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# Thread: Simple, Efficient DIY Chute

1. ## Simple, Efficient DIY Chute

Today my chute material arrived for my L/M project. It was pretty inexpensive, less than 10 bucks for 2 yards of 68" wide fabric:

http://www.efabricsupplier.com/product_p/269.htm

I have made 20" 24" and 35" chutes with this method before, but tonight I did most of the work of making a 65" chute. I'll sew on attachments for the risers tomorrow.

The design is to start with a single, full-size circle of fabric, and make some pleats to turn it into a 1-piece hemispherical chute. This design has minimal seams and no hems, so it's quick, easy, and packs very small. To get started:

I taped the fabric flat down onto the floor, and with my daughter's help, traced out a big circle:

Next I folded the canopy in half, marked 2 chute attachment points, folded it again and marked a couple more points, and then folded it in 45 degrees to mark 4 more points:

I also marked the center point, and used that later to help fold the circle between the center and the chute attach points.

I cut out the circle using a soldering iron. This melts the edges, so it won't fray and I didn't have to waste any time or packed volume on hems.

I brought it back in, folded it in half, and drew the shape of the cutout that I put at each of 8 chute riser attachment points:

I had calculated the amount I wanted removed from the circumference to get a hemisphere. For this example it worked out that I take out about 65" from the circumference. I haven't checked the algebra to verify that you would always subtract one diameter from the circumference, but that's probably it. I divided that among 8 shroud line attach points and folded that in half to determine where the line ends on the circumference. I knew that the seam should be nearly perpendicular to the circumference at that point.. I also knew from experience that I wanted the tuck to end about 2/3 or 3/4 of the way to the center, and that part of the line starts tangent to the fold. Then I just freehanded the line as a smooth curve in between. I drew all the seam lines and pinned them all so that I could open up the canopy to verify I didn't make a factor of 2 error anywhere. It looked good, so I got to sewing.

I set the machine for close stitching, in hopes of creating a stronger seam that way. It was just a simple stitch along each of those 8 seam lines, and then I got this:

It will be a nicer-looking hemisphere when the risers are attached, the pleats are cut off, and some wind is inflating it, but at least you can get the idea here of how the pretty-close-to-hemispherical shape was achieved.

Then I just took the canopy back out to the porch and trimmed off those tucks with my soldering iron, and the canopy is done. Look how small it packs down. That's a 65" chute, minus the risers. In the background are the cut-off pleats.

So there you go. A 65" chute canopy for \$10 in materials and about 3 hours of work, that packs smaller than anything I know of on the market right now.

Tomorrow I'll make the shroud line attachments. For smaller chutes I just sew the shroud lines on directly, but for this one I want to use 100 lb Kevlar which is a challenge to line up because the lines are so thin, and I want it built strong enough for a high-speed deployment.

2. Very nice. I may give that a try. I'd been considering ways to make a simple parachute instead of a parasheet.

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Very nice work Adrian. I like the simplicity of it. What do you think of the material?

As for stitching I typically use 8 stitches per inch - closer and you get the perforated paper effect if something happens. It tears easily along the lines.

Somewhere I probably have the formula for the curve you'd need to create to hem along where traditional gores would be. Then you could use a piece of masonite to heat seal the edges together and cut, then sew it. I use a heat gun all the time to tack parachutes together for sewing.

Edward

4. Originally Posted by Adrian A
For smaller chutes I just sew the shroud lines on directly, but for this one I want to use 100 lb Kevlar which is a challenge to line up because the lines are so thin, and I want it built strong enough for a high-speed deployment.
I couldn't get a good look at your seams, but I would suspect that since you didn't fold over the flaps and do a second line of stitching (a hem) that the seams will give out in a high speed deployment before the shroud lines will let go. That isn't all bad.

BTW, looking at the arc you had on the paper you used for the seams, if you arc it in the other direction, you will get more of a elipical shape for your chute.

Looking forward to a few pics of it in use.

