Reflex/Deflex Longbows

[steve58]

[quote=alanesq;143762]My currennt arrows are 70gram
the straw bosses we have tend to be difficult to pull any arrow out, but the foam ones they come out no problem

My arrows are 3/8" wide so it will take a more energy to stick them in as far as other arrows anyway
btw-If I fit a bodkin point then this makes a big difference to the damage they can do

my arrows having a lot of weight to them I can imagine they could nock a small boss over if not secured very well, but they dont offer to move the normal ones
of course a 200lb warbow with 1/2" arrows and bodkin points may well be more spectacular??
QUOTE]

70 grams? That's a BIG pointy thing! At least twice the weight of mine. Cannot for the life of me remember how to work out what that does to the energy they deliver (but this might be relevant? The Physics of Medieval Archery. Even so I think it would more than make up for the thicker shaft needing to make a larger hole for itself? My 5/16" arrows are lighter, but a little faster than my 11/32" ones and they all seem to go in about the same distance.

[alanesq]

My arrows are not achieving anything like the penetration on the boss as the compounds do
I would guess my arrows have more momentum in them so pushing a boss over (as someone reported to you) if it's not on the stand very well may be a possibility but its not something I have seen any hint of happening myself.

[steve58]

Originally Posted by alanesq

My arrows are not achieving anything like the penetration on the boss as the compounds do
I would guess my arrows have more momentum in them so pushing a boss over (as someone reported to you) if it's not on the stand very well may be a possibility but its not something I have seen any hint of happening myself.

This is why I was trying to remember the formula for calculating energy based on speed and weight so I could figure out the trade off between speed and weight. Joe Tapley, as ever, has all the info here TOPICS ON BOW MECHANICS AND ARROW FLIGHT (but decoding it is a bit beyond me!)

You missed a beautiful day at Wilford, hope you were out shooting somewhere, cheers!

[nelly]

Hi Steve 58

The calc your looking for is Velocity squared in fps x Projectile weight in grains all devided by a figure of 450240 This will give you Energy in ftlbs.

From Mark Strettons article in the Glade recently, his 140lb war bow with standard arrow was getting about 70 ftlbs about the same as a modern 22 short pistol round! No wonder the French died in their thousands.

[steve58]

Hi Nelly! I think I remember the article, didn't he calculate that a war arrow would be capable of delivering more than enough energy to kill by blunt force trauma even if it did not go through the armour? I think he also tested the effect of a target moving towards the arrow and found that this increased penetration as you would expect, head on collision and all that. What I was wondering was which made more difference, weight or speed? Seing the formula I guess the answer to that is speed, because it's speed squared? That would explain the spectacular penetration achieved by light compound arrows. Now... how do I work out the speed of my arrows? Thanks for the formula

[nelly]

Unfortunately you also have to factor in the physical properties of the target material, as some materials are weaker at resisting higher speeds and some heavy weights, all with the same total energy.

I have been told for example that whilst a war bow only has about the same force as a small caliber short pistol, an arrow shot from a war bow can penetrate certain types of bullet proof glass (Presumably because the glass is designed to defeat a totally different type of projectile with different energy characteristics) and im afraid to say i dont know the performance of Straw!!

I do know that whilst i love to see a heavy bow being shot our Equipment Officer would spit his dummy out big time if he saw a 140 lb bow being used at 40 yards on HIS bosses, mind you he hates all longbows so who cares!

[kernowtom]

It is with some trepidation that I venture to say anything contentious on this site as my last such post attracted some, umm, attention. However, I feel that with science on my side I can make at least one minor contribution to this debate. The kinetic energy of a projectile is caculated, in joules, as half the mass (in kilos) times the velocity squared (in metres per second). Using one of the sites quoted above we get a 60 gram war arrow with a terminal velocity of 40-45 metres per second. Being generous and using a velocity of 50 m/s gives a strike energy of 75 joules. For comparison let's take a full metal jacket .38 special round with a weight of around 8 grams and a velocity of 250 m/s. This gives a strike energy of 250 joules. Though perfectly capable of killing you dead, the .38 special was replaced by the .357magnum to provide a round for police use that would penetrate the early body armour. A .357 magnum round has an energy of over 733 joules. if stopped by a good piece of body armour it will not kill you (though, having shot .357 magnum rounds I would not want to be on the other end, regardless of what I was wearing...) Thus a war arrow, with only 10% of this energy, must have had to penetrate to wound or kill.
I await the arguments:-)
tom

[laminatekid]

To put in perspective a "good piece of body armour" would have cost more than a custom aston martin so would have been in the hands of a select few and with supply problems in the modern army apparent, one can only imagine the state of affairs with a medieval army. You would only have to wound the horse to send a man with 80lbs of armour crashing to the ground to get trampled and killed so an arrow storm would still wipe them all out.

[kernowtom]

yeah.. but I wasn't commenting on the overall effectiveness of the medieval longbow - I was just commenting on the earlier point about calculations on blunt force trauma...

[alanesq]

looking at it from the other side; if arrows would kill even if the armour did stop the arrow then why would they bother wearing it ?