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Bartek Strojek
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 Posted: Wed 18 Sep, 2013 9:53 am Post subject: |
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| Dan K. F. wrote: | The efficiency of the arrowhead in preserving its energy as it strikes the target would probably be what determines its effectiveness so a heavy arrowhead that decelerates too quickly wouldn't work well.
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But....
The heavier and slower something is for given energy, the slower it decelerates when it hits something, generally. 
It has more momentum, and deceleration is less violent, due to very fact that there's lower velocity to decelerate to '0' from...
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Guy Bayes
Location: United States Joined: 07 Oct 2012
Posts: 64
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Neal Matheson
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| Posted: Wed 18 Sep, 2013 10:20 am Post subject: |
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Hi Matt I think the Natal study is interesting as it is a modern study with tangible outcomes, unlike many discussions about history. It is interesting that the Natal study validated the basic hunting arrow design which was used for thousands of years as the most effective.
Interestingly despite this valuable work many hunting arrow designs which were shown to be horribly ineffective are still being made and used.
I can't comment on the physics of the Ashby report but do know that the study used alot of real life testing. I would have thought the physics was used to illustrate what was learned in the field, rather than the other way round.
Last edited by Neal Matheson on Wed 18 Sep, 2013 10:27 am; edited 1 time in total
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Matt Lentzner
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| Posted: Wed 18 Sep, 2013 10:21 am Post subject: |
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| Dan K. F. wrote: | I have limited knowledge and experience with archery but wouldn't it be reasonable to assume that factors affecting the armour penetration of arrows would be similar to those of other projectiles? If so, my assumption would be that the most important attributes affecting armour penetration would be the shape of the arrowhead, density of the material used in the arrowhead versus that of the armour, and speed. I don't think weight would necessarily be as important other than its effect on the speed of the arrowhead and as a result of its density. The efficiency of the arrowhead in preserving its energy as it strikes the target would probably be what determines its effectiveness so a heavy arrowhead that decelerates too quickly wouldn't work well.
Looking at modern day projectiles, a 45 caliber pistol round is heavy compared to other pistol rounds but has relatively poor performance due to its lower velocity and shape. An armour piercing 9mm round is smaller and lighter but has higher velocity and is made out of denser materials which makes it better at punching through armour but may possibly compromise its effectiveness against "soft" targets. |
You're on the right track, but a heavy arrow is going to decelerate *less* quickly. It has more inertia, especially compared to it's cross-section. Another item you didn't mention has to do with projectile integrity. The arrow itself has to be robust enough to deliver it's energy to the target without failing. A point that folds over or a shaft that shatters will severely compromise the arrow's terminal effects.
I think you can draw some parallels to guns, but only up to a point. Excepting artillery, guns are all direct fire weapons. Military archery on the other hand was often done at the extreme range of the weapon. Guns on the other hand can shoot much farther than anyone could hope to hit with. Guns are also a lot simpler to model than bows. Bow are pretty complex. If you want to increase the efficiency of your bow then using a heavier arrow is better although you would lose range (maybe). And in this case efficiency = anti-armor performance.
I wouldn't use handguns though. More so, the difference between a .45 and a 9mm is really only significant for gun enthusiasts. Maybe thinking about the difference between hollow points, ball, and saboted ammunition would be more fruitful.
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Matt Lentzner
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| Posted: Wed 18 Sep, 2013 10:40 am Post subject: |
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Hi Neal,
I didn't mean to disparage the study. In fact, I would say anyone's reasonable default should be that ancient people knew what they were doing. Empirical study can go a long way when it's your livelihood at stake. This probably applies to the longbow as well. By the HYW it was a highly evolved weapon system. We're just trying to reverse engineer what people figured out by trial and error.
My point was that a projectile's effectiveness against flesh is much different than it's effectiveness versus armor. In fact they are pretty much at odds with each other. The smaller the projectile's frontal area the better at penetrating armor it will be, but the worse it will be at wounding etc. One of the advantages of wearing armor in the first place is that it forces your opponent to use weapons that are much less efficient at wounding you.
