Selvedge loops when using a double-bobbin boat shuttle
I'm currently weaving a narrow piece using a double-bobbin boat shuttle, and am winding up with lots of loops at the selvedges. The problem seems to be that the bobbins feed out at different rates, and I can only tension one of them with my thumb as I catch the shuttle.
It isn't an issue for this warp, because the selvedges will be cut off (it's the double-happiness character ribbon for my wedding-dress, and the edges will be cut/turned under when it's sewn on), but I'm wondering what I can do for future projects where it might matter.
What, if anything, can I do to improve selvedges when using a double-bobbin boat shuttle?