The deceptive spine values of carbon shafts...

[Flying Dutchman]

After reading some topics about the misleading spinevalues of carbon arrows and some people don't know how to deal with it, I think it's about time to open a topic about this.

A nice subject for my 1000-th post!                    
 
Lots of people seem to think that a shaft saying 15-35 is meant for bows within the range of 15 to 35 lbs. This is not true!
The 15-35 comes out of the compound world and has nothing to do with our traditional bows!

Lets take a look at the most common values: 15-35, 35-55, 55-75, and 75-95. More important here is the deflection. This means how much the shaft flexes with a weight of exactly 2 lbs on it, supported on both ends at 26".
If you want to converse these values to more traditional spinevalues, you will have to do some maths. First we look for the deflection value (which is mostly printed on the shaft and is in 1/1000 of an inch) For example 0.600 means that the shaft flexes 0.6 inch when putting a weight on it from 2 lbs supported at both ends at a lenght of 26 inches. This is the same method as with wood, only with wood it is measured at 28 inches. Then we devide the deflection value by 26 and multiply it with 1,2115 which is the factor for carbon.

This should give you the following table:

15-35 or 0.600” becomes: 26/0,6 x 1,2115 =  52,5 lbs
35-55 or  0.500” becomes: 26/0,5 x 1,2115 =  63 lbs
55-75 or 0.400” becomes: 26/0,4 x 1,2115 =  78 lbs
75-95 or 0.300” becomes: 26/0,3 x 1,2115 = 105 lbs

On these calculated lbs values all normal archery laws are applicable: shortening the shaft means a stiffer spine, higher point-weight means a weaker spine.

So for my 45 lbs bow I use a 1535 shaft. On a full lenght of 30,5" and with a 85 grains fieldpoint and standard insert it flies great. Bareshafting tells the same. My woodies tell the same: I use on the same bow 53 +/- 1 lbs Sitka shafts.. That's pretty close to the 52,5 lbs from a 15-35 carbon shaft!

YMMV, so if you have other ideas, theories or whatever, don't hold back. Afterall we are here to learn and share! I am sure there are some people here who do know a whole lot more about arrows than I do          :D

[mrjsl]

It's been my experience with carbons that changing the length of the shaft and adjusting the point weight do not have the exact same effect and should not necessarily be considered an interchangeable fix. I believe that for a given problem changing one of them will work better than changing the other.

I do use a weaker spined carbon shaft than recommended anywhere, but they are the right shaft for my bow, regardless of what the calculators and charts say.

[jess stuart]

I am just getting into carbon arrows so don't know much.  So far my very limited experience would agree with the spine table you have listed.  Ordered what I thought were 3555 but put the wrong item number down and received 1535s they shoot great from my 46# recurve.  The only thing I did was put some nylon cord in the shaft to get the weight up a little.

[Flying Dutchman]

When shooting no heavy front weight, total arrow weight can become an issue. You can put something like cord in the shaft, paint the last part of the shaft, glue little leadballs in the nock which asks for a hevaier point, etc. I always take care that I shoot around the 9GPP at least with 10 GPP as max.

[SCATTERSHOT]

I spined some carbon shafts a while back, and your values are about what I came up with. I think that's what started the heavy point craze. You NEEDED 300 grain points to get those stiff shafts flying right.

[Flying Dutchman]

You might have nailed it  

[Matty]

Yup all good info there.  I use 500 and 600 spine (lon the longer end)on most of my bows from 45-55.  Fly awesome. And with 200 gr up front. To combat the weight issue. I've been using the grizzly sticks. They are considerably heavier.

[Orion]

Dutchman:  Your numbers are pretty close, accurate for the measurements you're taking, but the premise is a little off.

In the U.S., the 2# weight is used on shafts suspended between posts 26 inches apart, not 28 inches.  A similar set up has recently come into use for carbon shafts.  In this case a 1.94# weight is used on shafts suspended between posts 28 inches apart.  The two measurement devices yield similar, though not identical results.

