Knit fabrics - different drafting?
A little background: I've been sewing costumes for more than five years and have finally started to get a degree for what I do. Because I'm ambitious, I am studying to become a custom dressmaker. We study the Rundschau method and I go to class one evening per week. My exam for drafting patterns and taking measurements is in April, and it took us a year and a half to work up to it.
You could say I'm a little experienced at drafting, but we're mostly drafting gowns and coats (click for an example). Blouses, skirts, and especially pants are all pretty much glossed over, although we did do several blouses. I am getting pretty good at the dresses and have started drafting full-size patterns for myself.
Of course the basic gown block can be used to create pretty much any garment from (although the ease differs whether you're making a blouse, a dress, or a coat) and I've made myself a dress, a coat and a blouse from patterns I drew for myself from measurements that were taken in class.
Now comes the tricky bit.
I've asked my teacher, but she hasn't given me a definitive answer, so I'm turning to you fancy folks for help. I want to sew myself several shirts, made from a rayon-blend jersey knit fabric. I wear these often underneath jackets and vests, and it would be nice if they actually have long enough sleeves for a change (I am freakishly tall).
The last time I made a shirt for myself from a knit fabric, I took at least 5 cm (2 inches) out of the side seam to make it fit better. I am confident that there should be an adjustment for it in your drafting, but we're not taught that at school.
How do I adjust for knit fabrics in my pattern drafting?
The answer I came up with myself is to take a piece of the material and determine the stretch factor and account for that in the pattern. So if the pattern has a 10% stretch, I should draft my pattern 10% smaller if I want it to fit really tightly. But this doesn't really fit the bill, because I don't want to look like a sausage and it's not a swimsuit or lingerie.
The answer my teacher gave me is to use a basic block without a shoulder dart (dart-less setup is the best translation I can muster -- in Dutch it's called a "suçonloze opstelling") and to eliminate any horizontal ease. However, I know that the dart-less setup doesn't have much shape at all and I doubt this will work as well if you take my figure into account: I have a large bust and small waist, with big hips. If I use the dart-less setup the only shaping is done in the side seams, and I am afraid I'll just get a fancy bag that will stretch far too much on the boobs and have no waistline. I sure hope there's a better option!
On an internet forum, I read that the best way to go about it is to fold the pattern pieces down in the center and reduce the size that way. Because each knit is different, it's mostly a matter of modeling on the person who is going to be wearing it.
Although I set great store by the patterns we make, I realise that every garment needs to be fitted on the person, no matter how well you draft your patterns. It would be very nice to narrow the pattern pieces down in advance, so it will be easier to do, and I won't be wasting much time. In the end, I want to be able to create a pattern for myself to make draping like this and and this. It could be glorious in a knit fabric, but draping fabric like that from a basic block can only be done right when the block is already fitting well!