Blue Dude! My brain was broken by Math

So...we have a different technique for making the blue guy since he's the biggest/fattest...and making him out of a solid piece of foam would be costly, and more labour intensive to hollow out his insides.
Therefore...we got this flat sheet of 1 inch thick foam:















Using some math skillz, I drew out a rectangle on the foam. The length was what I wanted the final circumference of the dude to be. And the height of the rectangle was half the length.

Then I divided the length into 12 equal sections, and the height into 8 equal sections, thus-wise making a grid:















Then I found the midway point of the first column, and called it point "A" (half way was at 7.1 cm)















Then I put a mark "B" at half the height of the rectangle on the very left most edge.




















Then I tacked a string into point "A" and drew and arc slightly below point "B". I had to put some paper beside the foam to draw onto.




















Then I used the same length of string, and tacked it into point "B" and drew a similar arc. There are 2 points of intersection between these arcs.















I tacked string into the Left most intersection, and made a straight line through the 2nd one, and followed the string until it intersected the grid line that mark "B" is at (the line which marks half of the height)















The point where it intersected there is point "C".




















Then I tacked string at mark "C" and drew an arc at the left edge of the foam.That gave me the curve I needed to mirror in the 1st column, then repeated that curve into all 12 columns across the rectangle.















Then I cut it all out with an exacto knife.















Tada! Math skills at work! It's a globe shape.
Now at this point it's not glued together...I have T-pins holding it together to take this photo. I'll shave down slit-thingies on the top to make him more egg shaped rather than the rotund-globe-kinda flat in the middle shape it is now.




















But for tonight, blue guy can sit and chill with his buddies.