on the analysis of the hull, this repair was initiated as a split stopper. Boring a hole at one end of a split is a recognized way of minimizing a possibility of its spreading. The split was therefore caulked, a section of wood around the transom removed, and the repair block inserted and transom finished.

Designing the boat

Based on ethnographic evidence, it is assumed that this kind of log could be cut by use of some primitive stone or iron tools, but mostly by use of controlled fire. After the log was cut, it was transported (rolled or moved on other wood rollers) to the construction site. At the site, work generally had to start from the bottom of the hull and followed by shaping hull sides.

Before cutting a tree, the builder had to asses the log, its shape, length, areas of damage, the extent of heart rot, as well as ways to work the bow and stern. A major requirement while working with such an enormous log must have been to minimize the number of times the log had to be turn over. The first stage, therefore, would be to flat the external bottom and slightly upturn the bow and stern, shape the hull sides, as well as to bore holes (thickness gauges) in bottom. However, in case of Hasholme boat, those gauges were installed right at the turn of the bilge. The log would then be rolled over and placed on some sort of timbers so the access to the bottom would be still possible. The next stage would be to work the upper section of the log to produce a sheerline and then work the inside until thickness gauges were reached. Because of the presence of an extensive rot, hollowing was probably done by tools rather than fire. The thickness of the sides would be achieved by eye or by sound, simply by tapping the log. For the bottom, however, the holes left after thickness gauges were later plugged by tightly fitted and dried oak tree-nails to ensure maximum watertightness upon wood expansion. The log would then be finished internally, with all the rabbets for fitting bow timbers, transom, and washstrakes, and holes along the sheerline cut. As the final step, bow and stern timbers, which are not integrated with the rest of the hull, would be caulked with moss and the whole structure made watertight.

It is interesting to notice that for many measurements natural units, such as thumb, palm, foot, were used. For example, the thickness gauges were approximately one thumb in diameter, and the holes near the sheer approximately two thumbs.

The overall time to build Hasholme logboat would directly depend on the number of men involved. Based on other ethnographic evidence it was estimated that the total time would roughly a month. Even though, building a log-boat is always a communal effort, the complexity of bow and stern sections suggest that master boatbuilder with specialized knowledge had to be designated.

There is no any evidence suggesting that this boat had ever been fitted with a mast or sail of some sort. In case of Hasholme logboat, major means of propulsion were either paddles or long poles, while steering was likely done by an oar. Judging from the size of the boat, there were probably nine pairs of paddlers, 18 men total, and two steersmen. Paddlers would most likely paddle from the standing position, while steersmen would stand on the stern platform. With this arrangement, the major function of the boat would be to display power and high status of the group to their neighbors. The other function of the boat could be to simply transport cargo, for instance iron ore, rocks, timber, grain, or meat, among others, with maximum load even up to 9000 kg (9 tons). In this case, different arrangements and combinations of paddlers to amount cargo would be possible.

References:

* Millet, M. and McGrail, S. 1987. "The Archaeology of the Hasholme Logboat." The Archaeological Journal 144: 69-155.