Apparent wind

The apparent wind is the resultant wind that the iceboat experiences as a result of the real wind coupled with the wind generated by the speed of the boat itself.

Thought experiment A:

• there is no real wind
• a wizard pushes the boat due north at 10 MPH
• the apparent wind is 10 MPH coming directly from due north

Thought experiment B:

• there is a 10 MPH real wind coming from true north
• a wizard pushes the boat due east at 10 MPH
• the apparent wind is now comprised of two components
• real wind of 10 MPH from the north
• boat generated wind of 10 MPH coming from the east
• the resultant apparent wind is a vector directed over the port side of the boat at 45 degrees
• the magnitude of the apparent wind is the sqrt(10*10 + 10*10), or the sqrt(200), which equals 14.14 MPH

Thought experiment C:

• the real wind of speed W is coming from the north
• the boat is angled at T degrees to the real wind and is traveling at speed B
• the apparent wind has speed V
• the apparent wind has an angle of A to the boat

• from trigonometry
• V = sqrt((B+W*cos(T))**2 + (W*sin(T))**2)
• A = atan(W*sin(T)/(B+W*cos(T))

Significance of apparent wind:

• the iceboat generally travels at speeds that are in excess of 3 times the real wind
• the multiple of real wind speed generates high apparent wind speeds which in turn generates a large amount of lift in the wing
• the apparent wind angle is quite small which allow the iceboat to point much higher than a typical sailboat