Getting my Bow to shoot faster without losing KE?
07-20-2009, 06:47 AM
#1
Fork Horn
Thread Starter
Join Date: Jul 2009
Location: Ottawa, IL
Posts: 164
Getting my Bow to shoot faster without losing KE?
I have a PSE BowMadness XS set at 65# with 26" draw. a limbdriver fallaway. nothing in my strings except my peep. i do have the tube going to my cables for that. im shooting a 475 grain arrow at only 221. the IBO on this bow is 316. i should be shooting faster but cant figure it out
07-20-2009, 08:18 AM
#2
Typical Buck
Join Date: Jan 2008
Location: New Hartford, NY
Posts: 919
Well IBO speeds are tested with a 30" draw length. Since your draw length is four inches shorter that means the bow has a lot shorter power stroke which equals less speed. Also they get those IBO speeds shooting light arrows, not hunting arrows. So I wouldn't say there is anything "wrong" with your bow or set up. IBO numbers are really just a marketing gimmick
07-20-2009, 06:06 PM
#5
Boone & Crockett
Join Date: Feb 2003
Posts: 10,679
IBO is 316.
Subtract 40 fps (aprox. 10 fps per inch under 30) for your draw length and you start off at 276 fps with a 350 grain arrow.
Subtract 6 fps for your peep and you are at about 270 fps.
Calculate and subtract the speed loss of your arrow weighing more than 350 grains and you are at about 235 fps.
Subtract 15 fps (3 fps per pound of draw weight) for your 65 pound draw weight instead of the IBO 70 and you are right where you should be.
Subtract 40 fps (aprox. 10 fps per inch under 30) for your draw length and you start off at 276 fps with a 350 grain arrow.
Subtract 6 fps for your peep and you are at about 270 fps.
Calculate and subtract the speed loss of your arrow weighing more than 350 grains and you are at about 235 fps.
Subtract 15 fps (3 fps per pound of draw weight) for your 65 pound draw weight instead of the IBO 70 and you are right where you should be.
07-21-2009, 03:09 AM
#7
Typical Buck
Join Date: Jan 2006
Location: Fraziers Bottom, WV
Posts: 500
Wow that arrow is a BEAST!!! lighten that puppy up a little and you'll probably still have enough energy to blow through anything in North America! Drop down to about a 400 grain arrow and you'll pick up a good bit. Still have good KE too.
07-21-2009, 06:13 AM
#8
Spike
Join Date: Jul 2009
Location: Barbour Co. West Virginia
Posts: 90
Everyone posting from here up is spot on. I was thinking I had nothing to add so I reread them. While the answers are there if you know what to look for. I decided to help you sort them out of the fine responses above.
Big bull gave you all the answers if you are an archery nut which these guys obviously are. But if you are just learning the mechanics of archery it gets pretty technical sometimes and we all forget we didn't start out with 20yrs experience fooling with these things....(33 in my case). With that said, here's what you can do and why.
You can drop your arrow weight significantly. I can't imagine what kind of arrows you are shooting that are not really overspined at that weight anyway... unless they are extremely long. Your bow is obviously tuned decent if you can shoot well with those arrows. The drop away rest is helping.
In the KE equation....the speed is squared. That means speed has a greater effect on KE than the weight. Which means you can shed weight, add speed and actually increase your KE slightly in your case. However, there is a point of diminishing return on that as well. I would do it for the gain in trajectory. I never cared so much about how fast my arrow was going, but I did care about how flat it shot. How many misses are left and right? Not many. You either miss high or low. Putting that arrow on a diet will take some of the arch out of your archery and that will give you the speed and KE retention you want and the improved trajectory you need.
Go to an oline KE calculator and play around with the weights and speed and you will see what I mean. However you have to remember to come up with a way to get a speed increase to add as well. You can do that for your bow by adding about 1 fps for every 2grains of arrow weight you decrease . Your bow now shoots 221fps with a 475gr arrow, or about 1fps for every 2grs of arrow wt.
By the way what arrow/length/tip wt are you shooting? Also what type of broadhead.