Best,
Matt
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Guy Bayes
Location: United States Joined: 07 Oct 2012
Posts: 64
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| Posted: Wed 18 Sep, 2013 10:53 am Post subject: |
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An interesting side topic is did ancient people really "know what they were doing" with regards to simple machines like bows?
Lacking a theoretical understanding of Newtonian mechanics, they often substituted trial and error approaches, to what degree does that make up for actually understanding how things work?
Could the English, with materials available at the time, have built a drastically better bow if the theory had been available? Some thing more like a compound bow, using pulleys perhaps? Or a reflex/deflex longbow?
Several modern bow manufacturers routinely build R/D longbows that completely outperform an english longbow, however I am not aware of any that do so using entirely period appropriate materials
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Dan K. F.
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| Posted: Wed 18 Sep, 2013 12:47 pm Post subject: |
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| Bartek Strojek wrote: | | Dan K. F. wrote: | The efficiency of the arrowhead in preserving its energy as it strikes the target would probably be what determines its effectiveness so a heavy arrowhead that decelerates too quickly wouldn't work well.
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But....
The heavier and slower something is for given energy, the slower it decelerates when it hits something, generally.
It has more momentum, and deceleration is less violent, due to very fact that there's lower velocity to decelerate to '0' from... |
Deceleration happens in two stages. The arrow will gradually decelerate as soon as it leaves the bow string. In this respect a lighter, more streamlined arrow would have the advantage as it would conserve more of its initial velocity during its flight time. The second stage is the more sudden deceleration of the arrow striking the target. Even if the faster arrow loses more velocity when it hits the target, its higher initial and conserved velocity would likely give it a better chance of penetrating armour provided the arrowhead doesn't bend or shatter on impact. I was referring to the deceleration during flight time with my reference to a heavier arrow, not the deceleration caused by impact.
I'm not sure how a slower projectile would have more momentum than a faster one. Can you clarify?
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Timo Nieminen
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| Posted: Wed 18 Sep, 2013 5:50 pm Post subject: |
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| Guy Bayes wrote: | An interesting side topic is did ancient people really "know what they were doing" with regards to simple machines like bows?
Lacking a theoretical understanding of Newtonian mechanics, they often substituted trial and error approaches, to what degree does that make up for actually understanding how things work? |
Given time, trial and error works well for optimising a design. Doesn't work so well for coming up with completely new designs (and a theoretical understanding of the basic science doesn't automatically lead to new and improved designs either).
| Guy Bayes wrote: |
Could the English, with materials available at the time, have built a drastically better bow if the theory had been available? Some thing more like a compound bow, using pulleys perhaps? Or a reflex/deflex longbow? |
Probably not a compound (i.e., multi-string pulley thing). If you start with a straight stick, there's only so much you can do. Given that Turks and Russians and Tatars were using recurve-reflex bows, the English could have adopted such designs if they really wanted to, and were prepared to pay for such bows. But such bows are not cheap - more expensive than muskets.
The big modern developments are the compound bow and modern bow, string, and arrow materials. For basic bow shapes, most of the basic variations were tried and used. We see recurve bows, decurve bows, reflex bows, deflex bows, working recurves, static recurves, and even multi-arm bows: https://www.google.com/search?q=penobscot+bow
"In addition to being efficient, all pole arms were quite nice to look at." - Cherney Berg, A hideous history of weapons, Collier 1963.
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Guy Bayes
Location: United States Joined: 07 Oct 2012
Posts: 64
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| Posted: Wed 18 Sep, 2013 9:01 pm Post subject: |
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Well there are certainly a lot of conveniences that exist today in archery that were within reach of ancient people's but never developed
- clickers
- pin sights
- stabilizers
- mechanical releases
These are all accuracy enhancers essentially and taken together lower the practice required and barrier to entry for archery considerably
I think something compound bow like probably could have been rigged with medieval technology though it might have looked more like a ballista then a man portable device. I am not aware of any war machines that made extensive use of springs and pulleys
There is also a huge amount of things that could have been done with hydraulics and steam if people in ancient times had an understanding of the principles behind those things.
You also had things like Greek fire and concrete that were discovered once via trial and error and then never rediscovered again throughout centuries.
