Arrow Speed and Kinetic Energy

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Fast cars, fast computers, fast wide receivers, fast-drying paint, fast-acting weed-killer.....if it's fast, we love it. And when it comes to our archery equipment, it's no different. Show most guys a brand new bow, and their first question is likely to be "How fast does it shoot?" Right or wrong, speed is a major consideration for most archers. And it's great to see how advancements in materials and design technologies have made today's compound bows better, faster, and more fun to shoot than ever before.
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This is a thread for discussion of the article, Arrow Speed and Kinetic Energy, By Jon Henry. Here you can ask questions or make comments about the article.
 
Interesting article and as a physicist I would say that the only way to deal with impact dynamics is with momentum. However it is not really worth arguing about being as many of the K.E. rules of thumb correspond to good momentum numbers in the world of rifles. Most likely the archery numbers are also equivalent.
 
You should read Ashby's reports. Penetration is paramount. Speed and KE don't amount to much. If you want the best arrow performance, perfect the arrow by his methods.

There are some really good tests done with comparisions of components(particularly broadheads) on thousands of animals. Very interesting results, like "the only variables to show differences in blood trail quality are shot placement and whether or not the shot passed through. Broadhead type showed no dicernable difference."


I've seen a 45@28" longbow out penetrate the top coumpounds @ 70-80lbs shooting 290-340fps. Because the traditional guy had well setup arrows and the compounds didn't.

If you really want to see something cool look up "arrow penetration, african elephant", You'll know when you find the right one. 3 pass throughs.
 
ADMIN said:
This is a thread for discussion of the article, Arrow Speed and Kinetic Energy, By Jon Henry. Here you can ask questions or make comments about the article.
Click to expand...

Jon.

Great article, Hot fast bows and hot fast women will wear you out.
I found many years ago with recurve bows, that the correct spined arrow
for your bow will shoot far better than the next best. Choosing the correct
Bow to fit the Archer is usually a good starting place.

Then along came the compound Bow. The rules didn't change, there were
just a lot more of them.

Again, Very nice Article

1Hunter
 
Im no physics major, but I have some real world experience. I too believe the momentum equation more closely fits the performance of an actual hunting arrow. Many long bows, and traditional recurves would have trouble reaching the kinetic energy figures listed to cleanly take the various game animals. They don't have much speed (less than 190 fps) but what they do have going for them is very heavy arrows. I have seen heavy arrows pass thru bull elk and sail out the other side, killing them quickly. The way I see it the broadhead is what kills the game, it cuts the tissue and destroys organs. The shaft is just a way of getting that broadhead to, and through the target. You can put that broadhead on a straw and shoot it at a deer or you can put it on a shovel handle and shoot it at a deer. Obviously this is an extreme example but the extra weight of the shaft and increased momentum will push that broadhead through more muscle and bone than a lighter fast one. Maybe someone should find a uniform test medium and use one broadhead on several arrows with increasing shaft weights (the shafts would have to be the same diameter to keep it fair) and then see if the penetration results compare to the kinetic energy formula or the momentum formula. Just a thought. As far as speed vs weight for time of flight and range estimation, you are 100 percent correct. Faster arrows help with string jump, and if your range estimation off a bit that extra speed will help. Great article.
 
Hi, I'm new to the forum and was browsing the topics when this one caught my eye. Great Article and very well done. I shot a bow since 1956 and also had an archery shop in the 70's. I have killed many deer with recurves and compound bows and a large black bear in Canada. When I had the Archery shop this discussion came up many times. I don't see why the modern archer is so all consumed with speed when most of them carry rangefinders anyway. As far as "jumping the string" goes, a quiet bow shot with a heavier arrow will help with that. I used 32 inch 2219 arrows with my Bear Alaskan with a 145gr broadhead and if I remember correctly they weighed about 900 grains so I consider 600 about minimum. I also used the same arrow in my recurve. If you limit your shots to 30 yds and under for whitetails you will be fine with those 300gr arrows as long as you don't hit bone, but if you make a bad shot and hit the shoulder blade of a doe like I did, that heavy bow and heavy arrow will do the job I still have the shoulder blade with the 4 blade hole in it. The bows made now are much more efficient and will handle a moderately heavy arrow better. If you shoot game at a distance of 40 to 80 yrds the heavier arrow is the only choice.
 
rander3141 said:
Hi, I'm new to the forum and was browsing the topics when this one caught my eye. Great Article and very well done. I shot a bow since 1956 and also had an archery shop in the 70's. I have killed many deer with recurves and compound bows and a large black bear in Canada. When I had the Archery shop this discussion came up many times. I don't see why the modern archer is so all consumed with speed when most of them carry rangefinders anyway. As far as "jumping the string" goes, a quiet bow shot with a heavier arrow will help with that. I used 32 inch 2219 arrows with my Bear Alaskan with a 145gr broadhead and if I remember correctly they weighed about 900 grains so I consider 600 about minimum. I also used the same arrow in my recurve. If you limit your shots to 30 yds and under for whitetails you will be fine with those 300gr arrows as long as you don't hit bone, but if you make a bad shot and hit the shoulder blade of a doe like I did, that heavy bow and heavy arrow will do the job I still have the shoulder blade with the 4 blade hole in it. The bows made now are much more efficient and will handle a moderately heavy arrow better. If you shoot game at a distance of 40 to 80 yrds the heavier arrow is the only choice.
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I agree very much with what you have to say. I haven't owned an Archery
Shop, but, I have several close friends who do. I have found the advent of
fiberglass and then aluminum shafts. culminating with Carbon shafts has
changed the general structure of Archery. That's only some of the changes in the arrow. What about knocks, vanes and broadheads?

Consider the Bow sight and the magnificent strides the inventors have achieved.

The finger release has to be practiced and practiced to achieve
a release of the string any where near close to that of the mechanical release.

Finally the bow itself. There are very few Boyer's who can turn out quality
self bows, mainly due to the lack of material. Even the the laminated recurve
bows are a far cry form where they started.

Great strides have been made with the compound bow. Can you imagine trying to compete in an archery tournament using an old four wheeler with 35% letoff against the modern compound with up to 85% letoff?

The thing is that each of the styles of Archery has a place. whether or not we accept that, is up to the individual. The same arguments rage in the rifle community and their choices are up to the individual as well.
 
Supprized

I have been pulling a bow since the mid fiftys. I was 27 years old when I
began shooting the bow. I was taught to shoot a rifle at age 7.

Always know your target and what is behind and Practice, Practice, Practice.
 
If we are talking only about what happens when the arrow strikes an animal, then momentum is king. Arrows kill by penetrating a broadhead. no penetration, no kill. period. Kinetic Energy is much more at home with today's well constructed rifle bullets. It was in days past, with inferior cup/core lead bullets, where large bores and heavy bullets (high momentum) killed more animals. High KE bullets produces larger shock waves to be transmitted through the chest cavity, a very different internal phenomenon than an arrow/broadhead.

Also think about the construction of the Arrow. carbon fiber is fantastic at absorbing energy. Think carbon fiber bicycles, they are both light and dampen the shock from the road. The internal damping (energy absorption) of carbon fiber is higher than just about any material. Although carbon fiber arrows are hard to break, are they really what you want at the moment the arrows strikes the animal you've been stalking for a week? I know lots of archery hunters who are switching back to hunting with aluminum arrows because they have had bad experiences with light/fast carbon arrows not penetrating.

However, there is more to it than just penetration. Flat trajectory from higher velocity has a lot of merit. And as mentioned in a previous post, the correctly matched spine for your bow is going to be the best all around combination. As with everything the best place to be is a good happy medium with all factors.
 
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