Here I present a tool that will compute 3 different optimum angles for use with SOL. It grabs the polar and race course information from the server when you ‘login’ and thereafter updates your boat (location and wind data) every 20 seconds. You can use it to compute optimum VMG TWAs for both Upwind and Downwind, and also find the exact TWA for maximum boatspeed. The most flexible aspect is computing VMC.
You can compute VMC to the next Waypoint on the course, to a specific direction (useful in those ‘Just get me West ASAP’ situations) or to an arbitrary location, specified by latitude and longitude (as decimal degrees)
I intended to make this a ‘Run in the Browser, Flash’ application, but for various technical reasons that is not possible at this time. So the next best thing is to distribute it as an Adobe AIR application (AIR is the Desktop brother of Flash) – So, Operating System will not restrict you using this tool, although it may need you to install Adobe AIR (here)
[Edit:] As I now have server space (thanks to Markku/hmm) you can use a Flash version online here.
So, now to the application itself – I made it as simple as possible (but not any simpler)…
Start it up, a popup Window appears for you to login – select a race, input your login and click ‘Login’. You can also use the tool for multiple races simultaneously by selecting ‘All Races’ from the race list. This will log you into each race you are currently registered for.
Once login is completed, the Login popup disappears and the 3 lower buttons will become active and some numbers appear in the wind boxes… That’s pretty much it – now start clicking those 3 lower buttons! 😉
Here is the App when it first loads (it may take a few seconds to retrieve a list of races):
If you logged into a single race, the race name will be displayed in a disabled dropdown list at the top of the UI. If you logged into all races, then each race you are registered in will be listed in this dropdown (which will now be enabled), and you can easily switch between races by selecting one from this list. Below is a screenshot showing the tool logged into a single race on the left, and ‘All Races’ on the right:
Here is shown the Optimal VMG angles for the current wind conditions:
Maximum BS is self-explanatory, so here is an example showing optimal VMC to the next mark – the output also displays the boat type the Optimal Angle(s) were computed for, just to help prevent computing for the wrong boat when using with multiple races:
As you can see, you can specify a VMC (Velocity Made to Course) target in one of 3 ways – Use the next waypoint from the course, specify a direction (Bearing) or a location (lat/lon). Click the ‘VMC’ button and you will get output something like what you see here. It shows the maximum VMC for both Port and Starboard tacks, so you can also use it to confirm your own determinations of favoured tack etc…
All Angles are computed accurate to 0.01°, so if it says the optimal downwind vmg angle is 142.17 – don’t sail at 142.15, or .20 unless you have some reason to! 😉
So what exactly is this telling me? It reports the exact COG and TWA that you need to sail to achieve optimum VMC, and the Boat-speed you will have at that COG/TWA as well as, obviously, the VMC you will be making to your target. Clearly in the example above Starboard is well favoured – things get interesting when the tacks are close…
You can uncheck ‘Use Wind from Boat’ and the wind will stop updating (it will still get boat updates, just not change the displayed wind. This will allow you to enter your own values – Setting a TWA DC for in 3 hours time, when the wind is +5kn from now? just enter the TWS you will be in at the time and click ‘VMG’ to find the best angle to use. Checking the option again and the Wind at your boat location appears in the boxes again. The app uses whatever is shown in the wind fields to compute vmg/vmc.
There are tool tips over most of the UI to help you use it.
Note: This is NOT production quality software – If you click ‘Login’ without selecting a race or giving your boatname and password – There are no polite error messages…
Hope this helps you sail faster!
But remember, the trick is in choosing the best VMC target – not necessarily the mark! 😉
The Adobe AIR Installer should look something like this:
Download it from here.
Double click the file to install it – doing so again will allow you to uninstall it (but you wouldn’t want to, right?) – It *may* prompt you to install AIR if you haven’t already, or it may require you to have it installed already, I really don’t know 😉
Note: The tool updates your boat data every 20 seconds, and if you have ‘Use Wind from boat’ checked you will see the wind fields (TWS/TWD) change – but it does NOT redo the last computation, ie you need to click ‘VMG’ (or whatever) again to compute the optimum angles in the new wind (and location for VMC to waypoint or location)