# How much does the 'spine' change with point weight changes?



## nuts&bolts (Mar 25, 2005)

Fly2High said:


> Hi everyone,
> I read about using identical length arrows with the same weight points but change the spine of the arrows to find what works best.
> 
> Can you select a close spine and just change point weight?
> ...


You want to shoot barebow. So, what is the size of your barebow? 25-inch riser? 23-inch riser? Are you using ILF short, or medium or long limbs? What is the poundage on your fingers, at full draw? What is the brace height on your barebow?


----------



## Fly2High (Feb 25, 2019)

N&B,
this question is not directed at a particular format of archery. I was asking a general question on tuning and how far can a particular arrow be made to work based on tip weight.


----------



## nuts&bolts (Mar 25, 2005)

Fly2High said:


> N&B,
> this question is not directed at a particular format of archery. I was asking a general question on tuning and how far can a particular arrow be made to work based on tip weight.


Heavier vanes will make an arrow behave more stiff.
Less point weight will make an arrow behave more stiff.
Adding an arrow wrap at the back end of the arrow, will make an arrow behave more stiff.

Lighter vanes (shorter, smaller) will make an arrow behave more weak.
Going from plastic vanes to feathers will make an arrow behave more weak.
MORe point weight will make an arrow behave more weak.


----------



## nuts&bolts (Mar 25, 2005)

Fly2High said:


> N&B,
> this question is not directed at a particular format of archery. I was asking a general question on tuning and how far can a particular arrow be made to work based on tip weight.


with ZERO information about pounds on the fingers,
with ZERO information about the brace height for your recurve bow,
with ZERO information about bow size, bow draw length

we can give you only very very GENERAL guidelines.

LONGER arrow shaft will behave more weak. (start with full length shafts).
SHORTER arrow shaft will behave more stiff. This is what happens when we trim 1/4-inch off a full length shaft, and start point weight experiments again.

HOW far can a particular arrow be made to work....we can ONLY answer this question with brace height, bow length, draw length for the shooter, poundage rating on the limbs.


----------



## nuts&bolts (Mar 25, 2005)

Fly2High said:


> N&B,
> this question is not directed at a particular format of archery. I was asking a general question on tuning and how far can a particular arrow be made to work based on tip weight.


Need to know are we talking aluminum arrows?
Need to know are we talking carbon arrows?

So, one more time. Much easier to answer your questions, if we know YOUR draw length, and YOUR pounds on the fingers, and details about the bow.


----------



## nuts&bolts (Mar 25, 2005)

So, 25-inch riser. So, medium ILF limbs. This makes for a 68-inch recurve bow.
So, BCY 8125G string. So, let's ASSUME 28-inch draw length. Therefore, POUNDS on the fingers will be the weight rating for the limbs.
So, let's assume 38 lb limbs. Therefore, with a 28-inch draw length, we have 38 pounds on the fingers.
Brace Height is set at 9-1/8ths.

Let's assume carbon arrows. Let's assume target points. Let's assume VaneTec 187 vanes, so 1.87 inches long and 0.3-inches tall.
Let's assume no arrow wrap. Let's assume we are building outdoor arrows, so arrows need to shoot short (about 18 meters) and these arrows also need to shoot long (70 meters).

So, a REASONABLE FOC, would be 12%. But, YOU want to know how far you can go, to make an arrow work, based SOLELY on tip weight. If we go STUPID heavy on the tip weight, the FOC gets REALLY LARGE. If we go STUPID light on the tip weight, the FOC gets TINY, and borderline unstable aerodynamically.

With THESE assumptions, Easton Carbon One 810 spine rating, with 120 grain target points, and Easton G-nock (large groove) will work nicely.
No arrow wrap. 3 vanes. Medium plunger setting should get his arrow to tune. Carbon to Carbon tube length of 28-inches. So, that means Nock Groove to END of SHAFT = 28.5-inches.


----------



## nuts&bolts (Mar 25, 2005)

What if you use 150 grain target point? What has to change?

For the arrow to tune with 150 grain target points, the Easton 810 spine shafts would need to be cut to 25.25-inches. NOT SAFE to do, with a 28-inch draw length. So, 150 grain target points are a NO GO. DO not use 150 grain target points, with the Easton 810 spine shafts.

Well, if you add 10 grains of arrow wrap, then what? If you use 10 grains of arrow wrap at the bACK end of the Easton 810 Carbon One shafts, then, the 150 grain points would need a 26.25-inch carbon to carbon tube length. NOT SAFE for a 28-inch draw length, so again, a NO GO.

Well, WHAT if you goto a 100 grain target point, for the Easton Carbon One 810 spine shafts? No arrow wrap, you would need 30-inches of carbon to carbon tube length. End of shaft to END of nock groove would need to be 30.5-inches long. ONLY one problem. The Easton Carbon One 810 shafts are full length at 29.125-inches, so not possible to get 30-inch long carbon tubes, for the Easton Carbon One 810 arrow. 

So, for FULL length Easton Carbon One 810 shafts (29.125-inches) and 100 grain points, you would need to drop the brace height to 8-5/8ths.

What if you use 110 grain target points? Using FULL length Easton Carbon One 810 spine shafts (29.125-inch long tubes), and no arrow wrap, you could boost the brace height back up to 9.25-inches, and these would tune for you.

So, 38 lb limbs, 28-inch draw length, resulting in 38 lbs on the fingers, for a 68-inch recurve bow, and a brace height of about 9-1/4 inches to a brace of 8-5/8ths inches (YOU have to figure out the brace that works), you can tune Easton Carbon One 810 spine arrows, from 100 grains to 110 grains to 120 grains, assuming VaneTec 187 vanes. YOu can play with arrow wraps of varying lengths (more length on the arrow wrap, means MORE WEIGHT), which means the arrow will tune STIFFER.


----------



## pottergreg (Mar 20, 2015)

If you want to know about compound bow, go to the Victory Archery website under arrow guide/open spine selector and you can insert different point weights and shafts lengths. Bows vary depending on efficiency, IBO, etc. but my rule of thumb is about a 4 pound draw weight difference for 25 grains of point weight, the same for 1 inch of shaft length. So if you cut 1 inch off your shaft and went from a 125 grain point to a 100 grain point the dynamic spine of the shaft would be able to handle 8 more pounds.


----------

