Introduction | Variations. What if?

Being able to easily find the fastest route between two points, through complex weather systems, is certainly nice. Its also nice to arrive at a destination feeling good, with little or no damage to the boat, having burned little to no fuel, and during daylight hours.

It is often useful to know what the tradeoffs were in achieving the fastest route. How much slower would you arrive if you only allowed the boat to sail, not motor when it slowed down? If the route involves a lot of upwind sailing, do you really need to sail close to the wind, or can you fall off by some amount - what would the effect on the generated route be? What is the effect of sailing at 80% of boat speed, or 90%, compared to pushing at full speed? What is the best day and time to depart for your passage?

The LuckGrib WR system allows the following sets of variations:

  • try the route with and without motoring.
  • try the route with and without heaving to being allowed.
  • try the route with all available wind fields (for probability winds, ensemble winds, wind gusts, etc.)
  • generate variations where the minimum upwind sailing angle changes. Can you sail further off the wind and still arrive at a reasonable time?
  • generate variations where the vessel is pushed hard or you back off and be more gentle. Sometimes you can slow down a little and have little effect on the route. At other times its definitely worth it to push hard toward your destination.
  • generate departure time variations. Try multiple departures, spaced at a fixed time interval (every day, every two days, every 6 hours, every 3 hours during daylight, etc.)
  • try using more than one GRIB file, to see how closely the various forecast models agree.

You can combine these variations - so you could ask to see all of the solutions over three departures, testing routes where you can both sail and motor, or only sail, generating six possible routes.