Spine indexing.

[Pushbutton2]

So are we chasing a ghost?

[enewman]

No not so what ever. We have just been using the wrong terminology. What people say is stiff is no more then the high side of an arrow. The better the arrow the harder this is to see. You still want the high side up. What this does is make tuning so much easier.

To build the best rig you can have.

[Pushbutton2]

Ah!

[Quackedup]

I have an idea on this. I used to build custom fishing rods. The "spine" on a carbon fishing rod blank is where the carbon overlaps when it is formed. This is the "heavy" part that sinks to the bottom if you float it with the ends sealed. This is also the stiffest part of the blank, and should be put on the top or bottom of the blank, depending on what type of reel you are building the rod for. If you put this spine on the side of a fishing rod, when the rod is under pressure, it will try to torque to the weak side of the blank. The blanks are so long and flexible that you can put the tip of the rod blank in a corner and flex the rod. this will put the spine directly opposite the bend, ie, on the top of the blank if it flexes up.

In Arrows, the "spine" is considered how much flex the arrow will have when a certain force is applied to a certain length of carbon. In the process of making the arrow, it should still have the area of overlap that will give it a "heavy side" and a slightly stiffer "spine" on that side due to slightly more carbon in this area. I think In arrows, the overlap is a lot less noticeable, and creates a lot less stiffer area. I have float tested some arrows that had a definite heavy side, and would float with that side on bottom EVERY time. I have also tried to float test some arrows that that heavy side was a LOT less noticeable, and would not always work its way to the bottom. I think it depends on the grade of arrow, and how well tolerances are held in the manufactureing of the arrow. The process that I used was to fill up a bathtub three inches or so, add a little dish soap, and stir into the water. Sorry, I didn't count how many drops of soap I used. I just put a couple of squirts in the water. I used pieces of rubber pencil eraser to seal the ends of the arrows so they would float. Put them in the tub and give them a gentle spin. After doing all this, I couldn't tell a difference in the way the arrows grouped compared to arrows that I didn't index the spine on. I would still have some fliers in most batches, and just wouldn't shoot those arrows.

just my two cents.

[enewman]

When you float an arrow. You are not seeing a heavy side. What your are seeing is the arc of the arrow. A .006 May when floating settle to a certain point. An .001 will not move around.


The reason is the arc of the arrow. When you float the arrow.

[enewman]

When we look at spine indexing. What are we doing. If you have been reading the post above you will see that I'm saying there is no such thing as a weak or stiff spine of an arrow.
When you buy a arrow , you have a choice in straightness. This is where the better arrow is worth the money.
All arrows will have an arc. Like the pic below. If you put the weight on a spine tester to test spine. What you read is the spine of the arrow. This will be at 360 degrees around the shaft. Spine is spine
Now let's take a look at the top pic. If you where to place the indicator you would see less movement. What people are saying is this is the stiff side. When really all you are seeing is the high point in the arc. Same as if you look at the second pic. They are saying this is the weak. This is just the low side of the arc.
The better the arrow the less you will see. If your arrow is is a good arrow and comes. very straight. Then we could say a ram tester can not test this. You can but you will not be able to do this with a .001 indicator. This will require a . 0005 indicator. This is where the freq tester grim is talking about. If the arrow is so straight the indicator won't see then this is the tester.
But even then you are not testing for a stiff or weak point in the shaft.
There is not one spine is spine. What you are looking for is where the freq is at its highest point. This is where the arrow has the hardest time flexing. Which is against the arc..
If you had an arrow like in pic three. Perfect. (This cannot happen.)
The flex would be the same all the way around the shaft. Meaning no high point or low point. Also meaning the freq would be the same. On a flow tester the laser would be in a straight line.
Part of our post has been you cannot find this point with a ram spine tester. The reason for this is only the indicator that comes with the tester. You need better testing equipment.

[Quackedup]

I see what you are saying there. The difference I take with the example is that, at .006", the arrow is still almost exactly straight. If it had the curvature in the example, then it would most definitely be exactly as you say. It depends on the exact effect the slight curvature of a .006" has on the willingness of the arrow to roll heavy side down while in water. I think we are really splitting hairs when we get into how much affect spine indexing will have on a .006" arrow. These arrows aren't the best of the best to begin with. Is there a way to quantify the results, or are we basing it on our perception of how the arrows group? Is there a tangible difference in the way a .006" arrow will group if it is or isn't indexed? I am not sure that I could shoot good enough to make a measurement of group size.

[enewman]

With a fletched arrow and your bow is close. Then you want see a diff at say 40 yards or less. At a 100 big diff. Also with bare shafts you can see at 20 yards.