I have found that carbons can sometimes vary quite a bit in spine.  I have 10 Gold Tip 55/75 XTs, for example that spine about 85# (2# wt with 26-inch centers).  However, one of those shafts spine over 100#.  Maybe mislabled.  Don't know, but it's marked the same 55/75 as all the rest.

[Doc Nock]

All the scientific input is great, but the reality is that spine is somewhat relative...

Factors I've found over the past 15 yrs that affect spine with carbons are:

* Draw weight
* arrow length
* Point weight
* Tail weight
* Fletching size and shape
* Riser center cut amount

After factoring in all those things, recently I learned more interesting data from a chap who had built carbon and aluminum arrows for the demanding tournament circuit shooters, both compound and trad.

Enter a new conundrum!    

His information was that due to the demands of his clientele, he weighed, spined and batched all the arrows he bought.  He found that almost all carbon arrow makers have considerable spine variance in any given dozen... and some are worse than others!

Shafts I used were some of the worst...so I ended up bare shaft tuning each and EVERY shaft and found that I had to cut arrows different lengths...some, to get to fly right, were as much as a 1/4" different and some only 1/16th.

Lots of variables in carbon as with natural materials.  Learning to eliminate those variables goes a long way toward helping anyone be more consistent in their shooting.

Equipment and form. Variance in either is a real challenge!

[SCATTERSHOT]

Orion, I think the dutchman meant that the shafts were suspended at 26", and the values applied to a 28" arrow. That has been my understanding, anyway.

[Dimondback]

That explains some recent issues I have been having with the 5575 blems I just ordered for my 58# @28" R/D....Darn it!

[Trumpkin the Dwarf]

My experience with carbons has been limited because I found a combo I like and have stuck with it so far. That said, before even thinking about tuning arrows you have to have consistent form. If you plan to bareshaft tune to your bow you will find that the release is critically important. Assuming you have  good (a.k.a. consistent) form the rest is a lot of personal preference...some prefer to pick a point weight and trim the shaft, others build out their riser to weaken the arrow's spine, I like to leave them full length(32" draw does that) and pile on the point weight till it flies straight.

[Flying Dutchman]

Originally posted by Doc Nock:
All the scientific input is great, but the reality is that spine is somewhat relative...

Factors I've found over the past 15 yrs that affect spine with carbons are:

* Draw weight
* arrow length
* Point weight
* Tail weight
* Fletching size and shape
* Riser center cut amount

After factoring in all those things, recently I learned more interesting data from a chap who had built carbon and aluminum arrows for the demanding tournament circuit shooters, both compound and trad.

Enter a new conundrum!        

His information was that due to the demands of his clientele, he weighed, spined and batched all the arrows he bought.  He found that almost all carbon arrow makers have considerable spine variance in any given dozen... and some are worse than others!

Shafts I used were some of the worst...so I ended up bare shaft tuning each and EVERY shaft and found that I had to cut arrows different lengths...some, to get to fly right, were as much as a 1/4" different and some only 1/16th.

Lots of variables in carbon as with natural materials.  Learning to eliminate those variables goes a long way toward helping anyone be more consistent in their shooting.

Equipment and form. Variance in either is a real challenge!

You are absolutely right Doc Noc. That's why I sad: On these calculated lbs values all normal archery laws are applicable       .

I also putted my part of carbon shafts on the spine tester and found out that the the spine value of carbon is not very consistent to say the least. I found deviations as big as 7 lbs on 15-35 shafts. The weight however is very consistent...

I started this thread only to give an understanding how the carbon spine values really are and give a starting point for those struggling with it..
Thank you for clearing out that there is more in this game then static spine-value only, I couldn't agree more with you!    Dynamic spine value is another thing.

My post was more meant for people saying: "Ok I have a 60 lbs bow, so I have to start with a 55-75 shaft....

