Arrow spine question?

[matt steed]

Ok, a couple questions.

1. Will Arrows that have the same spine but different GPI shoot differently other than the overall weight of the shaft?

2. Will a small diameter shaft 9/32 like the Axis 400 bare shaft the same as a 5/16 400 shaft of the same spine? I was wondering if you would need to go stiffer with the 9/32? Or does it normally stay the same?

[Alexander Traditional]

I have wondered this same thing. I've often wondered how a shaft from say the same maker with two different gpis can be the same spine.

[grouseshooter002]

When spine is measured it is done in a static state [at rest] so weight doesn't enter into the equation. Weight will affect an arrows dynamic spine which is an arrow in flight.

Regards,
Grouse

[McDave]

I shoot the Gold Tip Ultralights and also the Gold Tip trads.  They are rated at the same spine, but the trads are heavier because of the woodgrain wrap.  I haven’t noticed any difference in the way they shoot, except the heavier shafts are slower, of course.

I also shoot Victory VAP’s in the same spine, but skinnier shafts.  There might be a little difference in arrow flight since the VAP’s lie closer to the centerline of the bow than the GT’s, but it’s really hard to tell.  I generally correct this by padding the strike plate a little for the VAP’s so they are both on the same centerline.

[Fattony77]

Originally posted by McDave:
I shoot the Gold Tip Ultralights and also the Gold Tip trads.  They are rated at the same spine, but the trads are heavier because of the woodgrain wrap.  I haven’t noticed any difference in the way they shoot, except the heavier shafts are slower, of course.

I also shoot Victory VAP’s in the same spine, but skinnier shafts.  There might be a little difference in arrow flight since the VAP’s lie closer to the centerline of the bow than the GT’s, but it’s really hard to tell.  I generally correct this by padding the strike plate a little so they are both on the same centerline.

I'm glad that you're confirming (through actual testing) what I was thinking the answer to this would be. I wanted to post something to the same affect, but don't have any ACTUAL experience to back it up, so I was just gonna keep my mouth shut. Lol.

[Orion]

1. Theoretically, yes, but probably not enough to notice.  Because one shaft is physically heavier, it will behave as dynamically softer.  However, because there's only a 15 grain or so difference, it's not enough so the shooter would notice.

2.  Maybe, maybe not.  Because the skinnier shaft is closer to the center of the bow, as McDave notes, it will behave dynamically softer as well. However, we're talking 1/64 of an inch difference here (10/32 minus 9/32 equals 1/32, i.e., 1/64 on a "side"). Again, not enough difference  for most folks to notice.

[matt steed]

OK. So if a 400 Heritage is a tad weak, the 400 Axis might be perfect since it’s closer to center shot?

[Orion]

Oops.  I screwed up.  Went back and edited my previous post.  If you move the arrow closer to the center of the bow the dynamic spine will act softer.

Look at it this way.  If your shaft is too weak, you would build out the side plate to increase its dynamic stiffness.  If you thinned the side plate, it would act weaker yet.  Reducing the shaft diameter has the same effect as thinning the side plate. That's why folks can generally shoot a spine heavier than one would assume is needed with skinnier arrows and/or bows cut past center.

So, if your Heritage shaft is weak, the Axis would act weaker yet. But, as I said before, the difference is so small, I don't think most archers are good enough to detect the difference.  You could stiffen the dynamic spine of either shaft by going to a lighter point or shortening the length of the shaft if you have room to do so.

What's your draw length, and what's the the draw weight of your bow at your draw length? Is your bow cut proud of center, to center, or past center? Are you shooting a low stretch string or dacron? Recurve, hybrid or longbow?  Answer these questions, and we should be able to tell you what spine arrow you'll need.

[matt steed]

Palmer recurve cut past center. Fast flight string.
I have a 30.5 inch draw. My bow is about 50 -52#’s
My arrows are 31.5 inches.

The Heritage 250 bareshafts pretty good with 125-145 up front. They weight about 515 grains.  

I was really wanting to try some Axis Traditional shafts. I was thinking about the 340 with 175 up front. I was thinking I might could get a little more weight up front.

[Orion]

Hmmmmm.  Heritage 250s are .400 spine, if I remember correctly.  You're probably right on the cusp.  .400 Axis would probably work with the same point weight, or you could build out the side plate a little to make it work.  If you want to load the front more, .340s would probably work.  

By way of example, I shoot 250 grains up front with .400 (black) axis cut to 29 inches for my 28-inch draw out of 50# Bear TDs. Think they would be a bit weak at a two inch longer arrow and draw length with that point weight. I can shoot .340s with 300 grains up front, but that's about 13 gpp, and the arrow is pretty slow. You would get better performance with your longer draw.   Any way you can get one or two of each to try.

Maybe some others shooting similar set ups will chime in with their experiences.

[matt steed]

Thank you sir. That is exactly what I am experiencing. I am right at the edge of either spine. A 400 with not much weight up front or a 340 with 175-200 up front. With a 31.5 inch arrow.

Thanks for all the information. Trad Gang is an amazing place with years of knowledge.