Now that your child has learned to sew straight stitches, pivots, and now curves, they are feeling quite confident. They feel that they have now mastered quite a few techniques and made a few projects with pride. About now I get the question:
Why does it matter if the seam is exactly at 4/8" or 3/8"? What difference does it make?
Now is a good time for the Wonder Woman Story.
If you are following the Summer Sewing Camp series, the Wonder Womas Story would come right after the eye mask project as part of Day Three.
The Wonder Woman Story
My goal as a sewing instructor is to teach sewing. The premise is that the student wants to continue to learn and progress in skills. In order to progress, this will require accuracy.
To continue making small projects, the seam allowance doesn't really matter that much.
But....if you want to be able to make a garment that fits you perfectly, accuracy in seam allowances matter a great deal!
I then show them the Wonder Woman costume and the photos. My daughter made this for herself when she was in the 8th grade. Including the center back, this costume has 7 seams. If you were to be off by 1/8 of an inch when you were making it, how much of a difference would that make?
1/8 of an inch difference on a seam allowance equates to 1/4 inch off to the actual seam because there are 2 pieces of fabrice sewn together at each seam.
Multiply 1/4 inch by 7 seams and you are off by 1 and 3/4 of inch. That is almost 2 inches off.
If your seam allowances are bigger by that much then the costume would be way too small. There would be a big gap in the back.
If your seam allowances are smaller by that much then the costume would be way too big. There would be a big overlap in the back.
I show them this with a tape measure to see the differences. This illustration may help in trying to keep sewing along the proper seam guide line.