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Spine relative to length

I don’t think on carbon it matters much once you’ve obtained enough spine to shoot your arrow of choice. Over spined out of a center shot bow never seemed to hurt much. At least by the time I cut my 340’s to 27”.

I don’t have any idea how much spine is affected by length in carbons. I just know it’s hard to see bad results due to being too stiff out of a modern compound bow. Underpinned is different.

All of those changes are taken into account in the spine charts. Put those inputs in along with your draw length, arrow length, etc and you will get what you need. Cutting the arrow will make it stiffer. Adding weight to the front will make it weaker.

Spine chart gets me the ballpark. To dial it in, I shoot each arrow bareshaft before fletching. Out of a dozen arrows I end up with slight variations in length and insert weight to get them all spined the same. I shoot a finicky finger bow and my setup is more sensitive to spine than most.

James- I miss the days of studying the Easton chart at Relos...that chart held critical info for a kid about to spend 2 weeks savings on a dozen gamegetters or really splurge on super slams.

Length alone deals with static spine.

Added weight upfront deals with dynamic spine.

Regardless, a shorter arrow will be more stiff no matter what.

Ohio, your shop guy is actually kinda right, insofar as the published deflection RATING of a particular shaft size doesn’t vary with length. Since the deflection RATING comes from placing a standardized test weight on 28 inches of suspended shaft. Of course actual static deflection would increase or decrease for different shaft lengths. And then, as mentioned above, there are DYNAMIC factors affecting stiffness behavior. Such as point weight.

Spine charts are always off for me, they all say I need a 350 but my best flight is with 250’s. Nothing fancy on the front end just a 100gr 3-blade fixed head. Agree that they should be a rough guide but have to wonder how many archers know that? I bet lots there’s tens of thousands of guys shooting suboptimal spines because that’s what the chart says, or some pro shop guy recommended it.

Suboptimal spine = less forgiving = more bad hits at crunch time.

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