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Wednesday, June 25, 2014

Irish Logboat Finds

An article in the current issue of Current Archaeology tells of multiple logboat finds in Lough Corrib, County Galway, Ireland. I haven't seen the full writeup (it's pay-to-read), but a decent summary appears here.

The five boats, found in various locations around the large lake, were discovered during a bathymetric survey, and they were preserved by the lake's soft mud bottom and (presumably) cold temperatures and still waters at depth. One of the logboats, dated to about 4,500 BCE (Early Bronze Age), exhibits 2-3cm raised features carved on the inner side of the hull. There is a lengthwise feature that serves as a kind of keelson, and four cross-members. The article speculates that these served to divide the hull into compartments, but I think it more likely that they served as strengthening members in the nature of ribs.
Bronze Age Irish logboat (Source Current Archaeology)
The Early Bronze Age logboat found in Lough Corrib is 12 meters long and probably had a crew of 10-12 paddlers. (Source: Current Archaeology)
A 3,400-year-old boat was apparently carved in two halves, held together by rods that passed through internal cleats on the interior of both halves, and probably supplemented by lashings through bored holes. (The article summary is ambiguous on this point.) This strongly suggests kinship with the sewn-construction techniques used in England, as displayed in the Bronze Age Ferriby boats and Dover boat.

Another Lough Corrib boat, dated to the 11th century CE, was found in conjunction with several battle axes. Although battle axes were introduced to Ireland by Vikings a couple centuries earlier, the article states that it is more likely that the boat carried Irish warriors who had adopted the Viking weapon. Clear evidence for the use of oared propulsion exists in the form of holes for four pairs of tholepins. Five thwart-seats were present, indicating that the boat carried a coxswain or some other non-rowing individual (e.g., a passenger, dignitary or the captain). Clinker-planked construction was common by the 11th century, and of course skin-on-frame curraghs were also in use in Ireland at that time, so it is interesting that logboats remained in use for apparently high-prestige purposes that late in Ireland's history.

6 comments:

  1. It is claimed that carved ribs in a logboat do not add to its strength as the grain in the rib is the same as in the body of the boat thus a split in the hull is likely to carry on through the rib as well. It is possible that some of these ribs were to brace the feet against when rowing.

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  2. Edwin. I see your point about a split. But would the carved ribs help resist a transverse fracture, as when striking a rock? It seems that the longitudinal member would strengthen the hull against forces in the hogging direction, comparable to "oil canning" in a plastic canoe.

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  3. Interesting question, the force from hitting a rock would be compressive and the rib would tend to resist the bending force on the hull. I can't recall any logboat though that has suffered damage in this way although same have sewn patches that might indicate collision damage.

    Most logboats are not found in rocky areas, mud being the preserver. However, I wonder if a rib helps to stiffen against bending both laterally and longitudinally when the prow is run up on a bank.

    Another item from that article is the boat held together with the"Ferriby" technique of transverse rods. I believe this is the first confirmation that this building method was used elsewhere than England and might indicate that it was quite widespread and such boats common.

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  4. Would you describe this logboat (based on its description) as a hybrid between a traditional Neolithic logboat and a Sewn-Plank boat. Or is this just a solid keel-plate on a Beaker style sewn plank boat?

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  5. Not familiar with the Beaker style boat by that name. From the description, it sounds like a "standard" extended logboat, i.e., a basic dugout hull, with the sides made higher by the addition of a strake.

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  6. Ribs might strengthen a little against twisting? And in compression, would resist oil-canning even if cracked?

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