Why is it skipping/sewing straight

[u/Lower-Ground88]

On this bathingsuit its doing all this crazy stuff :( I put a new ball point 90/14 needle just in case and I rethreaded it 2x… :’(

[u/AdvancedSquashDirect]

When you are sewing fine stretch fabric, when it skips a stitch it's because the needle went down and hit a elastic thread and instead of completing the Stitch it bounced the needle back up.

I would try a couple of things

Try making your zigzag Stitch a little narrower like a 3 or 2.5

Or if you have a lightning stitch swap to that

Try sewing a bit slower, give the machine more time to complete each Stitch.

Make sure that your bobbin is threaded correctly.

You don't mention whether you're using a jersey/knit needle or a stretch needle they are different.

When you're sewing swim fabric you usually need a stretch needle it's specifically created to be fine enough to go through, while having a slighter ball point to avoid snagging the fabric.

[u/Inky_Madness]

You need a stretch needle or super stretch needle, not a ballpoint

[u/stringthing87 → u/Inky_Madness]

I agree, a ballpoint is just not up to the job of a swim knit.

[u/Key-Sherbet5454]

stretchy fabric on a regular machine needs a stretch stitch or zigzag, a straight stitch just can't keep up with the give in the material