LEE BOW EFFECT

My understanding is that when beating against the tide, if the tide is coming at your bow from the lee side then it is effectively pushing you into the wind. This is good because firstly it counteracts leeway and secondly gives you stronger apparent wind as you get pushed into the wind. Sometimes the difference between stuffing and footing is the lee bow effect, which therefore makes it pay to stuff.

Obviously if tide is on the windward side upwind then you are fighting both wind and tide, so can sail anyway near as high or fast.