Spine Confusion

[bow101]

Could someone elaborate more on arrow spine.  So if the spine tester is done at 26" spacing would not a longer arrow have less spine..? And a heavier tip have less spine.  So what I'm saying is a 11/32" 30 inch arrow is spined to 50# cut off 2 inches now the spine would change.! But on the spine tester it is still 50#.   

[DGF]

The spine tester uses a gap of 26" to establish spine for a 28" arrow. For each inch of arrow length over 28" subtract 5# from the spine, and for each inch under 28" add 5# to the spine.

ie. An arrow has a spine measured on a 26" gap giving a reading of .520" deflection. That would be 50# spine on a 28" arrow. If that same arrow was 26" the arrow would shoot stiffer and act as though spined 60# @ 28" arrow length. That same arrow cut to a length of 30" would act like an arrow of 40# @ 28" arrow length.

If you want to keep all your shafts the same length you can also use point weight to adjust how an arrow acts. The AMO spine weights figure the use of a 125 grain point. If you add weight to the tip of an arrow it will act weaker, and if you subtract weight it will act stiffer. 

To answer your question you have two types of spine being measured. The static spine is what you are given by using a spine tester. It is the deflection of the arrow in the center over a 26" span using  a 2# weight in the center. The dynamic spine is how an arrow acts when shot. When arrow length changes the static spine doesn't change. It will still bend the same amount over a 26" span with a 2# weight. However, as you shorten arrows or adjust point and nock weights you do affect dynamic spine. That arrow will act differently when shot from a bow when those changes are made.

-Dan

[KHalverson]

x2

[bowtarist]

Yup, DGF is right on the money.  Well put Dan. I think I'll copy and past that one.    dp

[M-P]

Howdy,  I like DGF's explanation,too!   

This info is the starting point for pairing arrows with your bow.   Whether your bow has a shelf, or not, and how wide the handle ( if no shelf), the length of your draw and how clean your release is, all affect the spine needed to work well with your bow.
Ron

[bow101]

Thanks a billion....!

[Matt G.]

Excellent explanation!!!

[Danzn Bar]

I have to say also, "you done good DGF! " very good,  Simple and to the point
DBar

[crooketarrow]

  Hav'nt spined arrow in years other than just shooting it.
  If me and the bow shoots it I use it.