I am having trouble sewing 4 layers of ripstop. The top thread keeps breaking. I have tried both 14 and 16 needles and both universal and ballpoint. I am using Gutterman thread. I have also tried Coats and Clarks which was horrible. I am close to ordering thread from Speer as I am unable to identify the thread weight on what I have.

I have tried adjusting the tension on both bottom and top. Matter of fact I have zero tension on the top - spool to the spring. I have a old singer 15-91. I can sew two layers but I am obviously missing something.

Any ideas?