For an introduction, see the Kayarchy chapter Sea Kayak Construction Methods (5) Skin on Frame.
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Why skin-on-frame?
People build skin-on-frame boats for a lot of the same reasons they go kayaking. It's interesting, it's fun, it's active, it's a challenge, and it gives you achievable goals. And when you've built it, you have a thing of beauty. Greenland kayaks always look wonderful, whatever you make them from. The frame of a skin-on-frame boat has an additional beauty of its own, and SOF boats are often given a translucent skin. When they light shines through them, you have a boat that will turn heads anywhere. Here's a frame by Paul Sanderson:
SOF is also a faster and easier way to build a one-off boat than any other method of boatbuilding. It's great for making boats to fit a particular user; it's great for prototypes (if you have an idea for a new design, you can make a SOF version and test it quickly); and it's great for community projects, including youth projects. Picture by Marcin Bober:
The SOF building technique is usually used for kayaks, and for traditional open boats such as canoes, umiaks and curraghs. Because skin boats are light in weight, they’re more easily driven than conventional boats, so they need only small motors or small sailing rigs, and they can be great with paddles or oars. Because they’re strong, they can carry an enormous load if you want.
It’s fine for other shapes too. You can build any paddling, rowing or sailing boat, including classic boat designs. Artists have used the SOF technique to create all sorts of amazing structures. I’ve used it to build an 8-foot dinghy, and to put a lightweight cabin/deck on a 30-foot boat.
There are a dozen good ways to build a boat, and skin-on-frame (SOF) is one of them. A SOF kayak is not likely to be stronger, or faster, or more durable, or very much lighter, than a commercially-made boat, but it's a perfectly good way to build a light, strong, fast boat; and there's nothing quite like using a kayak that you personally built. In a consumer society, building a good boat is strangely satisfying. Another picture by Marcin Bober:
Also, a SOF kayak can be a design you like but which is not commercially available. It's not easy, for example, to find nice sea kayaks to fit young paddlers. And some adult sea kayakers have have three or four boats, one of which may be an extremely low volume design they use mainly for the more zen kinds of kayak rolling. Or you may have fallen in love with one of the classic designs revived, used and documented by Harvey Golden, or some other design, new or old.
SOF boats are easy to maintain and light to carry. They can be light but tough. With a skin like an inflatable dinghy, they bounce off when they hit slipways, docks and rocks. Unless they’re built ultralight, it’s hard to cause significant damage even with direct blows from a hammer. If you go for heavy-duty SOF materials and add reinforcing patches to double the thickness next to the stringers, a SOF boat can be better than GRP at resisting abrasion.
Again like an inflatable dinghy, SOF boats can be very durable. A synthetic skin combined with certain synthetic proofing compounds can last 10-20 years. In two ways, SOF boats are better than inflatable boats. First, you can make your boat any shape you like, within reason. Second, your boat won’t collapse if it gets a puncture.
With a lot of thought, trial-and-error and hard work, it’s even possible to make a folding kayak, with a removable skin and a frame that takes apart and fits into a couple of duffel bags for storage or travel. However, this is much harder than making a rigid skin-on-frame boat. A lot of good rigid SOF boats have been built by 12-year-olds, but making a good folding kayak is a job for a competent engineer - which is why they’re so expensive to buy.
The SOF technique is very flexible. You can use it to:
- Build a 17’ sea kayak that weighs 30-40 lbs (45-60 lbs for a double sea kayak)
- Or an 11’ one-man canoe that weighs 12 lbs.
- Or a 14’ Whitehall rowing boat that weighs 43 lbs.
- Or a 25’ sail boat that will bounce off ice floes but still weighs only 200-300 lbs. In wood or GRP it would weigh 600-900 lbs and go “crunch... glug glug glug” if it hit an ice floe.
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