WTF Are Tubercles?

[Matt]

Yes, and if you search “reflex camber foil” you get even more of my (somewhat ridiculous in some cases) drawings from this thread:

Reflex, camber, concave and aft loading foil section questions

A lot of talk lately about reflex curve, which I think is the word for the hollow in the trailing end of the bottom surface of the foil. As seen in newer Armstrong foils, but more subtle in many others. Questions: what does it do? My theory is it increases lift more with a given change in AOA, so less drag as you slow down(?). Also, K2 tails have a fair bit of it, which is interesting, not sure what that would do since the AOA changes in the opposite direction. Anyone with AFS notice the same in…