I have a vague memory (in general) of something called a 'Knightson' Computer - which is a piece of circular plastic on which you can mark the wind vector before you go. Once you've marked your chart with your diversion you can slap the plastic on top of the line and it will show you the drift component in one easy step. I tried a search on the net but nothing showed up - I'll keep looking, but maybe I might be confusing it with something else.. .. .Suction