# Arrow Spine Question



## TGUN (Dec 23, 2010)

On a carbon arrow a .500 spined arrow is what draw weight at 28 inches? For some reason, I can not wrap my head around the applicable use of .400 or .500, ETC.  I understand that a .400 is stiffer than a .500 and it is based on deflection of a 2LB weight on 26 inches of the shaft or a 1.94 on a 28 inches of the shaft (how do you know which one??), but what is the standard for these numbers as it relates to actual bow weight and what length is the arrow cut to give you this figure? Trying to determine if I can shoot a .495 out of my 43 lb bow if I leave it longer. Most reference charts say about 4-5 lbs change for each inch longer but I have no starting point. Is it 28 inches? Am I making any sense, because I think I just confused myself.


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## Shane Whitlock (Dec 23, 2010)

Bill, what is this a brain teaser? Got no idea?


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## Jake Allen (Dec 23, 2010)

TGUN said:


> On a carbon arrow a .500 spined arrow is what draw weight at 28 inches? For some reason, I can not wrap my head around the applicable use of .400 or .500, ETC.  I understand that a .400 is stiffer than a .500 and it is based on deflection of a 2LB weight on 26 inches of the shaft or a 1.94 on a 28 inches of the shaft (how do you know which one??), but what is the standard for these numbers as it relates to actual bow weight and what length is the arrow cut to give you this figure? Trying to determine if I can shoot a .495 out of my 43 lb bow if I leave it longer. Most reference charts say about 4-5 lbs change for each inch longer but I have no starting point. Is it 28 inches? Am I making any sense, because I think I just confused myself.



Kind of a rule of thumb; 500 spine, 50 pound draw.
Alot depends on the diameter and length of the arrow,
how close to, or far from center the bow riser is cut,
how slick the shooters release is, and how much weight is on the front of the arrow.

My feeling you will need 250 to 300 grains up front, and at least a 29" arrow to shoot a 500 spine carbon thru a 43 pound, cut to center bow. 

A GT 3555 is .530 spine and a 1535 is  .600 spine.
I feel you would do better with something around a 600 spine carbon.
Aluminum: 1913 or maybe a 1816
Wood: 45-50, (5/8" or so deflection), 5/16" diameter
Either shaft 29 ", or longer.


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## Barry Duggan (Dec 23, 2010)

That's why I said, in another thread, I thought carbon was harder to tune properly. What I  should have said, was it takes a little more thought to determine a starting point. In my go to bow, drawing around 50# at my draw length, I can shoot .500 spined arrows at around 28.5" bop, or .400 spined arrows around 29.75" bop, with both arrows having approx. 220gr up front. 

I am no expert, and I'm sure folks that know more than me might tune differently. However,I would take a .500 spined shaft, glue in the insert, decide what point weight I wanted to use, then start bare shafting with a full length shaft. Trim the shaft, from the nock end as needed to obtain proper flight. Unless I am way off, on the weak side, I trim in 1/4" increments. Don't get in a hurry to trim, cause once it's cut off...it stays cut off. LOL

If it helps any, I can also shoot a 30" bop, .500 spined arrow out of my old grizzly, pulling around 40#, at my draw lenght, with a couple hundred grains up front.


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## TGUN (Dec 23, 2010)

You are right Barry, the starting point issue has me confused. I am trying to get something flatter shooting for 3D. Not really interested in putting 200+ grains up front. the arrow I am looking at is 6.3 grains per inch. If left full length, it would still give me a more than safe 9 GPP with a 125. Just not sure if full length (32.5 inches) would be enough to go from what should be a 60 lb arrow-.495 ASTM (I am guessing about 60 lbs but who knows-hence my original question) to a 43 lb arrow. not cheep arrows, so I would like to be kind of sure. My bow is very close to center shot, less than 1/16th off. It is also an aggressive reflex/deflex with 3 carbon laminations inside the limbs. It acts more aggressive than an average 43 lb bow.


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## Barry Duggan (Dec 23, 2010)

One important question would be, what is you draw length?


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## TGUN (Dec 23, 2010)

HOUND-HANDLER said:


> Bill, what is this a brain teaser? Got no idea?



