# egzacly what does "spine" mean anyway???



## 'nothernoob (Apr 17, 2009)

Ok. I have a vague idea what y'all are talking about by "spine" but I'd like to understand it much better. It strikes me as important if I want to do more than play at archery (and I do want to.)

I understand that an arrow flexes in flight. The way I read "spine" is it's a combination of weight and stiffness. Is that right?

What I want to know, please, is what, exactly, does spine mean (in archery speak).
Secondly, what does it mean to the bow- How does it react in physical contact with the bow... in flight... What choices are better for what set of conditions, i.e., hunting vs target shooting- that sort of thing.

Thanks!


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## Viper1 (Aug 21, 2003)

'n -

There are two types of spine:

1. Static spine is simply the stiffness of the shaft, measured by setting the shaft on centers either 26" or 28" apart, hanging a 2# or 1.94# weight in the middle and noting how much it bends (AMO does it one way and Easton another - go figure. That serves as a starting point for arrow selection "Weight" has nothing ot do with it.

2. Dynamic spine is the way the ENTIRE arrow reacts to being shot from a bow. Since we're are generally talking about a finger release and a non-centershot bow, the arrow will flex due to lateral forces after release (Archer's paradox). Not only shaft stiffness, but length, head and tail weight, offset from centershot and even finger grip on the string will affect dynamic spine. One thing oft touted in some trad circles is nock fit (tightness), that's usually stated by someone who doesn't understand paradox, as the flexing has been established BEFORE the nock leaves the string. Unless the nocks are EXTREMELY tight (as in not fitting on the string without a sledge hammer) most chronographs won't pick up a change outside of statistical error either.

Viper1 out.


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## LBR (Jan 1, 2004)

Nock fit won't change your arrow spine, but it can affect arrow flight and noise. How much affect depends on how tight it is, the draw weight, etc.

One of the most reccomended sites for tuning on the www, www.bowmaker.net, warns about this, as do many others who make a living with bows.

The reason it has an effect is simple--it offers resistance when the arrow is coming off the string.

There's gobs of info. on arrow spine if you do a search, but it's basically arrow stiffness.

There's no chart that is fool-proof--too many variables. There's no one arrow spine that's going to shoot perfectly from every [email protected] bow on the market--but the better charts will get you in the ball-park.

Proper arrow spine is one of the variables you have to work on to get the best arrow flight--which results in less noise and better penetration.

Chad


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## 'nothernoob (Apr 17, 2009)

I don't know how much punch this thing is supposed to have but its no beggar now. Even with these 2117s (w/out looking, I think that's the number) it'll hit that hayroll with a thump! and punch them in half ways or better deep.


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## longbowguy (Nov 14, 2004)

The root of the matter is that an arrow shot from fingers does not fly straight. The butt of the arrow flips sideways off the fingers, flexes around the bow and wig wags to the target. This is part of what we call the 'archer's paradox'. Spine, in simple terms, is the flexibility of the arrow. A strong bow needs a stiff arrow and a weak bow needs a flexible one. If the arrow is too stiff it tends to fly to the left: if too weak, to the right. Finding a good match between bow and arrow is the basic goal of tuning our tackle. We want to tune it to shoot where we look, and finding the right spined shafts is the first step. 

But there are a lot of other variables, and they get pretty complicated. But it begins with spine. - lbg


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## 'nothernoob (Apr 17, 2009)

a-HA!
*"A strong bow needs a stiff arrow and a weak bow needs a flexible one. If the arrow is too stiff it tends to fly to the left: if too weak, to the right."*
My bow is just a plank bow and 40# @ 28' so it's no power house and my arrows are too stiff for it (2117s) and sure enough, they have been pulling to the left!
Thanks!


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## LBR (Jan 1, 2004)

> If the arrow is too stiff it tends to fly to the left: if too weak, to the right.


That's for a right-handed shooter--just the opposite for a lefty.

Chad


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## ArcherySupplier (May 20, 2014)

That's right.



'nothernoob said:


> a-HA!
> *"A strong bow needs a stiff arrow and a weak bow needs a flexible one. If the arrow is too stiff it tends to fly to the left: if too weak, to the right."*
> My bow is just a plank bow and 40# @ 28' so it's no power house and my arrows are too stiff for it (2117s) and sure enough, they have been pulling to the left!
> Thanks!


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## longbowguy (Nov 14, 2004)

Since the string pushes the flexing arrow from the back end, putting more weight on the front end, will make it bend more. That is the dynamic business. It will bend more and hit further to the right. But lower because of the weight. - lbg


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## rattus58 (Jul 9, 2007)

'nothernoob said:


> Ok. I have a vague idea what y'all are talking about by "spine" but I'd like to understand it much better. It strikes me as important if I want to do more than play at archery (and I do want to.)
> 
> I understand that an arrow flexes in flight. The way I read "spine" is it's a combination of weight and stiffness. Is that right?
> 
> ...


 Spine is how much an arrow will flex. You can measure it with weight and a ruler, so to speak... dial gauge better though.... and then again spine is affected by the shot, brace height, point weight, etc... dynamic spine... arrow behavior under way.... does it act weak or strong... does it fly right or left after we do something to tuning... my bit of observation anyways... :grin:


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## Bowmania (Jan 3, 2003)

Static spine is stated as .600, .400 ect NOT 3555 which means nothing except to the manufacturer of that brand.

Bowmania


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