[CA] [CA11] advanced sailing tools

[kevindr]

I used the layline feature last night for the first time utilizing boat polars. Wind speeds were relatively light, 6-8 Kt, but steady in both strength and direction. The laylines however were constantly and rapidly changing to the point where it would have been impossible to follow. I am wondering if changing the wind angle response and wind speed response would make a difference. Any thoughts on what a good setting would be ?

[Chuck - Raymarine - Moderator]

Welcome back to the Raymarine Forum Kevin,

I apologize for this late response. Our UK Product Support tech's experience when last using this feature is that he did not have to adjust anything and the Laylines were steady and very usable throughout the race.

The Layline feature will use the True Wind Angle and True Wind Speed calculated from Apparent Wind and boat speed. If any of the fundamental data (from sensors or required to calculate True Wind data) is not accurate or damped enough it would effect the Laylines. Additionally, if the wind is shifting as it may be in light airs the Laylines may shift around (it is noted that wind was steady when tested on your vessel).

The Polars table could also produce anomalies if there are errors, large gaps between the data, or if there are very few points of TWS & TWA. The software will interpolate but will be less accurate with larger steps in the table.

[kevindr]

Can you provide an explanation for the data items "tack heading" and "Steer to layline"

[Chuck - Raymarine - Moderator]

Tack Heading is the heading to steer to mirror the current true wind angle on the opposite tack.

I think it is also commonly called Tack Course.

The calculation is: Tack Heading = (Magnetic Heading + (2 * True Wind Angle)) % 360

So if the heading is 10° and the true wind angle is 30° to starboard then in order to get a true wind angle of 30° to port the boat would have to steer a heading of 70°.



In LightHouse II, the user can configure the Chart application to be overlaid with laylines. These show the best angle to take to tack towards a waypoint. (There are a number of layline types – I can describe further. One of them just mirrors TWA). In the example below, the boat cannot head straight to the waypoint, so must tack. The most efficient tack legs will be along layline 1 to point A then along layline 2. The STEER TO LAYLINE databox is suggesting turning 25° to starboard in order to sail along layline 1.