Sailing Polars, AWA, AWS and VMC

Rhino Grasshopper

This widget illustrates AWA (Apparent Wind Angle), AWS (Apparent Wind Speed) and VMC (Velocity Made good on Course) using a boat's polar data. Interactive dials and sliders adjust TWD (True Wind Direction), TWS (True Wind Speed), Heading and Course (bearing to next waypoint).

The slider 'TWS (from polar lookup)' determines which one of the polar graph lines appears in yellow. The lines correspond to the list of True Wind Speeds on the first line of the polar data.

TWD/TWS are dark blue
AWA/AWS are light blue
boat heading/speed are green

Notice as you change heading how the green arrow always follows the yellow line, precisely.

Features:

TWS slider to choose wind speed from polar data.
Set TWD, Course and Heading by compass bearings.
Reads polar data from .csv files; two samples included as "Internalized data": a 32' proa and a Mumm 30 monohull.
Two sample hulls included as "Internalized data" (proa and mono), or supply your own.
"Proa Reverse" mode for emulating a proa - re-orients instruments and vectors from port bow to starboard bow (the "now bow" on starboard tack).

Instructions:

In Rhino, use top view with no grid or grid axes ('View | Display Options... | Grid').
In Grasshopper, use 'View | Restore Named View | controls'.

Note: The download files below are identical code, just saved with different settings that anyone can change.

Download: polars_2015Jun28_PT_Vic_port_tack_Mumm30.gh

Boat changes heading (falls off) 32 degrees to increase AWA from 23 to 43 degrees.

Download: polars_2015Jun28_PT_Vic_port_tack_Proa32.gh

Boat changes heading (falls off) 33 degrees to increase AWA from 21 to 34 degrees.

Details

In normal use, only the controls and displays are visible (above, right). The full app (below) consists of configurable inputs on the left for boat geometry and polars data, a group of 'Output Preferences' at the top right, two "clusters" (code blocks) just to the right of the controls, and a bunch of vector preview components on the right. Most of which can be ignored, except to change polar data and boat geometry - or to change vector colors and locations.

Two sets of Sample Polar Data and boat geometry are included, or you can read your own polar data from comma-delimited files.

Polars Data must be formatted like this sample data, as follows:

first line is a list of wind speeds: 4,5,6,7,8,9,10,12,14,16,20,25
remaining lines have TWA followed by boat speeds for each wind speed in the first line.

It can be read from a file or copy/pasted into a panel, configured as 'Multiline Data' (right click).

4,6,8,10,12,14,16,20,25,30
33.0,2.76,4.08,5.08,5.62,5.90,6.04,6.11,6.10,5.84,5.18
36.0,3.04,4.45,5.47,5.97,6.23,6.35,6.42,6.45,6.28,5.80
39.0,3.30,4.78,5.81,6.26,6.48,6.59,6.65,6.69,6.59,6.28
50.0,4.07,5.69,6.57,6.88,7.05,7.17,7.26,7.36,7.37,7.26
60.0,4.54,6.16,6.92,7.25,7.44,7.58,7.69,7.85,7.93,7.90
70.0,4.82,6.38,7.11,7.54,7.76,7.94,8.10,8.35,8.53,8.58
80.0,4.92,6.46,7.21,7.71,8.06,8.31,8.52,8.88,9.22,9.43
90.0,4.97,6.66,7.42,7.80,8.25,8.66,8.95,9.53,10.13,10.57
105.0,5.05,6.68,7.50,8.11,8.56,8.96,9.40,10.57,11.63,12.58
120.0,4.70,6.46,7.34,7.94,8.68,9.45,10.10,11.33,13.24,15.15
135.0,4.08,5.85,6.93,7.68,8.43,9.24,10.01,12.20,14.79,17.17
140.0,3.81,5.54,6.72,7.49,8.21,9.05,10.07,11.91,15.34,17.90
150.0,3.25,4.83,6.17,7.02,7.68,8.37,9.19,11.58,15.49,18.58
165.0,2.49,3.77,4.99,6.08,6.88,7.51,8.12,9.66,12.46,16.25
180.0,2.18,3.30,4.39,5.43,6.33,7.01,7.58,8.77,10.86,13.73

Sources for Polar Data

Boat Data and Polars (l-36.com)
Boats & Polars (www.blur.se/boats/)