We have been doing some heavy duty canvas work for our boat, dealing with Sunbrella fabric. We were using a Brother home sewing machine. The last project, a sail cover, spelled finis for that machine. It just burned out but it had delivered yeoman service for many years.
Now we have a new project rebuilding the dodger. (A dodger is a canvas
-- Sunbrella -- enclosure with heavy clear vinyl windows, all supported on a metal frame with various big zippers to enable installation, removal and folding.) This job would need more than a small domestic sewing machine. So seeing a good buy, we bought an industrial high speed lock stitch sewing machine, a Yamata GC8500. This is one humongous mother of a sewing machine! It does 5,500 stitches per minute, is driven by a ½ HP motor and weighs, all up with table and motor, some 225 pounds. (For those interested, we bought it from Harbor Freight. Shipping for the whole shebang was only nine dollars. But some! assembly was required, like two weeks worth.)
We have figured out how to make straight stitches in any number of layers of fabric, though controlling the speed of this monster is a real and not yet mastered art. The problem lies with the clear vinyl plastic windows. We did this job once before with the old and now defunct machine and had no problems. But this machine is so fast it literally melts the vinyl, even causes it to smoke. We are not able to get more than a few inches of stitching of vinyl to Sunbrella before any number of bad things happen. The thread balls before the needle. The upper thread breaks. The upper thread shreds. There?s a bird?s nest on the bottom side. Etc., etc. Correcting one problem seems to cause another.
We are using best quality polyester thread. We bought a new presser foot made of plastic. We are using No. 18 needles.
Any ideas on how to deal with this problem would be most welcome.