It also took a really incredibly long time to develop simple things like stirrups, keels and functional sails on boat, telescopes, etc
I think understanding of fundamental principles is a huge deal in invention
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Matt Lentzner
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| Posted: Wed 18 Sep, 2013 9:57 pm Post subject: |
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| Dan K. F. wrote: |
Deceleration happens in two stages. The arrow will gradually decelerate as soon as it leaves the bow string. In this respect a lighter, more streamlined arrow would have the advantage as it would conserve more of its initial velocity during its flight time.
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Sorry Dan but that's still not right. If I had two arrows that were proportionally the same but one arrow was twice as heavy the heavier arrow would decelerate slower. This is because of the squared/cubed rule that says an object increases in mass as the cube of it's dimensions while the surface area only increases as the square. The heavier arrow has less than twice the surface area (read air resistance) so it will slow down less quickly.
For the same reason, big bicycle riders can go down hills faster than small riders. Likewise, for plunging fire at long ranges heavier arrows are better.
| Dan K. F. wrote: |
I'm not sure how a slower projectile would have more momentum than a faster one. Can you clarify? |
Momentum is Mass x Velocity. A arrow that is twice as heavy will be shot at a speed greater than half the speed of the smaller arrow because the efficiency is greater so it will have more momentum.
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Timo Nieminen
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| Posted: Wed 18 Sep, 2013 11:39 pm Post subject: |
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| Guy Bayes wrote: |
I think something compound bow like probably could have been rigged with medieval technology though it might have looked more like a ballista then a man portable device. I am not aware of any war machines that made extensive use of springs and pulleys
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For a Medieval compound bow to be a drastically better bow, it needs to be light-limbed (which includes light pulleys) enough so that the gains in stored energy are not wasted in moving heavy limbs, low hysteresis and other loss, fault tolerant, and, ideally, field-maintainable. The first two require modern materials, the 3rd modern materials and manufacturing, and the 4th is not achieved by modern compounds. A hard ask.
Given that the block-and-tackle was know close to 2500 years ago, and plenty about levers, including the quantitative science of them, a big part of the basic science was known. I think that adequate materials and manufacturing would have been a big problem for a Medieval attempt. Even then, it still isn't obvious - look at the lag between adequate materials and manufacturing becoming available, and the actual invention of the compound bow.
But some interesting things were done. As well as the above-mentioned Penboscot bow, see also http://www.myArmoury.com/talk/viewtopic.php?t=15759
| Guy Bayes wrote: | It also took a really incredibly long time to develop simple things like stirrups, keels and functional sails on boat, telescopes, etc
I think understanding of fundamental principles is a huge deal in invention |
Sure. As I said, trial and error works fine for optimisation, less so for innovation. Invention is innovation. Understanding of fundamental principles is not enough - one still needs to invent. But it certainly helps.
"In addition to being efficient, all pole arms were quite nice to look at." - Cherney Berg, A hideous history of weapons, Collier 1963.
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Timo Nieminen
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| Posted: Thu 19 Sep, 2013 1:47 am Post subject: |
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| Dan Howard wrote: | | Timo Nieminen wrote: | | For example, the buff coat. If it was effective against all threats, why would anybody ever wear a breastplate over it? But if it was useless on its own, why anybody ever wear it without a breastplate. Yet it was done. |
As far as I can tell, buff coats were mainly worn because they were not susceptible to powder burns. They could stop a sword cut, but so can any winter coat. |
Hmm. They seem rather bulky and expensive if that is their main function. I've seen a variety of stuff written about buff coats - good weather protection, poor weather protection, reasonably protective, not protective, etc.; what's the best source for info?
"Any winter coat:" seems a little exaggerated.
"In addition to being efficient, all pole arms were quite nice to look at." - Cherney Berg, A hideous history of weapons, Collier 1963.
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Bjorn Hagstrom
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| Posted: Thu 19 Sep, 2013 2:39 am Post subject: |
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| Dan Howard wrote: |
As far as I can tell, buff coats were mainly worn because they were not susceptible to powder burns. They could stop a sword cut, but so can any winter coat. |
Not to drag this Off Topic, but I would say that stamped wool cloth would withstand powder burn just as well as leather, and be easier to mend? Maybe leather in a buff coat could be thicker for less cost/better comfort than a wool coat?
