This statement was posted in another forum to define Point of Sail.
"A point of sail is the relative angle between true wind direction and the vessel's course." Thus when a boat is sailing with true wind at 90 deg to it's centerline.. it is on a beam reach. This would be the point of sail whether the boat was limping along at 1kt or blasting along at 8kt.... no matter what the apparent wind indicator was showing... the boat is still beam reaching across the course.
I disagree with it, but wonder what other folks think. I have always considered points of sail to necessarily be expressed in relation to apparent wind.
I was taught that the wind direction depicted is TRUE. I've always accepted the definition of points of sail as the relationship between the boat's course and the true wind direction.
The diagram is used to teach beginning sailors the relationship between the wind direction and the boat position.
Using the Points of Sail diagram to understand where to position a vessel's sails , initially, is the most common application for beginning students.
At this point is where the controversy exists. Do we define the point of sail by our sail's position (apparent wind) or do we define it by our boat's position/course to the wind (true wind).
Since the Points of Sail diagram gives absolutely NO REFERENCE to BOAT SPEED and WIND SPEED(factors that affect apparent wind).... it stands to reason that they are talking about TRUE wind in this depiction.
I choose the true wind explanation. It makes more sense to me. It is far more practical and useful a tool when used in the true wind context. The apparent wind definition has little practical use except to say where the sails are... and you don't use them in sail trim commands... yet you do when you instruct the helmsman .... "head up to close hauled" or bear off on a run"
While getting your boat rigged, if you decide to sail across the lake to an anchorage due west and you see that the wind is coming from exactly due north.... What Point of Sail to you anticipate? Why, a beam reach of course..... That's why you decided to go to the anchorage and have lunch... it's an easy beam reach across the lake.
Once you're on your course due west, you note your boat speed increasing and pushing your wind vane forward a bit, so you trim in... same course, same point of sail. Then... you see a gust of wind on the water, you want to maintain the same course, and knowing that an increase in true wind speed will move the apparent wind aft, you ease out the sails to prevent the boat from heeling over or veering off course....still beam reaching.
The entire time... the wind stays out of the north, you are travelling west, you are still beam reaching.. yet your apparent wind indicator has been all over place.
That is the way points of sail was taught to me... It's a tactical or navigational tool when defined by true wind direction. It allows you do make decisions, it helps you determine you tacking angles. When defined by apparent wind direction it has little practical use.
Tacking angles, for instance. When closehauled you are talking about your BOAT'S angle to True wind direction, not the smallest number on my AW indicator, that device is affected by speed... What you really want to know is how close to the wind can my boat sail and make progress if speed is not the issue. You can determine your tacking angle by sailing close hauled on either tack... up to the point where the sails start luffing.... then...note your compass course. Now tack over to the other side and do the same thing. The difference between the two headings will be your tacking angle. It may vary somewhat depending on conditions... you should make a note of that. But the point is, once you know your boat's tacking angle you can plan when to turn for the layline, or to clear out of a crowded anchorage, whether you can turn to cross another boat's path if needed.