Tuesday, 7 April 2009
Triangles of Velocities calculator
Ben lent me this piece of kit to try out and I really love it. It is a thick sheet of plastic with a compass rose and various scales on it. With this, a straight edge, a piece of paper and a marker you can very quickly plot triangles of velocities. I was quick with a drawing compass but this is even quicker....I can knock one out in about 30 seconds....and from it I know my heading and ground speed (quickly adding/subtracting variation and deviation afterwards).
Essentially, you draw in your Track Required (edge to centre); then your wind vector you draw in downwind of the centre (marking it off at the speed on the scale); using a piece of paper with a AS mark on it from its corner, draw an arc centred at the end of the wind line so that it intersects the heading line and draw a line between these points; then draw a line parallel to this from the centre out to the circumference....... Writing that took longer and seems more complicated than just doing it, trust me.
Flylight didn't invent the idea, but their version, with instructions printed on it (including a diagram example) is very neat and fits inside one of their A3 sized clear, zip-up map boards with a velcro leg strap. They are not cheap but they really are excellent.
Read here about the CRP-1 computer wizz-wheel....my other rather excellent calculator