Carbon Express Spine question
01-14-2010, 04:39 AM
#11
Nontypical Buck
Join Date: Feb 2003
Location: Middletown PA United States
Posts: 3,625
I have to agree with the later recommendations of NOT getting a 500 spine. Good golly. These would be so underspined as to be rediculous. At 29" they're more suited for about 50#. You're probably closer to using a 300 spine than you think.
I shoot a lot of 500 spined arrows and at 27# (arrow length and draw length) about the highest they tune well is 63#. It can vary with the aggressiveness of the cams, but at your specs they are way off the chart.
Of course there is a way to easily find out without spending any money. That is to just turn the bow down to about 65# and see if things get better.
I also agree that you might be having a contact issue. Underspined arrows usually won't group with broadheads. They'll fly erratically and scatter all over the place. Of course, the same can be said if your fletching is whacking the rest.
I shoot a lot of 500 spined arrows and at 27# (arrow length and draw length) about the highest they tune well is 63#. It can vary with the aggressiveness of the cams, but at your specs they are way off the chart.
Of course there is a way to easily find out without spending any money. That is to just turn the bow down to about 65# and see if things get better.
I also agree that you might be having a contact issue. Underspined arrows usually won't group with broadheads. They'll fly erratically and scatter all over the place. Of course, the same can be said if your fletching is whacking the rest.
01-14-2010, 07:32 AM
#12
Giant Nontypical
Join Date: Jun 2007
Location:
Posts: 7,367
BC, BG good advice! Definitely does not need a more limber arrow.
Make sure your arrows are spinning true with Broadheads attached. Just curious do you know what your FOC is? I'm thinking contact could be causing your problem, but hard to tell without being there, definitely check.
Dan
Make sure your arrows are spinning true with Broadheads attached. Just curious do you know what your FOC is? I'm thinking contact could be causing your problem, but hard to tell without being there, definitely check.
Dan
01-14-2010, 09:14 AM
#14
Spike
Join Date: Jan 2010
Posts: 92
I was offering a different arrow at 400 and one at 500.The arrow brand and model makes a differance I am shooting these out of the fastest bow I have heard of with zero problems. I would be the one with weak spine problems.my IBO is 375 and I am now at 334 at 70lbs 28'' draw. and as I said to him in this post I belive his problems lay somewhere else. A 340 arrow is stiff enuf for any bow
01-14-2010, 10:11 AM
#15
Guest
Posts: n/a
I was offering a different arrow at 400 and one at 500.The arrow brand and model makes a differance I am shooting these out of the fastest bow I have heard of with zero problems. I would be the one with weak spine problems.my IBO is 375 and I am now at 334 at 70lbs 28'' draw. and as I said to him in this post I belive his problems lay somewhere else. A 340 arrow is stiff enuf for any bow
01-14-2010, 11:04 AM
#16
Spike
Join Date: Jan 2010
Posts: 92
The arrows you are shooting are the right wieght for your bow as it is set up.I am sorry for misleading you as I ment to tell you what I am shooting for an arrow.I belive yoyr problem lies somewhere else.What I would do is 1st check for vane contact again.paper test at 5 yds and at 20yds. sometimes at 5yds you will look good and at 20 you will find a wobble.check your rest. alot of the fall aways have a problem with not dropping fast enuf causing contact and often gets over looked expecially with speed bows.Check the tune of your broadhead for wobbles.easton arrow chart reccomends a 340 for hunting and a 360 for target on your bow.
Last edited by blacktail4ever; 01-14-2010 at 11:12 AM.
01-14-2010, 11:16 AM
#17
Spike
Join Date: Jan 2010
Posts: 92
What is FOC?
If there's one variable of broadhead flight that's often overlooked, it's the arrow's front-of-center balance point, or FOC. In practical terms, FOC determines how much leverage the fletching has to correct the arrow's flight. The farther forward the balance point is from the center of the arrow--the FOC point--the longer the lever the fletching has to work with and the easier its job. The general recommendation for FOC is 12 to 15 percent for broadhead-tipped arrows. This compares to a recommendation of eight to 11 percent for field points (for pure target applications). The difference in suggested FOC is due, in part, to the longer length of a broadhead. It's also due, in part, to field points not having the ability to steer an arrow like a broadhead can.
