Carbon Arrow Spine
Spine rating (300, 340 400 etc) of a Carbon Arrow is only a measurement of its stiffness. The Sika Stopper carbon arrows have a number of stiffness options: the lower the number, the stiffer the carbon arrow.
For example, a 340 Carbon arrow is stiffer than a 400 spine carbon arrow. There are two kinds of spine but for this we will talk about 1. (stick with us, we promise not to get too technical).
That is static spine, which is how an arrow bends when an 880-gram weight is put on the middle of the Carbon arrow. The Carbon arrow must be 29” in length and supported by two points, which are 28” apart.
The number of inches the Carbon arrow deflects or bends X 1000 due to the weight is the spine size or measurement of an Carbon arrow. So, a 500 Carbon arrow bends .5-inches when the weight is applied.
Carbon Arrow spine can seem like a complex issue and to some degree it is - so we would like to break it down into a rough guide. This is not going to be as good as talking to your bow-tech for a perfect match, but if you’re not able to see your bow tech this will at least get you on the right path.
Factors that you must consider when selecting a carbon arrow.
1. Bow poundage
2. Carbon Arrow Length
3. Up front weight - insert and arrow head.
Bow poundage - These assume a standard set up of 28-inch carbon arrow with 100 grain arrow head.
30 to 44 pounds 500 spine
45 to 64 pounds 400 Spine
65 to 75 pounds 340 Spine
76 to 80 pounds 300 Spine
Carbon Arrow Length
· 28 inch - no change to spine from above
· 27 inch or less - Carbon Arrow becomes stiffer, so either increase arrow head weight or pick lower spine
· 29 inch or more - Carbon Arrow becomes weaker, so either decrease arrow head weight or pick higher spine.
Up Front Weight - These assume you have a standard insert of 15 to 25 grains
· 85 grains - Carbon Arrow becomes stiffer, so either increase arrow head weight or pick lower spine
· 100 grains - no change to spine from above
· 125 grains - Carbon Arrow becomes weaker, so either decrease arrow head weight or pick higher spine.
· 150 grains - Carbon Arrow becomes weaker, so either decrease arrow head weight or pick higher spine.
How to make your Carbon Arrow Act Weaker. (Create less Spine)
Increase peak bow weight
Increase point weight or the point\insert combination
Lighter string material reduce number of strands in the string
Lighter serving material or lighter nocking point
Increase Carbon arrow length
Increase brace height on recurve
How to make your Carbon Arrow Act Stiffer. (create more spine)
Decrease peak bow weight
Decrease point weight or the point\insert combination
Use heavier bow string material or add more strands to the string
Use heavier serving material and\or nocking point
Decrease brace height on recurve bows
Shorten the length of the Carbon arrow