My DIY Disk Gap Band Parachute Obsession

[Yukon@K-9 Rocket Tech]

In middle school I got into sewing because tents and sleepingbags were too expensive. I kept breaking my home sewing machine at home (taking it apart once a week and fixing it was no fun), so my Mom got me a heavy duty. I introduce you to the Humvee of sewing machines, the Thread Injector (obviously not the actual name). From then on have been testing and sewing parachutes for a while and it's a lot of fun. I got hooked to disk gap band parachutes after seeing the curiosity rover EDL. My first few iterations were pretty crappy, but I have learned a lot about suspension design, methods to deploy better, and ways to make it lighter and stronger. The Red and Blue one was what I call the first successful design. The rest are unusable really. I plan to fly these soon! Also I want to start making some bigger chutes

 

[boatgeek]

Nice work! I love a good solid sewing machine. I'm currently using my mom's early 1960's-era Kenmore, which is built to make a family's clothes for a year without taking a break. Bear in mind that a good machine like that can do some serious damage to your finger if you get it under the needle. Ask me how I know.

 

[ThreeJsDad]

I am not 54 and when in middle school I helped the teacher teach the Home-Ec class because I sewed so well....LOL

I have lost track of how many machines I have burned up. The old Kenmore's were work horses. I have one that needs some TLC that is more than I want to take on. For now my daughter and I are limping along with her Brother.

I have sewn professionally for both a drapery firm and a sail maker. Commercial machines are really scary at first due their speed and how much material they can drive a needle through. Sewing the corner patches on a large spinnaker was a real wake me up kind of moment.

 

[ThreeJsDad]

In middle school I got into sewing because tents and sleepingbags were too expensive. I kept breaking my home sewing machine at home (taking it apart once a week and fixing it was no fun), so my Mom got me a heavy duty. I introduce you to the Humvee of sewing machines, the Thread Injector (obviously not the actual name). From then on have been testing and sewing parachutes for a while and it's a lot of fun. I got hooked to disk gap band parachutes after seeing the curiosity rover EDL. My first few iterations were pretty crappy, but I have learned a lot about suspension design, methods to deploy better, and ways to make it lighter and stronger. The Red and Blue one was what I call the first successful design. The rest are unusable really. I plan to fly these soon! Also I want to start making some bigger chutes View attachment 409387View attachment 409388View attachment 409389

That is solid machine, They are often used in class rooms because they hold up to the abuse.

Nice work on your chutes.

A couple of years back my son and I found plans for full size paraglider wings. One of these days we will build them. I have enough fabric but we just don't have the time...

 

[Yukon@K-9 Rocket Tech]

Nice work! I love a good solid sewing machine. I'm currently using my mom's early 1960's-era Kenmore, which is built to make a family's clothes for a year without taking a break. Bear in mind that a good machine like that can do some serious damage to your finger if you get it under the needle. Ask me how I know.

I love those old machines! Built like a tank! Also oh gosh... I do not want to imagine. I'll be very careful

 

[Yukon@K-9 Rocket Tech]

I am not 54 and when in middle school I helped the teacher teach the Home-Ec class because I sewed so well....LOL

I have lost track of how many machines I have burned up. The old Kenmore's were work horses. I have one that needs some TLC that is more than I want to take on. For now my daughter and I are limping along with her Brother.

I have sewn professionally for both a drapery firm and a sail maker. Commercial machines are really scary at first due their speed and how much material they can drive a needle through. Sewing the corner patches on a large spinnaker was a real wake me up kind of moment.

Thank you! Yes I've seen the singer heavy duty at a lot of classrooms too. The machine I used before was a Brother too, the new ones with the computer built in so it auot stitches patterns. Not a fan because it jams pretty well and can't handle parachute sewing too well. I have seen industrial sewing machines and people using it in person. Yes they're so scary! It sounds like a minigun going off

 

[boatgeek]

I love those old machines! Built like a tank! Also oh gosh... I do not want to imagine. I'll be very careful

There's no plastic on my machine except on the knobs. Definitely a tank. It can send a needle through your finger, which is ... not comfortable. But mine healed up pretty quickly. Just keep your fingers out of the line of fire and you'll be fine.

 

[mbeels]

That parachute looks great, nice work! What is the advantage of the gap band parachute (besides looking cool)?

 

[Yukon@K-9 Rocket Tech]

That parachute looks great, nice work! What is the advantage of the gap band parachute (besides looking cool)?

Thank you! The benefit is it has a balance of drag and stability. Although not as much drag as a traditional chute, it's far more stable due to that huge gap around the entire chute. This allows air to evenly flow straight throuh the gap and increases stability. Occilation is significantly reduced with even air flow venting out. Also compared fo other chute designs with these characteristics, its simple and close to a traditional parachute. So it's easy to deploy easily and pack. The major advantage comes at supersonic airspeeds, but it's still cool to be using if at the model scale!

 

[Yukon@K-9 Rocket Tech]

There's no plastic on my machine except on the knobs. Definitely a tank. It can send a needle through your finger, which is ... not comfortable. But mine healed up pretty quickly. Just keep your fingers out of the line of fire and you'll be fine.

