A sail can't run directly upwind because the air flow is collinear to the direction of travel so there is no percentage of force available to propel the boat directly up wind but mine can sail at around 3/4 of true wind speed at an AOA of 30° to apparent wind.
My thinking is.
The land yacht changes the AOA over the propeller by altering the mechanical drive by 90°, and then again with the pitch of the propeller.
I have waterflow at 7.5° to the direction of travel. I was hoping in a dense fluid like water, 7.5° might add a knot or two ?
your foil application is nothing like the land yacht.
The lift generated by the foil would be normal to the direction of travel (ie not thrust). It's possible that adding lift at the stern may well increase the boat's drag by pushing the bows into the water.
But who knows ... go try it and let us know.
another day in paradise, or is paradise one day closer ?
Sorry, just working through this and it's all new to me...
If lift is perpendicular to drag and drag is collinear to the flow and the flow is 7.5° to the direction of travel of the boat then shouldn't a significant amount of lift be propelling the boat forward If I put a foil in that waterflow?