: PVC is simply too weak.

A piece of 3 inch PVC plumbing pipe (schedule 80) is a lot stronger than an aluminum soda can.

The problem with PVC is not the strength of the material, versus the strength of another material (say aluminum). Such comparisons would assume parts of equal size -- and we do not need to abide by this limitation. We can buy, and design around, any common product.

Because each material has different attributes it is not a simple matter of replacing one part with another made to the same size, but made of a different material.

If you want the strength of a piece of 3/4 inch aluminum tube with a given wall thickness, but you don't have any -- then you will probably have to get a larger piece of PVC tube, which will probably weigh more, but cost less.

If flexibility is an issue, then you need to change the design to provide suitable bracing to control the flexing. With wood-frame kayaks there are frames or supports, or ribs which are located at intervals which have been well tested over time. When we replace these wood elements with fiberglass or aluminum parts we can (and sometimes do) change the location and number of the supports. PVC is not as well explored as a building material for kayaks as aluminum and fiberglass are. Eventually experimentation should lead to some nice, inexpensive, kayak frames built from off-the-shelf PVC pipe.

PVC pipe is so easy to work with, economical and available that it practically demands that we find ways to use it. Hopefully you'll see something this summer from the people who are working with it now.

PGJ