Which is stronger - an inflatable kayak or a the best built hi-tek Carbon fiber/Kevlar composite? If you capsize them on the upstream side of a rock in a fast moving river, both will get wrapped around the rock. The inflatable will stretch and bend, the composite will crack. When you finally extricate the two boats, the inflatable will probably be ready to use and the hi-tek boat ready for the landfill.

Now run the two boats over a sharpened spike. The inflatable will fail much more readily.

By yielding to the load in the first situation, the inflatable survived better. By resisting the load in the second case, the stiff boat survived better.

A good case can be made for both methods of surviving loads. The old Grumman aluminum canoes were popular in whitewater before fiberglass and then Royalex took over. Aluminum generally finished the year dented but whole, it took a big hit to make a rip. Fiberglass didn't dent, but if it was hit hard enough it got a big hole. Royalex gets dented fairly easily, but pops back. Although Royalex is generally the heaviest of the three, it is the material of choice for most WW canoes.

> If the object was to not yield, the material has failed. I really don't
> think you're going to want a kayak that yields readily in use. Even if it
> were to retain watertight integrity, the paddling characteristics would be
> most adversely affected.

Roto molded kayaks yield very easily to most point loads, but that is part of their strength.