I sewed this ruched swim coverup myself from very lightweight jersey knit. And here's how I did it!
First, you need very accurate measurements--and a lot of them.
- High bust
- Under bust
- Lengths: high bust to bust, bust to under bust, under bust to waist, waist to hip, and waist (or hip) to desired skirt length, top of back of bodice (a bit below underarm height) to hip
Once I had my measurements, I subtracted a square for the back. (You can measure from side seam to side seam for an exact measurement--I wouldn't just divide all the numbers by two because the side seam will be farther forward on the bust than the waist.) You probably want to bring in the sides a bit at the small of the back:
You could sew the whole bodice as a tube, but that makes it hard to add the ruching, and generally in a sleeveless top, the back is lower than the front, so keep that in mind!
For the front of the bodice, take your other measurements, subtract the square, and divide that answer by two. If your fabric is really stretchy like mine was, you'll need to subtract another inch or two here to create negative ease. "Ease" is the difference between the fabric measurements and your measurements. Normally you want at least a couple inches so you can put on the clothing and move in it.
In a knit fabric, you can use negative ease to have a very fitted garment. Or, in this case, one that stays up. I definitely need more negative ease in mine!
Once you have all your measurements ready, using the length measurements and your halved and adjusted front bodice measurements, make the pattern (I believe this is similar/identical to making a sloper, a personal generic pattern). I use a piece of newspaper to make my pattern, laying out the adjusted widths spaced according to the lengths. Connect the measurements with curves.
Cut one piece like this. Then, to create the ruching, take your regular pattern and draw horizontal lines across it. I did mine about 1.25" apart.
Cut the pattern along these horizontal lines, and space the pieces evenly to double the overall length of your bodice. You'll have to redraw the curves here.
Then sew the back and front together.
For the skirt, draw a straight line on the angle from the waist to hip measurement. Extend this line to reach the desired skirt length.
My research favored a six-gore skirt, and the bodice is only the front half of your dress, so you'll want to divide that original skirt trapezoid into three even gores to get your final measurements or pattern pieces.
The full pattern will look like this:
Cut six gores and sew them together, then sew them to the bodice!
Here's a closeup of my bodice. You'll probably be able to see the lines of stabilizing stitches:
And just for fun, I got some cool pictures of the finished product on a breezy day before heading to the pool at our RV campground outside of Bryce Canyon!