Dan Ronnow, I really wanted to thank you for putting this together. After having tried in the past, and failed, I was easily able to put together some quality parachutes in the last week with your instructions and some practice. After buying supplies, I'm not sure I'm saving any money with the qty that I'm actually making (I'm scrapping a lot... I'm picky!), but the sense of satisfaction makes it worth it all. My stitching skills still stink, but getting better.
Regarding the rolled hem on the skirt, my preference would be to do that after stitching the gores together to have a continuous hem. Do you see any issues with that? Ideally, I'd like to embed a thin Kevlar line inside the rolled hem, but have not figured out how. My fingers are large and clumsy.
First, you're very welcome. I'm glad this thread helped you. And you're right about the satisfaction outweighing the costs and time involved. It's really pretty cool watching your rocket come down underneath a parachute you made.
To answer your question, yes, you can roll the hem on the skirt after the gores are assembled. There's no disadvantage, at least that I'm aware of.
Regarding sewing a length of Kevlar inside that rolled hem, it isn't as hard as you might think. In fact, explaining it in text would be harder. So I broke out the sewing machine and some scrap nylon, and took pictures.
This is how I would do it [Edit] if I were doing this on my parachute, a 36-inch semi ellipsoidal. If you're using flat Kevlar, just make sure the seam is wide enough (width of the Kevlar, plus 1/8 inch on each side for the zigzag and final stitching). [/Edit]
I'm sure there are other methods, but this works, and, as I've said, it isn't that difficult.
Note that I'm using a scrap to demonstrate this, so you don't see any radial seams.
1. Start by cleaning up the raw edges of the skirt of loose threads. Ripstop frays pretty easily, and those threads can get in the way of what you're doing.
2. Flip the canopy inside out. You'll be working on the 'wrong' side (the shiny side, if it's calendered ripstop). Measure up from the raw edge the width of your finished seam. (In these pictures, it's 3/8 inch.) Using a straightedge, mark each individual gore. Don't cross the radial seam with the line.
I don't know if you've got a pen that uses disappearing ink, but they're the best thing for marking up a parachute. The ink disappears after 48 hrs.
https://www.amazon.com/Dritz-Quilting-Mark-B-Gone-Marking-Purple/dp/B001UAKKYU/
You're using this line for a reference while anchoring the Kevlar. It helps keep the Kevlar, and your stitch, as close to the center of the hem as possible.
This is a piece of 200 lb. Kevlar (about 1.2mm) in position.
If you've got a rolled hem foot, it works well for feeding the cord as you sew—exactly like anchoring shroud lines. If not, pin the Kevlar to hold it in place.
3. Before you start stitching, grab a piece of scrap and set up a zigzag stitch that has about 8 stitches per inch, with the stitch width barely wider than your Kevlar.
Important! You're anchoring the Kevlar with a zigzag stitch that doesn't pierce the Kevlar, but locks it in place with stitches alongside. (You'll tear the nylon before you pull that Kevlar loose from the zigzag stitch.)
Piercing the Kevlar, now or when you finish the seam, will dull the needle in the space of about 5 stitches.
4. Start the zigzag stitch in the center of a radial seam. Don't worry about back stitching—when you get back to this point, you'll just continue your zigzag past your starting point by about an inch.
Move slowly, watching the edge of the fabric underneath the foot, keeping it aligned as closely as possible. If you're using pins, pull them out the side right before they reach the foot.
When you reach the next radial seam, stop with the needle down, in the center of the seam, then lift the foot and turn the nylon slightly to sew the next gore. Don't try and make the turn while you're sewing.
When you reach your starting point, keep stitching for an inch past it to lock the stitch. Then lift the foot and cut the threads.
[Edit] Depending on the size of your parachute, the following may be easier to do in sections (after you've laid the entire run of Kevlar). Managing a lap full of fabric with straight pins every couple of inches might get tedious. [/Edit]
5. You're going to fold and pin the hem, one gore at a time. Fold the edge over once, the width of your finished seam, and press along the fold with your finger to crease the fabric.
Then fold it over again, crease it, then pin it.
Follow the same process for the remaining gores.
6. If you changed out your presser foot for the rolled hem foot, put the presser foot back on, and set the machine for straight stitch, 10-12 per inch, zero width.
Now sew the upper stitch, keeping the stitch about 1/16 inch from the edge of the fold. Again, don't pierce the Kevlar!
When you reach your starting point, go past it about an inch, then back stitch to the beginning.
Note: I never had much luck back stitching ripstop. It always bunched up, even when pulling the fabric through. I stop the machine with the needle down, then lift the foot and turn the fabric 180 degrees, then stitch back.
7. Now do the lower stitch, 1/16 inch from the fold, all the way around, then back stitch.
And that's about it. If you iron the skirt, make sure the iron is on a nylon/silk setting. If the plate sizzles when you touch it with a wet finger, it's too hot.
I hope this helps. If you have questions, ask away!