Math..:(

A while back I came across a nifty tutorial on how to sew half square triangles. I believe it was on Nancy's blog. Anyway..I wanted to try it and this is how it's done:

First cut 2 squares, e.g. one light and one dark and put them right sides together. Sew all around with a 1/4 " seam allowance

Then cut twice on the diagonal

Press,fold open and tadááá...4 hst's and a quick and easy pinwheel.

Problem could be that all the edges are on the bias. If an alternating block is not, you should be okay. If your doing a quilt with only pinwheels...I don't know if it'll work. Solution? Cut your squares on the bias and your hst's are straight!

Next problem I came across was the math. I wanted a pinwheel with finished size 6". How big should my square be???? I googled a bit, drew a pic, did some trial and error, got a headache and then i found the formula:

In short:

When you cut in 2........add 7/8
When you cut in 4........add 2.5

So....where does that lead me with my squares? Finished size should be 6". I will cut it in 4 pieces so a square that's 6+2.5???
NO! That's where I kept going wrong.
I have TWO layers of fabric that I fold open...this meant that I had to divide the 6"by 2. So...6 : 2 = 3. And 3 should be the starter point. Adding 2.5 gave me a square that was 5.5..

In short:
When you cut in 2........add 7/8
When you cut in 4........add 2.5
When you have 2 layers: divide finished size by 2 and add 2.5 (if you cut it in 4 ofcourse!)

If you want 4" pinwheels, divide by 2 =  2 and add 2,5. You should start with a 4.5 square.

Pffffff, now you get the headache!
My sewingroom got awefully messy in the process..

and I also made a lot of these

Don't know what it'll look like in the end, fact is that I was very busy and i'm now completely covered with tiny threads. (and so is every room I've been in)
Another tip: do not wear a black dress while franticly cutting and sewing!