Large Bust One Piece

Mixing Two Blocks Of Differing Negative Ease!

NOTE: Part of what we all did at Fashion School was look at other people’s high fashion garments and see if we could work out how they were made. This was particularly the case for 3rd year pattern making. The teacher would show us a photo of something from fashion week and give us an hour to make a pattern for it … I loved those challenges. At the end of the hour, the teacher would demonstrate how she thought it should be done and why. Some people out there call this copying or “knocking off” someone else’s design … that’s not what we’re doing here … this is about learning how to make patterns by following a procedure … it’s what we all did and how we learned. I’m not telling you to take these instructions and go manufacture this garment for sale …that is wrong and illegal ... I’m using this design as an example to teach students how to manipulate a block into a pattern that resembles this style (albeit, probably not exactly).

Mixing two blocks is never easy, especially when they have different negative ease, but sometimes it's essential. For example, the 12% negative ease Women's Body Block is lined with normal soft swimwear lining, but the Buxom Bosom Block (love that name) which I'm about to splice with it is only 4% negative ease because we use Powermesh lining. In this tutorial I'm going to show you how to splice them. This particular pattern tutorial will only work for people whose natural bust point falls within 5-6 centimetres horizontally of the BP on the body block that fits them ... I'll do other tutorials later for those outside that range.



Step One

For this pattern tutorial we're going to imagine we're making a custom one piece for someone with a larger bust .... so let's start with some measurements (these are from my sample maker in Australia):

Bust: 102cm
Underbust: 80cm
Waist: 72cm
Hips 97cm
Mid Shoulder to Bust Point: 27.5cm

This means I can select the size 92 Body Block based on waist and hips, and the size 42 Bosom Block based on bust and underbust. To locate the Bosom Block on the Body Block we need to know how far above the waist line the client's underwire line is ... in the case of my client it's 7.5cm. So I measure up from the waist on the block and square all the way across both blocks at 7.5cm ... this is really the client's underbust line. We also know that the client's underbust measurement is 80cm (or 20cm per quarter). On the back block I measure out 20cm from center back along the underbust line and mark a guide point. I repeat this on the front block. You'll notice that because I disproportionately allow 4/7ths front to 3/7ths back for the side seam position on a B-C cup bust that the back block appears short at the seam line by about 5mm ... it isn't ... what we want to know is by how much so we can add that amount to the 20cm on the front underbust and maintain the proportion. (see the image below).

Now comes the tricky part. On your client you need to know where the bust point locates along the underbust line ... usually I discretely measure from CF along underbust to where I think the bust point sits perpendicular above ... it's rarely the same as the bust point of the standard block (especially as bust size increases) but in the case of my client it was! ... I've marked this position with a vertical line (blue). You could push it more central to create more side support if you wish.

Step Two

Draw up a guide line from the front waist at the side seam, through the outside of the little underbust extension ... this will become our new side seam.

Step Three

We can now remove everything above the underbust line on the front block (except the vertical BP guide). Place the Bosom Block on the vertical BP guide approximately 2cm up ... it's just a placement for ease of working and doesn't need to be precise.

Extend the front strap to match your client's mid shoulder to bust point measurement using the little slide rule ... the slide rule already takes into account reduction for height if using Powermesh. My client has a mid shoulder to bust point of 27.5cm (illustrated in red). On the back block we need to create a rectangular guide box the same width as the end of the front strap, placed vertically down from the mid shoulder point (the design in the photo). We need to shorten this guide about 2-3cm to allow for overstretching of a narrow band ... I've only gone for 2.5cm because the strap is a bit wider ... you'll need to judge each fabric and decide how much for yourself, but this will have shoulder ties so it's not that critical.


I've chosen the slightly lower leg line (red) to go with the design in the photos.

Step Four

On the back block, transfer the design in the photo as illustrated, staying clear of the armhole a little. We want as much side support as possible but we don't want a larger bust weight pulling the back panel through into the back of the armpit ... about 1.5 cm should be enough but be aware you might need to test depending on your fabric.

