Hey Tom, what do you think about fiberglass tube? There is a righteous assortment available from these guys:

http://www.mgs4u.com/fiberg.htm

and more info at the link below. Their tubes are designed to nest, and the prices look good too. At 1/8" wall thickness they may be stiffer than aluminum, but maybe we can just drop down in diameter to get optimum flexibility?

BTW, where did you find 3/4 X .049 ( 6061-T6) aluminum at $1.00 per foot? It goes for 2 or 3 times that around here.

: You mention the option of leaving the wood in place and building what would
: be a very heavy kayak. More important than the weight gain, would be the
: incredible rigidity of the tubes. This leads to another , but similar
: consideration. Since the scrap aluminum is from a ham radio antenna,
: my guess is that it has very thick walls ? If so, it may simply be too
: rigid in it's own right to assume the steep curvatures of the chines, and
: gunwales in particular.

: I've noticed on this forum that most builders, yourself included, are
: meticulous in wood selection, be it Woodstip, S & G, or SOF stringers and
: ribs.

: The selection of folding kayak materials is no less critical, but I've
: noticed that most builders attempting this type kayak, seem to view it as a
: poor substitute for the real thing, and therefore not worth the additional
: cost
: of doing it right.

: At $1.00 per foot, 3/4 X .049 ( 6061-T6) aluminum is the best all around
: tubing for strength, flexibility, and aluminum insert compatibility. An
: alternative is 3/4" X .035 as it is lighter, more flexible, and costs
: about 10% less. It's only drawback is that it's wall thickness is a sloppy
: fit with all available aluminum insert sizes.

: Wall thickness is critical, not only for weight, but for the flex required
: to conform to the shape of the hull. By selecting the correct building
: materials, your Anas Acuta will be not just a folding kayak, but rather,
: a sub 30lb. kayak capable of awesome performance.

: Perhaps the stubborn wooden dowels are trying to tell you something.

: Tom