Originally Posted by northsea junkie
I think something is lost in the translation and/or the transmission of this remark.

Look, apparent wind is the resultant of the true wind in the sail and the boatspeed in opposite direction. The last is derived from the so-called groundspeed.

So, when the current is with you, your groundspeed will be higher then in the situation when the current is against you.


I think the foils add more complexity to the equation.
The speed at which an AC72 starts foiling is determined by the speed through the water (23kts?).
So to reach the same speed through the water you would need to sail quicker over ground than if you where sailing against the current right? (Maybe 3kts or so).