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Packing & Securing Gear in a PakCanoe |
SKIN ON FRAME BOATS |
| It has been interesting over the years to see and hear references to "skin on frame boats" and to "folding boats". While native style "skin on frame" kayaks are often recognized for excellent performance - and copied in modern materials, the perception of skin on frame boats that fold is often that their only real advantage is portability. We seem to accept easily that the native populations of the north have developed highly efficient kayak shapes, but modern versions that fold are presumed to be much less efficient. Interestingly, it is often assumed that hardshell kayaks are even better because they can be made stiffer. I am not sure if this is a case of successful sales effort by the leading manufacturers. (Hardshell boats are stiff, so we'd better call it an advantage.) If it is repeated often enough, it becomes "the truth". Reality is a bit more complicated. Every boat is used under quite different conditions, and each design is a more or less successful compromise to fit typical loads and conditions. A boat that works well under one set of conditions may not be very good when conditions change. I am willing to bet that the native people who built skin on frame boats for hunting and travel would have been happy to use some of the stronger and more durable materials we have available today, but I am not at all sure that they would have opted for stiffer boats. I do not know the answer to the question of which is more efficient in terms of hull speed on a flat calm day. The best information I have been able to find is that it is complicated. What is obvious is that even a flexible hull will not flex all that much on calm water, so any difference in performance should be minor, assuming that we are comparing boats of the same size and shape. Experience in rough conditions has made it very clear that flexible hulls have a major advantage handling waves. It seems that a flexible hull will more easily ride over waves instead of through them - and it does. Last summer Laurel Archer pushed the envelope by running the Tatshenshini/Alsek (some boat/design feedback from her is included below). Other notable runs in PakCanoes include the Colorado River through the Grand Canyon and the Moisie river in flood conditions (discriptions of both are on our web site www.pakboats.com). Once you get used to the "different" feel of a flexible hull, it is actually quite reassuring. The whole hull works with waves in a way that stiff hulls don't. In most skin on frame hulls wear and tear gets concentrated in areas where the skin rests against the frame. This can cause damage very quickly. In hard boats, wear tends to get distributed over a much wider area, so more material has to be worn away before there is a problem. A solution to the abrasion problem was pioneered by the Norwegian manufacturer, Ally in the 1970's and was adopted by Pakboats when we started making PakCanoes in 1995. By placing a layer of closed cell foam in the bottom between the skin and the frame, the skin is removed from direct contact with the frame, and the skin is never abraded between two hard surfaces. This causes an amazing improvement in abrasion resistance. For quite a few years, the preferred material for "indestructible" wilderness tripping canoes has been Royalex. Royalex consists of an outer PVC layer backed by ABS plastic and a foam core. It is interesting to compare how the PVC layer on a Royalex canoe gets severely gauged and abraded when the same coating on a folding canoe skin does not. The reason is that in the Royalex canoe, the PVC layer is backed by a hard ABS plastic layer. In the folding canoe, the PVC layer is backed by a soft foam layer, and abrasion is sharply reduced. There is more to a folding boat than portability. Once you assemble one, you have a skin on frame boat that has much history behind it - and you really are not giving up performance in the bargain. |
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