Whether Racing or Cruising, the layline is key information to have when sailing. It helps sailors deduce when they can tack or gybe to make a specific mark and aids safe clearance of headlands – True Wind Angle is key to having accurate laylines.
At its simplest, the layline can be represented by Opposite Tack Heading, this is simply your current heading plus your tacking angle, giving you a new heading for the other tack – this can be compared to a hand bearing compass reading to see where you would be heading following your tack.
Some chart plotters now overlay laylines onto the navigation chart, so that it is possible to see exactly where the opposite tack is likely to take you in respect to the waypoint, hazards on the chart etc. This is very useful as you can use this tool to keep yourself in favourable tide, away from dangerous areas and to make the best approach to your waypoint.
In simplified form, your Tacking angle is equal to double your upwind True Wind Angle (if your True Wind Angle = 45, your tacking angle is 90), however on simpler instrument systems that don’t factor leeway into the calculation this will always be slightly incorrect, as the boat will slip sideways a small amount while sailing.
Course Over Ground (COG) is a valuable tool here – once you have tacked for a waypoint compare COG and Bearing To Waypoint (BTW) to see if you are gaining or losing ground to windward. If they are equal then you are following a course directly to the mark.
Don’t try to pinch excessively to make a waypoint, the boat will slow and leeway will increase – making the situation worse. This will be shown on the instruments by a reduction in VMG. It is almost always better to admit that you won’t make a waypoint early, sail at your normal angles and make one or two additional tacks.
And this is our tip of the week, but don’t miss the next chapter where we will deepen into the “Tides”. See you soon!