> Current folding kayak use Aluminum pipe as frame, that's need a lot of
> maintain. Why don't use steel stainless, bulk will less, weight only a
> lttle more.

The main reasons are cost and availability. People seem to accept a little added weight, and the bulk of the finished boat is the same. When you use tubing of a different size you make adjustments to the frames that support these tubes. You might lose an inch (25mm) of interior width, but the outside lines of the boat can remain the same.

There seems to be a lot of surplus aluminum tubing in Seattle and southern California. Perhaps that is because of the aircraft building industries near those areas. George Dyson sells aluminum tubing for building baidarkas, too.

Klepper kayaks use wood frames, and have done so for 90 years. I've seen Folbot frames that were made with fiberglass tubes. I may build one with PVC plumbing pipe one of these days.

If you have access to stainless steel you might as well try using it. Write back and let us know how it works.

Paul G. Jacobson