5. ## No such thing

Originally Posted by foamy
Very nice. I may give that a try. I'd been considering ways to make a simple parachute instead of a parasheet.
No such thing as a "parsheet"

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Jazz - it seems you are adamant about the parasheet thing. Care to expound?

Edward

7. The chute is complete now. The only thing special that I did for attaching the risers was hem them in for about a foot up the canopy. I'm kind of wishing now I had used the 300 lb cord, just because I would have gotten in a lot more hits with the needle. But each attachment at least has survived a vigorous pull test.

The chute packs into 4.5" of my 1.75" ID chute holder tube.

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Looks very nice Adrian. The bottom picture is dying for a caption contest

Do you have a cording foot?

You thread the cord through and it keeps it lined up with the needle.

I generally put my shroud lines up about 9", they pull out at 75 pounds, so I rate them for 25 pounds with a 3:1 safety factor. I figure when you have 12 shrouds that if you rip all of them out on a 10 pound rocket something is amiss.

Edward

9. Originally Posted by AlphaHybrids
Looks very nice Adrian. The bottom picture is dying for a caption contest

Do you have a cording foot?

You thread the cord through and it keeps it lined up with the needle.

I generally put my shroud lines up about 9", they pull out at 75 pounds, so I rate them for 25 pounds with a 3:1 safety factor. I figure when you have 12 shrouds that if you rip all of them out on a 10 pound rocket something is amiss.Mink

Edward
That cording foot looks like a good idea. I'd take a closeup picture of my shroud line attach stitching but I'm afraid it would break my camera, and I wouldn't want anyone to lose their lunch.
Last edited by Adrian A; 1st October 2011 at 06:08 PM.

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I had to modify the toroid to have 3 panels (and 3 seams) because 2 just wasn't cutting it. I'm going to seal the panels together with the hot knife I have, then I will just use a single row of stitching like you use. Should have 7 lines on it. I'll post some pictures when it's done.

Edward

11. ## Parasheet

Originally Posted by AlphaHybrids
Jazz - it seems you are adamant about the parasheet thing. Care to expound?

Edward
Yes I would.
The word parachute comes from two French words Para, wich means shield or protection from, and chute wich basicly means fall.
So any object that slows the fall of another object could technicaly be called a parachute.
The parasheet term is a misnomer, Stine says that a true parachute can not be laid out flat. This is UNtrue, the 28 foot C-9 and the 24 foot T-10R are FLAT circular parachutes. I work on these all the time, I even own some of my own.
Incedentaly the hemispherical chute is not Ideal either, it's drag coefficient is only .62 to .77. Flat circular is .75 to .80. The most efficient is thr tri conical at .80 to .96 but the regular conical is easier to make and is at .75 to .90.

I hope this helps

12. Senior Member
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But of course none of those even come close to the drag coef. of any sort of para-glider type chute. I'm surprised there hasn't been more testing in that direction by hobbyists.

All that aside, that looks like a great chute. I really need to get myself a new soldering iron and give the hot knife cutting a try. Hemming the seams on my last parachute was SUCH a pain, and really kept it from packing up small.

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If you have a rolled hem foot - you can easily finish seams on parachutes. It makes is very easy.

I think one reason we don't see a lot of para-glider/ram air chutes is that they induce a good forward speed on a rocket and they can travel. I've had rockets drift 3 miles with a little wind, imagine if they had a 10 fps forward velocity even in a calm day. A rocket that goes to a mile descending at 20 fps would glide a half a mile.

Edward

14. Senior Member
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Originally Posted by AlphaHybrids
If you have a rolled hem foot - you can easily finish seams on parachutes. It makes is very easy.
My sewing machine is a singer at least 50-60 years old that came without a manual, so feet are beyond my capabilities...

