need help with sewing downproof ripstop

[prince tony]

Hi everyone,

I'm putting together a down underquilt project, and I have a technical problem with my sewing results. My main worry is that, no matter how I set the tension, pressure length or width of the stitches the fabric displays a lot of stretch holes when put under tension,
00100lPORTRAIT_00100_BURST20191111202608645_COVER.png
now, this doesn't seem very downproof, and I fear that it will shed a lot of down over time, as my old sleeping bag does with even smaller stretch holes. I'm using 1.0 HyperD nylon from RSBTR. I have tried 90/14 and 70/10 needles, also I have tried mara 70 and tera 80 and also some regular polyester Gutterman universal thread, and really nothing seemed to change the result.
I suspect that my problem is the fabric that is too thin and elastic but maybe I'm wrong, maybe I'm being overly anxious about some details. I'm not very skilled at sewing so maybe there is something I'm not doing right.

anyone have tips on that?
And, if like I suspect the problem is the fabric, do you think I could improve the result using an heavier fabric or by changing for a polyester blend or full polyester fabric?

Regards.

[Firesong]

Mara 70 , and the tera80 are thick thread (Tera 80 less so but stiffer) Sometimes normal domestic machines have problems with it. The needles you mentioned are also too small for it. With general sew thread you would be okay with those needles. It almost looks like it’s pulled the thread too tight and caused the holes (pulled them open). It’s hard to really look at the picture (focus is off) and know for sure.

[sr1355]

We use Mara100 with 90/14 needles, based on the picture and the fact it is HD1.0 I would suggest shortening the stitches to about 10-12 per inch, looks like about 6-8 per inch in the image which leaves too much room for movement between each stitch. After that dialing in the tension so the stitches are not loose would be important, you should have a bit on compression in the fabric after sewing a longer run of stitches.

[WV]

I use Tera 40 for straps and heavy sewing, Tera 60 for most other hammock sewing, and Tera 80 for really light work such as underquilts. What is putting your UQ seam under tension? Tera 80 is very fine thread and shouldn't be causing any trouble. The UQ design shouldn't have any seams that are under much tension. Firesong may be right - check your needle size. 14 should be okay. I've used 11, but prefer 14.