The point I'm making is that we as archey has been saying when spine indexing. We are looking for the stiff side or weak side. What I'm finding. Is this is incorrect. What we are seeing is the high point or low point. Spine of an arrow will not change.

Spine indexing is no more then finding the high spot on an arrow and placing it at 12. What this does is helps you from having to knoc tune so much.

Cuts down on tuning.
I know that .006 vs .001 does not look like much. But it is a lot when tuning your bow.
The more the arc the harder it's for the arrow to have a consistent flex. Meaning the harder to tune.
Most people will never see this. Fletchings take care of this.

Truthfully if you had the straightest arrow you can get. Then get a stiff arrow. Very little flex. And your arrow is straight inline with the power stroke and knoc travel is level. That is the best it will ever be

[Quackedup]

I think this is the most thought out conversation I have ever had with someone in a forum type setting. Thank you sir.

I really think we are agreeing with each other. I would love to be able to visit an arrow making facility to see how these things are really built. How the carbon layers are sealed or formed together and where, if anywhere, there might be a difference in weight throughout the shaft.

You are right about the spine of an arrow being being the spine. It doesn't change. I think you are correct about the high spot of the arrow having to do with the way the arrow flexes. I wonder if this high spot is where the heavy side of the arrow is too. More material in this section could be the cause of the arc. Are arrows made in 32.5" lengths that we see in the store, or is it made in 10' sections and cut down to size, with the ends having more curvature and the center being straighter. Then arrows from the ends would be the .006', the arrows from the center would be the .001".

[enewman]

I would love to go and see an arrow being made myself. I've got several ideals and and other testing todo

Thanks quackedup for the post

[bowhuntntxn]

So from some silly research, I found out that notebook paper is .003 inches thick. So in theory, and in line with your end to end arc statement, you should be able to roll a full length .006 arrow across a stack of two pieces of notebook paper, and it will barely touch it. Remove one sheet, and there should be some measurable amount of space between them.

To test this I bet you could try it in a darkened room, with a light shining towards the shaft, just above the paper. When it touches it will block all the light from the paper.

In real world terms can you hypothesize how the apex of the thickness of 2 sheets of paper will improve or diminish performance based on a cylindrical location. And how much of the two sheets are removed when a shaft is cut down, which will effectively move the arc to the front or back, unless you remove an equal amount from both ends to keep it centered.

[enewman]

So from some silly research, I found out that notebook paper is .003 inches thick. So in theory, and in line with your end to end arc statement, you should be able to roll a full length .006 arrow across a stack of two pieces of notebook paper, and it will barely touch it. Remove one sheet, and there should be some measurable amount of space between them.

To test this I bet you could try it in a darkened room, with a light shining towards the shaft, just above the paper. When it touches it will block all the light from the paper.

In real world terms can you hypothesize how the apex of the thickness of 2 sheets of paper will improve or diminish performance based on a cylindrical location. And how much of the two sheets are removed when a shaft is cut down, which will effectively move the arc to the front or back, unless you remove an equal amount from both ends to keep it centered.

Not sure how to answer. This will be opinion only. I would think you would want the arc in the center. For flex purposes. This should make the arrow flex more even. Now if we move the arc up front This would make the arrow behind the high point react differnt. Making the arrow look more like a whales tail. This is just thinking out loud. We need I good high speed cameria.

All this is just fun and testing. It has put tuning into a new prospective for me.
Truthfully what I've seen. Stop buying .006 arrows.

[bowstalker210]

I just order mine from South Shore

^^^^^this

[Quackedup]

In buying arrows, a .006" does not mean it is guaranteed to be .006" of straightness. It is actually guaranteed to be no MORE than .006" total straightness. I have checked Gold Tip Expedition Hunter arrows that are supposed to be .006" arrows and found that some of them are much straighter than that. Even up to .002" to .003". I used these arrows because we stock a LOT of them and they come in from different batches. I have seen arrows from the same box vary from .003" to .006". This would lead me to believe that some of the grouping differences are based on the curvature difference in the arrows. In checking the Pro Series 22 3D arrows that I shoot, I have seen differences from .001" to .0005".

When I cut down tournament arrows, I cut off as close to equal amounts as I can from both sides of the arrow. This is supposed to leave the straightest possible section of the arrow shaft to shoot with. Even just cutting off one side will leave a straighter shaft than not cutting it at all. As far as the cylindrical location of the arc, I can't say how much impact that would have on how the arrows flies. In theory it would have some impact, but how much MAY be so small that it can't be quantified in real world shooting scenarios.

[Quackedup]

We need someone with a great super slow motion camera, and a willingness to let us shoot arrows in very close proximity to it. This could be fun!!!