Originally Posted by AlphaHybrids
I think one reason we don't see a lot of para-glider/ram air chutes is that they induce a good forward speed on a rocket and they can travel. I've had rockets drift 3 miles with a little wind, imagine if they had a 10 fps forward velocity even in a calm day. A rocket that goes to a mile descending at 20 fps would glide a half a mile.
I challenge you to make anything so precise that it will fly in a straight line. I made a glider once that few as straight as I possibly could trim it in my back yard, but it still flew in circles with a radius of only a hundred feet or so. Either way, the circles the paraglider will fly in are far less than the distance it will drift, and there is a 50/50 chance it will actually reduce your walk.

15. Originally Posted by Lentamental
I challenge you to make anything so precise that it will fly in a straight line. I made a glider once that few as straight as I possibly could trim it in my back yard, but it still flew in circles with a radius of only a hundred feet or so. Either way, the circles the paraglider will fly in are far less than the distance it will drift, and there is a 50/50 chance it will actually reduce your walk.
Good point. I hadn't thought of it that way before. Kind of a crap shoot, though. Also, I worry about ram air chutes getting tangled. One I have has lots and lots of shroud lines. Obviously, skydivers have figured out how to do it reliably, but I'm not sure it scales down to smaller chutes.

Also, horizontal velocity at landing tends to be worse than vertical velocity from a damage perspective. Some horizontal velocity is unavoidable, but adding some intentional velocity onto that could make a big difference. I'd like to see someone give this a try though, and report back on the experience from a few flights.

16. Where did you get the 65" material to start with?***edit.. The shinney object posted by Edward distracted me from that link.. -- Super cool chute***
Novel, I am tired of "over-built" chutes, they are expensive to replace too...

This wont hurt the pocket if it frazzles...

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I've gotten 72" wide material before and you can order it up to 100" with 1" selvages if you get it from the mill.

I guess you could do three stage recovery. Drogue at apogee, then at 2000' you could deploy the Ram air canopy. Then at 200' drop that and go with a normal parachute for zero vertical velocity.

Edward

Adrian, I've got the tiny toroid done. We'll see how it goes.
Last edited by AlphaHybrids; 5th October 2011 at 09:38 PM.

18. Originally Posted by Lentamental
I challenge you to make anything so precise that it will fly in a straight line. I made a glider once that few as straight as I possibly could trim it in my back yard, but it still flew in circles with a radius of only a hundred feet or so.
I had and Estes Eagle boost glider. I had more trouble making it go in a circle then a straight line. Flew it on a B motor once and it popped below 300ft and landed a 1/4 mile away. Flew staight as an arrow and very level.

19. Originally Posted by jazzviper1
No such thing as a "parsheet"
Many words in common use are portmanteaus (no, not the luggage...). So a "parasheet" would be perfectly cromulent. I've made what I call a "hankerchute". It's a reference to when I was a child and made parachutes from handkerchiefs. I used a square piece of ripstop nylon and tied 250lb nylon cord to each corner. Unfortunately, ripstop nylon is not heat-proof and it was melted/fused in a CATO.

20. New Member
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Originally Posted by sooner.boomer
Many words in common use are portmanteaus (no, not the luggage...). So a "parasheet" would be perfectly cromulent.
My lexicon has been increased... Although, cromulent is not in Merriam-Webster's...
Last edited by frankgh; 8th October 2011 at 04:10 PM.

21. Originally Posted by frankgh
My lexicon has been increased... Although, cromulent is not in Merriam-Webster's...
http://dictionary.reference.com/browse/cromulent

22. ## What? It NEVER comes down?

It just stays there at 200 feet?

Originally Posted by AlphaHybrids
I've gotten 72" wide material before and you can order it up to 100" with 1" selvages if you get it from the mill.

I guess you could do three stage recovery. Drogue at apogee, then at 2000' you could deploy the Ram air canopy. Then at 200' drop that and go with a normal parachute for zero vertical velocity.
Edward

Adrian, I've got the tiny toroid done. We'll see how it goes.
I know, I know, you meant 'horizontal' velocity.
Just couldn't pass it up.

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