Cruise Sailboat Attitude We share our experiences with you
How to read a Grib:
As you can see on the picture the basic reading of the arow is pretty simple
But what you read is the real wind direction and strength
An by the boat deplacement you will change this direction and strength an this get a hughe influence on the grib file interpretation
Apparent wind ( the real wind you will deal with )
Let's imagine you see on the Grib file a wind comming full East at 15 Kns and you plan to go North on your boat.
The first things you will think it's lets go we have the perfect wind to go!!!
If you receive a wind fron 90 degrees let's imagine your speed expectation will be 7,5 Kns.
So you will greate an apparent wind from your deplacement comming in the opposit direction so if you go north you will create 7,5 Kns
of wind coming from North in direction of the South
So the apparent wind you will really see if you sail will be:
The new vector from the basis of the 90 degrees wind from the Grib file to the end of the apparent wind you create
Let's do the math calculation:
With pitagore we will get the new strength and angle.
Now lets calculate the angle
So what wind you will get if you are going to sail:
You will receive 16kns of wind from the 63.... thats not going to be the sailing you were waiting for in fact you will be slowy and close wind......
Our advise :
If you have no proper timing wait to see at least a 90 degrees wind on your Grib to go to sail.... You will have a hudge chance to motor sail or just motor....