Author Topic: Aerodynamic penetration  (Read 1147 times)

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Online DC

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Aerodynamic penetration
« on: April 12, 2019, 09:41:49 am »
When I was playing with R/C planes in my teens I remember the glider(I think) guys talking about "penetration". All I got was that it was some kind of force(?) that a glider needed to keep going. Like "It needs more weight to improve the penetration." If it was too light it would flutter like a leaf.
I'm thinking this may be what is happening when a heavy arrow goes farther that a light one. I did a search on it and all I got out of it was that it does exist. Is it a measurable thing? How do you arrive at the right penetration?
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Offline avcase

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Re: Aerodynamic penetration
« Reply #1 on: April 12, 2019, 11:48:22 am »
Perhaps this relates to the ratio of momentum of an object to drag force?  A higher density object is less affected because it has more forward energy and momentum but same Drag force?

Alan
« Last Edit: April 12, 2019, 03:25:07 pm by avcase »

Offline Badger

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Re: Aerodynamic penetration
« Reply #2 on: April 12, 2019, 12:06:29 pm »
   I still think the 450 grain arrow will outshoot the 650 grain arrow if he can get the drag down. But he holds the record currently so that would make him the authority at this point.

Online DC

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Re: Aerodynamic penetration
« Reply #3 on: April 12, 2019, 12:13:33 pm »
Perhaps this relates to the ratio of momentum of an object to drag force?  A higher density object is less affected because it has more forward energy and momentum but same Dra force?

Alan

I think when Del said,"If the speed for both (dimensionally identical arrows) is the same, the heavier will fly further.... " It kind of sunk in. When I first read it I thought it must be a typo but Del's pretty good with the Queen's English so I thought I should think a bit. ;)
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Offline JNystrom

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Re: Aerodynamic penetration
« Reply #4 on: April 17, 2019, 06:10:23 am »
Perhaps this relates to the ratio of momentum of an object to drag force?  A higher density object is less affected because it has more forward energy and momentum but same Dra force?

Alan

I think when Del said,"If the speed for both (dimensionally identical arrows) is the same, the heavier will fly further.... " It kind of sunk in. When I first read it I thought it must be a typo but Del's pretty good with the Queen's English so I thought I should think a bit. ;)
It's true IF the speed is the same. But obviously it isn't. Light arrows fly faster.

I personally haven't had any good experience with heavy arrows, i've always had the best results with the lightest arrow you can still get enough spine with.
Mostly my 24" arrows range from 160 grains to 230 grains. 160 grain arrow was pretty light for a 90 pound short bow, but it still flew some 330 yards.

After all, the longest shots have been made with ridiculously light arrows compared to the draw weight. They were short, though (24" or so).
Of course, i'm talking about those 600+ yard records.

I don't know if my opinions are too conservative, but i think turks had it all figured out. :D I think the principles suit long draws also.
« Last Edit: April 17, 2019, 06:18:58 am by JNystrom »

Offline Deerhunter21

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Re: Aerodynamic penetration
« Reply #5 on: April 17, 2019, 04:10:15 pm »
penetration is how far or how much force is put on an arrow. I think about it like if I were to be able to put a arrow perfectly vertical without it going in on a target or something and then dropped a 50 pound weight (50 pound draw) penetration would be how far or deep it goes in.
"Only when the last tree has died and the last river been poisoned and the last fish been caught will we realise we cannot eat money." Cree Native-American Proverb

A amature practices untill he gets it right. A master practices untill he never gets it wrong.

Online DC

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Re: Aerodynamic penetration
« Reply #6 on: April 18, 2019, 08:30:52 am »
No, this is a different use of the word. That's why the title says "Aerodynamic" penetration.
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Offline 1442

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Re: Aerodynamic penetration
« Reply #7 on: April 19, 2019, 05:59:28 pm »
A glider wing doesn't spin like an arrow, so the shape can be manipulated to control the amount of air going over the top of the wing verses the bottom, and the distance the air travels across the top and bottom to create lift from forward movement.

Offline Deerhunter21

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Re: Aerodynamic penetration
« Reply #8 on: April 21, 2019, 07:25:33 pm »
Oh. sorry! wrong stuff! gotta pay more attention!  ::)
"Only when the last tree has died and the last river been poisoned and the last fish been caught will we realise we cannot eat money." Cree Native-American Proverb

A amature practices untill he gets it right. A master practices untill he never gets it wrong.

Offline jareddchazen

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Re: Aerodynamic penetration
« Reply #9 on: May 03, 2019, 07:09:14 pm »
Little while back (actually 12 years ago) I raced GP motorcycles and the term "penetration" was used often when speaking aerodynamics. A race bike had been built that was supposed to be revolutionary aerodynamically, but it really didn't go faster. Some experimenting and they realized it was the size. Two bikes, the same weight, one more aerodynamically efficient...and it was slower...because it was big. Two objects the same weight, driven by the same power, the one with a smaller frontal cross-section will go faster. Long story short, it punches a smaller hole in the air.

Theoretically (emphasized!), in archery, two arrows weighing the same but one longer and thinner with shorter fletching should go further than a shorter fatter shaft with taller fletching if both loosed from the same bow at the same draw length.

J
« Last Edit: May 03, 2019, 08:10:35 pm by jareddchazen »