The following has been my experience with making a 30" elliptical parachute, from finding fabric, to choosing a machine needle and thread, adjusting tension, etc. YMMV.
The material at my local Walmart is 1.7 oz ripstop, uncalendered. This is too heavy, and because it is not calendered, air passes through the weave, reducing the drag coefficient.
I get my nylon here:
https://ripstopbytheroll.com/collec...ucts/1-1-oz-ripstop-nylon?variant=11187595457
Wide range of colors, 1.1 oz. Be sure and select 'calendered'. And unless you're buying a roll, select 'cut and folded' for shipping. Way cheaper.
Ripstop nylon is difficult to work with because it doesn't stay folded. Hemming an end, for example, you'll fold it over a quarter-inch, press it with your finger, then fold it over another quarter-inch and press it again. Then run a stitch down the center of the fold. Ironing the fold (mind the heat) isn't that much better.
I use a fabric glue pen (like a glue stick but narrow, and water soluble)—glue an edge, fold and press, glue it again, fold and press, then stitch. The glue washes out of the fabric. Just soak the finished parachute in lukewarm water for 10 or 15 minutes, then hang it up to dry.
Glue pen:
https://www.joann.com/fons-and-porter-water-soluble-fabric-glue-marker/8666794.html
FWIW, I have two different presser feet for seams—a rolled-hem presser foot and a felling foot (for the flat felled seams that join the gores)—and neither of them work very well with 1.1 oz. ripstop. They're great for denim, cotton, etc., but not nylon. So I fold and glue, then stitch with the standard foot.
Sewing a flat feeled seam with a standard presser foot:
Next comes the needle and thread. Everyone in the sport-utility fabric-sewing universe says to use a 70/10 needle for sewing ripstop. That's a very thin needle, and works well for ripstop. The problem is that they also say to use a heavy nylon thread (upholstery thread). And while it's possible to thread a 70/10 needle with upholstery thread, it will NOT feed properly. You'll tear your hair out adjusting thread tension, trying to eliminate the inevitable looping bottom stitch, when all along it's not the tension at the top rollers or the bobbin that's causing the problem. It's the thread being too wide for the eyelet in the needle.
If you're going to use heavy nylon thread, use an 80/12 needle or possibly a 90/14. But be prepared for overly large holes in the fabric. If you're going to use a 70/10 needle, use a lighter weight thread.
Also, use a 'universal' needle, not a 'ball point'.
The spill hole (apex vent, according to the purists on these boards) keeps the parachute from oscillating on descent. If you've ever wondered why the rocket circles underneath the parachute, it's because the parachute wants to 'dump' air from beneath the canopy. So it tilts to release pressure, first to one side, then the other. This swinging motion causes everything that's suspended from the parachute to circle. The longer the shroud lines and shock cord are, the wider the circle will be.
Typically, the diameter of the spill hole is 20 percent of the total parachute diameter. This seems like a very large hole in the canopy, but it's just 3 percent of the total area.
Shroud line material is a matter of preference. Some use Kevlar. That's a little stiff for me, and because I'm wrapping the parachute in a Nomex blanket, I don't need the heatproof properties. I'm using this for a 30" parachute:
https://www.amazon.com/gp/product/B07FVN9V4X/
It's braided, pliable, but strong.
The shroud line attachment to the canopy is the most critical part of sewing a parachute. If these pull loose, you're toast. The following product page from Apogee has pictures of a 36" parachute. The fourth picture shows how the shroud line is attached. Note the loop, and the stitch going through the cord, not zigzagged along the sides.
https://www.apogeerockets.com/Build...Larger-than-24in/30in-Printed-Nylon-Parachute
Here are a couple of more sites with info on making a parachute:
Basics of making an elliptical parachute (from Fruity):
https://fruitychutes.com/help_for_parachutes/parachute-help/how_to_make_a_parachute.htm
More detailed info on elliptical chute design (plus excellent diagrams on how the fabric folds for flat felled seams):
https://www.nakka-rocketry.net/paracon.html
FWIW, Nakka uses seam-reinforcing tape on all of his seams. This would be important on a heavy rocket (3+ pounds) with a large diameter chute (maybe 40" and up). My 2.6" inch scratch-built, 40" long, weighs barely a pound. I don't need the extra weight from seam ribbon.
Finally, and quite apart from making a parachute is this:
I have a similar problem with my left hand. If it's numbness (pins-and-needles feeling) in the pinky and ring finger only, it's a condition called 'ulnar compression', in which the nerve that runs past the elbow comes out of the channel that is supposed to keep it in place. The result is a constant feeling of pins and needles in those two fingers, extending down across the palm. In my case, it also leads to cramping of the hand.
There's a sleeve you can wear that restricts movement of the elbow. But it's really hard to glue rocket parts together if you can't bend that elbow. And surgery has mixed results.
I just live with it.
All of the foregoing (both parachute making and hand numbness) is my experience only. YMMV.