What does 'the wind was 3 points abaft the beam' mean?

Think of how sailing ships actually get moving... As well as the basics of where things are.

The front is the bow, the rear is the stern, the beam is essentially when wind is coming from the side of the ship.

If you are facing towards the bow,the right side is your starboard beam, and the left is your port beam. going towards is bow is going forward (or for'ard) and the stern is always aft, so, "abaft" means, literally, "from the back". If you start at the main mast (usually the widest part of the ship) and draw a line from one side to the other, and from bow to stern, you have quartered the ship.

Now, when sailing, most of the ships were better at sailing down wind (coming over the stern) and you could NOT sail forward if the bow was pointing into the wind, so "wind on the starboard quarter" would mean the wind was coming from behind, but the angle between the bow to stern line and the wind would be around 135 degrees (actually between 120 and 150 degrees)

'Points' were essentially degrees, so "3 points abaft the beam" would be three degrees off the perpendicular to the bow to stern line, either to starboard or to port.

Note that this has little to do with the compass rose -- unless the ship was going directly north. It was the direction the ship had relative to the wind.

I have read all 20 Aubrey and Maturin books and I can honestly tell you that it doesn't matter, you get the sense of what is meant by the text that precedes and follows these phrases, all you need to know is that Port is left and Starboard is right.

65