Glenn Ashmore wrote:
I am not sure you exactly grasp the forces that act on boats at sea. About
the only thing that would make ABS pipe strong enough to stand up as a
Bimini frame would be a stainless tube on the outside. :-) Same is true
for that copper tube support on your windvane. One good quartering wave and
it will collapse against the transom. Most of the failures of commercial
stering vanes are in the stainless support structure. 316 Stainless has a
tensile strength of about 580 Mpa while hard drawn copper tube is under 200
Mpa. Heating to assemble it will soften it even further so soldered copper
tube doesn't stand a chance.

Same with the Bimini. The bending forces in tubing is all in the outer
fiber. Nothing you put inside (other than a steel tube) that will help
much. One good blow or an accidental steadying grab and it will be headed
for the recycling yard.

Idle curiosity acting here. Suppose...............you filled the PVC
(or copper or whatever) with urethane foam. You know, the foam they
sell for filling voids around windos at Lowes and Home Depot. I think
that they now actually sell it in a couple of different formulations.
Anyway, the stuff is a closed cell foam. I think it is pretty tough in
compression and does not add much weight.

Just wondering.