The cups of Merckwaerdigh BHS10, View D fit me pretty well out of the envelope, with the exception of the diagonal seamline falling about 1/2″ below rather than across the apex. The last time I made it I did a quick and easy adjustment where I just chopped the extra off the upper cup and added 1/2″ to the lower cup, but I knew it wasn’t completely accurate. I had to ease in the lower cup into the upper cup. It worked for that particular bra because the lace was such an open weave, but for future renditions I wanted a more accurate pattern.
I wanted to raise the seamline for fitting purposes, but you can also use this method to change the seamline for style purposes, like changing from diagonal to vertical seaming.
To change the seamline of your bra pattern you’ll need a ballpoint pen, a couple of pieces of paper, and some bramaking foam. Any foam is ok as long as it has NO stretch. (I’m using the Make Bra foam for this tutorial.) I also like having my SACurve ruler handy.
Start off by tracing off your pattern pieces. If there’s any arrows marking grainline or direction of stretch make sure you trace those off too. Don’t add seam allowances. If the pattern has seam allowances included, trim them off.
Transfer these pieces onto the foam. If there’s an arrow marking the grainline or direction of stretch transfer that too. Cut out the pieces.
If you are already aware of where you want the new seamline to fall it would be easiest to mark that now. (In this case I wanted to raise the entire seamline 1/2″.)
Butt the edges of the foam together at the seamline and sew using a 3-step zigzag stitch. If you haven’t marked the seamline yet, do so now.
Cut the cup apart at the new seamline you just marked.
Place one of the pieces onto a piece of paper. If it is the piece without zigzag stitching (like this upper cup piece) you can just hold it in place and trace around it with the pen. Don’t forget to transfer any arrows marking the grainline or stretch.
For the piece with the zigzag stitching you’re going to have to go about it a little differently since you want to preserve the seamline shaping. Place the foam piece on the paper. Hold it on one side. (You’ll notice how it tips up and doesn’t completely flatten out due to the seamline shaping.) Trace the outline of the foam onto the piece of paper, very carefully holding the foam down only in the area you are tracing. You almost want to “roll” it around on the paper as you trace. Make sure you don’t let it slide around though! Don’t forget to mark any arrows indicating grainline or stretch.
I like to use SACurve ruler to smooth out the traced outline. Then I start adding seam allowances.
Top pieces are “before”; bottom pieces are “after”. (I also added a little bit of width to the neckline edge to the upper cup.)
As always I highly recommend you test your pattern pieces before cutting into your “good” bramaking materials. You want to not only make sure you didn’t make any mistakes while tracing the foam onto the paper, but that the new seamline is really where you want it to be.