Before we cut and sew our beautiful fabric, we will have to prepare our pattern and make a muslin. Vintage patterns can be tricky, so it's important we test our fit. If you are making the longline bra, you may also want to make some adjustments.
I am adding 1/2" Seam Allowance to ALL edges. I am applying a 1/2" elastic to the top and bottom edges of my bra, so I am adding 1/2" to the top and bottom edges of my pattern. If you are binding your top and bottom edges, do not add Seam Allowance. If you are turning your edges under, add the appropriate amount of seam allowance.
For the Long Line Bra, the original Pattern instructions tell us to OMIT the darts for the lower cup. I sewed a couple of test garments, and this just doesn't seem to work right for me. So, I sewed a cup with just the FIRST dart, and omitted the second dart. I also sewed a cup with both darts. I found, for myself, the cup with both darts contoured much better than the cup with one dart. If you are larger chested, a D cup or over, you will likely prefer the cup with 2 darts. This version will require additional pattern manipulation.
I highly recommend you sew the cups both ways to see which one contours around your body best. You literally just need to sew the cup and hold it over your... ahem... boob.
Start by closing your darts - I have just pinned mine closed. I have also pinned my front corselette pieces together, stitching lines lined up.
Walk your lower cup along the upper edge of the corselette.
Walk you upper cup along the lower cup. You'll notice you are also short here. Tape a scrap piece of tracing paper along the side seam edge of the upper cup. Extend your cutting lines. The lower seam of the upper cup should follow the upper seam of the lower cup. Extend a straight line to form the side seam, using the lower cup side seam line as a guide.
We're now ready to cut out our muslin and test our fit!