Hi there - it's taken a lot longer than I would have hoped to get this up. I picked up a sinus infection and my whole family has been enjoying it as well. I'm still not quite the thing but I am bored and itching to get something up. So here goes...
In this first picture, I've started pinning the muslin to my dummy (Beatrice). I'm working with a vintage newspaper pattern for a "soutien gorge" and it included two different cup styles - a four panel cup and a two panel, vertical seam cup. I am not really sure which I am likely to be happier with so I figured I would drape both and see what I get.
This photo shows the seams that define the center front panels of the bra cup. Given that I am a "bit" (ahem) more busty than the average gal of the 1930's, I can't just work from the dimensions given for the panels in the article. A center bust seam of 3 inches would be laughable. I'm pretty sure that falling out over and under the garment would ruin the effect!
Moving on, my first pass with the pins is meant to get the general form in place, followed by tweaking to ensure that the fabric is smooth and not stretched out of shape or too far on the bias. You don't want to have to do this twice - it's a great technique, but it is fiddly and repetition leads to frustration.
Once you have the seams and the edges defined neatly, trim some of the excess away, but not too closely. I also number and mark the panels so that I don't loose track of where they are supposed to fit. Some patterns are easier to eyeball than others. Given that there are both vertical and horizontal seams that will be meeting up in the center of the cup, I snipped the muslin to be better able to create a neat seam. There will be plenty of time to compensate for flaws, but this makes things go smoother from the beginning.
Another thing to bear in mind about any item you might drape a pattern for is that it is always easier to make a neckline lower than to bring one up...this holds true for anything except armscyes.
After all the panels have been pinned and marked, the excess material gets trimmed away as neatly as you can get it without making yourself nuts. Remember, you will be able to smooth out the lines once you pull the muslin off the dummy. Plus, this is the perfect time to eyeball the developing pattern to see if you have overlooked something. After I took this shot, I noted that I needed to neaten up the alignment of the vertical seam! I can't tell ya how many times it is the camera that lets me see where I have goofed!
I also like to put in grading marks at this point since I won't have a better opportunity to align the pieces prior sewing up the first mock-up.
Here are the pieces following unpinning and trimming up the edges. You can see the grading marks better here. This is prior to adding any seam allowance or doing anything to refine the curves and angles of the pieces.
Neatening up and adding allowance will be done as part of transferring these pieces into a paper pattern. You could use them as is and lay them out on the fabric you intend to use for your mock-up and add seam allowances at that point, but I find I screw up less by taking the extra step of putting it all on paper. I'm sure you can imagine what a mess leaving out SA's can make of a garment!
Okay, as I said, I am still not in the best of health, so I am going to close here and will post the draping for the other cup style as soon as I can.
Nyquil, take me away!