At least my practical experience with fire and woolen clothes is that they handle heat and spark really well.
There is nothing quite as sad as a one man conga-line...
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Benjamin H. Abbott
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| Posted: Thu 19 Sep, 2013 11:03 am Post subject: |
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| Dan Howard wrote: | | There is really no such thing as "light armour" on the battlefield. Textile armour is just as effective as light plate - it is just thicker and weighs more. If the armour didn't protect adequately then you either add more layers till it did, or you discard it completely. A heavy warbow isn't going to get through any kind of armour unless it is at close range. |
Dan, you mentioned lighter armor earlier in this very thread. As I've said before, the historical record does not support the idea that warriors invariably piled on layers of text armor, mail, or scale until it protected as well as light plate. Did this happen? Absolutely. Bernal Diaz's account of Spanish soldiers who wore very heavy cotton that could stop any arrow comes immediately to mind. However, not every warrior needed or could afford the same level of protection. Various sixteenth-century sources ranging from Fourquevaux to Smythe specifically assign lighter and less protective armors to certain troops, particularly archers. Henry Barrett in 1562, for example, assigned light armors or none to archers. Smythe thought eyelet-holed doublets able to resist the thrust of a sword decent armor for archers. He didn't write that such doublets could stop any arrow or even most arrows; to the contrary, he gave an instance of an arrow fatally piercing mail on the battlefield. Because of their role on the battefield, shot tended to move around more than pikers, so it stands to reason they'd carry a lighter load so as to ward off fatigue. Adequate protection means different things depending on what you're expecting to face. Shot in the sixteenth century worried primary about bullets, arrows, and swords, while pikers would come against bullets, couched lances, pikes, halberds, swords, and daggers as a matter of course.
Now, it's worth noting that Humphrey Barwick did think Smythe's lighter armors - brigandines, mail, jacks, eyelet-holed doublets, etc. - laughable because of their inability to reliable defend against couched lances and bullets. Barwick apparently considered plate the armor appropriate to the modern battlefield.
As far as earlier sources go, Bertrandon de la Broquière wrote that Turkish arrows - famously light - might pierce light mail but wouldn't pierce even light plate. Assuming that's accurate, and given what we know about Turkish archery from recent studies, that suggests approximately 80 J to defeat light mail. A heavy English warbow arrow might mange that at extreme range. Various accounts of English archery against Scottish troops and others described as lightly armored but not completely unarmored suggest that warbows could penetrate such armors at range and that this mattered.
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Jojo Zerach
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| Posted: Thu 19 Sep, 2013 12:25 pm Post subject: |
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Thanks for the interesting responses.
In art from the time you often see longbows with a small amount of recurve near the tips. Would this have had much of an effect on arrow speed over a similar bow without it?
Simple recurves are fairly common in western European art, but sometimes you also see more extreme examples like this
http://en.wikipedia.org/wiki/File:Luzerner_Sc...andson.jpg
It looks like the Mendlesham longbow might have also had some shaping to the limbs.
http://www.buryfreepress.co.uk/what-s-on/life...-1-2998512
Last edited by Jojo Zerach on Thu 19 Sep, 2013 11:18 pm; edited 1 time in total
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Dan Howard
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| Posted: Thu 19 Sep, 2013 2:48 pm Post subject: |
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People don't seem to realise that there is a difference between "penetrate armour" and "injure the wearer"
"the Franks were drawn up in front of the cavalry, stood firm as a wall, and every foot-soldier wore a vest of thick felt and a coat of mail so dense and strong that our arrows made no impression on them… I saw some with from one to ten arrows sticking in them, and still advancing at their ordinary pace without leaving the ranks."
Bahā’al-Dīn, "The Life of Saladin" (Ch. CXVII), in What Befell Sultan Yusuf, by Abu el-Mehasan Yusef ibn-Rafi ibn-Temun el-Asadi.
