Although getting the most speed out of your boat is important when beating, massive gains can be made by reading the wind properly. Equally, distance can just as easily be lost by getting it wrong.

As we all know, the wind is constantly changing in both speed and direction. These changes may be oscillating shifts which continually return to an average or mean direction, possibly at very regular intervals or they can be biased shifts where the mean direction is also changing, perhaps as it follows the sun in the course of a day. 
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This is very common on sea breeze days, for example on the South Coast of England. There may also be massive sudden shifts which change the whole character of the race. Further complications occur as the wind bends around topographical features such as cliffs, hills, large buildings or trees. It can even change in direction as it leaves the land and blows across water. The key to understanding and using shifts to best advantage is observation and recording. If you want to pick up regular oscillating shifts or a gradual direction change, you need time and a constant reference point.  Easily the best reference is a compass but transits can be used on enclosed waters. A recording diagram shown in Fig. 1 is valuable but quite a time is needed to make a worthwhile survey.The object of the exercise is to take wind direction readings  every  five minutes. The simplest method is to go head to wind and when the boom is amidships read your compass course. Completing the form like Fig. 1 will show which of the various types of shift you are having to deal with.

If you discover that you have shifts on top of an average direction, you can establish your best heading on port and starboard tacks when the wind is in the average direction, then ensure that during the race, you spend time on each tack according to the favoured side of the shift (Fig.2).

Knowing the mean direction also prevents you making that easy mistake of tacking when you are headed (i.e. forced to bear away) by a shift which is still on the good side of average (Fig.3). So,  if  your  research uncovers a changing basic wind you will need to set off on the tack which is suffering headers and ride out a few before tacking, then gain lift after lift to bring you quickly up the windward mark (Fig.4). Wind  bends  (i.e. a constant and persistent shift in direction as you sail into it) are actually quite easy to spot. They can be discovered by beating up the course, noting your headings.

The rule then, just as with a changing basic wind is to sail towards the bend taking the knock. Do not tack early because you will be on the outside of the bend taking the great circle route to oblivion. On the other hand leaving it too late and overstanding will bring other boats up underneath you.   

The trick then is to tack a bit earlier than you would normally do to lay the mark (Fig. 4). You can always tack back again later if it looks as if you are falling below the mark and still find room in the boats stacking up on the starboard layline.

Don't forget also, that you must consider whether tidal streams or waves will override these windshifts, especially in light or heavy conditions. So make a note of the current direction and always try to keep it on your lee bow. We'll talk about this in our next article. (Uncle Al's note: Mike and I are still arguing over this one. I'm of the opinion you can only lee bow the tide if you're in water that's shallow enough that your centreboard is in less adverse current than your hull!)

Finally, the best way of thinking of headers and lifters is: a header is a change in wind which forces you to bear away from your previous course and therefore to sail further away from the windward mark, whilst a lifter is, funnily enough, exactly the reverse!    Auntie Alb