I know! Fun times. We'll I heard back from Fons and Porter's answer line. Answer: they don't know their wedge angle. Still wondering! so if anyone stops by and reads this and has one, it would be nice to know. I'd prefer if it was 10 degrees. However judging by our own calculations it's about 9.5 degrees, which wouldn't make a circle.

I have the Fons & Porter wedger ruler... It doesn’t say on it what the degree it is but I know it is 4 inches at it’s widest & 2 inches at the narrow end & 12 inches long... if anyone is good at math could you please tell us what degree it is? I haven’t even gotten to use it yet so I don’t know if it will make a circle yet... hopefully tomorrow I will get to play with it! Just got it today...

Can you use a protractor to measure the degree on it?

Okay, so I asked my son, who lives and breathes math and he gave a good explanation which I hope helps. He got his math genes from my dad and my hubby, not from me!!

He wrote:

If I understand the problem right, the angles on each side of the bottom wedge should be about 4.8 degrees, meaning both angles together should take up about 9.6 degrees of a full 360 degree circle. Because of the very small angle of the wedge, it would take about 37.5 of these wedges to make a full circle, if I did everything right. Pictures and math are attached
https://scontent-iad3-1.xx.fbcdn.net...9c&oe=5BD559B9

...I didn't see this post when I originally asked the question. So a day late and a dollar short, thank you SO much for your reply! And thanks to your son. It's nice to have a math genius in the family ;-).

I bought the template thinking it was a Dresden by another name. I found it needs 10 pieces to make a 1/4 circle fan. My pieces were 7" tall and the fan is 16.5" tall. The center will need to have a radius of 9.5".

For my purposes its not good but some of you more advanced quilters might make a medallion for the center (18") and then you could surround it with the circle.

(I tried to attach a picture but can't figure it out)

I believe it is 9 degrees when you take off the seam allowances therefore 360/9 = 40 wedges but there will be a big hole in the middle as Rff1010 said and the finished "40 gon" will be 43 inches!

Seam allowance is added to the wedge ruler. So take off 1/2 inch of actual size template.