Mandolin couldn't cut sweet potatoes: what did I do wrong?
After years of fear of cutting off bits of my fingers, I gathered my courage and bought myself a benrinner mandolin. I tried to use it to cut sweet potatoes into fries yesterday, but had little success. I peeled them, cut them to a size that fit nicely on the mandolin, attached the finger guard and tried to push the 'tater through the blades.
The best I did was to get about halfway through a single cut, at which point the potato got stuck. I tried pushing a bit harder, and the finger guard ripped through part of the potato.
I know the blades were properly attached, and I'm fairly certain I followed the instructions correctly. It seems odd that the benrinner can't cut a sweet potato when it has such a reputation for lethal sharpness, so what did I do wrong? Is there some step the instructions left out to prep the blades?

America's Test Kitchen adds shredded apple to their blueberry pie to help keep the filling together. I've used the same technique with other berry pies with great success. Perhaps their recipe will provide some inspiration?