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# Thread: HELP!! I need a quilting math genius!!

1. I am trying to make a quilt for my son and decided I wanted to make the quilt more of a rectangle instead of a square. To do this I want to put pinwheels on point above and below the main square. Ok, I did the math and using my quilt design wizard have found out that to make an 8" square on square pinwheel (to make them look on point) I need a pinwheel that is 5 5/8 inches finished or 6 1/8 inches unfinished. Does ANYONE know how I would be able to make them this size? I haven't even made one of these, but they look fairly simple so I know I can do it, just can't get my mind around anymore math. Thanks to everyone who tries to help me.

2. cut your squares 7 inches square.... then use a tutorial like this http://www.psiquilt.com/2010/02/half...-tutorial.html to make your half sqaure triangles that make up the pinwheel!

the math for making HST like this is by adding 7/8 inch to the unfinished size of the HST. so if the unfinished size is 6 1/8+7/8=7 inches!

3. Just quickly off the top of my head I wondering if you could make the blocks 5 3/4 or 6 1/2 and then cut them down to make them 5 5/8 or 6 1/8? Since both measurements are only 1/8 off from the easier size, I can't believe it would make any difference in the block. I would try making them with other fabric and see how they come out. I would bet that the block will look fine. JMHO

4. Make your pinwheel half-square triangles finish at 3" square.
Sew them into the pinwheel that will be 5.5" unfinished.
Cut 2 (background squares) at 5" square; subcut these on ONE diagonal to make 4 triangles.
Sew the triangles to the sides of the pinwheel block.
Square up to your required 8" block.

Doing it this way has several advantages:
1. The 5" pinwheel is a measurement you can easily divide to work with.
2. The 2 background squares cut on one diagonal will give you straight grain of fabric on the outsides of the finished block, preventing stretching.
3. The pinwhell will "float" within the on-point block, preventing you from losing any of your points.

Jan in VA

Well, you certainly can't see that!!!!

The words and arrows in the TINY graphic point to the overlap of the setting triangles which allow the pinwheel to "float".

5. You could achieve this without doing any math if you draw the block on paper in the size you want and then add the 1/4" seam around one of the triangles using a ruler. Now you can measure that and you know what size you need.

For ease in sewing the HST's you can measure the short sides of these triangles (including seam allowance) and cut squares that size, pin one light and one dark with right sides facing and mark the center diagonal, sew 1/4" on each side of the line, then cut apart on the line between the seams. I prefer this method because if you start with the larger square and cut both diagonals those are bias cuts, whereas the 2-at-time method has the bias stabilized with stitches before you cut, and the outer edges are straight grain. Also, they are easily chain pieced.

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