| No - I do not agree. The bidirectional board is gives better
| windward performance than unidirectional rudders. The bidirectional
| board is better than rotating rudders because the rudders are
| symmetrical foils so will be less efficient at generating lift than
| the board designed for a narrow range close to zero AoA.

Yep I had a brain problem. Rotaters need to be symmetrical. My mistake.

But flipping rudders can be unsymmetrical, unidirectional, sharp trailing edged and otherwise, fully optomized.

| We aimed
| for 3mm radius on the edges of the board and achieved close to that.
| The unidirectional rudders were built at a boat yard and actually
| have thicker trailing edges thicker than that. It is not unusual
| for unidirectional rudders with a 500 chord having a trailing edge
| with larger radius than 3mm.

Yep, sharp trailing edges in glass are a problem. There are several techniques, but the bidirectional board needs to be small radius and round, not sharp. AFAIK, tough to do. Good job on getting there.