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  • 1 Post By MarkN
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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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  3. #3
    Member MarkN's Avatar
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    Apr 2020
    I've been practising. Some photos below. I find it useful to keep a record, so I know what to improve.

    I think I've got the bow more or less sighted in and I'm working on my form and arrow choice.

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    This are the cheapie 500 spine (that I measured was more like 1,000 spine) at 20 yds

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    These are a mix of (I measured) 500 and 1,000 spine at 30 yds

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    These are 340 (I measured 500) spine at 30 yds

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    This is my substitute hare with the 400 (I measured 500) spine 31" arrows with 125 gn small game blunt heads, at 20 -ish yds. I wandered around and shot from different angles, the head shot went through the nape

    ...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
    rewa likes this.

  4. #4
    Join Date
    Sep 2020
    Hutt Valley
    My personal approach is (albeit I shoot 50, 55 and 60lb recurve and hybrid longbows) is:

    - Buy full-length (32") GoldTip (Hunters or Hunter XT) shafts suitable *or slightly too stiff* for the weight I'm pulling
    - Determine the point weight I want to achieve at least 18% FOC and an arrow weight over 500grains (momentum trumps kinetic energy when bowhunting)
    - Cut 1.5" off the end, resulting in an arrow still longer than I need
    - Square the cut end, put in insert and point (say, 100grain insert and 200grain point)
    - Put in nock
    - Mark a point on the ground 10m away from my target
    - Shoot the bare shaft at a point on that target, with my best form, with my bow exactly above this mark. Shoot 10x shots
    - Look at angle the shaft sticks out from target: nock will be angled left, indicating dynamic spine of shaft is too weak
    - Remove nock, cut off 1/4" from nock end this time. Square the cut, and put nock back in
    - Repeat 10x shots and keep cutting back until the the nock is dead straight, aligned with the point in relation to my ground mark
    - Now, walk back 5m, and repeat. Fine tune the cuts this time down to 1/8", as needed, until the arrow flies true.
    - Walk back finally to 20m, and ensure the same.

    If the arrow flies absolutely true at 20m, I have all bow energy going into that shaft, and am now ready to fletch. I have the perfect arrow for that bow, and I don't need to paper tune, or bare-shaft tune against fletched shafts. The point of bare-shaft tuning is that you see how the arrow really flies, without all the compensation and 'guidance' smoothing over poor form and dynamic spine issues. Very revealing! In fact I find it so revealing that I always keep a bare shaft in my quiver, to see how much my form sucks, or doesn't suck. A bonus too is that your broadheads (which are basically wings on the front of the arrow, fighting with the flights at the back) will tend to shoot like points once your arrow is properly tuned.

    Works great. Plenty of good videos on YT about the benefits of bare-shaft tuning. Clay Hayes, especially good.

    Last edited by Remote; 08-11-2020 at 03:23 PM.

  5. #5
    Bubba...? Ftx325's Avatar
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    Jul 2020
    It's been many many years since I drew a bow , 40lb compound l used to have. And this was before sights were common place and it was all done by sight picture and mental calculation looking down the arrow to determine sighting.
    Anyway , my 5 cent's worth is this.
    Practice , practice , practice...and then practice some more. The more you use your bow the stronger you become and the more comfortable you will be with bow in hand. Try and relax into the shot , being all tensed up will do you no favours as far as accuracy and consistency go.
    And did I mention practice...
    I used to spend every spare minute in the back fields shooting at sparrows at all distances which I found worked really well as it helped with the mental calculations for range , and aiming at a small target helps immensely with accuracy. As the saying goes aim small miss small has never been more appropriate than with a bow.
    And did I mention practice....
    I reached the point where I could graze a coke bottle lid in the side of a haybale with a bladed hunting tip at any range up to 40 yards most of the time. And that was without sights of any kind. But did I spend ALOT of time practicing....
    So get as much time shooting as you can as regularly as you can... even just ten minutes here and there , and don't overthink think it when it comes to aiming. When you have done enough shooting practice it will all come naturally. Just be consistent with where you hold the string to your cheek and again try and relax into the shot.
    And did I mention practice...
    Micky Duck likes this.
    born to hunt - forced to work



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