Construction of 14 gore 44" semi hemispheric chute

So I needed a bigger parachute for my rocket, so decided to construct one myself. By myself I mean supervise/assist/irritate one of the female species in my house.

The raw ripstop:


After the gores are cut:


Sewing in progress:


Matching shroud lines:


More to come...

Go Georgia! I would recommend that you baste these together with a hot knife before sewing. That way the ripstop doesn't slip and everything get out of line. You also can have someone basting sections together while you sew them and assembly goes fast. I made a 16' modified toroidal parachute for a local college competing in ESRA this year and with three people we were able to cut, baste and sew the gores together (18 gores) in just under three hours.

Edward

Looking good, I get my wife to sew them for me, she make me cut them out. The reason she sews them is she treasures her sewing machine. My last chute was a 15 gore 60" for my L2 rocket in Red, White, and Sage Green, it was an experiment in using an odd number of gores. It works great but is not as easy to pack as a even number of gores due to having two groups of shroud lines after flaking the chute, instead of all lines in one group off one corner of the flaked gores.

Is there a reason you all are using so many gores on these smaller parachutes? About 8 years ago I compared the descent rates of 96" parachutes (semi-ellipsoidal) that had 8 gores, 12 gores and 16 gores. They all used 16 shroud lines. I could tell no difference in the descent rate calculated using the same drop weight. The important factor was using the same number of shroud lines to form the canopy better. It also resulted in a lot less sewing.

Edward

AlphaHybrids said:

Is there a reason you all are using so many gores on these smaller parachutes? About 8 years ago I compared the descent rates of 96" parachutes (semi-ellipsoidal) that had 8 gores, 12 gores and 16 gores. They all used 16 shroud lines. I could tell no difference in the descent rate calculated using the same drop weight. The important factor was using the same number of shroud lines to form the canopy better. It also resulted in a lot less sewing.

Edward

Click to expand...

Looks mainly for me, I like the look of a parachute with more gores but not so many they are hard to sew.

Two things for me. First, I printed out the pattern with 8.5x11 paper, each gore maxed out the width. I could tape more and more pieces together, but this allowed good use of the fabric also, allowing eight gores on a single yard of fabric.

Using fabric efficiently is one of my goals as well. In 2002 when I started in HPR I was sewing semi-ellipsoidal parachutes. Then I went through a phase where I didn't like sewing all the gores and developed a pattern for three piece hemispherical parachutes. Then I worked with a high school group and got back interested in parachutes with gores. I figured if I was going to sew all those gores together I'd like the most efficient design and settled on a modified toroidal parachute. With that shape it allows you to mirror two-three gores on the standard width of nylon (58" wide) It also is nice because when you cut down the side of one gore you are cutting the opposite side of the other. For a while I was doing fancy laser cut gores, but then as the gores got larger I went back to CNC cut masonite patterns. It goes fast if you have two or three people you can get it all sewn in a night. The shroud lines, however, are more time consuming. At one time I used to sell the patterns for different parachutes plotted on plotter paper. You could glue that to a sheet of masonite and cut your pattern from that.

Edward

Glad to see you making your own chutes. That is something I enjoy and I don't think I've ever bought a chute, other than what comes in a kit. In my house, I'm the only one that knows how to use the sewing machine.

A few things I've learned along the way is to cut out the nylon with a hot knife. I used a scissors for the first chute I made and after a cow chewed on it and got it soaked with slobber, it disintegrated in the wash machine because the edges frayed and the seams all came apart. Using a hot knife melts the edges together and prevents fraying of the edges.

Another thing you want to watch is the direction of the weave. I always use the same weave direction for each gore. I keep the center-line of pattern parallel to the direction of the weave. This means there is less stretch and shock resistance in the gores when the chute opens than if you cut your material on a 45 deg. bias. Cutting on the bias will use more material, make it harder to assemble, but make the chute able to withstand high speed deployments better. However you decide to cut your material, you should make sure all the gores are cut on the same angle to the weave.

Here's a link to my largest chute build, Build Thread - 9 ft, 24 Gore, Semi-Elliptical Chute. I had a conversation with my baby brother, who was a licensed parachute rigger about this chute. He said I did a great job, but a 6" zig zag of the shroud line to the gore seams would have worked fine for a chute used in a rocket with our low deployment speeds, <100 ft/sec. I've been to using a 2" to 4" zig zag to attach shroud lines to smaller chutes. I may go as high as 6" in the future if I build another chute over 8 - 10 feet in diameter.

As for making the chute with many gores, I agree, using lots of gores just looks a lot cooler and is worth the effort. After all, it's a hobby and you should be spending time doing what you enjoy. If that means spend 2X or 3X as much time building the chute you want, so be it.

Good Luck

Ended up doing 16 gores for even shroud lines between orange and black.

What/how did you trim the edge? Looks like a black strip with orange thread/twine on the edge.

Decorative piping found at the local quilting shop, as soon as I saw it I grabbed it

I'll have to look for some next time I build a chute.

Thanks...

For the edges you can also make bias tape out of ripstop nylon. I use a 2" wide strip and it gets folded in a bias tape maker to a strip 1/2" wide. The strips generally come from the excess of the parachute.

Edward

I use a rolled hem foot for my edges

Using the rolled hem foot is pretty awesome too. I used a 5mm rolled hem foot to great success

Yeah, it can be a pain to get it started, but once you figure out a technique that works for your project and material, it's a pretty slick toy. I got mine for my wife's machine from Ebay/China and waited several weeks for it to get here, but it turned out to be well worth the $5.

By the way, that's nice work on the parachute! I have similar pictures of me running and jumping with an 8 gore 36 inch elliptical that Handeman provided some advice and guidance on!

I'll be starting a parafoil here soon to color match this parachute. I'm still trying to find some math for parafoil size to drag ratios. I might end up using comparable area to a flat parachute to start. Of course the shroud lines on a parafoil get more interesting.

I also made a 4 gore 12" 50%ish hemispherical parachute for a little action figure to come down on as well

Jeffmhopkins said:

I'll be starting a parafoil here soon to color match this parachute. I'm still trying to find some math for parafoil size to drag ratios. I might end up using comparable area to a flat parachute to start. Of course the shroud lines on a parafoil get more interesting.

I also made a 4 gore 12" 50%ish hemispherical parachute for a little action figure to come down on as well

Click to expand...

Umm....steerable? Otherwise, doesn't that have the potential to fly your rocket into the next county? Where does one find a reliable pattern for such coolness?

Yes steerable. I already have a parafoil from Hobby King, but I want a different more robust design, not to mention color matching. I'll base the design from other kite and full size parachutes.

More information at my project page:https://hackaday.io/project/6381-high-power-experimental-rocket-platform

Here's the 4 gore 12" hemispherical parachute:

Jeffmhopkins said:

I'll be starting a parafoil here soon to color match this parachute. I'm still trying to find some math for parafoil size to drag ratios. I might end up using comparable area to a flat parachute to start. Of course the shroud lines on a parafoil get more interesting.

I also made a 4 gore 12" 50%ish hemispherical parachute for a little action figure to come down on as well

Click to expand...

I didn't have any drag number when I made my 7-cell parafoil, but looking at man rated chutes, the beginner/training chutes are sized at 1/2 lb per square foot. The expert chutes are sized at 2 lbs per square foot. I made mine at about .6 lbs/sqft. YMMV

That's a good starting point. I'm looking at doing a 5'x2.5' 6 cell parafoil right now, seems like a decent size. The rocket right now is looking at about 6lbs loaded.