31.5" Semi-Ellipsoidal Parachute Build [Part III]

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Dane Ronnow

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[Continued from Part II]
(https://www.rocketryforum.com/threads/31-5-semi-ellipsoidal-parachute-build-part-ii.164479/)

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The rolled side of the fold (on the orange piece) is visible through the white piece. The stitch will run just inside that rolled edge. Use the existing stitch (on mine, it's joining the orange and white pieces) as a reference point to keep your stitch straight. Line it up with some part of the foot, then focus on that as you feed the fabric through.

Important! For rockets weighing more than 2 or 3 pounds, I would add a second row of top stitching, 3/16" from the first.

The right side of the finished gore pair:

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A close up of the right side seam:

18.jpg


And the seam on the wrong side:

19.jpg


The seam at the spill hole:

20.jpg


Important! Rather than sewing a finished gore to the gore pairs already assembled, building the parachute bigger as I went along, I sewed all of my gores in pairs, then sewed the pairs together. The reason for doing this was that if I messed up a length of stitching—for example, finishing the gore pair only to discover you had the shiny side up instead of the dull side—it minimized the amount of work I had to redo. (I made that mistake.)

Keep this in mind:

If you're sewing denim and you mess up a stitch run, you simply cut the first stitch with a seam ripper, then pull the thread loose. When that's done, you can't see where the stitch was because of the weave of denim.

If you do that with ripstop, the first thing you'll notice when you pull the thread loose is a row of holes that are essentially a perforation. That perforation on a finished parachute is where the fabric will separate under the stress of deployment.

In other words, if you mess up a length of stitching, you toss that piece of fabric and start over. If you're sewing gore pairs first, the most you waste is one gore pair. If you're building on the previous gore pair by sewing the next one to it, you can't throw out the one you messed up because it's attached to a previous pair, and so on, and so on.

The only thing you can do in that situation is to cut the bad seam off the gore, then redo the seam, making that gore slightly narrower.

That said, assemble the remaining gores following the steps above. If you're building a large parachute, it gets a little unwieldy once you get half the parachute assembled and you're trying to stuff it through the machine opening to lock a stitch.

When you reach the last flat-felled seam, join the two ends of the canopy and sew it just like the previous ones, paying attention to right sides and wrong sides.

Here's my completed canopy:

21.jpg


Notice the seam at the 7 o'clock position. It's the only orange top seam on the whole canopy. It was the last seam, and I wasn't paying attention to right sides and wrong sides. (If you're wondering why the gores are different widths at the spill hole, it's because the white fabric was always on top of the seam (except for that one), rather than alternating.)

At this point, take a break. Relax. Have a beer or three. Post a pic of your finished canopy.

[Continued in Part IV]
(https://www.rocketryforum.com/threads/31-5-semi-ellipsoidal-parachute-build-part-iv.164482/)
 
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