Sewing a Straight Piece to a Curve Piece
Posted: 03 August 2014 12:01 AM   [ Ignore ]  
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The first time I tried sewing a practice hood, I was surprised to find that the pieces ended up being mismatched by nearly two inches! And along a seam which was only 18” long!

I know what you’re thinking: sloppy patterning and cutting. Nope. I am kind of a perfectionist and I measure, re-measure, and re-re-measure seams when doing the patterns until I am 100% sure that the seams (on paper) are within 1/16” or less of each other. I knew it had to be something else.

Up came Google but surprisingly, I could not find much addressing the problem, which I suspected was trying to sew a straight seam to a curved seam. Long story short, I am still not sure exactly what was going on but I found that if you sew with the straight piece on top, you get much better results.

I tried several times, and each time I tried with the curved piece on top, the pieces were mismatched up by at least one inch. Each time I tried with the straight piece on top, the seams were nearly perfect.

After a bad mismatch with the curved piece on top, I even seam-ripped the two pieces apart to try with the same exact pieces (this time with the straight one on top) and it came out perfect. If AYCE has any insight into this, it would be much appreciated! ;)

Since I spent a lot of time trying to work this out, I thought I’d add my experiences in case that helps someone shortcut the learning curve and reduce some frustration. This was one of those situations that felt like there was a devious gremlin inside the sewing machine.

Here’s what ended up working pretty well, in terms of sewing a straight edge to a curved edge:

With the needle down and the presser foot up, align the fabric edges for about an inch in front of the needle. You might need to move the top fabric around to make it parallel and to smooth out any folds; a stiletto/wooden skewer works great here. You might need to slightly stretch the fabric a little to make sure the edges are lined up perfectly. And even though you are lining up the edges, what matters, really, is that the SEAMS are lined up. But the fabric edges seem to be an adequate proxy.

In bullet point form:

At any given adjustment point while sewing the seam…

1. Needle down, presser foot up.
2. Rotate bottom fabric (ie, the curved one), so it is parallel to presser foot at needle.
3. Rotate the top (ie, straighter one) so the edges of both fabrics line up. The key here is that it might only be lined up for an inch past the presser foot.
4. Stitch slowly. On the real curved sections, I hand-turned it and only did TWO stitches before going back to Step 1.
5. If the edges are both relatively straight, you can sew much further but still very slowly as it gets off track very easily.
6. Pinning very UL fabric in this situation seems to be counter-productive.

As noted in Step 6, a surprising thing was that I found it sewed much better with no pins. I usually pin a lot and with the seam shapes being so different, I really expected that a lot of pins would be necessary to keep things aligned. Instead, using a lot of pins made things MUCH worse. When I tried with NO pins, the pieces ended up aligned much better. Go figure.

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