Gore pattern help

[AtomicStorm]

Just wondering if anyone had a Gore pattern they could lend me for an elliptical parachute. Let me know what you have, im looking to make a 18"-36"

 

[mo2872]

http://scottbryce.com/parachute/spherical_parachute.html
or here:

https://www.nakka-rocketry.net/paracon.html

 

[AtomicStorm]

http://scottbryce.com/parachute/spherical_parachute.html
or here:

https://www.nakka-rocketry.net/paracon.html

Oh yessssss thats it! Easy peazy i guess lol so my first design was based on a 320gram mean machine. Does a 45% hemisphere work good or do most people do 50%? Also should the spill hole be a certain size comparison to the diameter of the chute? Thanks!

 

[AtomicStorm]

Ok so im a little stumped here. I printed off the pattern and the seem allowance is exactly 1" and that is correct but the length of the gore is 14.5". Which i think is wrong. It suposed to be a 32" chute with a 20" dia. Spillhole, so shouldn't the gore only be 6" and not 14.5"??

 

[Handeman]

You have to define your terms. It seems every manufacture has a different way to measure chute diameter.

If you are making a 32" inflated diameter chute and it's an elliptical design, I would expect the gore to be about 20 to 22 long, depending on diameter of the spill hole.

With 32" diameter, the distance up and over the top and back down the other side should be about 40 to 44 inches. A 32" diameter spherical chute would have a side to side distance across the top of the chute of 1/2 * pi * 2* r . or half the circumference of the sphere (pi * r) or about 50".

If your definition of diameter is the distance from side to side of the chute material when laid flat, which is used sometimes, then 14.5" would be about right, but the inflated diameter would probably be less then 32".

The same holds true for flat chutes. Some manufactures define diameter as the distance when laid flat from one straight edge to the other. Other manufactures use the point to point distance as the diameter.

The bottom line is, saying a 32" diameter chute doesn't mean much. It could be completely different sizes, Cd, and decent rates, depending on the manufacture's or designers definition of diameter and the shape or manufacturing method used to make the chute.

In your case, a 32" diameter elliptical with a 20" diameter spill hole, 14.5, minus 2" seam allowance (1" per end) leaves about 12.5" of mostly vertical chute material that curves upward toward the spill hole. That sounds about right to me.

 

[AtomicStorm]

So it took me having to make them too small to relize that instead of making a 2d circle im making a 3d half sphere where the diameter is 32" . I realized the gores are alot longer then the diameter and now i understand why they work so well. Its because theres so much surface area in a small space. Chute, im starting to unterstand everything now.

 

[AtomicStorm]

I got my gore patterns done and have cut out the 4 orange gores, tomorrow i will trace and cut out the 4 black ones. Waiting for the shroud lines and seam tape to come in the mail.

 

[AtomicStorm]

Decided to scrap the 8 gore and go with a cooler 20 gore design. 32" dia. With a 10" spill hole. I will use the 8 gore 32" diameter, 20" spillhole chute for my next build. After cutting the ripstop with scissors i figured out that its much easier to to cut ripstop with a pencil style soldering gun. Anyways, the first step after cutting out the gores was to glue stick the seams together longways with the soft or flat sides of the gores facing each other. Otherwise you wouldn't be able to sew them together without slipping out of place. I glued one seam line making 10 x 2 gore panels. Afterwards i connected 2 of the 2 gore panels the same way by glueing 1 mismatched seam and then sewing that seam which made 5 x 4 gore panels. I continued the same steps until i had a full 20 gore chute. After i had all of the gores connected i folded over the spill hole seam to the inside and glued it down fallowing up With a double stitch around the spillhole diameter. Then i glued, folded and sewed the outer diameter hem allowance with a single stitch of nylon thread. I also glued the inside seams towards the black gores so they wouldn't show through the orange before folding and sewing the spillhole and outer diameter hem. Next is connecting the shroud lines. I used 400 lb. Paracord i got off ebay. I have 1 done so far. I finally got the presser foot on the sewing machine adjusted as well as the thread tension after 6 or 7 test pieces. I had fo go with the thinner cotton thread because the needle didnt want to go through the paracord with the nylon. I tried with everything i had to break the stitch and i couldn't do it so i figured its good enough. A few more 19 to go and she'll be ready to roll up and shove down a tube. Pip is photo-bombing as he usually does.lol

 

[AtomicStorm]

 

[AfterBurners]

View attachment 464985View attachment 464986

cute pup!

 

[AtomicStorm]

Done with the chute, alot of work but it looks nice! Thought about cutting the lines off and making them from a lighter material though. Fits snugly in a bt60 airframe. Would be best for a 2 or 3" airframe or larger. I love the looks and im sure its very strong.

 

[sriegel]

Done with the chute, alot of work but it looks nice! Thought about cutting the lines off and making them from a lighter material though. Fits snugly in a bt60 airframe. Would be best for a 2 or 3" airframe or larger. I love the looks and im sure its very strong.View attachment 465934

Looks like a worthy effort! You might look up braided PE fishing line. I use 200 lb 8-strand braid with a narrow zigzag stitch and it works like a champ.

Also, a handful of straight pins is your friend when sewing the gore seams. I find a pin insereted perpendicularly to the seam every 6-8" or so is sufficient to control the sliding between layers. You can use more until you get the feel for keeping the two edges aligned over a larger gap. Don't run the pin parallel to the seam as it has a tendency to catch under the presser foot that way.