BC... Our GA Drag Model/ Drag Coefficient
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BC... Our GA Drag Model/ Drag Coefficient
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Topic: BC... Our GA Drag Model/ Drag Coefficient (Read 1790 times))
JungleShooter
How ironic 🤦🏼♂️: All my life I had to be a jack-of-all-trades. And now since getting into airgunning all of a sudden they call me an
Expert
Posts: 1751
There is a bug. It's called AG. It bit me! Bad.
Real Name: Matthias
BC... Our GA Drag Model/ Drag Coefficient
«
on:
July 05, 2019, 11:52:17 AM »
Our GA Drag Model/ Drag Coefficient
Strelok Pro has an option to enter custom drag profiles, and when going to that function the user can choose to "email" the data and in reality it is a "share" option.
The content of the text file (.txt) that Strelok gives me is listed below and No, it does not make sense to me so please, ballisticians, chime in!!
The first number in each line is the drag coefficient (Cd), the second the mach number (though when entering this data in Strelok manually these are switched around).
Why would there be velocities beyond mach 1?
Do these number look right?
Matthias
CFM, GA, 0.0, 0.0, 0.00000, StrelokPro, 0.000, 0.000, 0.000, 0.0
Chairgun GA retardation table for Diabolo Airgun Pellet
0.250 0.000
0.235 0.100
0.221 0.200
0.207 0.300
0.196 0.400
0.189 0.500
0.189 0.600
0.202 0.700
0.241 0.800
0.329 0.900
0.488 1.000
0.597 1.100
0.649 1.200
0.669 1.300
0.672 1.400
0.667 1.500
0.657 1.600
0.644 1.700
0.630 1.800
0.616 1.900
0.602 2.000
0.589 2.100
0.577 2.200
0.566 2.300
0.556 2.400
0.548 2.500
0.540 2.600
0.534 2.700
0.529 2.800
0.524 2.900
0.521 3.000
0.521 3.100
0.517 3.200
0.514 3.300
0.510 3.400
0.507 3.500
0.503 3.600
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Lima, PERU
rsterne
Member 2000+fps Club
Bob and Lloyd
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Real Name: Bob
Re: BC... Our GA Drag Model/ Drag Coefficient
«
Reply #1 on:
July 05, 2019, 01:18:01 PM »
That is indeed the GA Drag Model, although I have not seen the numbers past Mach 2.... It is nearly the same as the G1 Drag Model, except slightly lower drag between Mach 0.2-0.7 and slightly higher drag at Mach 0.9 and over.... The two curves intersect at Mach 0.8 (900 fps) . You are correct, we don't care what the numbers are in the Supersonic (over Mach 1.2), and I suspect that for many airgun pellets the drag is greater than shown in the Transonic.... There are many different Drag Models, here are some of them....
I only plotted up to 1500 fps to expand the scale to make it easier to understand.... Note that all projectiles have a huge increase in drag in the Transonic range (Mach 0.8-1.2) .
Bob
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Coalmont, BC, Canada
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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! 🇺🇦
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1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).
anti-squirrel
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Posts: 9733
Wadcutter fan
Real Name: Peter
Re: BC... Our GA Drag Model/ Drag Coefficient
«
Reply #2 on:
July 05, 2019, 03:20:24 PM »
Mathias, thank you.
I suspect I might not be the only person who find value is just knowing this information is available as a reference, despite not really using it day-to-day.
LOL, I can only imagine what would happen with a wadcutter pellet at mach 3.5...
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Quinton Virginia
Slingshottist and antique tool junkie
EdGuns, Crosmans, and a couple big-bores from the Far East
rsterne
Member 2000+fps Club
Bob and Lloyd
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Real Name: Bob
Re: BC... Our GA Drag Model/ Drag Coefficient
«
Reply #3 on:
July 05, 2019, 03:25:19 PM »
Good example of a mismatch between the pellet and the drag model.... Wadcutters show their increase in Transonic drag much sooner (ie at a lower velocity) than do round-nosed pellets.... and their drag when Supersonic will be much higher....
Bob
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Coalmont, BC, Canada
🇺🇦
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! 🇺🇦
Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).
JungleShooter
How ironic 🤦🏼♂️: All my life I had to be a jack-of-all-trades. And now since getting into airgunning all of a sudden they call me an
Expert
Posts: 1751
There is a bug. It's called AG. It bit me! Bad.
Real Name: Matthias
Re: BC... Our GA Drag Model/ Drag Coefficient
«
Reply #4 on:
July 06, 2019, 02:42:58 AM »
Thank you for confirming this.
And yes, I think we really need
CDMs (custom drag models)
for long range shooting...!
Matthias
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Lima, PERU
rsterne
Member 2000+fps Club
Bob and Lloyd
GTA Senior Contributor
Posts: 26958
GTA Forums Person of the Year 2017
Real Name: Bob
Re: BC... Our GA Drag Model/ Drag Coefficient
«
Reply #5 on:
July 06, 2019, 12:57:39 PM »
After I retire, I will be purchasing a LabRadar . The plan is to try and develop one or more drag models for airgun pellets.... I will start by working on the popular JSB Exact series to see if I can come up with a single drag model that will be suitable for most or all of them.... If that works, I hope to do a similar drag model for wadcutters.... Most likely a third drag model in between would provide ballistics modelling close enough for any Diabolo pellet by choosing one of the three.... At least that is the plan....
Bob
Logged
Coalmont, BC, Canada
🇺🇦
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! 🇺🇦
Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).
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BC... Our GA Drag Model/ Drag Coefficient