Rigging a bow

[victorgaldonv]

Hi

 I'm trying to rig a bow using this technique where Ik chains are used for deform the bow and another one-bone-IK to point the pinch where it's supposed to be the hand.

https://www.youtube.com/watch?v=3NuiiPZqot0

It sound nice but when doing that the rope twist in a weird mode as seen in the picture 

How could I avoid that?

or... Does it exist a better way to get that bow rig?

Thanks