Spine variation with carbon shafts

[bigbadjon]

The spine of the arrow changes as you rotate the shaft. One reading is the stiff side and the other is the weak side. As I said in an earlier post depending on how the shaft is laminated it can make a huge difference.

[**DONOTDELETE**]

Hey Bisch,  I've got a home made tester i set up for woodies at 26" span & a 2# weight.... Do i have to remodel this to 28" and reduce my test weight to be accurate?....  i can post a picture of this ting if it will help.

[bigbadjon]

I'm glad you said something because I put 28" in my post but have now corrected it. You can test it with the spine tester you already have it just won't give you the same read as the factory. It will tell you if they are matched. I had a conversion chart blown up into a poster and hung it at my work bench so I can easily switch from amo to Easton scale.

[bigbadjon]

http://www.rangersarchery.com/sites/default/files/fileupload/Spine-deflection_chart.jpg

Here is a link to the chart I use.

[**DONOTDELETE**]

Originally posted by bigbadjon:
 http://www.rangersarchery.com/sites/default/files/fileupload/Spine-deflection_chart.jpg  

Here is a link to the chart I use.

Ok ... i think my spine tester is a bit back woods. It uses a protractor and gives me degrees of deflection that i convert with a different chart.

The numbers that show on your chart... lets take a 55# spine shows .47  & .57 on the easton tester. What do these numbers represent? Inches of deflection? or what?

[bigbadjon]

Yes it is showing inches of deflection. This chart just adds the a row for the method Easton uses to spine shaft. So for the 340 shafts I just tested to be accurately marked they would need to read .280 on my tester.

[**DONOTDELETE**]

Ok.... i get it... thanks.

[yth-mnstr]

Interesting stuff guys. Thanks for sharing and teaching.

[beyondmyken]

Well, this explains why I don't shoot as well as I should.  

But seriously, any suggestions for those of us who don't have access to a spine tester?

[beyondmyken]

Well, this explains why I don't shoot as well as I should.  

[Orion]

Beyond:  You can do what Howard Hill did.  Just shoot all your arrows and throw out those that consistently fly off track.  However, probably won't work for two reasons.  Most of us aren't that good/consistent of a shot to be able to do it, and 2, even though the spine and weight may vary some on carbons, or woodies (not so much on aluminums) the variations probably aren't enough to make much of a difference.  Smaller differences than our own inconsistencies in shooting form cause. In short, small inconsistencies among a group of shafts aren't worth worrying about.

[Kevin Dill]

Orion speaks the truth.

If your draw is 1/2" shorter...

If your anchor moves 1/4" up or down...

If your release is a touch slow...

If your bow hand moves upon release...

There are infinite 'ifs', but the bottom line is that minor shaft inconsistencies can usually only be detected in the shooting of those who are extremely form-conscious and seldom vary in their technique. When I shot woodies I had to toss out the occasional weird arrow, and the problem was always traceable to bad spine or out-of-straight. I haven't had a carbon act that way for me ever, but I've only ever used Beman or Axis in identical configurations. I also used to require 5.5" HP fletching on my POC customs, but have even better flight using regular height 5.0" fletch on Axis customs.

Then there is also the unknowns of dynamic spine (deflection) vs static spine. It's one thing to know how a variety of shafts react to a 2# weight on a test unit, but quite another to prove what they do with 250 grains of broadhead in front and 60# of thrust behind them.

[GANDGOLF]

I was told of a fella (supposedly a World class shooter), that plugged both ends of his new shafts and threw them in a bath tub of water. Marked the stiff side accordingly.    

[bigbadjon]

I knew some one was going to bring up dynamic spine. You must have matched static spine before anything else. if all of your arrows start with the same static spine then they will all have the same dynamic spine with identical length and components. Also plugging the ends of the shaft and floating them will tell you the stiff side but you won't know if they are matched in spine.

[DanielB89]

man, and to think I have been shooting carbons because of their "consistencies".  Now i'll just say it is because of their durability..  

[last arrow]

So if you want consistent weight and spine, go aluminum?

[Kevin Dill]

If you want consistent weight and spine think like an Olympian. There's a lot more to the equation of good flight (consistency) than matched deflection in a dozen shafts. It starts there of course. Then again, what about the shaft's ability to maintain straightness through much shooting and perhaps some odd hits? Aluminum can bend and remain bent. Wood has the tendency toward memory when bent, which is why you can flex it and sometimes overcome a crooked shaft. You can also take a straight wood shaft and put a crook in it by flexing it repeatedly in the same direction. All shafting has its unique characteristics, and thus all is not equal.

I agree with the assertion that dynamic spine will match up (per dozen) as long as everything else is matched. The problem here is that dynamic spine (deflection) will be much affected by real-world factors such as the shooter's form and release, poundage (force) applied to the arrow, temperature, and other variables. Dynamic spine for the hunter inherently means a host of variables apply in actual use. In the end, we want an arrow which reacts well and with forgiveness...is not touchy or sensitive...to our errors.

[bigbadjon]

I agree and matching your shafts is the number one way to achieve a forgiving arrow. How can you be sure of your form ,or anything else, if your arrows do not match? Another thing to moniter is that carbon shafts do eventually weaken to shooting fatique so you must also moniter that. Aluminum is the best shaft for tolerances off the shelf but carbon is longer lasting.

[McDave]

Just to see what I've been shooting, without trying to change anything, this is the range of weights and spines on six of the VAP arrows I've been shooting lately. As I mentioned, VAP states that they orient the nocks from the factory so they are aligned with the "grain" of the spine of the carbon arrow.  I used the same static spine tester I use for wood arrows, with the nock openings facing up, since that's all I have. I don't have any bare shafts to test, so the weight differences could result from variations in the weight of the glue or fletching, I suppose, but that wouldn't account for the spine differences.  To put it in perspective, the range of spines from 475-500 is the equivalent of 52-55# spined wood arrows, according to the scale on the spine tester.  I suppose I'm okay with these variations, as they are probably way less than any variations I might introduce myself from shot to shot.

318 grains  -  500 spine
314............500
317............475
315............485
316............475
314............485

[last arrow]

I guess the real question has anyone started orienting shafts to match spine seen an improvement in shooting?  That's the only way to know if it matters