Bumpy leading edge foils... from hand shaped wood to 3d printed polycarbonate.

The Earl was an eyeopener. Here's video of the Earl

Next we wanted to make the fins for shorter boards:

The tubercles are sized relative to the length of the foil so
 as the fin gets smaller the bumps also get smaller

The wooden Earl fin with the NACA 16-012 foil compared to
the RAE102 foil on the polycarbonate fin in the box.

Get some here