DIY Parachute gore forumulas

[Issus]

Rocketry season is approaching again here, and with several new rockets I want to fly I'm looking for parachutes. I thought its about time I try making my own.

I've read most of the threads I can find on here about *making* the chutes however I'm struggling to find any resources on designing a parachute.

Does anyone know of websites or books which may contain formulas (as in mathematical) for gore outlines of various types of parachutes? I can find a bunch of calculators which give you general dimensions however only a couple actually use a formula or algorithm to generate these points. Any websites which do the calculations in javascript or excel spreadsheets are fine too

Secondly, I can calculate the Cd of a parachute easily enough in the real world (car, airspeed sensor, loadcell) however does anyone know of a way to calculate the way a parachute will fill? I'm looking to try to figure out the frontal area of the parachute as its descending, so I can figure out the CD and therefore perhaps optimise my parachute design.

So far I've found:

Parabolic parachutes, however no formula. Could figure them out from the picture of the graph as shown.
https://www.vatsaas.org/rtv/systems/Parachutes/Chute.aspx

Spherical parachutes, formula in javascript.
https://www.tedberets.co.uk/chutedata.html

X form:
5 equal squares.


And yes, I know I can just build them from the various how to guides by adjusting their measurements, but where's the fun in that More than half of my enjoyment of rocketry comes from designing rockets and related things, even if I don't build or them (never enough time or money)

 

[Zephhyr]

I use the spread sheet from Vataas.


View attachment Chute Calc.xls

 

[Davidtmp]

See if you can download SpaceCad. It may have a 30 trial period. They have a parachute pattern program built in. I printed off a bunch of different sizes that I can go to later and cut out the gores and sew together. You pick the size and number of gores you want.

 

[AlphaHybrids]

Use the sticky at the top of this Forum - Technical References for Parachute and Recovery Systems.

That will tell you all you need to know. As for the frontal area, it is generally an number derived empirically.

Gores for *most* parachutes can be derived with some geometry and algebra (and occasionally calculus). Once you get that down you can automate the process into Excel. I calculate all my patterns in MATLAB, and check with Excel. I then have import a point file into AutoCAD and print out patterns. You can make it as complex or as simple as you want.

Edward