Using mandolin - watery salad.
I sliced some fennel and radishes using a mandolin. They came out paperthin and beautiful, but the salad was sort of watery. I dressed it with some salt and pepper and lemon and olive oil. Should I have salted or drained the vegetables first?
Interesting. Both fennel and radishes are not particularly "juicy" vegetables, unlike cucumbers or tomatoes. I guess draining would be the way to go, if liquid pools at the bottom of the container. Or salting and draining, in the fashion of cucumber salad or coleslaw, the result, though, being lose of crispness.
Are you sure the "watery" aspect wasn't just your dressing?
That's a new one on me.
This is just a guess: the wording of your post suggests that you put S&P directly on the vegetables rather than into the lemon and oil. That MIGHT have burst the cell walls of the thin slices. I'd suggest you try making the dressing separately before tossing, and see if that makes a difference.
I just dress it right before eating; the salt will leech out the moisture if you let it sit to long.