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Thread: Arrow spine

  1. #1
    Member MarkN's Avatar
    Join Date
    Apr 2020

    Arrow spine

    I've just spent a happy hour testing the spine of all my arrows.

    I used the following as the standard:

    Static spine, is how an arrow reacts when an 880-gram (1.94 lbs.) weight is suspended from the centre of the arrow. The arrow must be supported by two points, which are 28 apart. The number of inches the arrow deflects or bends X 1000, due to the weight, is the spine size or measurement of an arrow.

    So, a 500 arrow bends .5-inches when the weight is applied.

    Wooden arrows (arrow braced at 26 inches with the weight suspended at the 13 inch center) and modern carbon and aluminum arrows (arrow braced at 28 inches with the weight suspended at the 14 inch center).

    What I found was that the 500 spine, cheap arrows I'd bought were much closer to, 1,000 spine.

    The 350 spine and 400 spine, also cheap arrows were almost spot on, at 500 spine.

    This is fine, whilst I'm still getting proficient, with my bow and form and so on.

    I'll be interested later on, when I buy some better quality arrows in NZ to see how accurate their spine is.

    Just for interests sake, I now have:

    Set A - 1,000 spine approx 550gn

    Set B - 1,000 spine approx 350gn

    Set C - 500 spine approx 480gn

    Set D - 500 spine approx 380gn

    ...again this stuff is new knowledge to me, I post what I've learned, out of interest.

    Maybe it's helpful, to another newbie like me

  2. #2
    Member MarkN's Avatar
    Join Date
    Apr 2020
    I finally got to try my bow again, after all the re-jigging of the ::

    Draw weight ~ 50lbs
    Cam timing
    Cam lean
    Centre shot
    Measured all my arrows for grain weight, spine, straightness and discarded the ones that were furtherest from average.

    A rough sighting of 20 yd pin in the living room, on the basis that the difference between 7 yds and 20 yds, will not be toooo much...

    Photos below, 1st of a group at 15 yds and then the second group at 20 yds.

    My conclusion ::

    I'm going to have to practise more, to build up my left arm strength, pain in the shoulder on the upper end and a twinge in the elbow end, of the Triceps muscle in my left arm.

    I'm quite pleased with the lateral grouping of the arrows. I can feel it in my shots, that I'm not steady enough in the vertical axis, so that accounts, for the splay there.

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    Name:  20yds.jpg
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