How much KE are you hunting with?
02-12-2010, 04:24 AM
#13
Giant Nontypical
Join Date: Jun 2007
Location:
Posts: 7,367
Thanks Jeff!
It comes from lots of practice, many years hunting, and the God given ability to read an animal and know when to release and when not to. I think also the fact that I knew I was only shooting 40# made me concentrate that much harder.
It's really not like a guy was shooting at a small target. The lungs are really a Big target, but none the less I do feel Lucky and appreciate the congrats.
Dan
It comes from lots of practice, many years hunting, and the God given ability to read an animal and know when to release and when not to. I think also the fact that I knew I was only shooting 40# made me concentrate that much harder.
It's really not like a guy was shooting at a small target. The lungs are really a Big target, but none the less I do feel Lucky and appreciate the congrats.
Dan
02-12-2010, 05:27 AM
#14
Fork Horn
Join Date: Oct 2008
Location: N.E. Wisconsin
Posts: 411
That is pretty good for a bow that IBO's at 300.
Running these numbers (26" dl, 50# dw, 500 grain arrow), I show your bow doing right around the 170fps, producing about 32 lbs of KE.
Now more realistic numbers (everything the same, but a 354 grain arrow), I show your bow doing around 214fps, producing about 36 lbs of KE.
I have always been told that is takes about 40#'s to pass thru a deer and 50#'s to pass thru and elk. I think anything over 60#'s will work for most anything in North America.
My current setup (Hoyt Cabon Matrix, 383 grain arrow, 68#'s, 28.5 dl) is shooting right around 285 fps, producing right at 69 lbs of KE.
Running these numbers (26" dl, 50# dw, 500 grain arrow), I show your bow doing right around the 170fps, producing about 32 lbs of KE.
Now more realistic numbers (everything the same, but a 354 grain arrow), I show your bow doing around 214fps, producing about 36 lbs of KE.
I have always been told that is takes about 40#'s to pass thru a deer and 50#'s to pass thru and elk. I think anything over 60#'s will work for most anything in North America.
My current setup (Hoyt Cabon Matrix, 383 grain arrow, 68#'s, 28.5 dl) is shooting right around 285 fps, producing right at 69 lbs of KE.
02-12-2010, 08:24 AM
#15
Nontypical Buck
Join Date: Jan 2008
Location: Southern Illinois
Posts: 1,559
Can you or someone explain how to work the formula? Being a "layman" and not knowing how to get my FPS I guess would pretty much stop the equation right away? I just pulled the "Birth Certificate" of my bow and it says 296 FPS w/ a 350grain @ a 29" draw. I am shooting a GT expidition hunter 5575 with fixed Thunderheads, I BELIEVE 150grain ( cant find the package),28" draw @ 55lbs Bowtech Black Ice. Am I mis-matched? The arrow seems to have good flight and I get good grouping. Thanks Damon
Most companies advertise a bow's IBO speed. IBO speed is the speed your bow shoots an arrow at with the dl set to 30", dw set to 70#'s, and 350 grain arrow (5 grains per # of dw).
The most accurate way to determine how fast your bow is shooting is to shoot it thru a chronograph. But there are some tools on-line that can get you a pretty close estimation by suppling information about your setup.
http://www.backcountrybowhunting.com/articles/tools.php
The above is a quick and easy tool to use. Put your bow's IBO speed in, your dl, your dw, arrow weight, and the weight of anything you have your string (loop, peep). The above tool will give you an estimated speed and ke number. While it is not 100%, it is normally very close. You can double check what the tool is telling you by running the numbers yourself.
Get your bow's speed by shooting thru a chrono and weigh your arrows on a grain scale. Now you have all the information you need to calculate your KE and Momentum. Simply plug those numbers into the below forumulas.
KE - weight(in grains) X velocity(in fps) X Velocity(in fps) / 450,240.
Momentum - weight(in grains) X velocity(in fps) / 225400
Follow the below steps to calculate the your front-of-center (FOC) % for your arrow setup. For fixed blades, I personally like to be around 12-13%
1. Measure the arrow shaft from tip of broadhead to the end of the nock. Divide it by 2 to find the center point (ie. 30" shaft divided by 2 = 15)
2. Mark center point with a felt tip marker. Now balance the shaft.
3. Mark the balance point with a felt tip marker. Divide the distance between the two marks by the overall length of the arrow then multiply by 100. (ie. distance between two marks of 30" shaft is 2.5" then 2.5 divided by 30 times 100= 8.33%)
I do want to add, that while knowing all this information is pretty cool, that any of the newer bows on the market are capable of producing more than enough KE and Momentum to hunt most anything in North America if they are tuned properly.
A properly tuned bow is the single most important factor. This includes ensuring you are shooting an arrow that is spined correctly for your setup and there are several tools out there (Archer's Advantage, TAP, OT2) that are very good with helping with this. While properly tuning a setup can be time consuming, it the only way to ensure you are getting all the performace you can get out your setup. Not to mention, what else are we going to do in the off-season other than playing with our bows?
02-12-2010, 08:42 AM
#16
Fork Horn
Join Date: Jul 2009
Location: Surry County, Va
Posts: 334
Very cool information!! Not sure what my KE is cause I'm too lazy to tried to calculate it up, plus I just don't know what the heck I'm doing(math is not a strength) however I would like to know your opinions in my set up. I shoot a Hoyt Vectrix set at 68lbs with a 28inch DL, 350 CX maxima with a 100gr Thunderhead, blazervanes. This seem about right?? I group pretty good
02-12-2010, 12:23 PM
#17
Giant Nontypical
Join Date: Jun 2007
Location:
Posts: 7,367
Very cool information!! Not sure what my KE is cause I'm too lazy to tried to calculate it up, plus I just don't know what the heck I'm doing(math is not a strength) however I would like to know your opinions in my set up. I shoot a Hoyt Vectrix set at 68lbs with a 28inch DL, 350 CX maxima with a 100gr Thunderhead, blazervanes. This seem about right?? I group pretty good
Dan
02-12-2010, 05:29 PM
#18
Fork Horn
Join Date: Oct 2008
Location: N.E. Wisconsin
Posts: 411
Definately great information. Thanks for taking the time to go into it as well as you have. I am not exactly sure either as far as the info the "Birth Certificate" says. It is a tag followed with other info written in w/pen and other info includes. "Draw Wt." >1 (this is in pen) "Arrow Wt." and in pen 350gr "Draw Lt." and in pen 29 (although I have had it adjusted to 28 1/2 "IBO" 296 (pen fps, then who built it and who tested it. Again, thanks for all the information and once I read it over thouroughly iI am sure it will be of great use.
02-12-2010, 05:39 PM
#19
Nontypical Buck
Join Date: Jan 2008
Location: Southern Illinois
Posts: 1,559
Very cool information!! Not sure what my KE is cause I'm too lazy to tried to calculate it up, plus I just don't know what the heck I'm doing(math is not a strength) however I would like to know your opinions in my set up. I shoot a Hoyt Vectrix set at 68lbs with a 28inch DL, 350 CX maxima with a 100gr Thunderhead, blazervanes. This seem about right?? I group pretty good
Figuring you are shooting just a peep and loop, it looks like you should be getting right around 284 fps, producing right at 65 lbs of ke and .456 momentum.
Again, this is making some assuptions.
If everything is correct, I would think your arrow is slightly too stiff (and I like to shoot a stiff arrow). You could tweek the setup by adjusting your dw up 2-3 lbs, or increasing your arrow lengh 3/4" to help break the spine. I only say this because I like to tinker.
If you are not having issues with bh tuning, then what more could you ask for.