Key Info For When Selection The Right Shafts
One of the keys things to when selection the right arrows shafts when shooting is getting the correct spine of shaft. It is highly recommended that if you can you go to a archery shop or similar that has a large amount of made up arrows as there ‘practise’ or ‘test’ arrows to get a arrow matching done to the bow you are shooting and the style of shooting you are doing. By doing this it means you get the best experience when shooting, all of your shooting kit matches you and the bow. If you shoot multiple bows and different styles do it for each one. Narrowing down the ‘static spine’ of the arrow with in 1-2lb will improve your shooting massively. Get this right first and if you want to ‘weight match’ arrows (in grain mass) then do so at a later time, but you will find you won’t need to if you get a closely matched set of arrow shaft in ‘static spine (lb).
The difference between ‘static spine’ and ‘dynamic spine’
When talking about ‘static spine’ this is the spine of the arrow shaft that is measure on a arrow spining jig. For wooden arrow shafts this is measured over 2 fixed points 26″ (66.04cm) apart with some sort of gauge in the middle at the mid point (13″ – 33.02cm). A 2lb weight is then applied / hung from the arrow shaft as close as you can to the mid point near the reading gauge. This then normally gives a reading in Inches which you then can look up on a spine chart, basically some clever maths has been done to convert the deflection reading in Inches to a value in Pounds (lb). This lb value is your stiffens of the arrow.
With ‘dynamic spine’ this is very very hard to measure or get a value of. Basically ‘dynamic spine’ is what the arrow shaft is doing once it has left the bow, how much it is flexing / osculating. You are aiming to reduce this as much as possible by trying to get the correct spine of arrow shaft for your bow, the way you shoot and style you shoot. Reducing the flexing / osculating after the arrow has left the bow means you will get a faster arrow from you bow and more likely to travel further. The more the arrow is flexing / osculating through the air the more energy / power it is to go in a straight line, meaning less distance and speed.
Dynamic Spine Adjustments – All over the below can affect what arrow shaft spine you need.
If your arrow setup deviates from a 28-inch cut length or a 125-grain field point:
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Arrow Length:
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Add 1 inch in arrow length – Softens dynamic spine by approx. 3–5 lbs. Select 1 group higher (stiffer) wood spine.
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Subtract 1 inch in arrow length – Stiffens dynamic spine by approx. 3–5 lbs.
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Point Weight:
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Going from 125 gr to 145/160 gr – Adds front-of-center weight, softening spine by ~3–5 lbs.
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Going from 125 gr to 100 gr – Stiffens arrow dynamics by ~3–5 lbs.
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String Material:
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FastFlight / High-performance strings release energy faster than Dacron B50 / B55, requiring a shaft 3–5 lbs stiffer.
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Other things that will affect what spine arrows shafts you need
If you are using shafts smaller that 5/16″, like 9/32″ & 1/4″ then due to reducing the cross section mass of the arrow shaft and the mass of the arrow you will likely find that you might have to go up in spine(s) of shafts to compensate. Again as said in the first part of this page it is advised to go to somewhere to try out arrow to what is called a Arrow Matching session.
If you are tapering or barrelling you arrow shafts or getting them from a shop, manufacture, supplier, etc. Then due to reducing the shafts at either nock end or pile end or both you will need to go up in spine from a parallel shaft to achieve the stiffness of arrow shaft wanted. Also it is advised to not do the tapers more than 9-10″ or this affects the spine off the shaft a lot, as well as the dynamics of how the shaft works with the bow and in the air.
The confusing caused by how wooden arrows are measure and what the charts are worked around
To make things really confusing for all wooden arrows are measured on a spining jig that has 2 fixed points at 26″ apart, but you will find on many arrow charts or searching the internet they will talk about the arrow charts being based on 28″. Simply ignore it all it all comes down to when this was all being worked out back in the 60’s & 70’s using recurve bows. There a point where the hand grip is, which should be around about where a arrow rest should be / rest button hole should be. Then they added an extra bit on to work with clickers etc. SO YES MAKES IT CONFUSING and the reason for this is the measured aluminium arrows back then during these tests over 28″.
So;
Wooden arrows are measured over 26″ with a 2lb weight to be truly ATA Standard.
Aluminium and now carbon arrows are measured over 28″ with a 1.94lb weight to be ASTM Standard.