No Fingers Beyond Yellow Caution Line

All jokes aside, I haven't got my finger poked by the needle (and I wish to keep it that way), but I have had my finger get pinched between the foot rasing mech. Anyway I think as long as the user pays attention to the buisness end, it's pretty safe.

 

[boatgeek]

No Fingers Beyond Yellow Caution Line

All jokes aside, I haven't got my finger poked by the needle (and I wish to keep it that way), but I have had my finger get pinched between the foot rasing mech. Anyway I think as long as the user pays attention to the buisness end, it's pretty safe. View attachment 409405

You're in the right track! I was running fast and held the fabric all the way into the machine. Fortunately, you only do that once.

 

[ThreeJsDad]

In 40+ years I have no stitched my finger but I have gotten a good thump from the screw that locks the needle in place.

 

[ebruce1361]

First of all, @Yukon@K-9 Rocket Tech I love that name! Thread Injector!

I REALLY need to upgrade my machine. I began experimenting with sewing my own parachutes last summer, and I have learned enough to know that I have a lot to learn. One thing is certain, my wife's $60 Brother from Walmart isn't going to last me long (she bought it specifically to make one outfit a few years back, so not much of an investment).

I've been wanting to get into more complex designs such as gap band, toroidal, and ringslot parachutes, as well as play with reefing. So far, I have made six 21 inch parachutes with 20 gores each, and re-purposed an 8 gore umbrella into a 42 inch parachute. With the umbrella one, I made sure to go over each seam again because I don't know if I could trust the original stitching to withstand the forces of deployment, and then I tried to add a 2 inch band to the bottom. It *kinda* looks like yours, but will undoubtedly work as well as yours. Here are a few screenshots of a test video I tried to do on a gusty day. Perhaps you might have some observations or tips on how I can get the band to behave better?

 

[Senna]

In middle school I got into sewing because tents and sleepingbags were too expensive. I kept breaking my home sewing machine at home (taking it apart once a week and fixing it was no fun), so my Mom got me a heavy duty. I introduce you to the Humvee of sewing machines, the Thread Injector (obviously not the actual name). From then on have been testing and sewing parachutes for a while and it's a lot of fun. I got hooked to disk gap band parachutes after seeing the curiosity rover EDL. My first few iterations were pretty crappy, but I have learned a lot about suspension design, methods to deploy better, and ways to make it lighter and stronger. The Red and Blue one was what I call the first successful design. The rest are unusable really. I plan to fly these soon! Also I want to start making some bigger chutes View attachment 409387View attachment 409388View attachment 409389

In middle school I got into sewing because tents and sleepingbags were too expensive. I kept breaking my home sewing machine at home (taking it apart once a week and fixing it was no fun), so my Mom got me a heavy duty. I introduce you to the Humvee of sewing machines, the Thread Injector (obviously not the actual name). From then on have been testing and sewing parachutes for a while and it's a lot of fun. I got hooked to disk gap band parachutes after seeing the curiosity rover EDL. My first few iterations were pretty crappy, but I have learned a lot about suspension design, methods to deploy better, and ways to make it lighter and stronger. The Red and Blue one was what I call the first successful design. The rest are unusable really. I plan to fly these soon! Also I want to start making some bigger chutes View attachment 409387View attachment 409388View attachment 409389

Dear Yukon,

We are students from the TU Delft, currently working on a project called the Small Rocket Project. In this project, we are trying to launch a rocket with an egg up to 1 km, with the goal of later retrieving the egg AND rocket safely. To achieve this, we have decided on crafting a disk gap band parachute for the egg. Before we start working on this, we were wondering if we could ask you some questions.

Approximately how long did it take you to create the parachute? Since we only have a selected period of time to complete the project.

What schematics did you use for the parachute? And do you have a rough estimation of the drag coefficient?

Thank you so much for sharing your DIY, and we hope to be hearing from you soon!

Greetings,
Senna Hoornstra, Anna Stolk, Jadon Cooper, Dimi Istomin, Primož Perko, Max Raonic

 

[Handeman]

You resurrected is a 3 year old thread, and @Yukon@K-9 Rocket Tech hasn't been on the forum in 5 months so I doubt you will hear anything.

You can probably get all the info you need from the Parachute Recovery Systems Design Manual. Just click the "View the full text of this report" link and you can save the .pdf file.
This THE AERODYNAMICS OF PARACHUTES may also help.

Try searching on "aerodynamics of parachutes" in the DTIC page and you can find both those documents and more.

From the looks of Yukon@K-9 Rocket Tech ring gap parachute in post #13, I would say he doesn't have enough gores and the gap is too big.

The Disk Gap Band parachute is designed for supersonic deployment of thin bodies. I think the original was made for probes going into Mars atmosphere.
a search https://duckduckgo.com/?q=disk+gap+band+Parachutes&t=chromentp&ia=web will give you more info.

 

[boatgeek]

Dear Yukon,

We are students from the TU Delft, currently working on a project called the Small Rocket Project. In this project, we are trying to launch a rocket with an egg up to 1 km, with the goal of later retrieving the egg AND rocket safely. To achieve this, we have decided on crafting a disk gap band parachute for the egg. Before we start working on this, we were wondering if we could ask you some questions.

