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32812Re: What to do when you are always overspined?

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  • The Greys
    Mar 7, 2013
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      As long as we are discussing spine let me share what I have learned about the subject and arrow making. First the basic rule is for longbow match spine to draw weight of bow. For recurve add 10 pounds to the spine. Thus 45 pound longbow, spine 45 - 50. 45 pound recurve, 55 - 60 spine. However, this is only a starting position as technique may cause need for more or less spine.

      Next is the issue of how spine is measured. It is measured on 28 inch centers. Thus a 40 - 45 spine shaft is such only if 28 inches long. Every inch added reduces spine by 5 pounds. Every inch less than 28 increases spine by 5 pounds. Every coat of finish added to the shaft adds back 5 pounds of spine. Thus cutting a 45 - 50 spined shaft to 30 inches reduces it's spine to 35 - 40. Add two coats of finish and you are back to 45 - 50.

      Next is how you orient the nock to the grain of the shaft. Basically the string/nock should be perpendicular to the grain of the shaft. This way you get maximum stiffness out of the shaft - read here, more accurate spine - and consistent flex between shafts/arrows.

      Point weight is the next factor. The basic rule here is 10 % FOC (Forward Of Center) for completed arrows. However, a heavier point tends to cause the shaft to hit harder (more mass) but drop faster. A lighter point, tends towards less impact (less mass) and floats a bit more - longer distance.

      And lastly fletching. Straight fletching = less drag. Helicoil fletching = most drag. Diagonal fletching = between straight and helicoil. All shafts spin in flight. How much spin you get is determined by how the fletches are oriented on the shaft, helicoil most, straight least. However, the jury is not in on spin increasing accuracy of the shot. However, air drag on fletching is seldom an issue in the SCA due to the shorter distances we shot. If you are going for flight arrows then straight fletching with very small, i.e. height from shaft, fletches.

      And we haven't even gotten into how well bow and arrow are set up, i.e. shafts "swimming" sideways or waggling up and down during flight. All issues that could cause the need to aim way off center of what you are trying to hit.

      And who would have thought a string on a bent stick flinging another stick would be so complex?!?


      --- In SCA-Archery@yahoogroups.com, William Davis <willied0296@...> wrote:
      > I too had a problem with arrow spine when I first started shooting.  I had 35 lb bow, so figured I should be using 35 lb arrows.  I actually bought 40-45 and they worked okay, but I too had to aim at the outside edge of the black ring, to achieve a center hit.  My next set of arrows, turned out to be poorly spined, ranging from 33 lb up to 50 lb, so they were all over the target.  I decided to change arrow suppliers and in doing so, discovered the following chart, which shows that I should be using arrows spined at around 50 lbs, so I ordered 50-55s.  My aim point is now dead center.  
      > http://www.allwoodarrows.com/SearchResults.asp?Cat=1831
      > If the link does not work, just go to Allwoodarrows.com, and click the spine chart link at bottom of the header banner.
      > Gwilym of Fflint
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