Primitive Archer
Main Discussion Area => Bows => Flight Bows => Topic started by: DC on October 29, 2016, 11:53:19 am
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How do you measure arrow spine on an arrow that is less than 26" long?
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How about this? take an aluminum shaft and slip it over the end, lengthening the shaft. Since the arrow mostly bends in the middle, the aluminum shouldn't have much effect
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How do you measure arrow spine on an arrow that is less than 26" long?
I measure spine at the actual length of the arrow. I don't need to know spine according to archery standards I only need it for my own purposes.
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I think you divide distance between the two supports by the deflection, so it works the same for 28, 26, 24 " etc
Obviously the further apart the supports the greater deflection and thus the easier it is to measure it and there is less error.
It should be easy enough to check with a long arrow, do the test at different distances and see how the results tally (If you do it, please let us know how it works out)
Mind like Badger says, it's all relative anyway, as long as your method is consistent, the figures will be meaningful for your tests.
Del
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Just a curiosity thing. It finally clicked that flight arrows were often shorter than 26" and it made me wonder.
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Just make another post for your spine tester. It is all relative anyway.
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Actual arrow flight trumps spine.
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So based on the equation to the far right we can solve for a deflection from a shorter arrow to a longer arrow. The little squiggly thing in equation 2 represents deflection, therefore using the second equation you can solve for the theoretical deflection at 26 inches.
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For example, If you measured a deflection of 0.35 inches at 24 inches then to get the deflection at 26 inches you plug it in.
D1 = D2•(L1^3/L2^3) = 0.35•(26^3/24^3) = 0.35*(17576/13824) = 0.35*(1.27) = 0.44
Therefore the deflection at 26 inches is 0.44 inches or 59 lbs.
But like Badger said that's helpful if you want to compare to 26" shafts. If you don't care about that then just get a deflection value and use that to compare to other 24" or whatever length shafts you happened to measure.
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Ace makes one that will spine a arrow 15" or so. It hangs on the wall . About a 100-150 bucks. I got one for a hundred at Denton Hill last summer.