Sian made a few suggestions for me to try to increase the loops I was(n't!) making in my initial set of samples. Tone work was nice but the whipping needed more whipping :) And as it happened #13 turned out not to be so unlucky for me, this time anyway (not that I'm supersticous, of course!)
I began by trying out Sian's suggestions, which included reversing the tension, i.e. loosening the top and trying either tight or normal for the bobbing tension. I couldn't get either to work for me. Then Sian suggested I try a slightly thinner thread in the bobbin to fool the machine into thinking that the tension is looser. That didn't work either! Seems these newer models are quite difficult to trick into whipping stitches. They seem to adjust automatically to compensate!
So I went right back to the beginning, only this time taking it to the very edge - I pretty much loosened the bobbin screw until it was about to fall off, and tightened the top tension as far as it would go [#10 on my Bernina]. And it worked! I love my loops!!
The sample was worked on 2 layers of white cotton, using a zig zag stitch. I altered the length and width of the stitch as I progressed. Also discovered that the faster I machined the bigger the loops! I had to start and stop stitching at the end of each line to avoid serious puckering of fabric. I also had to be careful when pulling the work away from the machine to cut the threads that the thread didn't pull out unravelling the stitches.
All in all very pleased with the results of this sample :)