09-01-2019, 03:20 PM | #11 | |
Join Date: Feb 2005
Location: Berkeley, CA
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Re: Video of arrows vs. armor using period materials
Quote:
As far as behind-armor blunt trauma goes, that could easily be occurring with the dents they showed, and in any case they didn't have a testing setup that would be able to answer how much risk it is. |
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09-01-2019, 05:40 PM | #12 | |
Join Date: May 2010
Location: Alsea, OR
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Re: Video of arrows vs. armor using period materials
Quote:
Further, they did mention scratching A 1/2" deep, the dent potentially breaks a rib, either on the deformation, or a following hit; 120 J is well capable of breaking a rib (it's approximately the standard .22lr energy), even through padding. Plus, 160 to 200 is a 25% increase in energy, which should be around 1.25^0.75 times the penetration. The largest dent looked to be about 1/4"... but add better energy transfer from deeper scratching... just enough variable to make the 200lb worth testing. Also would be interesting to see a competent slinger with a lead bullet. |
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09-01-2019, 06:37 PM | #13 |
Join Date: May 2005
Location: Oz
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Re: Video of arrows vs. armor using period materials
Very likely, but I would have liked to see it demonstrated anyway. While they had the rig set up and an archer on hand capable of shooting accurately with such a bow there was an opportunity to do the test and show the results. I would have liked to have seen it done.
__________________
Decay is inherent in all composite things. Nod head. Get treat. |
09-01-2019, 06:37 PM | #14 | |
Join Date: Feb 2005
Location: Berkeley, CA
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Re: Video of arrows vs. armor using period materials
Quote:
It would probably be more practical to just test with a modern compound bow, once the arrow leaves the bow the difference won't matter and you can get the same energy at less than half the draw weight. |
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09-01-2019, 08:26 PM | #15 | |
Join Date: May 2010
Location: Alsea, OR
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Re: Video of arrows vs. armor using period materials
Quote:
Also, you don't need to increase the projectile mass any - it's already sufficient to destroy the projectile's integrity on impact (that was a surprise to me). Velocity is a better carrier of the energy, and since the projectile is doing secondary shrapnel damage (wood shrapnel is known to be a killer, and is commented upon by several naval historians; we see plenty of it from those arrows...). |
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09-01-2019, 09:25 PM | #16 | |
Join Date: Feb 2005
Location: Berkeley, CA
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Re: Video of arrows vs. armor using period materials
Quote:
If the 0.75 power comes from G3G, it's probably a translation of the DeMarre penetration equation. Which is intended to model the performance of TL 6 naval cannons, applying it to arrows is a stretch. |
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09-02-2019, 09:16 AM | #17 |
Join Date: Aug 2007
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Re: Video of arrows vs. armor using period materials
The rule of thumb I found in research is that a hunting arrow should have a mass of between 10 and 15 grains per lb of draw. There is an overlap zone for 160 and 200 but you'd have to have been on the higher end of mass for 160.
If I was increasing my pull by 25% I'd increase my arrow mass by the same. If I had been at an optimum mass for 160 I'd probably stay at the same velocity for 200 lbs and see a 25% increase in KE.
__________________
Fred Brackin |
09-02-2019, 09:39 PM | #18 | |
Join Date: May 2010
Location: Alsea, OR
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Re: Video of arrows vs. armor using period materials
Quote:
Having watched the video, if one were to increase the mass, I'd do it on the head alone (increased length), not in the wood- the shrapnel effect is quite valuable against formations. It doesn't matter if Sir Tank doesn't take the shrapnel if Sir Guy next to him has his eye, jugular or carotid impaled with splinters. |
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09-03-2019, 09:21 AM | #19 |
Join Date: Aug 2007
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Re: Video of arrows vs. armor using period materials
You can not necessarily increase speed freely. Bows and arrows have hard limits on speed due the mechanical limits of the elasticity of the bow/arrow system. I haven't heard of an arrow achieving over 250 feet per second. After you reach that level increasing KE comes from increasing mass or it doesn't come at all.
__________________
Fred Brackin |
09-03-2019, 10:09 AM | #20 |
Join Date: Feb 2005
Location: Berkeley, CA
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Re: Video of arrows vs. armor using period materials
Bow performance has very heavy falloff as you reduce arrow weight; more and more energy is consumed moving the body of the bow.
If you have a bow that's at 50% efficiency, which looks to be about where the sample longbow was, increasing draw weight by 25% increases the weight of the active elements of the bow by 25%, which will reduce efficiency from 50% to 44%, for a real energy improvement of only 11% and a 5% increase in velocity. |
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