# Choosing the Right arrow spine



## TMan51 (Jan 25, 2004)

Try this: http://www.tap46home.plus.com/mechanics/

And this: http://home.att.net/~sajackson/archery.html

There are books on tuning, some are helpful, most are outdated. There's more information on the internet. Many Physics Professor/coaches maintain sites that are really good, and their papers are on line.

Arrow spine is a confusing topic in a lot of ways. Arrow calculators can approximate a static rating for a given DL/PW for a given tip weight. That doesn't mean that it will fly from your bow, or that all 0.400 spine arrows, for instance, will have the same dynamic properties. I shoot mainly 50 or 60lb bows, and I have 6 different shafts for those two weight classes. Usually one of them will work. Not always.

Your 6GPP comment may be a useful starting point, but for ease of tuning 7-9GPP will be easier to tune for in most cases, because the arrow is moving slower. But arrow selection has a lot of if's and maybe's, and if you can find someone who sells singles to try, you will be surprised at the differences. There is no "best" shaft, but there will be a best for you.


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## bfisher (Nov 30, 2002)

Shooting a given grains per pound which determines the arrow weight has virtually nothing to do with arrow spine. Spine is determined by combining the diameter and wall thickness of the arrow.

It's not all that hard to get bare shafts to fly well, but first you have to get some thing in order. One is setting the bow up, paying attention to details such as cam lean and such. Set the rest close to the dynamic cneter of the bow, which may not be the physical center as viewed from the back. Set a loop or nocking point perpendicular to the string.

Next you look at a shaft that is within a certain spine rating for your bow's particular draw length and draw weight. Also computed in here is the length of the arrow, fletching type, and tip weight (not broadheads).

Start at a short distance like 6', shooting at shoulder height. You may have to get on your knees. Adjust to get the arrow shooting square, making vertical adjustments first. Keep working backwards, fine tuning as you go.

Here's something that I consider almost false information, if you will. Some of the computer programs will tell you, as an exmple, that your shaft should be cut to some length, say 27 5/16. This, IMO is a joke. Normal people don't measure their arrows that close, nor does it matter. This doesn't have anything to calculate any form abnormalities you may have or bow torque. We are not machines.

I cut my arrows to a certain length. Normally 27". I could care less about 1/4" so long as they are all the same. Doing this for 35 years I have a very good idea of where to start with centershot so a rarely ever move the rest. If the shaft planes a bit one way or the other I play with the limb bolts---adjust the draw weight. 

This is where many people screw up. They'll play around with centershot, different shafts, different point weights and a lot of other stuff. Play with the draw weight. Don't get caught up HAVING to shoot a certain poundage. Limb bolts are on a bow for a reason and it sure isn't just to hold the limbs in place. It's easy and it's free.

I would also add that I never paper tune. Once I have my bow shooting bare shafts out to 30 or 35 yards I might pound an arrow through paper. I'll also try other methods of tuning such as French or Walkback tuning. Sometimes a combination of these will show you little nuances that just one method won't.


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## fletched (May 10, 2006)

bfisher said:


> Shooting a given grains per pound which determines the arrow weight has virtually nothing to do with arrow spine. Spine is determined by combining the diameter and wall thickness of the arrow.
> 
> It's not all that hard to get bare shafts to fly well, but first you have to get some thing in order. One is setting the bow up, paying attention to details such as cam lean and such. Set the rest close to the dynamic cneter of the bow, which may not be the physical center as viewed from the back. Set a loop or nocking point perpendicular to the string.
> 
> ...


Very good post.

I bare shaft tune. I start out by shooting a fletched arrow through the paper. Once I get it right, I switch to a bare shaft through the paper. Once I get a good hole, I start shooting it a longer distances. This is where playing with the poundage will help. If you are impacting left or right from fletched arrows, you may need to adjust the poundage. I like when my bare shafts hit with my fletched shafts at 30 yards. It makes for a great shooting bow.


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## SonnyThomas (Sep 10, 2006)

I agree with TMan and bfisher. For problem bows I shoot through paper just to see what's going on. For fine tuning I perfer French tuning.


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## konrad (Mar 29, 2009)

http://www.eastonarchery.com/products/selection

I start here when selecting shaft spine for any given shaft length (from the base of the throat of nock to the front of the insert), bow draw weight and desired point weight.

Very easy to use and works well.

Easton Technical also maintains an e-mail contact site but sometimes they take a couple of days to answer.

Remeber to follow throughhhhhhhh!


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