Actually, I understood the question perfectly. Just did a terrible job of making the point I was trying to make.[&o]
There are two things needed for establishing a bowhunter's effective range. Being able to hit where you're aiming is only half the story. Hitting with an arrow that has enough power to give enough penetration for that quick, clean kill is the other half.
Silverbackpete, here's the deal. For a long time, I was confused by all the talk I was hearing from the compound guys, about how well their light little knitting needle arrows were penetrating in game. It didn't make sense. We all KNEW you had to have at least 9 grains of arrow weight per pound of draw weight for decent penetration on game. Was it the speed? Did it have something to do with the kinetic energy numbers they were coming up with, 70, 80... even 90 foot pounds?[:-] Kept me stymied for a long time, until I got on the ballistics table calculator at
www.bowjackson.com and did some numbers crunching.
Well, I decided to run the numbers on an "IBO" arrow, 350 grains at 300 fps, and compare it to a more traditional arrow, twice as heavy and half as fast - 700 grains at 150 fps - like you might see from a selfbow. So... the 700 grainer came out with 35 foot pounds and ..4655 pound/seconds of momentum. The 350 grain arrow came up at 70 foot pounds and .4655 pound/seconds of momentum.
THERE was my answer! It wasn't the speed or the KE, the light arrows were traveling fast enough in those hard cam bows to equal a heavy arrow's MOMENTUM! They had to travel at twice the speed and with twice the energy of the heavy arrow to do it, but they did it.
Well, when you go without those hard cams and shoot a recurve, they don't look so good.
Slow that 350 grain arrow down to 200 fps, which is realistic for a 50 pound recurve, and you get 31 foot pounds and .3104 pound/seconds of momentum. The lighter arrow doesn't cut through the air very well, so it slows down as it goes downrange. At 30 yards, wind resistance has cut it's speed to 183 fps, KE drops to 26 ft lbs and momentum has slid to .2838 pound/seconds.
Take a 500 grain arrow with the same bow. It'll likely shoot around 180 fps for 36 ft lbs and .39904 pound/seconds of momentum. The heavy arrow still loses some to wind resistance, but it does much better than the light one. At 30 yards, it arrives going 170 fps with 32 foot pounds of energy and .3760 pound/seconds of momentum.
The light arrow flies flatter to make it easier to hit at longer distances, but carries a lot less 'oomph' downrange for penetration potential. The heavy arrow has a higher trajectory, making it problematic to hit at longer distances, but it carries a lot more of it's power to where it's going.
You need to balance the flat trajectory with enough power to do the job. It doesn't do any good to be able to hit a deer at 35 yards if the arrow only makes a flesh wound and bounces off. Or, even worse, gets only one lung and leaves you with a long, fruitless tracking job.
That's what I meant by being concerned about your reasoning for using carbon arrows so you can make good hits downrange. It doesn't do any good to be able to hit 'em if your arrow doesn't carry enough power with it to finish the job.