Formwork 1

Creating and ellipse is harder than previously imagined. To make the form I bought a 1/2" sheet of melamine faced OSB. The overall table dimensions were about 4' x 3'. Next we wanted to draw an ellipse on the board. With all the computer software out there, you would think this would be easy. No sir, back to the times of Brunolleschi, when all you had was a piece of string, some charcoal, and a couple of sticks.
We used this website to find the foci of an ellipse.

Next, we pounded a couple nails into the board, and cut our string; then, attached the charcoal to draw the ellipse.

We wanted to somehow anchor the side walls (masonite) into the base of the form: in comes the router. With a 1/4" bit, we fixed the string to the router handle and routed out the shape.

Then added a few T-shaped supports around the ellipse to prevent any collapsing sides, and VOILA, the formwork is ready!