Bjorn - "Are you sure the wing has a trim tab?"
The trim tab is on the stabilizer that is trailing the wing.
Bjorn - "A sail doesn't necessarily have a bad lift coefficient. It might even be better than a two element wingsail, depending on the shape that can be made with the sail."
A wing coefficient of lift without a flap can be 1.5. A sail has a hard time exceeding .8 typically around .6. A Wing with a flap can have a lift coefficient around 3 (but the drag goes up.) Lift/drag ratios of sails are around 30 to 1, where a wing can be around 140 - 1. With a flap the wing drops down to the 30-1 range similar to the sail.
A wing can be around 4 -5 times more efficient than a wing sail depending on how perfectly the sail is trimmed. If the sail is poorly trimmed who knows? ^^
Bjorn - "The wingsail doesn't drag very much unless it's far from optimum trim."
The wingsails lift can equal the lift of a wing, if properly trimmed but it will always have higher drag because of the form. I have seen some wingsails though that have the same shape and camber as a wing, so they are probably equivalent.
I need to emphasize, it is the wings lack of drag that is its advantage, not total lift. If the boat is heavy and draggy, a lot of inefficient sail area is better than a wing.
Talador