Hemispherical Parachute Design and Build

[kenstarr]

Built me a parachute over the weekend for my LOC Warlock. I used the famous Richard Nakka design information to spit out a semi ellipsoidal canopy as described and produced from his Excell gore generator. A big shout out to member Jquavins for inspiration and motivation to build some parachutes because it's been a handful of years since I've made any.
First step was figuring out the descent rate I needed, 20 fps at whatever weight I measured. I didn't save any of the info except the template I made.
Second step was plotting points on some paper to make paper pattern which I cut out and transfered to some 1/8" hard board.
Using my trusty Xtra cheap soldering iron filed to a knife egde I cut out 10 gores. Then I decided I wanted the top half one color and the bottom a different color... You'll note there is no seam allowance for that... My professionalism in chute construction is lacking.

See how the top doesn't line up appropriately? Live and learn. I sewed the two parts with a straight stitch then ironed the seam over flat and hit it with a zigzag that overlapped the cut edge as if with a serger even though the fabric won't fray because of getting cut with the hot knife.

Here is a completed gore.
Pretty neat!

 

[kenstarr]

I made 10 gores. Half black on bottom, half orange on bottom so I could alternate them. I started up by sewing two gores together, repeated five times. Then I sewed two of those sets together then the whole mess together. Made up a new technique. Probably not new but new to me. Each gore was sewed with a half inch seam allowance and a straight stich. Then I laid the set flat ironed the seam to one side and ran it through the rolled hem foot with a zigzag stich.
My crude drawings will probably demonstrate the results better than my lousy photography.

So it approximates a flat felled seam... maybe? Then I sewed on some shroud lines. I used 95lb cord and my customized foot for sewing on such cord.

 

[kenstarr]

Here is the finished cord attached to the canopy. Zigzag up, then zigzag back down the chosen length. I'm not worried about this being a weak point because the stitching penetrates the cord and its sewn into the middle-ish area of the rolled seam. Maybe I'm wrong but I've never had a parachute fail from shroud lines ripping off.

And finally, this was a fun picture... Took several attempts as I got tangled up in the lines trying to hold the chute.

I can also wear this as a cape for Halloween .
Well, that's all folks. If the rocket gods are willing and the creek don't rise I'll get some pictures of it in action. And if there is a catastrophic failure there will be pictures and discussion regarding lessons learned.
Ken

 

[Handeman]

Great job! I agree, the shroud line attachment points won't be a failure point.

I've made a number of chutes like this and really appreciate seeing other doing the same. I tend to enjoy building the chute as much as the rocket.

I'm sure you learned a lot about sewing the chutes and pattern making. I'm still learning more every time I build one.

Can you show a little more detail about the custom foot for sewing the shroud lines. I need to make me one or two of those also.

Thanks for the thread.

Jeff

 

[sriegel]

Great effort!

A couple ideas to ponder. When you lay out your hardboard templates, make the shape /size you want and then add a 1/2" rectangle the width of the cut to *each* piece for the seam allowance.

Your rolled and zigzag stitch should work just fine on the seam finishing. I do similar but just put a straight stitch down the outer edge of the folded over margin.

Your line attachment is spot on. I typically use 10% of the canopy diameter, up to 7", on the attachment length. I like 200 lb braided Spectra for strength and small packing.

If you leave an apex vent (I use 20% of canopy dismeter, just 4% of area), baste a 1/4" (smaller chutes) - 3/8" (6' and above) twill tape at the margin and then roll the hem. It will gather a tiny bit but makes a clean finish and is very strong.

Be careful, once you start cutting patterns it becomes addicting!

 

[kenstarr]

Here is the foot I modified to sew the canopy lines on with. It began life as a cording(?) foot. I have no idea what it's original purpose was. Look it up, it's a thing, I guess. It came in the set. It looked like it would be useful to modify to my will so I removed the little springy thing and filed a nice groove with a small chainsaw file. (they are the best round fine cut files that are easy to find!) a small zig zag stitch works great and the foot directs the cord.
Ken

 

[cls]

wow, custom sewing machine feet, you are hardcore!

 

[kenstarr]

Sriegel, thank you for the tips! I barely know what I'm doing to be honest. About 10 years ago I convinced my wife we needed a sewing machine... For parachutes. She has spent a little time on it and made some baby blankets. My knowledge has been trial and error and a few books but not really any YouTube!

 

[sriegel]

Sriegel, thank you for the tips! I barely know what I'm doing to be honest. About 10 years ago I convinced my wife we needed a sewing machine... For parachutes. She has spent a little time on it and made some baby blankets. My knowledge has been trial and error and a few books but not really any YouTube!

Feel free to shoot over questions as they arise. I got some great help from a couple folks as I got started sewing chutes, happy to pay it forward.

