Lapped seams are discussed in nearly every sewing manual and are often mentioned in blog posts. A search will provide many good examples and instructions. Essentially instead of sewing right sides together or wrong sides together, the seam allowances are over lapped a pre-determined amount and then top stitched. The top stitching is placed just before the edge of the seam allowances and then repeated so that the unseen edge is also secured. You end up with two lines of top stitching and one visible edge. I suppose, one line of stitching would be sufficient, but I’ve never seen lapped seams with only one line of stitching. An alternative to making two separate lines of top stitching, is the twin needle or if 3 lines were desired a drilling needle. Any time a twin needle is an option, the cover stitch is an option.
I’m still working on the sweater knit shown in the Faux Ribbing post. I wanted to give this typical T-shirt shape in a plain knit (albeit the slightly heavier sweater knit) a little something extra. I opted to cut apart the front, back and sleeves into horizontally. I’m using the purl side of the fabric as the public side for the upper portions and the knit side public for the lower portions. It is color blocking at its simplest. No color-coordinating fabrics needed. The stitch structure and available light create the color blocked effect. A similar result can be obtained with corduroy, velvet and most napped fabrics. I opted for Lapped Seams to joint the upper and lower portions. Firstly, just to do something different but also I wanted the seams to be as flat as possible. I anticipated these seams might chafe because of their location. A flat seam rubs less than a lumpy one.
First step for a lapped seam is marking where the seam should be. My sweater knit wouldn’t hold chalk and ignored disappearing ink. I was grasping at straws when I spied the masking tape. I keep several widths because masking tape is handy in different widths at different times. For this seam treatment I’m using 1/4″ masking tape. I placed my clear quilter’s ruler over and 1/2″ down from what would be the top of the lower bodice. I aligned my masking tape along the edge of my quilting ruler. I was a little late taking pics, so here you see the seam already under the needle, but with upper SA lifted out-of-the-way so that the masking tape and under SA are clearly visible.
I arranged the upper layer to just meet the masking tape and then pinned profusely. Not kidding, the pins were about 1/2″ apart and doubled dipped (two pin bites instead of the usual single) when I sat down at the CS. Pins are not the only option for securing the two layers. Use your favorite method. I used normal settings i.e. serger thread in both needles and the looper, stitch length 3 mm, Differential in neutral; and stitched away:
I removed pins as the foot approached them but didn’t remove the tape until the seam was complete. I liked using the tape as a guide for my foot during the stitching.
The public stitching is practically invisible. I’m hoping that with time, the fabric edge will curl adding a little more emphasis to the seam. Side note, the masking tape was stickier than anticipated and required careful removal.
The back side is a little more obvious
My garment received lots of handling. Much more than I expected and the edges were stretch and loopy. I made a second pass of the CS trying to really nail the seam into place. I’m hoping that the garment will last a few years. Regardless, the double stitched seam does look slightly different. Private side:
and the front has an interesting welt/ribbing effect:
I think either single or double stitched are neat and could be even more interesting with contrasting thread.
Using a twin needle at the SM would give greater flexibility in the width of the top stitching. Twin needles are available (I think) between .8 and 5mm wide. I most often use the 4mm so the CS which is easiest to thread and adjust, would most often be my choice. My second most often used twin needle is the 2.0 and maybe 2.5. I have the others, but seldom use them. Whereas my 4mm and 2.0 have had to be replaced due to wear and I’ve purchased both ball point and sharp twin needles. In retrospect, the 3-needle CS might have been a better choice for me. But I would use 3 needles or even the 2.0 spacing so seldom that I don’t get excited and have no plans to trade my 900CPX.
^^^^^^^^^^^^^^^^^^^What’s in the CookBook: