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I'm taking this thread from a response I posted in another forum because it actually belongs in this category based upon the fact it's an Advanced Technical Topic that should stand as a topic of it's own, as opposed to an answer to a more basic question on the topic of Crossbow Tuning. .

Taken from the thread entitled “Super Tuning”, my entry.
In reading some of the threads that have come out over the past year I'm beginning to realize that we still have some valuable information to discuss and share, especially the more senior members that have access to the advanced technical forum that have been on these forums for many years.

For openers, when we talk about "Tuning a Crossbow" we shouldn't be looking at and discussing just the crossbow itself. Your crossbow is a part of system of components and every component within this system needs to be tuned and well matched to the other pieces, if you intend to get the most out of it.

That said, within the archery world we've always had two distinct sides of the field. There are those who are predominantly hunters and their equipment and focus is on hunting equipment and being proficient enough to stay within the vitals area of the game they hunt. The other side of the field is the target shooters. These make up a much smaller percentage of the population, but this is where the top talent and knowledge lies. These are Target Shooters who predominantly are chasing lifesaver sized dots on targets even at extended distances of 100 yards or more. These people understand in detail not only how tune everything, but they also live by the belief that "Good Enough is the Arch Enemy of Better and Best"! Target shooters understand the science and physics behind the operation of the bow or crossbow, but more importantly the laws of physics as the apply to arrows and arrow flight. I should know because it's the world I came from and was raised in beginning at age 12.

Enough with the history lesson, since we're here to talk about "tuning". Several years ago, I had introduced into these forums the topics of "Spine Matching Arrows, F.O.C. (Front of Center) and Weight Balancing Arrows in a series of articles, or threads if you prefer. For a few years these were hotly debated topics, but between Jerry, Dorge, myself and a few other knowledgeable members people finally started to understand the importance of these factors. Today, much of this is now taken as a defacto standard.

Here's where I may upset the apple cart a bit. I've come to realize that many members have a certain level of knowledge or understanding, but not a deep enough one to fully understand how to get the most performance out of what they're making or buying. There's a level of misunderstanding that's clouding the arrow building process and if you'll stay with this thread you'll learn why.

There seems to be some level of misunderstanding of the terms "Spine Matching" versus "Spine Orientation". These terms are not the same thing and are not interchangeable. To be clear the process of performing "Spine Matching" is the process of measuring an arrow shafts "Deflection Range Values" using a spine tester capable of reading the full range of oscillation characteristics around the circumference of a shaft. This is a "Static" measurement because the shaft is at rest, versus a "Dynamic" measurement which would take place when a shaft was in motion. The key importance of what I just stated is the fact we are not just attempting to identify the "Stiff Side Plain" of an arrow and mark the shaft where it is.

Instead, we are recording on paper the gauge readings of the highest and lowest reading on each arrow around the shafts circumference. After all shafts have been measured and the deflection values have been recorded on paper we are then comparing these values on each arrow to ensure they are in a very close match from one arrow to the next. Any arrows that are not within a close match to the others should be culled out and removed from the group you're building.

Why you ask? Simply put, deflection values essentially are the oscillation range or frequency that each arrow performs within as its shot. How can you expect any two arrows to perform identically if they flex (oscillate) differently. It would be similar to using two entirely different bullets in the same gun and expecting them to hit a target in the same spot.
Remember, the single most important element in arrow performance is Spine Matching!

Far too many people are believing that Identifying and Orienting the Stiff Side Plane of an arrow is Spine Matching. It's not even similar because you may have lined up the spines on each arrow in an identical manner, but you've done nothing to achieve similar oscillation frequencies within the group.

So in summary, if we want tuned arrows the first step in the process has to be accurately measuring and matching the highest and lowest “Deflection Range Values” on each shaft and recording these values on paper. Then cull and sort out the shafts so only those with very similar high and low values are selected for the next step in the build process.

Personally, I won't buy raw shafts without paying the extra money for “Spine Matched Shafts" and since there are only one or two sellers that I know of who sell them, your choices are highly limited as to who you can obtain your shafts from.
After receiving my arrows the second thing I do is to Spine Test every shaft and record the values on paper for each. Anything that's outside a tight range is returned for a replacement of what I ordered. After recording the spine deflection measurements I can tell a seller exactly what he needs to send me as an acceptable replacement.

Notice above I stated it's the second thing I do? Why second?

I'm sure you have no idea, so here's the bigger can of worms that may blow the lid off many people’s understanding of what they're buying and shooting. Most people believe if they order very high quality arrow shafts such as Black Eagle Executioners, or Zombie Slayers or Spinal Tapp's or any other high end carbon shafts in a straightness factor of .001 that they are getting what they ordered. This may be completely false and untrue. Carbon shafts have a shelf life which is relatively short as measured in months. Usually, 4 to 6 months at best and each month a percentage of warpage takes place on raw shafts regardless of how they're stored.

When the shafts were first manufactured they may have been .001, but by the time you receive them there's no telling what they might be. Therefore it's absolutely necessary to test the straightness factors on each shaft before you begin putting in the many hours required to go thru a build process. Do not take anybodies word for the fact you're receiving good, straight shafts or it could be to your detriment.

To test all shafts just use a cordless 3/8's inch drill. Place one end of a shaft into the chuck and tighten softly, so as not to damage the carbon in any way. Position the drill and shaft in either a horizontal or vertical position. Turn on the drill with a slow to medium speed and watch the arrow shaft. It should spin relatively smoothly. If you notice any significant wobbling action then you know you have a warped shaft that's way out of spec. for what you purchased. Send it back and get what you paid for and requested.

No arrow seller will ever admit to these things. The reason is simple. They're in the business of selling arrows and arrow shafts. That means everything they buy, not just the very best of their stock. Their waste product alone would be so high they couldn't stay in business. So do yourself a favor and be very careful and be smart about what you're buying.

My last piece of knowledge on this topic to pass on to those of you who've managed to read this thread this far is the case for building your own arrows. Yes, it's time consuming and laborious, however if you understand the importance of shooting tightly spined, matched arrows, then ask yourself one question. “Where do you think all those warped, unmatched arrows are going”? That's correct - the average guy who calls up and requests a dozen or a half dozen top grade arrows for his bow or crossbow and is willing to pay a little extra for the better brands is in fact getting a complete mix of unmatched shafts that may well contain any number of less than straight shafts in the group he purchased.

So what do we constantly here on the forums in terms of arrow grouping questions?

I was shooting at 40 yards and my first two arrows were right where I aimed, but the next arrow was off by 5 or 6 inches. I can't figure out what's wrong? Does anybody have any idea's as to what's causing my problem?

As I stated in my opening, tuning is far more than just elements on the crossbow. If we want to achieve superior performance then we need to tune or balance much more than just one piece of equipment. I hope this information is helpful to your knowledge base and it will help you improve your shooting accuracy.

It's also worth explaining the fact that once an arrow is built, has been cut down in length and contains anything from additional carbon sleeves, plus inserts, plus nocks and vanes it becomes very resistant to further warping. So if you receive them straight and build them before any additional warpage can occur, they retain the original straightness.

Jon Henry
 

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Discussion Starter #3
Every once in a while we all need a refresher
Thanks
Boy John, you hit the nail right on the head with your comment. If I’m away from building arrows for any length of time I start dropping small pieces of information I know by heart. I think can be said with many things, not just arrow making.

This why the different threads that get produced or replied to are so important. For some it’s a learning curve, for others it’s a good refresher!
 

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Quite interesting...Learn something new almost every day on CBN. I was not aware of "shelf life" on carbon arrows. I always figured that extreme temp changes on the bare shafts could have an impact, but just assumed they were likely never subjected to such extremes enough to alter them. Never thought of the drill trick either, as I have always used a commercial "arrow roller" to look for any wobble in a finished shaft, but not a bare shaft. Thanks for the information!
 