Finger shooters, and those shooting shafts less than 26 inches in length, should probably look for a higher FOC. This is because shorter arrows are inherently less stable, and finger shooters, once again, need a little extra help to correct the normal arrow wobble upon release.
Note that it's possible to shoot very accurate groups with field points with less than eight percent FOC, but again, field points are more forgiving than broadheads. Just as with fletch size, it's better to err on the large side with FOC. You don't want to go overboard, though (past 18 percent). Too much FOC makes your arrows point-heavy and less aerodynamic downrange.
How do you figure out your arrow's FOC? The Easton computer program that I mentioned earlier in the article has a calculator that will do the job for you. If you don't have the program, you have to do the math yourself. Here's how I do it, and since I'm no math wizard, it's pretty simple. The formula is: [(ABP ÷ TAL) - .50] x100 = FOC%
ABP is the distance to the arrow's balance point from the nock of the arrow, and TAL is the total arrow length. (This formula is different than the one recommended by the AMO. It provides the same answer, but I've found it a little easier to use.) All you need is a tape measure and something to balance an arrow on (like a pencil) to use the formula. First, balance the arrow and mark the balance point with the pencil. Then measure from the throat of the nock (where the string fits inside the nock) to the mark you made at the balance point. This is the arrow's balance point (ABP).
Next, measure the length of your arrow from the throat of the nock to where the insert goes into the shaft. This is the total arrow length (TAL). (If you use carbon shafts with outserts, measure to where the point screws in.) Finally, input the figures into the FOC formula. For example: If you had a 30-inch arrow that balanced at 19 inches, the formula would read: [(19÷30) - .50] x 100 = 13.3 percent FOC.
What do you do if your arrow's FOC is too low? You might have to use a heavier broadhead or change shafts. Be careful here. Adding a heavier head can change arrow spine, meaning you might have to use a different arrow or, at the very least, re-tune the bow.
If you really don't want to change shafts or components and you're shooting vanes, try switching to feathers. They're typically much lighter and could move your FOC forward by two percent or more. You can also try using a lighter nock.
If there's one variable of broadhead flight that's often overlooked, it's the arrow's front-of-center balance point, or FOC. In practical terms, FOC determines how much leverage the fletching has to correct the arrow's flight. The farther forward the balance point is from the center of the arrow--the FOC point--the longer the lever the fletching has to work with and the easier its job. The general recommendation for FOC is 12 to 15 percent for broadhead-tipped arrows. This compares to a recommendation of eight to 11 percent for field points (for pure target applications). The difference in suggested FOC is due, in part, to the longer length of a broadhead. It's also due, in part, to field points not having the ability to steer an arrow like a broadhead can.
Finger shooters, and those shooting shafts less than 26 inches in length, should probably look for a higher FOC. This is because shorter arrows are inherently less stable, and finger shooters, once again, need a little extra help to correct the normal arrow wobble upon release.
Note that it's possible to shoot very accurate groups with field points with less than eight percent FOC, but again, field points are more forgiving than broadheads. Just as with fletch size, it's better to err on the large side with FOC. You don't want to go overboard, though (past 18 percent). Too much FOC makes your arrows point-heavy and less aerodynamic downrange.
How do you figure out your arrow's FOC? The Easton computer program that I mentioned earlier in the article has a calculator that will do the job for you. If you don't have the program, you have to do the math yourself. Here's how I do it, and since I'm no math wizard, it's pretty simple. The formula is: [(ABP ÷ TAL) - .50] x100 = FOC%
ABP is the distance to the arrow's balance point from the nock of the arrow, and TAL is the total arrow length. (This formula is different than the one recommended by the AMO. It provides the same answer, but I've found it a little easier to use.) All you need is a tape measure and something to balance an arrow on (like a pencil) to use the formula. First, balance the arrow and mark the balance point with the pencil. Then measure from the throat of the nock (where the string fits inside the nock) to the mark you made at the balance point. This is the arrow's balance point (ABP).
Next, measure the length of your arrow from the throat of the nock to where the insert goes into the shaft. This is the total arrow length (TAL). (If you use carbon shafts with outserts, measure to where the point screws in.) Finally, input the figures into the FOC formula. For example: If you had a 30-inch arrow that balanced at 19 inches, the formula would read: [(19÷30) - .50] x 100 = 13.3 percent FOC.
What do you do if your arrow's FOC is too low? You might have to use a heavier broadhead or change shafts. Be careful here. Adding a heavier head can change arrow spine, meaning you might have to use a different arrow or, at the very least, re-tune the bow.
