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Monday, December 26, 2011

Different Coats for Different Boats

The skins with which skin-on-frame boats are covered differ considerably from place to place, and even from boat type to boat type within a geographic area.


The angyapik (umiaks) of St. Lawrence Island, Alaska, just south of the Bering Strait, are covered with the hides of female walruses. Removed from the carcasses after the spring hunt, the hides are stored until the hunting season ends in June or July. Any flesh or blubber that still adheres is then scraped off, then the hide is folded up into another old skin and left in a warm place for several days or weeks. This "sours" the skin so that the hair can be scraped off easily.
St. Lawrence Island woman splitting a framed walrus hide stretched on a vertical frame. In her right hand she holds a honing stone, with which she frequently touches up the blade of her ulu knife. (Click any image to enlarge)
The edges of the skin are split 1"-2" (2.5-5cm) deep, then holes are punched into the blubber side and the skin is hung and stretched  on a vertical frame. The skin is then split from the top down with an ulu-type knife, great care being given to maintaining equal thickness on both sides. The two halves are not separated completely: they are left attached all along the bottom edge, so that the hide can be "unfolded" to cover very nearly twice its original surface area. It is then stretched and laced onto a larger, horizontal frame and left to dry for two to four weeks, after which is is soaked for up to a week in fresh water just before it is laid over the upturned hull with the blubber and hair side facing inward. The blubber-side half of the split hide goes bow-first, it being considered better able to resist abrasion from floating ice than the hair-side half. Women, by the way, do all the hide preparation and sewing. 
The walrus hide has been split but the two halves remain attached. (See the raised line along the center, just to the right of the center timber.)  It will dry on this stretching frame for several weeks.
Some 200 miles north, on King Island, in the Bearing Strait, the walrus hide is split completely, but only the hair side is used to cover boats. This means that twice as many hides are required. (A typical St. Lawrence Island angyapik requires at least two full hides, and often part of a third for patches to raise the sides amidships.) On Diomede Island, close by King Island, the two halves of the hide are separated completely, but both parts are often used, with the blubber-side half placed toward the bow, as on St. Lawrence. (In contrast, kayaks of the region are skinned with seal or sea lion hides, not walrus.)
Fully-skinned angyapik of St. Lawrence Island, Alaska. Two full skins are sewn together amidships in a straight seam. Also visible are ridges halfway between the center and the ends, where each split hide remains attached. Note the large side panel, required to make up the full width of the hull. 
To sew the hides together, women use thread made from  whale or caribou sinew. For the main hull seams, they use a blind waterproof stitch in which the thread does not completely penetrate either of the pieces. With the two pieces overlapped by 1"-2", the needle is inserted into the side-edge of one piece then down into the underlying piece, where it takes a U-turn within the thickness of the hide before emerging just outboard of the top piece's outer edge. The same procedure is followed on the opposite side, for a double row of waterproof stitches with no holes through the hide.


Half a world and perhaps 1,000 years away is the leather-covered curragh used by early Irish Christian missionaries, as reproduced by Tim Severin in The Brendan Voyage . While it's impossible to know the real details of the boat used by St. Brendan (c.489 - c. 570 or 583), Severin conducted careful and persuasive research in attempting to recreate the type of boat that might have been used to cross the Atlantic long before the Vikings. What he concluded as the most likely covering was ox hides tanned in oak bark solution and dressed with raw sheep's-wool grease (i.e., lanolin). As these 6th-century boats were made in and for the use of monasteries, I feel we can safely assume they were built entirely by men.
Ox hides being installed on Tim Severin's curragh Brendan.
Severin bought his hides from one of only two or three traditional tanners remaining in the UK in the mid 1970s. He observed the process by which hides were first soaked in a lime  solution, then stripped of their hair with hand scrapers. They were then soaked for weeks in an oak-bark solution. After drying, they were dipped into a hot bath of wool grease, then laid out flat one atop another with more hot grease poured between each one. After soaking thus for weeks, the hides had taken up 30-37% grease which, I think, means that the weight of the hide increased by that amount.


