Perfect Ellipse

by Edwin C. Hackleman

Well, this is about midway between a shop jig, a
shop technique, and a
project.I believe your website visitors will love this one. I built a cutting board that is not a rectangle, a square, or a circle. Instead, it's a perfect ellipse.See my attached diagram.Drawing a perfect ellipse on a board takes a little skill. 12.2"W x 17"L. but those on the same row have to be
the same width.the outside two or three boards should all be full length to entrap
the shorts. hickory, ash, and
cherry pieces in a somewhat random pattern, never gluing up more than
three rows at a time.(foci), that are needed to draw the ellipse takes a little math.foci are each located an equal distance, c,
from the center along the length.Step 1) Divide the length (major diameter) of the ellipse
in half.Call this a.Step 2) Divide the width (minor diameter) of the ellipse
in half.Call this b.Step 3) Apply the formula:
c = SQRT[a^2 - b^2]c = 5.92.foci locations,
about 1/4" deep. 2c + 2a.In my case, this was 28.84". added 1/2" to this to compensate for the
bend around the nails and the end of the pencil.foci for a pair of hole locations.
After removing the two nails, I drilled a pair of 11/16" holes
right through the foci.That completed a dandy project. BTW, keep the string that you used to trace the ellipse. You can use it along with the two holes to show people how the technique worked to draw it. It's a great conversation piece. Best, Edwin |

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