 

[Dane Ronnow]

Nice work on the parachute. Like @Handeman, I like making parachutes. It's very satisfying to see your rocket descending under your own handiwork.

I like what you did with the foot. I used a hemming foot to 'feed' my shroud lines, but I think yours might work better.

 

[kenstarr]

Nice work on the parachute. Like @Handeman, I like making parachutes. It's very satisfying to see your rocket descending under your own handiwork.

I like what you did with the foot. I used a hemming foot to 'feed' my shroud lines, but I think yours might work better.

View attachment 535313

I feel like I had tried this in the past with so so results. Also, your seams here look immaculate! Good work!

 

[Dane Ronnow]

I feel like I had tried this in the past with so so results.

Are you talking about using a hemming foot? Or sewing shroud lines in general?

Also, your seams here look immaculate! Good work!

Thanks! My mom taught me how to use a sewing machine when I was about 12 years old. So I had quite a bit of experience by the time I started making parachutes.

I think the key to straight stitches is focusing on the position of the edge of the fabric relative to the edge of the foot, not the center where the needle is. In the pic below, the right edge of the fabric is 1/16" from the right side of the foot. That's all I look at as the fabric moves through, keeping that distance at 1/16" (or whatever the distance might be as you set up for a seam stitch).



If you watch the center of the fold where the needle is, the fabric may move left to right, or right to left as you're feeding it front to rear, and it's harder to see that happening.

 

[kenstarr]

Are you talking about using a hemming foot? Or sewing shroud lines in general?



Thanks! My mom taught me how to use a sewing machine when I was about 12 years old. So I had quite a bit of experience by the time I started making parachutes.

I think the key to straight stitches is focusing on the position of the edge of the fabric relative to the edge of the foot, not the center where the needle is. In the pic below, the right edge of the fabric is 1/16" from the right side of the foot. That's all I look at as the fabric moves through, keeping that distance at 1/16" (or whatever the distance might be as you set up for a seam stitch).

View attachment 535377

If you watch the center of the fold where the needle is, the fabric may move left to right, or right to left as you're feeding it front to rear, and it's harder to see that happening.

Yes, I tried the hemming foot to sew on shroud lines in the past and it worked fair but not great. Thank you for the tips! Do you typically fold and iron the edges that will be hemmed?

 

[Hobie1dog]

I'm envious of your skills

 

[Dane Ronnow]

Do you typically fold and iron the edges that will be hemmed?

Always. It's the only way you can get a straight, even fold going under the sewing machine foot, which means a straight, even stitch.

Here's my method of pressing folds for hems.

First, using a straight edge ruler and a disappearing ink pen, I draw a line 7/8" in (seam allowance) from the raw edge that will be hemmed. (The strip of paper in the first pic is 7/8" wide. That's my guide for placing the straight edge.)

Then I fold the edge up to the line (a 7/16" fold), flatten it with my thumb and finger, then press it with the tip of the iron between my fingers. Then I fold it again (the second 7/16" fold) and press it.

Ripstop nylon won't lie completely flat after pressing. But it gives you a crease for easy refolding as the fabric moves under the foot.

Then run your stitch.



That was my first parachute, everything single-row stitched. Here are a couple of pics from my second parachute, double-row stitched hems and radials.



One of the most important considerations when sewing riptsop nylon, is the needle and thread. I wrestled with thread tension (causing thread to bunch on the bottom stitch) for hours, not realizing my thread was too heavy for the needle, dragging as it passed through the eye.

My stepdaughter—who forgets more about sewing than I'll learn if I live to be a hundred—pointed me to Schmetz Microtex needles (they're sharper), and Gutermann 80 thread (thin, but strong). A perfect combination for sewing ripstop.

My first thread on TRF was for a 31" ellipsoidal parachute. In addition to the step-by-step (like I've done above), I list sources for ripstop, thread, needles, pins and presser feet. Plus a video on sewing flat-felled seams.

You might be able to glean some worthwhile information there.

https://www.rocketryforum.com/threads/31-5-semi-ellipsoidal-parachute-build-part-i.164478/
(Note: I did that build in four separate threads (Part I, II, etc.) due to the 10-picture limit on TRF posts. It wasn't until later that I realized all I needed to do was add more posts to the first thread.)

Anyway, I hope this helps.

 

[Dane Ronnow]

@kenstarr -- An important note when ironing ripstop nylon: Set the iron's temperature control on Nylon/Silk. If it's too hot, the ripstop will melt. After setting the control, let the iron come up to temperature, then wet your finger and touch the plate. If it sizzles, it's too hot. Adjust accordingly.

 

[n3tjm]

Curious question; where do you guys get your nylon and chord. What thread do you use?

