You would rarely make all the gains available. But the better information you have about the shifts of the wind the greater your gains. 

  When you sail with the Ansar 2 or 4  compass you always know if you are sailing in a lift or a header. 

  If you use an ordinary compass you have to note the readings of the compass and later compare these with the reading of the compass to determine if you are sailing on the right or wrong tack. Yes, I almost forgot, before you can do this you must calculate the mean wind direction - for each tack. 

  When sailing with an Ansar 2 or 4 compass you also know everytime the relative size of the lift or header.

  When you sail with the Ansar 2 or 4 compass you will not miss a shift in mean direction of the wind: 

  Let's say you have sailed the first windward leg and the pointer has at the best lifts been up to the "best lift marker". 

  You are now on the second windward leg and on starboard tack. When you look at the compass you notice that the pointer has gone considerably beyond the "best lift marker". This means that the lift on this tack now is larger than it has been before. 

  This probably means that the mean direction of the wind is shifting clockwise and you can gain many valuable meters or yards by heading out on the favorable side of the course, that side that will be to windward when the wind has shifted further. 

  If you sail with an electronic compass or an ordinary compass you must keep track of its readings and not miss when you are lifted more than before on either tack. For most sailors this means taking notes.