Arrow weight and bow speed, Why would you want to know these numbers & what can it mean for you?
Well, these are the key components in figuring out the KE (kinetic energy) of your bowhunting set-up and in turn how well your set-up will do on the game you hunt. Of course, we all know or should know these sets of numbers are not the end-all to taking game. Practice, practice and more practice. Technology has come a long way baby.
Most new bows of today with a 50-pound pull weight should produce adequate kinetic energy for hunting. For example, a bow that will shoot 255 fps with an arrow weight of 350 grains will give you about 50 ft-lb. of energy. Ad a cut on impact type broadhead, an archer that has put in their time on the range and you have a complete set-up that should produce a pass through shot on any game animal here in the states.
Well, with the extra speed that comes with the higher poundage and the heavier arrow that is needed to absorb the extra energy the heavier bow will produce, comes a higher kinetic energy. For example, a 70# bow shooting 290 fps with an arrow weight of 420 grains will give you about 78 ft-lb of energy. Most hunters are aware of the large shoulder & leg bones that are very close to the aiming point of their target, so this extra KE can be a big help if your shot is a little off its mark. The heavier bow & arrow set-up with higher kinetic energy is more likely to break through the bone and finish its job.
I hope this answered some of your questions about kinetic energy and how it can help you.
Formula for kinetic energy: (Total arrow grain weight) divided by (450,435) multiplied by (speed of bow) X (speed of bow).
Over the last few years we have been bombarded with info about KE (kinetic Energy). Mostly from the manufactures but guys like us as well. We like to use the numbers from the KE charts to show how well our bowhunting set-up will do on game. Another reason is that most of us havent had any other way to calculate KE or Energy in general. This is all fine and dandy because most of todays bows produce enough energy to shoot right through a bull elk. The problem I have had in the past is the way we get to this arbitrary KE number that is Enough.
The manufactures and retailers will have you believe that achieving a KE number of lets say, 72 ft-lb through high speed & lite arrows is the same as achieving this 72 ft-lb through heavy arrows with slower speeds. I knew something just was not right, after all I do have about eight years of shooting and hunting with a recurve. Along with reading stories of hunting in Africa and the set-ups those hunters use is not the same as the hunters here in the states. Knowing in my mind that there was a difference in the end results as to how we achieved our KE was one thing, proving it was quite another.
The other day, as I was doing some reading on-line, I came across some writings of Dr. Ed Ashby. He discusses the subject of KE vs Momentum and witch is better for describing the energy from our bows. OH YA BABY! This theory of Momentum gives a scientific look at energy and in my opinion, a better way to calculate KE for hunting.
If you are a numbers person you will love this. If you are a hunter this will be very useful. Click on the link,
Thanx for askÕn, Wildarcher
