Forums: Skydiving: Safety and Training:

Sep 17, 2012, 12:19 PM
Post #1 of 9 (2572 views)
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 Exit separation spreadsheet Can't Post
I read through the latest "45 degree rule" thread recently and remembered that I did the maths for exit separation a while ago for a piece of coursework.

I've attached an excel spreadsheet if anybody's interested. It shows how much separation you'll have on opening with different times between exits, and the different speeds of each group.
All the green cells are editable. All units are in metres and seconds, but I've added a unit converter.
Group 1/2 TV is the terminal velocity of each group. This is used to estimate their coefficient of drag.
Total throw is your horizontal distance between exit and pull.
K1 and K2 are the 2 groups coefficients of drag.

If anybody wants to check the maths or have a look at how it's done, I can upload the write up.

(This post was edited by gs8613 on Sep 17, 2012, 1:12 PM)
Attachments: Exit seperation.xlsx (30.4 KB)

erdnarob  (D 364)

Sep 18, 2012, 10:25 AM
Post #2 of 9 (2298 views)
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 Re: [gs8613] Exit separation spreadsheet [In reply to] Can't Post
Sorry but I cannot open your file. Could you change it in simple XLS.

I am into mathematics therefore I am interested to see more details.

I made a program a couple of years ago on my graphing calculator HP 48 GX to calculate the spot based on wind direction and speed at 0, 3000, 6000, 9000 and 12000 ft. In this program I took in account the forward throw due to the ground speed of the airplane at altitude. In summary, this program makes a sum of 4 vectors (direction and length) and the result is like : 3500 ft at 340. We can really fast find out the spot on an aerial picture of the DZ on which I have drawn circles every 500, 1000, 1500, 2000, 2500 ft ...etc including geographic radials from 0 to 180 to 360 degrees by increments of 10 degrees. If intersted just tell me. My program let you know each operation and tell you what it actually does. I have also a sample calculation by hand to validate the program.

erdnarob  (D 364)

Sep 18, 2012, 10:29 AM
Post #3 of 9 (2294 views)
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 Re: [gs8613] Exit separation spreadsheet [In reply to] Can't Post
Sorry again, I didn't realize that when clicking on the file it was being downloaded. I have your XLSX file

Sep 19, 2012, 3:18 AM
Post #4 of 9 (2168 views)
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 Re: [erdnarob] Exit separation spreadsheet [In reply to] Can't Post
Erdnarob - I'd be interested to see that program. Did the excel file open okay for you in the end?

I've attached part of the write up for this. It's too big to upload as 1 document so I've split it into 2 PDF's

If anybody wants to use this I can easily modify the excel doc to include wind speeds and directions, and therefore actual throw from the aircraft
Attachments: Exit Seperation - 1.pdf (190 KB)
Exit Seperation - 2.pdf (282 KB)

erdnarob  (D 364)

Sep 19, 2012, 12:26 PM
Post #5 of 9 (2089 views)
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 Re: [gs8613] Exit separation spreadsheet [In reply to] Can't Post
Thanks for your calultaions. In my calculation the jumper forward speed at exit due to airplane speed (provided it is flying horizontally against the wind at altitude over the calulated spot) is the : (ground speed of the airplane x 5 seconds)/2 which represents the horizontal distance made by the jumper at exit. See explanations.
Attachments: Program for the spot with HP48G.doc (122 KB)
SPOTTING.pdf (259 KB)

mjosparky  (D 5476)

Sep 19, 2012, 7:26 PM
Post #6 of 9 (2018 views)
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It is tough to get people to count 10 between exits…….your stuff is a little over the top.

Sparky

kallend  (D 23151)

Sep 22, 2012, 5:28 PM
Post #7 of 9 (1908 views)
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It is tough to get people to count 10 between exits…….your stuff is a little over the top.

Sparky

Education isn't like it was in our day, eh Mike?

strop45  (D 957)

Sep 22, 2012, 10:52 PM
Post #8 of 9 (1860 views)
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Education isn't like it was in our day, eh Mike?
So you're saying the standard of teaching has gone down since you were a boy...

kallend  (D 23151)

Sep 23, 2012, 5:55 PM
Post #9 of 9 (1815 views)
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Education isn't like it was in our day, eh Mike?
So you're saying the standard of teaching has gone down since you were a boy...

Fortunately by the time graduate school comes around it seems to be OK.

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