 

[Banzai88]

Curious question; where do you guys get your nylon and chord. What thread do you use?

Ripstopbytheroll.com for fabric and Guterman thread (good info there on how to sew the fabric, too) kite cord from Amazon.

https://ripstopbytheroll.com/

 

[n3tjm]

Oh so many choices. How do I know which one to order?

 

[Banzai88]

Oh so many choices. How do I know which one to order?

I've used just about everything from 1.9 to the lightest that they have to offer, calendered and not, coated and not. The lighter stuff is harder to handle and harder to 'tune' your sewing machine for, but packs tighter and lighter. The heavier stuff is more forgiving to work with, but the penalty is weight and volume.

The 1.6 HyperD is a good balance of the two, especially if you're just getting started as it is easier to work with than the 1.1 but is a little more forgiving of machine set up a lot like the more readily available (JoAnnes) 1.9. I've made several dozen parachutes and never seen calendered to matter one way or the other in assembly, handling, or performance.

I've tried the various high end coated varieties as well, and for a variety of reasons I don't think that they're worth the extra money for what we're doing.

As always, YMMV. Everyone has their individual preferences, and I don't think that there are really any 'wrong' answers. Each machine is a little different, as is each of our skill levels, so like most things the first one that you do will teach you just about everything that you need to know for your second and subsequent one!

ETA: over the years I've used everything from paracord to kite string for shroud lines and dollar store to high end thread for sewing. I've had a few 'off nominal' parachute deployments (both drogue and main) with my home brew creations......and with proper stitching technique, even with the lowest grade of thread or shroud lines (within reason) I'm of the firm belief (based on empirical evidence) that the fabric will fail WAY WAY WAY before the stitching or shroud lines will.

 

[Dane Ronnow]

Ripstopbytheroll.com for fabric and Guterman thread

+1 on ripstopbytheroll.com, and Gutermann thread. Here's where I got my thread (Gutermann TERA 80). It's the only place I could find it in white.

https://www.rockywoods.com/Gutermann-TERA-80-Polyester-Thread
If you're going to use TERA 80, you'll need needles that are sized for it. Schmetz Microtex size 10 are perfect. They're ultra sharp and very fine (diameter):

https://www.wawak.com/sewing/needle...-needles-15x1-130705-h-m-5pack/#sku=smns15110
Note that a common cause of improper thread tension on a sewing machine is thread that's too heavy for the needle, causing drag as it passes through the eye.

 

[kenstarr]

I haven't had to deal with it yet but adjusting bobbin tension may be necessary. I came across it in a PDF file about sewing ripstop. Can't remember what the file was titled though
Ken

 

[Dane Ronnow]

I haven't had to deal with it yet but adjusting bobbin tension may be necessary. I came across it in a PDF file about sewing ripstop. Can't remember what the file was titled though

I've got a Singer Talent 3323. It's pretty basic but the thread tensioning on it is standard across most consumer-grade machines. Here's a link to download the manual. Page 28 is all about tensioning.

(Click on Full Manual 3323)

https://www.singer.com/search/support?title=Talent 3323
I would recommend loading the machine with any kind of thread that will pass through the eye of your needle easily, with no drag at all. Then adjust tension. Run test stitches on the same ripstop you'll be using for your parachute.

Also, with ripstop, or any other coated nylon, you're not sewing through fabric as much as you're poking holes in a bread bag. (In fact, when the needle gets dull (around 3-4 hrs of stitching with the #10 Microtex), you can hear it go pop-pop-pop-pop as you're running a stitch.) So you want to keep your stitches loose (I run them at 8 per inch). Too tight, and you've got what amounts to perforations running up the canopy, two rows for each gore.

I used 1.1 oz riptop from RBTR, Schmetz Microtex 10 needles, and Gutermann TERA 80 thread, on two 36" ellipsoidal parachutes I've made, all sewn with 8 stitches per inch (loose for any other fabric). And unless I get into super heavy rockets—and I won't—I have no reason to do it any other way. Once you get used to sewing ripstop, sewing gores for a parachute is pretty painless. I wouldn't call it a breeze, but I'm never swearing at my work.

 

[cls]

Lots of good advice here about setting up the machine. Thread, sharp needle, stitches per inch, how to lay the shrouds in the hem.

I found the foot pressure is critical to get right. Usually takes a few runs with scraps to get it to work nicely. Too light, the ripstop just slides around, too heavy, it bunches up and jams.

I preferred using the French foot for a neater hem with no fraying strings, but when I'm lazy the straight foot is good enough.

I've tried ironing the hems, tacky glue, and pins. Ripstop is slippery stuff, all of those help but nothing works really well.

Edit: my experience from the good old days when my eyes and fingers worked..