The experienced need read no further....
To the less experienced read on:
1. When this is discussed always determine the basis for the measurement.
2. If only using your wind instrument at your guide, first consider if you are reading apparent wind angle of true wind angle.
3. Understand there are sources of error in the equipment
. For instance, the wind vane
sends only apparent wind angle data, with true being calculated instantaneously using vectors derived by your speed log (another potential source of error) and the anemometer (potential error).
4. You may "tack through" 60-65 degrees apparent, but this may be 90+ true.
5. If you tack displaying the true wind angle, you wil appreciate the difference and this will reflect you actual tacking angle, but only withing the medium i.e. it assumes the water
in which you are sailing is not actually moving itself (as in current), and that you have no leeway (which will be false).
5. Your track on a GPS
based plotter reflects "actual and true" tack angle (inclusive of leeway and current) as it references
to the planets surface not the medium (water on which you are sailing).
6. True "performance" to windward is best appreciated by understanding the concept
of velocity made good VMG or course made good CMG. which take into consideration the various factors that influence just how quickly you are making your mark directly upwind. This is more complex than it seems.
7. In its most simple form, as in the VMG display on the wind instrument, it relates to boat speed at differing angles of attack (consider that although you may potentially sail a shallow angle to windward, you will slow down in doing so). This is pure but simple trigonometry. Essentially, a given boat's VMG will be optimal at an angle that is usually greater than it's best angle of attack. This will be further amplified by leeway which increases the closer to wind you sail.
8. In more complex performance modelling, as in competitive racing, the VMG and CMG systems will also take into consideration issues of leeway with varying application of underwater appendages on offer, drag, tide and current, not to mention the the various imponderables that relect the the art of racing that include wind shear, wind shifts, knocks and lifts etc.
9. Finally, and to expand on 44C's comments, one needs to reflect on just how much boat speed will influence apparent wind angle and one's perceptions of what is a "good angle". When up wind, the faster you can go the more the apparent wind comes forward ultimately requiring course change to leaward to avoid stalling. Your true course will be more off the wind but as your speed is so advantageous, it is irrelevant in terms of making the mark quickly. Remember very fast boats like the AC72's actually sail to windward (apparent) even on a (true) downwind leg, potentially being hard on the wind where ever they go.