The 36'-LOA Brendan required 47 hides to cover. They were sewed with hand-twisted flax cord made of 14 individual threads and rubbed through a mixture of black wax, wool grease and beeswax. Although the needles pierced straight through the seams, the thread's grease coating, and the high grease content of the hides themselves effectively sealed the needle holes against water. On the trip across the Atlantic, seepage through the hull was never a problem.
The finished Brendan.
The differences in materials between the umiaks of Alaska and the curraghs of Ireland imposed significant differences in usage. Because the umiak skins are neither tanned nor dressed, their waterproof performance is extremely limited. They must be removed from the sea every day and allowed to dry, or they will become quickly waterlogged. This will promote rot but, long before that happens, the skins would become too weak to maintain any integrity, and they would simply fall to pieces. This being the case, the umiak/angyapik is strictly a coasting vessel. Although trips lasting several weeks might be undertaken, the crew must land each evening to dry the boat's cover.


The curragh's leather cover, on the other hand, resisted both waterlogging and rot over a period of months at sea, at least in cold waters. (The Brendan voyage took the "stepping stone" route from the British Isles to the Faroes, and thence to Iceland and Newfoundland. Severin speculated that it might not have performed so well had a more southerly route been taken.) The leather-covered curragh, then, was a true ocean-going craft, capable of extended voyages and not requiring drying-out time.


Acknowledgments:
Angyakpiks/umiaks: Information and photos from The Skin Boats of Saint Lawrence Island, Alaska , by Stephen R. Braund
Curraghs: Information and photos from The Brendan Voyage , by Tim Severin
This post was inspired by a communication from Carlos Pedro Vairo, director of the Museo Maritimo de Ushuaia, Argentina, and author of The Yamana Canoe: The Marine Tradition of the Aborigines of Tierra Del Fuego .



3 comments:

  1. It seems to me that Tim Severin made a good case that someone could cross the Atlantic in both directions in a small boat, and that the boat could have curragh style construction and a tanned leather skin. But even after Severin's voyage, we don't know any more about the particulars of Brendan's voyage than we did before. What Severin did establish was that a skin of tanned cowhide saturated with lanolin will hold up for the length of a trans-atlantic voyage. When I first read Severin's book, I was suspicious of Severin's use of tanned cowhides. I am not sure whether it was just lack of familiarity with this technology or the feeling that sewing that many heavy skins together was excessively complicated, but it somehow struck me as an unlikely solution. It seemed rather like a beta version of a skin that actual usage would have improved on. That is, if in Brendan's time people were covering their boats with ox hides, they would have had a more elegant approach.
    And as long as we are in the realm of the speculative, there is Farley Mowat's book, The Farfarers. Mowat contends that people of the British isles covered their boats with walrus skins and used these boats to travel to America. Walrus skins which apparently were available in parts of the British isles at a time when walrus were more plentiful would have been a way to cover curraghs with a lot less sewing being necessary.
    Finally, a modern innovation in the Arctic is to paint walrus hide covered umiaks to minimize water absorption. See for instance John Bocksoce's book Arctic Passages: A Unique Small-Boat Journey Through the Great Northern Waterway as an example of using a painted walrus hide covered umiak for a long voyage, albeit one along the coast with plenty of opportunity to dry out the boat.

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  2. Severin's boat design was based as far as possible on his historical source, "Navigatio Sancti Brendani Abbatis" (The Voyage of St. Brendan the Abbott), which was explicit that the boat was fat-cured oxhide over a wood frame. The first known ms. of the Navigatio was published about 200 yrs. after Brendan's life (ca. 489 AD), and since technology developed slowly then, it seems reasonable to assume that, had the voyage occurred at all, the description might be accurate. Certainly, they knew how to sew leather then. And the Irish church art of the period demonstrates how church types were not at all put off by immense amounts of finicky, repetitive work.
    Since the only (?) good evidence for Brendan's voyage is the Navigatio itself, it makes sense that Severin would have followed the boat description therein as closely as possible, since his objective was to test the historical accuracy of that source. (Since the boat's design wasn't described in Navigatio, he used "modern" curraghs, obviously of rather antique heritage, as the basic design brief, combining that with the description of materials in the Navigatio.) He did, however, diverge from his source by installing a foremast. Navigatio refers to "the" mast, in singular, many times, but Severin found a single more or less contemporary image of Brendan's boat with a foremast, and chose to follow that lead instead.

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  3. All boat building requires an inordinate amount of finicky work, whether it is sewing a bunch of skins together, or cutting out ten pairs of planks, each pair different from the others and cut to fit an oddly shaped space perfectly.

    Actually, compared to spiling, cutting, and fitting the planks for a comparably sized lapstrake boat, sewing skins together sounds easy!

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