Converting Darts to a Princess Seam for the Jasika Blazer

Hello all! Celine here. I am the in-house pattern maker for Closet Core Patterns and I am here to share a pattern-making tutorial with you. We spent a lot of time in the studio discussing how to make our Jasika Blazer work for larger busts, and while we do have C & D cup options for the pattern, princess seams are one of the best ways to fit a large bust. You might also choose to add princess seams for purely aesthetic reasons - either way, I'm going to walk you through it in this tutorial.

If you think you want a more fitted Jasika Blazer (or any other jacket for that matter), or if you need more shaping around the bust, using the existing darts to draft a princess seam is a good way to go. Waist darts ending in the pocket is a pattern staple for tailored jackets and what’s been done for ages to give a little shaping to an otherwise pretty boxy garment. Tailored jackets in the early days of tailoring were drafted for men exclusively. When tailoring came into fashion for women, designers emphasized the waist and bust a lot, creating an hourglass shape and adding a lot of seams everywhere to make it snug. That’s when the famous princess seams that Dior utilized for blazers became iconic. Later on, menswear became trendy for women as well and boxy made a big come back!

Our Jasika blazer is a good combination of both, with true tailored blazer style and a semi-fitted shape (since the waist dart is relatively small) with a decent amount of shaping. But the good news is, you can shape it and style it some more! Switching from darts to adding a seam to a bodice is actually not that hard and requires just a few steps. Then again if you don’t need more shaping but just want to change the style lines you can do that with a princess seam -- you’re the designer here! I’m going to show you how to add a princess seam to the Jasika regular front, but also on the FBA C cup and the FBA D Cup (with two darts) in the armhole and shoulder.

DESIGN AWAY AND TRACE A LINES ON THE FRONT

First you have to determine your bust point location. There is a reference point on the pattern already, but you might want to do a quick muslin of the Front to check on yourself if it is really at the apex. Then draw where you want your princess line to be: it can be anywhere in the armhole to the shoulder, as long as it goes through or very near the bust point.

ADD NOTCHES AND CUT ALONG YOUR DRAFT LINES

You want to have a smooth curve at the bust so make sure your lines are not making any weird shapes. I would recommend getting rid of the bustpocket here as you want to see the nice curved shape of your princess seam.

ADD SEAM ALLOWANCES AND GRAINLINES

When your pieces are cut, draw your seam allowance (we are using a 5/8” seam allowance) and transfer your notches. At that point you can walk your seams or measure them making sure they all match. If you have a bit of excess on your side panel curve it is no big deal, you can smooth it when sewing and pressing. Decide if you want your princess seam to go all the way down or stop at the pocket. I've shown it both ways here; on the right side I cut the bottom from the center front piece and merged it with the side panel. When your pattern pieces are taped together, check the seams are matching well and add a grainline perpendicular to the pocket opening.

MAKE A MUSLIN

Make a muslin of the front with your new princess seam! For the example drawn here, the overall shape of the blazer is the exact same, so it should fit the same. If you want to adjust the fit you can do it on your muslin, pinching the extra fabric along the seam and then transderring those adjustments on the pattern.

PRINCESS SEAM IN SHOULDER ON A JASIKA C CUP FRONT

For a seam ending in the shoulder, the drafting is pretty much the same. To have a consistent line from shoulder to hem you can draw your line a bit off the bust point and adjust your curves: the amount you take on one side should be added to the other side. In this example, I drew my line 1/4” toward center front and so curved the side panel also 1/4” out. Again, if you want the jacket to be snugger, you can leave a small gap between your drafting lines and adjust later with your muslin. With the princess seam in the shoulder, you could also keep the bust pocket. You may find you need to smooth or adjust the side panel curves to  get a closer fit.

PRINCESS SEAM IN SHOULDER ON A JASIKA D CUP FRONT (WITH TWO BUST DARTS)

Follow the same steps as for the princess seam in armhole, however, we will also have the option to remove the bust dart. Here's how to do that:

On your new side panel, before adding your seam allowances, draw your dart so the dart tip touches the seam. Close the dart, folding your paper or cutting one dart leg and taping it to the other dart leg. Your seam is now crooked so you need to smooth it and make it a nice curve, checking the measurement are still matching along the center front panel.

For more help with making these adjustments, we wrote a fitting tutorial/ebook on princess seams for the Fiona Sundress. The principles are the same for a jacket so if you are having fitting issues, this should help you out.