How about a sand pit? It works for bowfishing arrows that have barbs on them, but may require resharpening.



BTW, nice experiment.
I did notice after reviewing the video a few times that it appears the cucumber broke with the impact force several inches below where the center of the head (and blades) actually hit it.

If this is so,the 'beheaded' veggie left standing does not show the actual slices made by the blades. Since you were impressed by their cutting ability, I'm assuming that the pieces on the ground were sliced pretty neatly?