A layline is a straight line (or bearing) extending from the next mark to indicate the course a boat should be able to sail on the one tack in order to pass to the windward side of the mark. The layline will correspond to one of two CNM readings in your instrument panel because there is always a port layline and a starboard layline.
When the next mark is a gate or a finish line then one layline extends from the right-hand buoy and the other extends from the left-hand buoy.
The computed layline is affected by wind shifts however stream (or current) and any obstructions are not factored into the computation of a layline.
The layline is not necessarily the same as the proper course to the next mark simply because a skipper may need to factor such variables as wind shifts, stream, tide and obstructions into the process for deciding upon a proper course.
Display automatically computed laylines Edit
The red port and green starboard laylines can be enabled or disabled for display in the radar view if the host has enabled Arcade mode for the current race. When either Tactical or Simulation mode is enabled the laylines will not be displayed in the radar view however, a skipper can always calculate the layline using simple addition and subtraction.
Manually computing the layline Edit
The instrument panel has four possible numeric panels. Select the numeric panel that displays 3 rows of numbers.
The numbers you will need to compute the CNM for the layline are TWA, TWD and HDG. If you want to anticipate wind shifts then you will need a good memory for the extremes of TWD as well as any apparent rhythm (or periodicity) in wind shifts that you may have observed since the pre-start.
Upwind leg Edit
TWA is always the difference between HDG and TWD. Positive when on starboard tack and negative when on port tack. Twice this TWA is the angle through which you boat must turn in order to change to the opposite tack and assume an equivalent point of sail.
When you are sailing close-hauled to the windward mark you note your heading (HDG) and mentally add or subtract twice the TWA to compute the heading that your boat would be on if it was sailing on the opposite tack. If that computed heading is the same as the present CNM then you are crossing the layline.
In practice the computation for a windward leg is best done by adding or subtracting the present TWA from TWD and completely ignoring the present HDG altogether. (TWD + TWA) or (TWD - TWA) will give you either the present HDG or the CNM that indicates when you are crossing the layline.
Downwind leg Edit
The computation is just a little bit more taxing on your brain when on a downwind leg because the wind is crossing the stern instead of the bow. Your fastest point of sail is not dead downwind (180 TWA) but rather a broad reach (150..165 TWA depending on wind speed and the type of spinnaker you are carrying).
In practice it is easiest to ignore TWD completely and work with HDG, TWA and the constant 180:
- Noting the TWA for your current point of sailing calculate the difference between that TWA and 180 then double the result. viz. 2 x (180 - TWA)
- This is the angle through which your boat must turn in order to gybe to the equivalent point of sail on the opposite tack.
- Therefore you add or subtract this number to you present HDG to compute the CNM that you must watch for to signal that you are crossing the layline to the next (downwind) mark.
Small adjustments Edit
When the next mark is a gate or the finish line you must compensate for the fact that the CNM displayed in your instrument panel is relative to the center point between the two marks for that gate or finish line. You can make use of the in-game camera angle rotation to help with this adjustment.
With some practice you'll be doing these calculations with little effort and with even more familiarity you will simply eyeball the angles and surprise yourself at how accurately you've become able to judge the best moment to change course. Don't be tempted to simply rely on following the course you see boats ahead of you sailing. You may one day find yourself in the lead and because you have not trained yourself to compute with confidence your optimum course you might find yourself in a panic and lose that lead you fought hard to win.
When you tack you typically need to sail a few degrees below close hauled in order to accelerate to maximum boat speed. Therefore you should allow for this when fetching an upwind mark. You will want to overstand (sail beyond) the layline to allow for this. When you gybe you do not lose as much boat speed and so you can afford to understand (gybe before reaching) the layline.
Understand downwind and overstand upwind
Always anticipate the congestion you might experience at the next mark. It is generally best to make your final approach on starboard tack and you should avoid changing tack inside the zone. Therefore as you are deciding when (relative to the layline) you should change tack always be playing through in your mind the maneuvers you will need to execute close to the next mark.