Per Al Deveron:
I wonder if that's true. Consider this: Using a kayak paddle, each
stroke wastes a certain amount of energy in trying to make the boat
turn towards the opposite side.

The same is true of the single-blade canoe paddle.

The wisdom that I gleaned (correctly or incorrectly...) from a surf ski mailing
list is that outrigger canoes are not competitive with surf skis because of the
single-bladed paddling technique.

I'll leave it to greater minds than mine to explain why.
--
PeteCresswell