Now comes the tricky bit. The bra panel is reduced only 4% while the body panel is reduced 12%. this means we need to stitch the the two together by stretching the body panel to line up with marked points on the bra ... in this case those points would be CF, the two darts and the side seam ... but where do we put put those marks on the body panel? let's start with the darts. On the bra panel the dart is 27.1mm from the center line. Now we know where the center line on the body panel is already so we can measure 27.1x(0.88/0.96) = 24.8mm ... so we create a mark for a notch 24.8mm either side of the center line.


Next we need to know how wide the section of the bra panel to the center front of the dart is so we can mark that on the body panel too ...this is 54.6mm ... which on the body panel is 54.6x(0.88/0.96) = 50.5mm ... we mark that on the body panel and then measure the remaining distance to CF.  In this case that's 18.6mm.


The design in the photo above calls for the bra panels to meet at CF so we can now extend the center side of the bra panel by 18.6x(0.96/0.88) = 20.3mm (marked in red). You can click on the little image at the bottom for a full sized image of the measurements ... what we're doing is matching the bra panel to the body panel using notches which correspond to the darts and the center front of both panels.


Step Five

In the photo the point at which the two bra sections meet at CF is raised about 2cm above the underbust line and then the style curves down to the center of the bra panel. We need to match this on both panels.

To do so, you need to close the dart in the horizontal as pictured ... you can cut anywhere as you're not specifically rotating anything, just be sure that the darts meet at the end and everything is horizontal ... much easier to do in CAD! draw a rectangle 2cm high from the center of the bra to the center front and draw in the style line curve. The rectangle is 102.5mm long which should be 102.5x(0.88/0.96) = 93.9mm on the body panel from center bra guide to center front ... check, don't assume ... or your bra section may be the wrong length.


Step Six

Open the dart to the right position again and curve off the bra panel smoothly from center front. Transfer the style line you checked previously to the front body panel. 


I've curved off the side seam line at the waist smoothly (green) on both the front and back body panels.


Separate the back bra panel from the back body panel, being sure to mark the point at which they meet near center back. You will notch this point in your seam allowance when you cut out the fabric.

Step Seven

I've just cleaned up the uneccessay lines at this point and placed a notch guide on the front body panel which corresponds to the center-most dart in the front bra panel

Step Eight

This time we're going to do the same thing to side seam side of the bra panel. Place the whole bra panel over the body panel such that the side dart lines up with the guide we created earlier and rotate it so that the extension of the bra block is horizontal, as illustrated. On the front body panel, measure the distance from the dart guide to the side seam ... mine is 64.4mm. On the front bra panel this corresponds to a length of  64.4x(0.96/0.88) = 70.3mm. Measure this distance on the front bra panel and draw a new side seam line parallel to the old one. Remove the unneeded section from the front bra panel.


Step Nine

Place the back bra panel alongside the front bra panel using the side seam. Curve in the front armhole style line to match the design in the photo, meeting the back armhole at the side seam. Place a notch guide on the front body panel which corresponds to the side-most dart in the front bra panel

Step Ten

The design in the photo also has tie straps (bow) on the shoulders. For this we need fashion fabric on both sides of the bow. I've decided to make mine 25cm long so I simply create a rectangle this long by the width of the strap ... you can make them as long or short as you like or add shape to them ... the ones in the photo look square so this is how I've done them. Once the garment is complete and elasticated, the bow simply stitches to the right side and is then flipped over and the seam allowance tucked inside and stitched from behind.

Lastly add 10mm seam allowance all around for both seams and fold over elastic. Label all your pieces with the style name, panel name, how many to cut, the size, date/version and author.

This is now a pattern splice of two different negative ease blocks. The front body panel is stretched to meet the bra section during stitching. It may look a little odd when off the body, but should sit better on the body. A way to eliminate that appearance would be to change the front body block to 4% and use Powermesh as the liner here too ... this is typically what most people would do, including myself, but in this particular case I wanted to demonstrate splicing blocks of differing ease.

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