Circle skirts and bias

After 2 depressing days wrestling with the Great White Whale, I've turned my attention to a project that feels easier.

I've got a huge polkadot king size sheet from a charity shop that I'm pleased with, but my skirt is a disaster zone.

50s skirts are supposed to have
waistlines on the waist, not belly
dancer style

So, er, guys -bias REALLY affects circle skirts. Fabrics have a horizontal and a vertical grain. Cutting on either has slightly different results if you're an expert, and for the rest of us is just how you get a nice, correctly sized pattern piece. But if you cut pattern pieces so that they are sat on the diagonal, they droop in interesting/nightmarish ways (see: the 1930s). Because circle skirts are circular, some parts of the pattern are always on the bias.

While making my pattern, I found this really good tutorial which advised shrinking your waistband measurement by 4inches - which sounds huge. Well, I did it and it still came out too big.

Measurements:

Fabric: cotton print
My waist: 75cm
Pattern waist [waist minus 4in]: 69cm

Circumference of circle I cut out: 70cm

Circumference of skirt waistband: not sure. If I put it on the table and measure the area I can see, it's 74cm, but the actual edge is rippled and measured with a tape comes out at 82.5cm.

Holy shit.

So they weren't kidding about cutting a smaller measurement than you need. And 4in was too small by far. My misunderstanding of maths is that, if making my waistband smaller by 6cm results in it being bigger by 7.5cm, then I'd need to make it smaller by like, 12cm at least.

Check out the way that fabric is rippling. It won't lie flat, and all I did was cut it out.

Or in any case, start super small and then keep making it bigger. 

Thank goodness I found that tutorial, otherwise I can't imagine what a disaster it would be?

I am disappointed, but I think I can probably save it by gathering it into the waistline, and it'll still look like an ok skirt.