I came across this piece of research when I was trying to learn a bit about fin foils.
It looks like a Chapter from a PhD thesis on the effect of tubercules on the leading edge of the fin foil:
http://www.wpi.edu/Pubs/ETD/Available/etd-121307-115034/unrestricted/dcustodio.pdf
I dont know if this has been posted before, so apologies in advance if it has.
The conclusion in this study seems to be that for a given set of conditions, the leading edge tubercules do increase drag for a given AOA where the foil is not stalled.
HOWEVER…the advantage of these features manifests itself when the foil is stalled. It looks like these features maintain lift under these conditions.
From what I understand the transition of foil into stall is accompanied by sudden drop in lift and a concurent increase in drag. It seem that the tubercules make this transition smoother, avoiding the abrupt drop in lift/drag ratio.
(TaylorO…thanks for reminding me to post this with your “SwayStoke” thread.)