The slide rule side is just proportions, so 10 over 20 you will see is the same as 40 over 80 and so forth.
So 95 kts over 60 minutes = 95 miles in 60 minutes or 9.5 miles in 6 minutes.
The numbers can represent anything.
So 5 apples over 10 (say £1) = 10 apples over 20 (£2).
For the wind side i always start by drawing the vector triangle on the chart, you don't really need the whizz wheel.
But then show how to draw the same on the whizz wheel.
Unfortunately there are one or two crap methods which totally confuse students, because some instructors don't understand it themselves.
So on a chart draw a line from A to B say 120 miles long. Your Track.
Then at point B draw a line from wind direction to scale so let 1mm = 1kt. So 25 kts would be 25mm long.
Call the end of the wind line point C.
Now measure out on the rule say 95mm to represent cruise speed of 95 kts.
Now place 95 at point C and rotate rule until it touches line A B and mark as point D.
All done. The angle formed is drift and the distance D to B is groundspeed.
Last edited by BigEndBob; 23rd July 2018 at 21:12.