Arrow spine and FOC.

Discussion in 'Tech Talk' started by mab, May 22, 2013.

  1. mab

    mab Weekend Warrior

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    Just curious about the 'technical' aspect of the spine of an arrow. I recently purchased the PSE Radial Xweave STL Hunter 200 arrows. The spine is .424. My draw length is 27" and my draw weight is 52.5 lbs. Although, the dw is going to be 55 lbs. or higher by hunting season. My question is about my spine and my foc. I should also mention that I am using a 100 grain field tip/broadhead. What can some of the techs here tell me about this setup concerning the spine and foc on my setup? Thanks.
     
  2. Jdicenhour

    Jdicenhour Weekend Warrior

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    With that setup I would think a 500 spine would be better. Try to get foc around 12% an you should be good to go on flying broadheads
     
  3. tfox

    tfox Grizzled Veteran

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    Depending on your arrow length, your spine should be "ok". You are most likely a on the stiff side, unless your arrow is a little on the long side. A 500 would most likely be a little closer match but you shouldn't have any issues with those arrows.

    Your foc should be ok as well, depends on how the arrow is fletched and how long they are.

    sent from my samsung note 2
     
    Last edited: May 22, 2013
  4. mab

    mab Weekend Warrior

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    Thanks you two. My arrows are 28" in length. I do have an FOC calculator online here, so I will check that. So, I am looking for about 12 percent foc? I did use a ke calculator and it said my setup is around 47-49 psi.
     
  5. mab

    mab Weekend Warrior

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    Also, I should ask. How much difference is it going to make if I go around 58 lbs DW?
     
  6. tfox

    tfox Grizzled Veteran

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    First, don't force the weight. Keep it comfortable.



    The spine you have now should be about perfect at 58#.

    sent from my samsung note 2
     
  7. Jdicenhour

    Jdicenhour Weekend Warrior

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    Going to 58 pounds would improve your kinetic energy an bring u closer to to the correct arrow spine since your arrows are 28" your spine is basically. 424 there are alot of variables so it's hard to give you an exact answer on what do. If I were you I'd go to a good bow shop an asked them to help you because dealing with that issue is better done in person rather than online
     
  8. J-Daddy

    J-Daddy Weekend Warrior

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    Your not gonna notice a big increase in KE, speed or anything else by bumping the draw weight up 3lbs...It'll change, but not much... A .400 spine will tune fine from your setup, normally a stiff spine isn't an issue when tuning a compound bow if you shoot with a release.
    The old adage of stiff spines causing tuning issues dates back to the days of finger shooter & stick bow shooters because you have to have a certain amount of flex in an arrow because of the paradox in the arrow at the shot to get the shaft to sort of bend around the bow riser and gain clearance at the shot....
    With a compound bow using a release aid it's not a real issue....If you look at most target setups they are lower poundage, say 50 to 60lbs on average but then if you look at a big number of the "FAT" target shafts they are extremely stiff spine, like a .300 or even .250 spine shaft and they tune just fine out of lower poundage bows. Over the years we have tuned .300 spine shafts out of 60lbs bows and never had an issue, never had to do anything special and they always shot fine.
     

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