this post was submitted on 02 Feb 2025
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How to calculate spine values (feddit.org)
submitted 4 days ago* (last edited 4 days ago) by [email protected] to c/[email protected]
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I want to build myself a spine tester to calculate the spine value of arrow shafts using the ASTM F2031 standard. I do know that I need a 880 gram weight and that I have to measure the amount of flex that the shaft produces when I hang said weight at the center of a 28 inch span off the shaft.

Well, but what then? I can measure the amount of deflection I have then but let's say the shaft is deflected by 1/12th of an inch or some millimetres. How do I calculate a spine value that ranges between 20 to 80 from that?

Can anybody give me a hint or solution?

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[–] [email protected] 2 points 4 days ago

According to https://www.infocusarchery.com/advice/a-completeish-guide-to-arrow-spine spine is the deflection in 1"/1000. As in spine 730 means the deflection is 0.73"