# Finding arrow spine



## bosoxfan (Apr 19, 2007)

What is the best way to find the spine of an arrow? - the "backbone" running the length of the arrow?
Thanks.
Will


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## AKRuss (Jan 10, 2003)

Spine is meaured with a spine tester. The current ATA spine standard is measured across 28" centers with a 1.94# weight suspended from the center. The measurement is the deflection or the distnace the weight make the shaft bend at the center, expressed in inches. The measurement is taken with a run-out micrometer or a pointer with set marks. A "340" spine means the shaft's deflection is 0.340". A 340 spine is stiffer than say a 500 (0.500") spine. A good spine tester can be spendy.


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## bosoxfan (Apr 19, 2007)

*?*

I'm not sure how to phrase my question. Shouldn't you put the cock vane on the stiffest part of an arrow? I have heard that some people put their arrows in water and the side that is below the water is the stiffest part of the arrow - this is were you would put the cock vane - keeps your arrows more consistent. Any other ways of doing this without putting your arrow in water?


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## Spotshooter2 (Oct 23, 2003)

The only other way is if you have a spine tester to run them on.


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## scudrunner (Dec 31, 2008)

*Would "spline" be the proper term here?*

I am new to this but have read a bit. Is Spline the more correct term? When floating the shaft, how do you keep the water out? And then, if the stiffest part (spline?) is down in the water, how do you get an accurate mark?


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## bfisher (Nov 30, 2002)

scudrunner said:


> I am new to this but have read a bit. Is Spline the more correct term? When floating the shaft, how do you keep the water out? And then, if the stiffest part (spline?) is down in the water, how do you get an accurate mark?


 The correct term is "spine". Spline refers to grooves machined into a shaft such as those on the end of a yoke of a drive shaft where it slides into the transmission of an automobile.

I am interested in what is used to plug the ends of a shaft also. I imagine that a nock on both ends would work, but will wait to hear from others that have done this. As for marking the shaft accurately? My guess woud be to mark the side of the shaft this is "up" and then guestimate 180 degrees difference when fletching the shaft.


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## SonnyThomas (Sep 10, 2006)

Floating a arrow will find the heaviest side of the arrow and thus, should be the spine. Nocks plugging both ends will work, but there is a company that makes matched plugs (for weight I guess). As for vane placement, the cock vane can be on the spine side or opposite the spine side. I understand it doesn't matter just so long as the spine is aligned to the power stroke of the bow string.


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## AKRuss (Jan 10, 2003)

I've always thought the float test is more likely to show which side of the shaft is bent. I guess if each shaft was perfectly straight (not likely with an all carbon shaft) the heaviest side would be down but even then there is no way to tell if that's the heaviest spine without a spine tester. Another thought, do you want to orient your shafts with the heaviest spine or the most common spine of the group? Lastly, I've done a lot of rotational spine testing on shafting and generally find very little difference, even with fairly crooked ones.


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## ceebee (Dec 3, 2002)

I would think with the equipment used to make arrows now that spine is not as important. Cock feather up or out? Do you shoot fingers? I would place the cock feather out, with a 'release' cock feather is up or down, depending on rest. Fingers can be touchey about stiff or weak spine, release shooters can shoot an arrow that is way over spined and get by with it. I don't worry about spine as much as front of center. I like about ten percent FOC this seems to be the best for me shooting indoors as they tend to group better.
ceebee


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## AllenRead (Jan 12, 2004)

ceebee said:


> I would think with the equipment used to make arrows now that spine is not as important. Cock feather up or out? Do you shoot fingers? I would place the cock feather out, with a 'release' cock feather is up or down, depending on rest. Fingers can be touchey about stiff or weak spine, release shooters can shoot an arrow that is way over spined and get by with it. I don't worry about spine as much as front of center. I like about ten percent FOC this seems to be the best for me shooting indoors as they tend to group better.
> ceebee


With compound bows shot with a release, the spine is less important, but what is very important is that the spine match from arrow to arrow. 

Guys with 26" draw length shooting 2613's from 50 lb bows have demonstrated that spine isn't all that big a deal. But as with everything to do with arrows, the better that they match, the better they will shoot.

As you pointed out, spine is much more important with any bow shot with fingers.


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## tjroadie (Dec 27, 2007)

*floating*

I only thought people floated large carbon arrows since the are wrapped in layers and the wraps end up in a different concentric orientation?


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## camomano (Sep 20, 2006)

*Here's a quick way*

I build fly rods and you find the spline by placing one end of the rod, usually the heavy end, on a hard surface. Hold the other end with one hand and with your free hand, spin the rod/arrow in the center. You will feel the rod or arrow "jump" at the stiffer spline line when it is slightly bent under rotation. To get the feel of this, try it with a fishing rod section. The guides should be either on or opposite the spine line. It depends on the manufacture.

With arrows, it's much less pronounce but it's there. I go back and forth over the hump to nail it down, then place a piece of tape on it to mark it before fetching.


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## camomano (Sep 20, 2006)

camomano said:


> I build fly rods and you find the spline by placing one end of the rod, usually the heavy end, on a hard surface. Hold the other end with one hand and with your free hand, spin the rod/arrow in the center. You will feel the rod or arrow "jump" at the stiffer spline line when it is slightly bent under rotation. To get the feel of this, try it with a fishing rod section. The guides should be either on or opposite the spine line. It depends on the manufacture.
> 
> With arrows, it's much less pronounce but it's there. I go back and forth over the hump to nail it down, then place a piece of tape on it to mark it before fetching.


I forgot to mention that with your free hand you must deflect the shaft slightly as you roll it. Then you'll feel the "jump".


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