The turning effect is all about the yarn.
Shiruku is a single-thread yarn without twist.

Some single thread yarns has this effect on the knitted work.
Why? I guess it depends on the spinning process.
But I wanted to use this, to work with the yarn instead of against it.
If you want it straight you can always block it or choose some another yarn with same tension. F.eks Gima, last picture.

SIZES
To fit bust:
81-86 86-91 91-97 97-102 102-107 cm
32-34 34-36 36-38 38-40 42-44 in
Actual hipsize:
80 84 90 96 102 cm
31½ 33 35½ 37¾ 40 in
Sleeve - Sleeve:
87 92 96 101 106 cm
34¼ 36¼ 37¾ 39¾ 41¾ in
Finished length:
50 52 54 56½ 59 cm
19½ 20½ 21¼ 22¼ 23¼ in

My inspiration:
(Turning Torso is the tallest skyscraper in Sweden.
You can Google it for pictures.)