CWO Zeezeilschool | RYA Training Centre | Jachtverhuur | Est. 2000

Lesson 13 Routing with qtVlm

The most commonly used routing software is qtVlm. The main advantage of this program compared to, for example, popular navigation programs such as Navionics is that it takes into account the polar diagram of your ship and uses grib files for the wind direction and strength and current. If you have to beat up against the wind, the program itself calculates the ideal course and predicts the speed depending on the wind strength and direction that could be different every hour.

You can download and install the software for PC, MAC, Linux and Raspberry for free. You can also download the App from the App store and Google play. It works best if you use a combination of laptop or PC with mobile. You can then do the preparations on a large screen and export the routes to your smartphone. After this brief introduction, it is recommended to read the full qtVlm manual.

Imagine we are preparing a trip from Falmouth to Cork, so we can drag the boat to Falmouth and put a POI on Cork with a right mouse click and choose New Mark.

new mark qtvlm

Next, we need to place a barrier on the Lands End TSS, so that qtVlm does not calculate a route navigating through this TSS.

barrier qtvlm

Then we go to Boat Settings and give the boat a name and choose the polar diagram that belongs to the boat. If the type is not listed, you may be able to request it from the shipyard, regatta club or find it online.

boatsettings qtvlm

Next we select the entire area with the Selection button.

select images qtvlm

Then go to Grib - Gribslot 1 - For example, select Zygrib and download the gribfile.

Then we can make the routing. Right-click on the Cork POI and choose Create routing toward this POI.

create routing qtvlm

qtVlm calculates the fastest route taking into account the ideal wind angle when crossing and crossing and also takes into account the VSS at Lands End.

Then we will create a number of routes, each with a different departure time and / or date.

different etd

Then we can see if it matters a lot in terms of travel time on which day/time we leave. If the wind direction changes a lot, the time of departure does of course matter.

compare different etd


Go to or install the app on your smartphone: Do not forget to set the unites on Nm, draft 2 meter, 5 knots cruising speed, 4l/hr fuel consumption. 

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