If you really don't want to change shafts or components and you're shooting vanes, try switching to feathers. They're typically much lighter and could move your FOC forward by two percent or more. You can also try using a lighter nock.
01-14-2010, 11:30 AM
#18
Spike
Join Date: Jan 2010
Posts: 92
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Most of the X-Forces like an arrow that is underspined. I shot an UL400 at 70# (29") and got bulletholes with the shaft straight over the grove in the shelf and at 90 deg. to the string (level). I should mention that I had to use a PSE micro prong to do that...drop aways didn't paper tune at all.
I tried a Lightspeed 340 spine....and WOW...it tore 1 1/2" straight up thru the paper. Many others said same thing about the X-Forces preferring an underspined arrow to get bulletholes. Your shaft selection is extremely stiff for the poundage of that GX.
This is the quote off archery talk And there are alot of other post on other sights that say the same.It might not seem right but test are proving it.I am only trying to offer help here if people don't like it oh well don't listen.I know my bow and it likes under spined arrows better.I hunt with a 400 axis infused and shoot league with a 500 fmj axis at 70# 28'' out of a monster Xlr8 it's what works for me oh and might I add I have won every shoot this season and with two weeks left I am far enuf ahead in points I can miss a day and still win.
Most of the X-Forces like an arrow that is underspined. I shot an UL400 at 70# (29") and got bulletholes with the shaft straight over the grove in the shelf and at 90 deg. to the string (level). I should mention that I had to use a PSE micro prong to do that...drop aways didn't paper tune at all.
I tried a Lightspeed 340 spine....and WOW...it tore 1 1/2" straight up thru the paper. Many others said same thing about the X-Forces preferring an underspined arrow to get bulletholes. Your shaft selection is extremely stiff for the poundage of that GX.
This is the quote off archery talk And there are alot of other post on other sights that say the same.It might not seem right but test are proving it.I am only trying to offer help here if people don't like it oh well don't listen.I know my bow and it likes under spined arrows better.I hunt with a 400 axis infused and shoot league with a 500 fmj axis at 70# 28'' out of a monster Xlr8 it's what works for me oh and might I add I have won every shoot this season and with two weeks left I am far enuf ahead in points I can miss a day and still win.
Last edited by blacktail4ever; 01-14-2010 at 11:34 AM.
01-14-2010, 12:06 PM
#19
Guest
Posts: n/a
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Most of the X-Forces like an arrow that is underspined. I shot an UL400 at 70# (29") and got bulletholes with the shaft straight over the grove in the shelf and at 90 deg. to the string (level). I should mention that I had to use a PSE micro prong to do that...drop aways didn't paper tune at all.
I tried a Lightspeed 340 spine....and WOW...it tore 1 1/2" straight up thru the paper. Many others said same thing about the X-Forces preferring an underspined arrow to get bulletholes. Your shaft selection is extremely stiff for the poundage of that GX.
This is the quote off archery talk And there are alot of other post on other sights that say the same.It might not seem right but test are proving it.I am only trying to offer help here if people don't like it oh well don't listen.I know my bow and it likes under spined arrows better.I hunt with a 400 axis infused and shoot league with a 500 fmj axis at 70# 28'' out of a monster Xlr8 it's what works for me oh and might I add I have won every shoot this season and with two weeks left I am far enuf ahead in points I can miss a day and still win.
Most of the X-Forces like an arrow that is underspined. I shot an UL400 at 70# (29") and got bulletholes with the shaft straight over the grove in the shelf and at 90 deg. to the string (level). I should mention that I had to use a PSE micro prong to do that...drop aways didn't paper tune at all.
I tried a Lightspeed 340 spine....and WOW...it tore 1 1/2" straight up thru the paper. Many others said same thing about the X-Forces preferring an underspined arrow to get bulletholes. Your shaft selection is extremely stiff for the poundage of that GX.
This is the quote off archery talk And there are alot of other post on other sights that say the same.It might not seem right but test are proving it.I am only trying to offer help here if people don't like it oh well don't listen.I know my bow and it likes under spined arrows better.I hunt with a 400 axis infused and shoot league with a 500 fmj axis at 70# 28'' out of a monster Xlr8 it's what works for me oh and might I add I have won every shoot this season and with two weeks left I am far enuf ahead in points I can miss a day and still win.