"…and whilst the Turks were fleeing before him, they (who shoot as well backwards as forwards) would cover him [Walter of Châtillon] with arrows. When he had driven them out of the village, he would pick out the arrows that were sticking all over him; and put on his coat-of-arms again… Then, turning round, and seeing that the Turks had come in at the other end of the street, he would charge them again, sword in hand, and drive them out. And this he did about three times in the manner I have described."
The Memoirs of the Lord of Joinville, (Ch.XVII).
It takes a certain amount of energy for a particular arrow to penetrate a particular type of armour. It takes significantly more energy for the same arrow to go through the same armour and inflict an injury severe enough to incapacitate the wearer.
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Timo Nieminen
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| Posted: Thu 19 Sep, 2013 2:57 pm Post subject: |
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I think this is more likely to be a case of the arrows penetrating 1 or 2 layers of a 2 or 3 layer armour (or even just sticking in the outer layer, without even penetrating).
"In addition to being efficient, all pole arms were quite nice to look at." - Cherney Berg, A hideous history of weapons, Collier 1963.
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Dan Howard
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| Posted: Thu 19 Sep, 2013 3:01 pm Post subject: |
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| Timo Nieminen wrote: | | I think this is more likely to be a case of the arrows penetrating 1 or 2 layers of a 2 or 3 layer armour (or even just sticking in the outer layer, without even penetrating). |
There are plenty of accounts where arrows penetrate armour yet the wearer fights on unaffected. Analysing one small aspect of a situation in isolation is counterproductive. Producing a test where an arrow "penetrates" a piece of armour with no contextual supporting data tells us nothing about whether the wearer would have been incapacitated.
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Timo Nieminen
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| Posted: Thu 19 Sep, 2013 5:11 pm Post subject: |
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| Dan Howard wrote: | | Timo Nieminen wrote: | | I think this is more likely to be a case of the arrows penetrating 1 or 2 layers of a 2 or 3 layer armour (or even just sticking in the outer layer, without even penetrating). |
There are plenty of accounts where arrows penetrate armour yet the wearer fights on unaffected. Analysing one small aspect of a situation in isolation is counterproductive. Producing a test where an arrow "penetrates" a piece of armour with no contextual supporting data tells us nothing about whether the wearer would have been incapacitated. |
References to such accounts? Of course, we have accounts where people were hit in unarmoured spots, and fought on "unaffected", so there should be some. But accounts where lots of arrows penetrated the armour but did little to the wearer would be of interest.
But yes, to be useful, you need to both penetrate the armour and do something effective to the wearer of the armour. We see plate armour as thin as 1mm or so. Not breastplates usually - those tend to be 2-3mm, to stop arrows in pre-firearm days. The former can be penetrated, but penetration will take, say, 100J. The latter can't be penetrated by even the most powerful bows. So of what use are 130-150J bows? At least they will allow significant damage to be done through the lighter portions of the armour.
"In addition to being efficient, all pole arms were quite nice to look at." - Cherney Berg, A hideous history of weapons, Collier 1963.
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Dan K. F.
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| Posted: Thu 19 Sep, 2013 5:30 pm Post subject: |
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| Matt Lentzner wrote: | | Dan K. F. wrote: |
Deceleration happens in two stages. The arrow will gradually decelerate as soon as it leaves the bow string. In this respect a lighter, more streamlined arrow would have the advantage as it would conserve more of its initial velocity during its flight time.
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Sorry Dan but that's still not right. If I had two arrows that were proportionally the same but one arrow was twice as heavy the heavier arrow would decelerate slower. This is because of the squared/cubed rule that says an object increases in mass as the cube of it's dimensions while the surface area only increases as the square. The heavier arrow has less than twice the surface area (read air resistance) so it will slow down less quickly.
For the same reason, big bicycle riders can go down hills faster than small riders. Likewise, for plunging fire at long ranges heavier arrows are better.
| Dan K. F. wrote: |
I'm not sure how a slower projectile would have more momentum than a faster one. Can you clarify? |
Momentum is Mass x Velocity. A arrow that is twice as heavy will be shot at a speed greater than half the speed of the smaller arrow because the efficiency is greater so it will have more momentum. |
The last time I took physics was 11 years ago and I guess it shows  . Thanks for the explanation.
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