Approximately how long did it take you to create the parachute? Since we only have a selected period of time to complete the project.

What schematics did you use for the parachute? And do you have a rough estimation of the drag coefficient?

Thank you so much for sharing your DIY, and we hope to be hearing from you soon!

Greetings,
Senna Hoornstra, Anna Stolk, Jadon Cooper, Dimi Istomin, Primož Perko, Max Raonic

If you have a limited amount of time, you will probably be better served to make an 8-gore semi-elliptical parachute with a spill hole. That will be plenty of difficulty to design and make, but you can also make it in a weekend or two.

 

[sriegel]

Dear Yukon,

We are students from the TU Delft, currently working on a project called the Small Rocket Project. In this project, we are trying to launch a rocket with an egg up to 1 km, with the goal of later retrieving the egg AND rocket safely. To achieve this, we have decided on crafting a disk gap band parachute for the egg. Before we start working on this, we were wondering if we could ask you some questions.

Approximately how long did it take you to create the parachute? Since we only have a selected period of time to complete the project.

What schematics did you use for the parachute? And do you have a rough estimation of the drag coefficient?

Thank you so much for sharing your DIY, and we hope to be hearing from you soon!

Greetings,
Senna Hoornstra, Anna Stolk, Jadon Cooper, Dimi Istomin, Primož Perko, Max Raonic

Hi.

Your project sounds very much like The American Rocketry Challenge (TARC) with flying an egg to a specific altitude.

My TARC students use simple octagonal flat sheets, maybe 15"-22" depending on how fast they need to come down, with lines at the corners. They cut the lines so they extend 1.5x the canopy diameter from the corner to the bridle. They also cut a roughly 2" vent in the center of the chute. These have worked very well for them and are quick and easy to make. The Cd is 0.75.


If you want a fancier chute, Richard Nakka has a nice spreadsheet that will generate the gore shape for ellipsoid (domed) parachutes with Cd of 1.5. I use that for my own chutes. You can choose the number of gores and diameter. I like 12 gores but you can do fewer. The spreadsheet then generates the X,Y coordinates of the shape. I plot the points on cardstock, add seam allowance, and then use that master pattern piece to create a wooden cutting template. I trace the cutting template with a hot soldering iron to cut out my nylon fabric. I've made chutes from 12 inches to 18 feet across with this method.

Feel free to message with questions and good luck on your project.

Steve

 

[sriegel]

Couple of additional notes. The Cd I quote requires you to know the "reference area" for the number. In the flat sheet, it's just the area of the sheet. For the ellipsoid, it's area of the main opening, pi*r^2 where r is the constructed radius of the chute. This makes is easy to calculate your drag based on changing the diameter of the chute.

Some sources always reference back to the actual fabric area of the canopy, regardless of shape, as a way of trying to normalize Cd comparisons. Just be aware of what reference area is being discussed when you compare different styles of chutes!

Steve

 

[Blast it Tom!]

Couple of additional notes. The Cd I quote requires you to know the "reference area" for the number. In the flat sheet, it's just the area of the sheet. For the ellipsoid, it's area of the main opening, pi*r^2 where r is the constructed radius of the chute. This makes is easy to calculate your drag based on changing the diameter of the chute.

Some sources always reference back to the actual fabric area of the canopy, regardless of shape, as a way of trying to normalize Cd comparisons. Just be aware of what reference area is being discussed when you compare different styles of chutes!

Steve

Not to derail, but that's always been kinda my thing - Cd should be based on the form, "A" by the dimension of that form, so that your drag is always a product of the coefficient and the area. That's tough as you note, some using the actual fabric area and some the planar area of the main opening. I've picked here and there at trying to get a comparison between the flat sheet and Nakka semi-ellipsoidal so that I could say, for example, "This rocket is supplied with an 18" hexagonal flat sheet chute, therefore I need an "x" inch semi-ellipsoidal. But I think I've had to default to, "Supported weight is so-and-so ounces (or grams), therefore I need an "x" inch semi-ellipsoidal 'chute.

 

[sriegel]

Not to derail, but that's always been kinda my thing - Cd should be based on the form, "A" by the dimension of that form, so that your drag is always a product of the coefficient and the area. That's tough as you note, some using the actual fabric area and some the planar area of the main opening. I've picked here and there at trying to get a comparison between the flat sheet and Nakka semi-ellipsoidal so that I could say, for example, "This rocket is supplied with an 18" hexagonal flat sheet chute, therefore I need an "x" inch semi-ellipsoidal. But I think I've had to default to, "Supported weight is so-and-so ounces (or grams), therefore I need an "x" inch semi-ellipsoidal 'chute.

My experience in HPR says that many vendors seem to aim for about 20 fps with the supplied flat chutes. If I swap a similar diameter ellipsoid, I get about 15 fps. It's not a perfect fit but it's a decent starting point for me. But I wrote a spreadsheet to calculate rates anyway. Plug in mass and presumed Cd and either chute diameter or descent rate. It's done pretty well for my needs.