confusing myself about spine

[dano140]

I broke some tips off my arrows last weekend and was going to shorten them but am confusing myself about the spine they will be once I cut them down.

The arrows were 32" 50-55. If I cut them down to 28 1/2 does the spine go up to around 60 -65?

I was reading that lengthening arrows makes decreases the spine and shortening increases the spine. But then I read that the shafts are tested (spined?) at 26". So I am confused. Maybe I just haven't had enough coffee this morning.

I also want to check my setup with some of y'all that responded to getting the correct spine. My setup is a 65# Longbow, dacron string, 125gr field point, 3 fletch helical, and a 27" draw length. The longbow doesn't have a shelf, but is tapered in at the grip.

I figured that my draw is 63# and I should be shooting 60-65# spine arrows . Does that sound right?

Thank you!
Daniel

[coaltroll]

This is from an inexperienced guy so take it for what its worth. 1st,There is a difference between the static spine and the dynamic spine of an arrow. Static is what you measure on the tester. Dynamic is in action. By cutting your arrow shorter you are in effect stiffening the dynamic spine, which may possibly be compensated for by using heavier points. 2nd, As far as the arrow spine you are using a lot depends on how close to center your bow is, sound like it may have to shoot around the riser. A center cut shelf will take stiffer spine. Having to get the arrow to flex around the riser you may need to go with a little lighter spine. I personally shoot 59# 301/2 inch arrows spined at 55, with 160 grain points out of my longbow and they fly straight and true. That combo will shoot better than I can. If none of this makes sence just disregard, like I said pretty inexperienced.

[Dr. Ed Ashby]

Tim, inexperienced or not, your explination of 'spine' is 'spot-on",

Ed
TGMM Family of the Bow

[laddy]

Arrows are measured at 28'', so 50-55 is what your arrows are at 28''.  For your bow and draw 50-55 sounds just right at 271/2'' -28''.  At full length you may have been underspine.  If the shorter ones act stiff you may need to drop to a lower spine.  What kind of bow is it?

[Tim L]

Arn't Wood arrows spine measured at 26" and others measured at 28"?

[dano140]

Coaltroll,

Thanks for the explanation of spine. I  understand the concept, it is putting it into practice that I am confused about.

Is it like Laddy says and the 32" 50-55# shafts I had are actually 50-55# at 28" or did the spine increase when I cut the shafts down to 28"?

Laddy,

Thanks for responding! I really don't know if the shorter ones are acting stiff or if the longer ones were acting weak.

The equipment is much better than I am right now. I have been shooting the longer arrow (full length) for about 6 months and I have worked my point of aim out for them. When shooting the shorter arrows they tend to go left by around 12-18". If I change my point of aim I can get either to go where I want them, or at least as close to where I want them as I am capable of right now.

The bow I am shooting is an old York Longbow. Don't know how old. It doesn't have a shelf, but is tapered in to the a small grip, more in the American Indian style, rather than having larger, rounder grip like an English style longbow.

Thanks again!
Daniel

[SteveB]

Static spine remains the same.
The dynamic/working spine changes with arrow length and point wght.

Steve

[coaltroll]

Daniel, It's like SteveB stated, as the arrow is shortened the dynamic spine changes. It sounds like your shorter arrows are a little stiff. You will either need to go with a heavier point or lighter spined arrows. You may want to try going up to 160 gr points and possibly up to 200 gr with the shafts you have, see how that works. From the sounds of things, you still have to shoot around the riser so that mean you bow will be a little more critical of spine. If the riser was cut with an arrow shelf close to or to center it allows for a little stiffer spine. Hope this helps, and maybe some more people with more experience will give more/better advise.

[soopernate]

Tim L...

It is my understanding that wood arrows are measured at 28 inch shaft lengths on 26 inch centers.

If I am wrong someone correct me.