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Wasn’t aware of the shelf life thing either. I have been spinning shafts and components for a long time though. My first ah ah moment was close to 20 years ago shooting a compound bow. I had to be an early adopter of the then new Easton Axis arrows. After a while, I seemed to be having trouble with tight groups. They would shoot to the same POI as the ACC 360s that I also had. One day when I was definitely shooting well for me, I shot three Axis into about a 3” group at 40 yards. Shot 3 ACCs at the same spot (I did that back then ;) ), and they shot a nice 1” group, right in the middle of the Axis group. Put the axis on the spinner, and it was obvious why. Around then, I also made my first spine meter. After measuring my ACCs and several all carbons at that time (early 2000s), I came to the conclusion that the money I spent to make the spine meter would have been better spent on more ACCs.:rolleyes: I found not only Axis arrows but also Vapor brand arrows would warp and show a bad spin in a few months of heavy shooting. Last anecdote, one day I went to our club range toshoo a crossbow, and discovered several Carbon Express Piledrivers someone had put in the trash can.o_O Two of the half dozen were broken, but 4 looked fine. Figured they were in the trash can, not laying on or around the table, so I took them home, figuring I could maybe cut them down to shoot in my bows. The fact that they were in the trash painted the picture of quite a frustrating range trip. When I got home and spun them, only two of them were straight, the rest had a moderate to horrible wobble. Probably an anomaly, but I can’t help but think about that any time I see someone on forums or Facebook recommend piledrivers.;)
 

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Wasn’t aware of the shelf life thing either. I have been spinning shafts and components for a long time though. My first ah ah moment was close to 20 years ago shooting a compound bow. I had to be an early adopter of the then new Easton Axis arrows. After a while, I seemed to be having trouble with tight groups. They would shoot to the same POI as the ACC 360s that I also had. One day when I was definitely shooting well for me, I shot three Axis into about a 3” group at 40 yards. Shot 3 ACCs at the same spot (I did that back then ;) ), and they shot a nice 1” group, right in the middle of the Axis group. Put the axis on the spinner, and it was obvious why. Around then, I also made my first spine meter. After measuring my ACCs and several all carbons at that time (early 2000s), I came to the conclusion that the money I spent to make the spine meter would have been better spent on more ACCs.:rolleyes: I found not only Axis arrows but also Vapor brand arrows would warp and show a bad spin in a few months of heavy shooting. Last anecdote, one day I went to our club range toshoo a crossbow, and discovered several Carbon Express Piledrivers someone had put in the trash can.o_O Two of the half dozen were broken, but 4 looked fine. Figured they were in the trash can, not laying on or around the table, so I took them home, figuring I could maybe cut them down to shoot in my bows. The fact that they were in the trash painted the picture of quite a frustrating range trip. When I got home and spun them, only two of them were straight, the rest had a moderate to horrible wobble. Probably an anomaly, but I can’t help but think about that any time I see someone on forums or Facebook recommend piledrivers.;)
To be clear Joe, when we talk about the shelf life on carbon shafts this only applies to unfinished raw shafts. Once inserts, sleeves, vanes and glue are all applied they limit or restrict the carbons ability to both warp or twist.
Also, raw shafts are much longer than those you use to build your crossbow arrows with. Even Jerry at South Shore Archery orders his raw Tapp Nation and Zombie Slayer Shafts at 26” so he can cut up to two inches off both sides or up to 4” off a single to compensate for minor bends.

Today’s carbon shafts are becoming more and more complex to test or to even understand. There are several different weaves of carbon fiber that can make up the outer layer of carbon, but some manufacturers are also using a high tech.process to bond an inner shaft within the outer shaft. This totally changes the spine characteristics of the finished arrow and makes identifying the deflection points much more difficult.

The advice I try to give most people is to order Spine Matched shafts with the inserts shipped loose. I ask to have the stiff side plain marking left on each shaft. Once I receive the order I first place them in my drill and spin them on a medium speed to test for any wobble. If they pass this test then I number the arrows and put each one on my own spine tester and record on paper the deflection values for comparisons of every shaft to every other shaft in the dozen I’m building.
If everything checks out Then I can begin the building process.
 
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