October 30, 2013

Adapting a block pattern into something else pt. 4 T-shirt to Cardigan

For review read part 1, 2, and 3 of this series.

All of the major pattern pieces are now done. Next up is to do the neckband, the elastic casing for the back waist, and pocket. These three pieces are just rectangles. In a CAD pattern making environment, I will make pattern pieces for all rectangles and squares. Pattern makers, graders, marker makers and cutters all handle these kinds of pieces a little bit different, so ask if you are not sure.

For me, working on a personal pattern in my own workspace I handle rectangle and square pieces one way. I figure out the dimensions and note them on my style sheet. You can do this for patterns* that will be used in a factory setting too, but you will need to create a cutting guide for any rectangular pieces which might be graded. For now noting the cut dimensions is sufficient.

Up to this point I haven't really needed to consider how the cardigan is to be constructed. The majority of the cardigan has rather simple construction that mimics the construction of the t-shirt. But the neckband can be constructed and attached in a number of different ways. I also have to consider the stretch factor along the back neck. Do I want a 3-piece neckband with seams at the shoulders or a 2-piece neckband with a seam at center back? How do I finish the neckband at the hemline? How wide? All these things have an influence on the dimensions of the cut piece.

I like to keep things simple so I opted for a 2-piece neckband with a seam at center back. A 3-piece band might be necessary if the fabric width is too narrow. A 1-piece neckband might be possible if the cardigan was smaller. Begin by measuring the front and back neckline of the cardigan patterns.
Now it is a matter of math. There really isn't a formula for this. It's just adding and subtracting.**

Neckband width = (front neck+back neck) - (front and back shoulder seam allowances + hem allowance) + seam allowance for center back + seam allowance at hemline - some stretch factor for the back neck.

Neckband length = 2 * (Desired finished width + seam allowance)

It seems as though I might have mixed up my lengths and widths above. But I promise I did not. The neckband will be cut across the width of the goods like this:

Dimensions should be written as Length x Width. In this case the Length is the shorter measurement. My neckband pattern piece will then be something like:

5 x 30 inches

A CAD version or hard pattern will look something like this with a pattern number assigned instead of the words neckband:

You'll notice that I have two notches. The notch along the length (the narrow end) instructs the sewing machine operator to stitch the neckband pieces together at that end. The other notch along the width (long direction) is the match point between the neckband and the shoulder seam of the cardigan. This notch is necessary because I reduced the back neck to account for a stretch factor. This will help the back neck fit better rather than stand straight up.

Since I am just making one size and working at home I will draw a picture indicating the notch placement with a measurement along with the cut dimensions for the neckband.

*Managing rectangular and square pattern pieces is the subject for at least two additional blog posts! Yep, it's hard to believe but there is a lot to say on the subject....

**I do all this adding and subtracting right at the calculator.

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