What are the merits, if any, in paddling a folding kayak like Feathercraft vs a hard shell kayak in the ocean?
I know folks who take them on planes.
I believe TsuanmiChuck who is banned here takes his often to Japan, and paddles in serious offshore conditions.
Remember a boat like a feathercraft is much more like the first skin on bone or wood kayaks that inuit and other native people used to explore huge coastlines and do very long ocean crossings. They are flexible and this actually has interesting effects in heavy seas.
I’ve owned 3 Feathercrafts (Kahuna, K-1 Expedition and most recently a Wisper) and have paddled all three in the ocean (as well as paddled various “hard” boats offshore). I actually prefer the Feathercrafts, especially in heavy waves. The skin on frame boats absorb a lot of the wave energy and they even will pop over rollers that hit you broadside much more reliably than a hard boat. The “sea sock” that comes with them is great, adding warmth and keeping water from penetrating into the hull.
I find the FC’s generally more comfortable overall for a long day’s paddle. Even if you do flip, the inflatable sponsons and light weight and buoyancy of the boats make them easy to right, drain and re-enter. Many people have made significant ocean crossings with skin-on-frame boats, including Feathercrafts. If I was going to do so myself, it would be my boat of choice.
You do have to be meticulous about cleaning seawater out of them though, and keeping the frame well-lubed at the joints or they will corrode and sieze up.
You might get more feedback on this specific question over at http://www.foldingkayaks.org
We’ve seen them in Maine
And downeast, where it's all rocks. So it appears they hold up if you are careful about your landings.
No idea from paddling one myself though.
The only “merits” that I can see;
is the fact that they are much easier to transport to remote reaches, which allows you to have your own boat rather than having to rent a hard shell.
Other than that for the price of the high end ones, you can get a much nicer hard shell, with much more compartment space for camping gear, etc