Piping is designed to strengthen a seam, as well as add a decorative element. In this vein here is a quickie guide to piping in stretch fabrics, especially PVC where mistakes can ruin an entire garment very quickly due to stitch marks leaving irreparable holes.
pre-cut garment pieces
piping- elastic cord of desired thickness
pi[ing cover- strip of stretch fabric twice seam allowance plus circumference of cording
Align the top of your first piece with the top of one strip right sides together. Overlap the strip by about half an inch or 1.5cm and zig zag right on the very edge to secure the two fabrics together.
Once you have sewn one side then match up the other side of the seam with the matching panel:
This is the side-back seam of a bodysuit with full length piping.
As this seam is rather curvy it is extra prone to the fabrics stretching unevenly under the foot so a few pins as close to the edge as possible are used to make sure the strip and both side pieces are matched up with no extra stretch anywhere.
Next you repeat the zig zag stitching along the other side:
It is possible to skip the above steps, but it really does make the following infinitely easier and more importantly neater than if you didn’t.
Next you need to set your machine to the simplest stretch stitch. This is seen here as stitch “14”. Essentially it is two or three forward stitches with one or two back stitches.
You also will need a piping foot.
Now you take your cording and place one end at the top of the strip and match edges of the pieces and place under the foot of the machine.
You will need to to a little tweaking of where the needle sits (as far left as possible without going through the cording) and where the fabric sits under the foot.
Sew along the seam. Again you do not need to secure the ends, the stitch is already set to go back and forth.
E voila, a piped seam:
For the intersection of the short seam and long seam: The short seam is sewn first then the two full length panels sewn (long seam). The long seam is sewn from top to intersection, then bottom to intersection and then very carefully hand sewn at the point to neaten. This is to reduce bulk from the piping and multiple layers of fabric.