Center shot bows and arrow spine

[JohnnyBa]

Not really sure I understand all there is to the arrow, and as a beginner, have used the spine charts from dealers that have it online and I assume they pretty much all shake out about the same. It does seem to me that the closer you get to shooting true center shot, that you could end up using a lighter spined shaft even though still finger releasing. I am guessing(another assumption here) that the goal for archers is to have a release that gets the fingers out of the way ASAP to impose a minimum amount of pluck pressure left or right on the string and arrow. Then I really don’t get the whole GPI of an arrow at different spines. What exactly does the GPI mean to an arrow besides weight. Does a higher number make it stiffer? Two 600 spine arrows, one 7.0 GPI and the other 5.7, what’s the ideal situation for each one? It sure seems that all 45# bows do not eat the same ammo, or should I not even worry! I just know some arrows shoot and feel better than others.

[PrimitivePete]

You are touching on a point that most arrow charts can't factor in, besides the bow the greatest impact on arrow flight is the ability of the archer. The charts get you close, your form gets you closer. If you are in the beginning stages of developing your accuracy I wouldn't go too crazy on finding the best arrow choice, get close so you don't damage you bow, build your form and when you have achieved realistic consistency, start to experiment in tuning and only then begin getting picky about arrow choice.

[Roy from Pa]

https://www.fenderarchery.com/blogs/archery-info/basic-tuning

[Alexander Traditional]

Gpi is how heavy the arrow will be if you measure it and calculate what they say it should be. I don't know how some can be heavier and still be in the same spine range of lighter ones. I guess it's the amount of carbon in the shaft. Most  charts,and advice you will get will point you in a too stiff of a shaft.

Forgot to add gpi means grains per inch.

[McDave]

Grains per inch is only indirectly related to spine, and the two measurements are used for different purposes.

You want an arrow of a certain weight, whether to exceed the minimum weight requirement under the warranty of your bow, or to go even higher than that if you want a heavier arrow for hunting.

You want an arrow of a certain spine so it will tune correctly for your bow, as discussed in Ken Beck’s video posted by Roy.  Arrow weight and arrow spine are arrived at independently of each other.

Actually, the closer you get to center shot, the higher spine you can use.  Normally, the further out you are from center shot, the weaker the spine needs to be to tune to your bow.

You are correct that you need a release that gets your fingers out of the way as quickly as possible.  What you may not realize is that the less input you have into this process, the more likely it is to make that happen.  You cannot release the string fast enough to get your fingers out of the way of the string.  Instead, you need to learn to relax your fingers and let the string push them out of the way.

[JohnnyBa]

I thank all for the inputs, and I do think I get the GPI for getting minimum weight required for safe shooting. I even understand the stiffness/spine a bit, but the more I understand it, I find that there are really few things written “in stone” about all of it when combined. I get that I can use a stiffer arrow when using a true center cut, that just makes sense. Example: I pull 40# at my DL. My goal is to use 400ish grain arrows for backyard shooting and practice and 500ish for hunting. IF I determine I want to use a 600 spine arrow, and these can get pretty light, Warrior 600’s are 5.7GPI, I cut my arrows at 28 for straightest flight and best groupings(for me). Thats 159.6 for shaft, I use min 50 gn insert, 150 grain point, 20 gn fletches, 15 gn nock just to get the 400 grain total. But when going up to hunting weight, would that 600 spine arrow then push an additional 100 gr point, making it 300 grns up front. Does that make sense or should I just use 500 spine arrows?

Grains per inch is only indirectly related to spine, and the two measurements are used for different purposes.

You want an arrow of a certain weight, whether to exceed the minimum weight requirement under the warranty of your bow, or to go even higher than that if you want a heavier arrow for hunting.

You want an arrow of a certain spine so it will tune correctly for your bow, as discussed in Ken Beck’s video posted by Roy.  Arrow weight and arrow spine are arrived at independently of each other.

Actually, the closer you get to center shot, the higher spine you can use.  Normally, the further out you are from center shot, the weaker the spine needs to be to tune to your bow.

You are correct that you need a release that gets your fingers out of the way as quickly as possible.  What you may not realize is that the less input you have into this process, the more likely it is to make that happen.  You cannot release the string fast enough to get your fingers out of the way of the string.  Instead, you need to learn to relax your fingers and let the string push them out of the way.

[MnFn]

Thanks Mcdave,
I am sitting here at a kids swim meet going brain dead. I was thinking the closer to true center shot on a bow would allow you to shoot a stiffer arrow  and the further out the riser is would require a more flexible shaft to compensate for proud riser?

[Gunru]

From what I know, your bow type, draw length, poundage at DL, arrow length, tip/insert weight, nock/fletch weight, and distance plus or minus from center will pretty much determine your arrow spine for you. Have you used a spine calculator like Stu's or the one on Three Rivers? You can play with them and see how changing the values impacts spine. They are only ballpark values but will help you learn. Things like bow type, poundage, draw length, string type determine how much energy potential or dynamic spine your bow requires. Things like arrow static spine i.e. 400, length, amount of weight up front your trying to push like tip and insert, amount of weight offsetting it at the back like bushing, nock and fletch will give you your arrow's dynamic spine when acted upon by your bow. Those two numbers should be pretty close. You can adjust from there. Your arrow spine will be dictated by your choice of tip weight, total arrow weight, etc. provided that you bow is cut before center and you are willing to adjust side plate to suit the needs of your arrow. If that wasn't all stuff you already knew, I hope there's something in there that helps.

[McDave]

Thanks Mcdave,
I am sitting here at a kids swim meet going brain dead. I was thinking the closer to true center shot on a bow would allow you to shoot a stiffer arrow  and the further out the riser is would require a more flexible shaft to compensate for proud riser?

That's correct

[McDave]

A 28” .600 spine shaft should work pretty well for a 40# bow shooting target points; that is, a 125-150 grain point plus a 15 grain insert.  Put 300 grains up front and you may well be looking at a .500 spine shaft instead.

[SS Snuffer]

McDave is right on. He really knows his stuff! He has helped me and many on here many times and is always here
to help.