I started by drawing the major and minor axes on poster paper. My ellipse was to have major diameter 15" and minor diameter 9".
|Axes drawn longer than size of ellipse|
I set the two trammel points to a distance of 4 1/2" and 7 1/2" from the pencil - these are half the ellipse diameters.
Then got a piece of scrap with one square corner and laid that in one quadrant of the drawn axes. I used some plywood that was thicker than my trammel pins are long. That way, the edge of the trammel from which the pin protrudes (the wooden part) can ride on the edge of the board and the points won't dig into the poster paper.
Then, while holding the scrap board down firmly, I run the two trammel points along the two squared edges of the scrap board (both trammel points must remain in contact with the board at all times), while dragging the pencil trammel on the paper.
Then it's a simple matter of moving the scrap piece to the different quadrants and repeating that process.
And here is the result - a very pleasing shape.
I'll use this as a template for laying out the tops of the stools. More on that later.
|Setting the trammel pencil and the two points|
|Using a squared-up scrap to guide the trammel points|
|Starting the ellipse - pencil point is right-most|
|Sliding the trammel points along the board, keeping both in contact with an edge|
|Finishing the first quarter of the ellipse|
|Working the next section of ellipse ...|
|... and the third quadrant ...|
|... and the fourth|