Not the recumbent's fault. The rims I'm using have rim inserts that allow you to use Presta valved tubes. Apparently at the lower pressure for mtb, it allows the valve to flex and sheared a hole in two tubes. Thanks to Doug, though, who stopped then rode home and back for a tube to try to get me back on the road. Such actions restore my faith in human nature.

And anyway, it's not a "bent".