3 Panel Hemispherical Chute

Had a launch today, but didn't get to launch due to 20-30 mph winds all day. I decided to take a couple pictures of the chutes I've been working on. I really like them due to only have 2 seams to sew and they create a hemispherical parachute. Here is a picture.

Edward

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I'd be interested in the pattern, if you'd care to share.

I'll second that!!! Very cool chute.

Me too! Nice 'chute!

I've started compiling everything into a white paper on how to make them. I've also thought about selling the three cut out pieces of fabric and you sew them together.

Edward

VERY nice. I'm impressed that 3 pieces can be made into such a perfect hemisphere.

Just a simple exercise in flattening non-Gaussian shapes.

Edward

I love it. I'm looking forward to seeing that paper. If you start selling the parts, post here. I'd probably buy some just to make it simple.

edwardw said:

I've started compiling everything into a white paper on how to make them. I've also thought about selling the three cut out pieces of fabric and you sew them together.

Edward

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I would buy those pieces in a second! Would they come in various sizes? About what range?

edwardw said:

Just a simple exercise in flattening non-Gaussian shapes.

Edward

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I'd be very interested in what resources you are using to flatten non-Gaussian shapes. Is that a program (CAD or otherwise) or a book with text and equations?

[edit] It seems like that would be useful for building paper nosecones as well.

Like the pattern of the cover on a baseball? Half a baseball anyway. ???

Peartree,

If you are doing a conical nose cone then it is a Gaussian shape and can be flattened w/o any distortions. To flatten the sphere I just started with what I thought I needed and calculated a bunch of equations for a 1/2 sphere and then calculated the error on that. It took 3 times to come up with the correct way to divide a sphere to get the most spherical shape. It also helps that this semester I'm taking a math course and my professor is a great applied and numerical mathematician. He's helped lead me in the right direction.

As for what is on a baseball, I looked at those. It turns out that the leather is smaller and they count in it stretching to shape to form around it. They bend and stretch the cover with the seams. That is great for that purpose, but it doesn't translate well to a parachute where the fabric doesn't stretch.

As for the ranges I was going to fly a couple of them this weekend to get my descent values - but the one you see is rated for 6 pounds at 10ft/s at 8800' MSL, where I fly.


Edward

Peartree said:

I'd be very interested in what resources you are using to flatten non-Gaussian shapes. Is that a program (CAD or otherwise) or a book with text and equations?

[edit] It seems like that would be useful for building paper nosecones as well.

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https://www.modelersnotebook.com/ mabey there are some copys left

stymye said:

https://www.modelersnotebook.com/ mabey there are some copys left

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Nope...We bought 'em out!*


*Mad rush of TRF'ers after your previous thread about said book!:lol:

Here is a way to make smaller chutes. Just plug in the numbers. The author claims a hemispherical chute provides about twice the drag as a flat plastic chute. I guess you could scale up the drawings for larger chutes. The program is limited by an 8 1/2" x 11" piece of paper to print out the patterns.

Spherical parachute patterns

I used to make mine like that. But 6 gores means you have 6 seams to sew and that stiffens and makes the parachute harder to pack. That is why I wanted to go with the least amount that would be reasonable for a parachute.


Peartree,

I just thought that if you are making a complex, say Von-Karman nosecone out of paper the best way I can think of to do it is use the 'gore' method. You divide the nosecone into 6 or more gores. Then you call the base Station 0 and then make station points say every 1/8 to 1/4 inch. You record the diameter at each station and then divide by 6 to get the width at each point along your pattern. They will be evenly spaced along your center line that runs from the middle of each gore at the base to the tip. You just space out all of those lines and you get something that you can cut out and with 6 of them you get an accurate representation of your shape. You'd just still end up with some bending/stretching places.

Edward

Edward,
Did you ever do anything about this?
I would be very interested if you have.
Ed

edwardw said:

I've started compiling everything into a white paper on how to make them. I've also thought about selling the three cut out pieces of fabric and you sew them together.

Edward

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I'm interested in this, too, if you've had time to do the paper.