Put spiling board on a piece of paper, in order to see what shapes you're looking for (the floor works fine too). Draw a X onto your paper by placing the point of the compass on any two points of the arc and swinging the lines until they cross. Do this for each arc. Connect the dots. There is your strake line, precisely and quickly. You can do this for the bottom of the strake as well, or just measure down from the top line.
Now find two boards that will cover the drawing when placed at the proper angle. Then scarf the boards together at that angle.
Glue that bad boy up.
Once that's set up, go ahead and spile the lines on precisely, cut it, plane it, and rivet it on. Repeat as necessary.
The good news is that we still have enough wood to remake the strakes, and the mistakes (mistrakes?) will get used in the deckwork and bulkheads. Whew.
Okay. Now where were we two days ago?