The Graphic Rule

This excerpt from our latest book, “From Truths to Tools” speaks to a rather esoteric, but highly useful, rule for use with scaled drawings:

For example, here’s a typical, traditionally-drawn small boat plan:

To find the dimension of any particular part of the boat, we simply set the divider to the part–here the cap on the centerboard trunk:

Then we transfer the dimension (what the Greeks called, more precisely, a “magnitude”) to the graphic rule…

….and read the numerical distance of three feet, six inches. This technique eliminates the need for a scaled ruler and, furthermore, works no matter what scale the drawing is made to.