Umiaks of this type were constructed in much the same way that a wood planked boat might be, with chines and floor timbers defining the bottom, and relatively few ribs and stringers making up the sides. The builder would begin by building the bottom and end, then adding the gunwales.The gunwales, and stem and stern posts were of fairly heavy scantlings.
Keels were sometimes flat, but often square sectioned. Some form of external keel, to protect the skin and act as a skid was usually incorporated. This went on after the skin. Ivory or bone plates may be lashed onto this member to act as abrasion protection, and to make it slide easily. On some boats, the bow seam was sewn off-center to avoid the worst effects of ice abrasion.
A characteristic feature of Umiak construction is the headboard, basically a piece of plank on the flat that connects the gunwales and serves as an anchor point for the top of the stem or stern post. Beside its' construction functions, the headboard allows the builder to carry more beam into the ends, and to build in more side flare. Both features help in stability and load carrying ability. The gunwales may be separated by 6 to 8 inches forward, and 12 or more aft. The gunwales themselves were often extended -unskinned- past the headboard, where they served as handholds and grab points.
As a side note, the use of exposed frame members, independent of the skin is thought to be a holdover from the earliest skin boats of the Neolithic period, when this was a usual way to finish off the keel and gunwales, and to join them.Petroglyphs from Norway and other places seem to show this, although archeologic opinion is far from being in agreement. In view of the umiak's antiquity, this is an interesting idea. Whatever the case, umiaks are the direct, unbroken descendants of working craft from 3, 5, or 10,000 years ago!
Umiaks of this period were paddled and sailed.
Hunting umiaks frequently operate in the ice, which calls for a strong and tough boat. Light weight is also important, because these boats are habitually beached, and dragged over leads in the ice to find open water. Flexible construction, similar to that used in kayaks, helped create a resilient boat to survive these trying conditions. This was achieved by use of relatively few frame members, and lashing for fastening. The tough, flexible walrus hide covering was an important element in the sucess of this design. The hide was split before use, but still might be as much as 1/2 inch thick. All hide preparation and sewing was done solely by women.
Although lashed construction is an important part of umiak building, bolts, screws and nails have been used whenever they became available, and should probably be considered part of the umiak's heritage by now. This is not the contradiction it may seem to be, because, especially with heavy scantlings, solid connections pose no disadvantage. Where a 4x4 stem meets a 4x6 keel, bolts may indeed be the fastener of choice.
When Yankee whalers entered the arctic in 1848, native peoples came in contact with the round-bottomed New Bedford whaleboats. Often these boats were used in payment for services, and left behind after the season ended. This practice continued until the collapse of the whale fishery in the 1930's. The wood-planked whaleboats didn't stand up very well under local conditions. It was said they " broke too easy". Ice and cedar planks isn't a marriage made in heaven.Their great weight - 1200 pounds or more - made them cumbersome too. A comparable umiak might weight 200 or so pounds. However, their shape and seaworthiness were much appreciated. Skin versions of the whaleboat were not long in coming, given the Peoples' ingenuity and the availability of bending oak and dimensional lumber as trade good .
These new, round-bottomed umiaks offered several advantages over the older model. They are perhaps somewhat more seaworthy. They are definately easier and quicker to build - bent-rib construction cuts down on the number of parts a builder needs to make, and reduces the need for complicated shaping, cutting, and fitting. Having built umiaks of both types, I can vouch for that.
Construction is simplified because all the builder needs to do is set up a backbone of the keel, end posts (with headboards) and gunwales. This lets him skip the time consuming job of building the complex bottom assembly. Once the backbone is set up, adding bent ribs is the next step.
The Irish Curragh was a large skin boat of European origin which is sometimes compared to the umiak. In general, it was more rigidly built, with more,and closer-spaced frame members. It was sailed and rowed. Some of the Irish skin boats were large, 30 feet or so, and carried cattle and other cago. In terms of conception and execution, the curragh might better be said to be a wood-planked boat that happens to be skin covered.
The bent rib umiak is a relatively new permutation of an old species. St. Lawrence Islanders are said to have learned to build them from King Islanders, but it would be impossible to really say where, when or who built the first of the new type. At any rate, it spread throughout the Bering Strait area, one builder copying another. The older , flat-bottomed type was eventually supplanted by both the whaleboat and the newer model, partially for the reasons discussed earlier, but also because they were not as well suited to outboard motor power, which rapidly became the preferred form of propulsion.