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what lbs makes it a warbow insted of a longbow
alanesq:
I guess the only way to know for sure is do some experiments?
I may give it a go myself some time
As posted above as I was typing this; Mark Streton published some great results on the arrow speed at different distances in The Glade a good while back which shows a graph of arrow penetration against distance which shows nicely how arrows can have more energy at greater distances but I dont think he compared same distances shot at different elevations?
e.g. it shows an arrow shot 180 yards penetrated 6" where as an arrow shot 200 yards penetrated nearly 8"
but this would suggest that shooting 180 yards he would get more penetration if he had shot a much higher arrow ?
so at least in some cases this shows my theory would be true (how often this is the case is another question?)
adb:
An object (an arrow or a sky diver or a rock) when falling will reach terminal velocity. It can not and does not accelerate. Terminal velocity is around 90 mph. Objects will deviate from this due to air friction or drag. So, an arrow can not magically accelerate beyond terminal velocity while it is falling. After reaching its apex, the arrow will begin to fall and reach this terminal speed. It will have the most energy upon realease, so in fact, you're both correct. It will have its greatest energy upon realease, its least at apex, and then something slightly higher after reaching terminal velocity upon returning to earth.
alanesq:
I agree, this means the arrow has an ultimate max speed it can attain when falling
in fact I have thought in the past it would be good to drop an arrow from a great height to find out what its terminal velocity is
The question is; is terminal velocity (assuming they fall from high enough to reach it) greater than the speed the arrow would be doing if shot flat
From Mark's results it suggests an arrow shot high to 200 yards is doing about the same speed an arrow shot flat at 40 yards will be doing, so an arrow shot flat further than 40 yards will presumably be doing less than this (from the same bow etc.)
btw - this is just from looking at the graph so is estimates
ChrisD:
--- Quote from: Yewboy on July 09, 2009, 12:43:25 pm ---Mark Stretton did some similar tests regrding penetration at various distance and these were measured at the Defence academy test centre at Shrivenham, the results were that:
0-40 yds maximum penetration
40-80 yds minimal reduction in penetration, 2-4% less
80-100 yds penetration was down by 8-10%
100-180 serious reduction in penetration at its worst at 180 yds, approx 15% less
180 -200 a marked increase in penetration from the 180yds penetration approx 8%
200-240yds again an increase in penetration, this time only approx 6% loss from maximum penetration.
So I'm afraid Chris I do agree with Alan on this one.
--- End quote ---
Thank you for sharing. What we were actually talking about was impact velocity last time I checked - penetration would be affected by many variables although I accept that velocity would be the prime factor involved.
I have to say that I would view those results as eye opening, even bizarre and I'd be grateful for the reference in a peer reviewed journal if you have one as I've never been tempted to buy the DVD. The reasons for my scepticism are
1 because it isn't what I'd expect given what I've said before and
2 it is wildly different to the impact velocities & energies given in the experiments run through a chronograph in the appendix to 'Great Warbow' which quote velocity losses of 19-24% (less for the heaviest arrow) at the end of the trajectory of a 45 degree shot with a variety of arrows and bows- which is what I would expect given the above.
3 Predictions based on coefficient of drag and velocities later in the same paper indicate falling impact energy with increasing range in a more or less linear fashion for all arrow types
Much as I admire Marks writings on other topics, I agree with Alan that an attempt at replication would be worthwhile - but using a chronograph rather than a hand held camera.
C
alanesq:
The problem is you cant really use a chronograph to measure the arrow speed at the target (unless you are VERY accurate at 200 yards)
this is why Mark used the penetration method as this was the only option available to him at the time
I understand the radar they were using couldn't measure it but I think this will be because you need a radar looking straight up at the incoming arrow
I have spoken to him about this in the past as I think there are more options available now
I first considered using a radar speed gun pointing up at the target to measure the incoming arrows speed and I even converted my radar gun so I could trigger it by radio control (as I didn't fancy standing at the target ;-) but never got round to actually trying it (story of my life ;-)
but since then I have got my high speed camera and I think there is a lot of potential to use this as you can use the zoom to film the incoming arrow from a reasonable distance and as the frame rate and arrow length is known you can figure out its speed
it would also be interesting to have the oportunity to test this against a chrono to see how accurate it is
BTW - If you watch a arrow coming down which has been shot at a high angle, one thing is clear - its coming down at a very high speed !
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