Shane, I think I hurt something just writing it.


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## TGUN (Dec 23, 2010)

Barry Duggan said:


> One important question would be, what is you draw length?



25.5 inches


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## Shane Whitlock (Dec 24, 2010)

Bill, I was just messing with you. I had to read it a few times  to understand it.  That 's why I love shooting the recurve, it's not very picky on arrow selection. You can shoot just about anything out of it and with a little adjustment you can make them fly pretty good. 

It's amazing how we think we found the perfect arrow.....then  we start trying different things to get better performance. Then the next thing you  know you got a pile of arrows and points , you'll never use again.


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## yamapup (Dec 24, 2010)

Try Stu Miller's Dynamic Spine Calculator. it's on the net. Follow directions and see what it shows you. It will certainly get you in the ball park, and you can play with arrow length. point weight, arrow spine and see what changes. Actually it's kinda fun. Pup


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## RogerB (Dec 24, 2010)

Understanding the difference in "Static Spine" and "Dynamic Spine" is the key to you question. Arrows that are .400, .500 or .600 are telling just the Static Spine. There are many many factors that go into Dynamic Spine (Static Spine is just one of them). To ask what spine arrows (static spine) one should shoot from a certain # is an impossible question to answer. If you go to Stu Miller's Spin Calculator you will see that you can take a stiff arrow (say .400) and add point weight or length and make it a weaker dynamic spine than a .500 arrow.
Each bow you shoot (and the same bow will be different for different people, that's why one person can't tune anothers bow) needs a different dynamic spine (even if they are the same #). What you are really trying to do is fine an arrow combination that will dynamic spine the same as the bow wants.


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## TGUN (Dec 24, 2010)

I have Stu Miller's Calculator. I Have used it in the past with success, but only to tune arrows I had. If all my settings/measurements are right, it says I can use them full length with a 125 tip. A buddy of mine says no way will those arrows fly out of my bow without 200+ grains up front. I will go with Stu and try the .495 arrows and see. My real question was more about the base "Static Spine" numbers in a "bow weight"  that match the .500, .600, Etc but I guess I am chasing an almost irrelevant, very large ball park figure that is heavily effected by the bow, the length of the finished arrow, the tip weight, the shooter, and more. I Guess I am trying to pin down a number that is not pin down-able (is that a word??)  

It is clear as mud.


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## Al33 (Dec 24, 2010)

I don't know the difference between dynamic and static spines or what either of them mean.


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## Barry Duggan (Dec 24, 2010)

TGUN said:


> I have Stu Miller's Calculator. I Have used it in the past with success, but only to tune arrows I had. If all my settings/measurements are right, it says I can use them full length with a 125 tip. A buddy of mine says no way will those arrows fly out of my bow without 200+ grains up front. I will go with Stu and try the .495 arrows and see. My real question was more about the base "Static Spine" numbers in a "bow weight"  that match the .500, .600, Etc but I guess I am chasing an almost irrelevant, very large ball park figure that is heavily effected by the bow, the length of the finished arrow, the tip weight, the shooter, and more. I Guess I am trying to pin down a number that is not pin down-able (is that a word??)
> 
> It is clear as mud.



Naw, I think you could be a little more vague, if you really put forth the effort.


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## missalot (Dec 24, 2010)

i had a black creek banshee longbow 43# ,i was shooting goldtip 3555 pro shafts full length ,3 .4" feathers,and 170 grain point ,and they flew great


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## dtala (Dec 24, 2010)

missalot said:


> i had a black creek banshee longbow 43# ,i was shooting goldtip 3555 pro shafts full length ,3 .4" feathers,and 170 grain point ,and they flew great




this is probably close to what you want.

Get a coupla GT35/55 shafts, leave em full length and try the point weight you want. If they bareshaft too stiff(nock right) then try a heavier point. Too weak, then try trimming length, 1/4" per try from the nock end.

I'm thinking with your draw length you WILL want them shorter than full length

I'd start testing with a .500 shaft, you may have to go to a .600 to get em shorter....

  troy


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