( I should have asked that first, but I don't think it is going to matter a lot)
Remember do not go below 5gr total arrow setup wt for every pound of peak draw wt. which in your case is 325gr total arrow wt. Remember to add for fletching, glue and nock. roughly 25gr total w/Blazers, more w/longer fletch. If you didn't actually weigh your arrow or add that in, you may be closer to 500gr.
Bottomline...... Cutting that 150gr off your arrow could potentially bring your arrow speed up by 75 fps.....But I would guess more like 60 or so. Remember, there is a point of diminishing return. And I bet you a nickel that you will be able to get rid of one of your pins out to 30yds.
Go play on the KE Calculator and see what happens. Put in 325gr arrow and 285fps. Then try some numbers in between.
Also as far as arrows yo should be able to get that length down to 25 3/4" if you want. That makes them faster and something you prob. never thought of....easier to carry in the woods/brush. Also it has been proven that a shorter arrow flies better with a FOC of 10% or more. If you aren't familiar that means it should balance about 2 3/4" or further forward of the center point of the arrow with the broadhead installed.
I know you asked for the time I built you a watch...but if you are like me, I gotta know why it works before I do it. And if I know why, I will more likely have confidence that it will work.
Good Luck Buddy, Holler at me if you run into snags or if you find I am way off base.
Dryridge
Dryridge
Big bull gave you all the answers if you are an archery nut which these guys obviously are. But if you are just learning the mechanics of archery it gets pretty technical sometimes and we all forget we didn't start out with 20yrs experience fooling with these things....(33 in my case). With that said, here's what you can do and why.
You can drop your arrow weight significantly. I can't imagine what kind of arrows you are shooting that are not really overspined at that weight anyway... unless they are extremely long. Your bow is obviously tuned decent if you can shoot well with those arrows. The drop away rest is helping.
In the KE equation....the speed is squared. That means speed has a greater effect on KE than the weight. Which means you can shed weight, add speed and actually increase your KE slightly in your case. However, there is a point of diminishing return on that as well. I would do it for the gain in trajectory. I never cared so much about how fast my arrow was going, but I did care about how flat it shot. How many misses are left and right? Not many. You either miss high or low. Putting that arrow on a diet will take some of the arch out of your archery and that will give you the speed and KE retention you want and the improved trajectory you need.
Go to an oline KE calculator and play around with the weights and speed and you will see what I mean. However you have to remember to come up with a way to get a speed increase to add as well. You can do that for your bow by adding about 1 fps for every 2grains of arrow weight you decrease . Your bow now shoots 221fps with a 475gr arrow, or about 1fps for every 2grs of arrow wt.
By the way what arrow/length/tip wt are you shooting? Also what type of broadhead.
( I should have asked that first, but I don't think it is going to matter a lot)
Remember do not go below 5gr total arrow setup wt for every pound of peak draw wt. which in your case is 325gr total arrow wt. Remember to add for fletching, glue and nock. roughly 25gr total w/Blazers, more w/longer fletch. If you didn't actually weigh your arrow or add that in, you may be closer to 500gr.
Bottomline...... Cutting that 150gr off your arrow could potentially bring your arrow speed up by 75 fps.....But I would guess more like 60 or so. Remember, there is a point of diminishing return. And I bet you a nickel that you will be able to get rid of one of your pins out to 30yds.
Go play on the KE Calculator and see what happens. Put in 325gr arrow and 285fps. Then try some numbers in between.
Also as far as arrows yo should be able to get that length down to 25 3/4" if you want. That makes them faster and something you prob. never thought of....easier to carry in the woods/brush. Also it has been proven that a shorter arrow flies better with a FOC of 10% or more. If you aren't familiar that means it should balance about 2 3/4" or further forward of the center point of the arrow with the broadhead installed.
I know you asked for the time I built you a watch...but if you are like me, I gotta know why it works before I do it. And if I know why, I will more likely have confidence that it will work.
Good Luck Buddy, Holler at me if you run into snags or if you find I am way off base.
Dryridge
Dryridge
Last edited by dryridge2; 07-21-2009 at 06:25 AM.