[30coupe]

Doc,

I found the same thing as far as variation with some. My son also bought some high dollar carbons for his wheelie bow and out of a half dozen, only three flew well, one so-so, and two wouldn't work with his broadheads at all. Oddly enough, the shafts I have found to be most consistent were also the cheapest: Beman ICS Bowhunter. They are not perfect, but they are the closest I have tried. I didn't spine them, as I have no tester, but paper tuning and broadhead tuning gave me very consistent results with them. GT 35-55s are supposed to be .500 spine, but I have to leave them at least an inch longer than the Bemans with the same weight up front. Out of two dozen Bemans, I have had only one that refused to cooperate.

[stickum]

I was thinking about some Beman Bone collectors or some Easton AXIS, has anyone compared these for spine consistancy?

[Todd Brickel]

Great post.  I agree that centershot is a huge variable.  I have a number of recurves from the same bowyer, and the lightest in the group (54#) shoots .400 Beman MFX Classics, just like the 60#.  But the 56# and 57# need a .500.  Centershot is a major determining factor.

[Doc Nock]

Flying D,

IT was a worthwhile motivation...and I was just building on that... not trying to counter.

I would bare shaft 3 and fletch 3 and then trim to get them all to fly the same...but I'd see "tailing" when I'd get back to 20-25 yards and ignored it...cause they hit the same... uh-huh-uh!

So while you had their attention, I just was hoping to encourage folks to NOT figure because they're high tech carbon that when they get one or 3 to fly well, to cut them all the same...cause there are big variances in a given dozen.

I was AMAZEDin how much effect in flight an 1/8" in length made in how they tailed either left or right!

there is research about indigenous tribes in S. America that tune EVERY arrow to THEIR bow! They may have natural fiber shafting with steel points and each one in their quiver might be a different length... so nothing new here.

And yeah, form is critical...which is why my tuning source recommends shooting 2 shafts at a time and shooting them both at least 4-5 times with total focus on form... to see if you get consistent results before cutting.

[Flying Dutchman]

Now worries Dave,I didn't see it as a counter...I seldom do. As I said we are here to learn form each other and to share.
I have no problems in cutting woodies to the same langht, but they are spined properly, that is within + or - 1 lsb.
Suppose you would have carbons spined very precise, would tou still have to cut them at different lenght you think? And Yes, carbon is very vulnerable for lenght!

Here is what I learned about carbon shafting recently. I shoot Gold Tip 55/75 XT Hunter shafts. I had my bow shooting perfectly when I set it up a couple years ago. Last year a guy was shooting thru the paper and I shot a couple thru it just cause I was there. At this point my arrows were showing to be stiff. I had no clue why and just thought it was something I was doing different than before.

Fast forward a couple months and I ran across a great deal on a good spine tester. This is one of the ones for carbon arrows and uses the 1.94# weight and gives you a deflection reading in inches. So now I started to run arrows thru the spine tester and I was amazed at what I found. All of my arrows were factory marked as if they were .400 spine. I tested 3 dozen shafts and found NONE OF THEM to be .400 spine. They were all stiffer than .400 ranging from .342 to .371, with most of them being in the .360 to .380 range.

So here is what I now believe: when I initially set my bow up I had shafts that were a bit lighter spined and they tuned perfectly. When I shot thru the paper at the shop I was using other shafts than I had used at first and they were probably stiffer and that is why they showed stiff in the paper.

I now run all my shafts thru the spine tester and group them in .010" sets to use as needed. And Doc Nock was right. Each group needs to cut just a tad bit different to tune perfectly.

Bisch

[Green]

Carbon's tricky.     :D

Last week I traded for some GT XT Hunter 5575's to play with.  I removed all inserts, fletching and wraps.  I then put them on my spine tester and rotated them about an 1/8" and respined all the way around.  After doing a few to see what the range was, I then marked all of them where they spined .380 and then finished them out with the cock feather opposite this mark so that I had the .380 side against the riser.  Even though all shafts are cut the same at 30", I have 2-3 out of 11 that just won't group with the rest and probably need to follow Doc's advice and tune them all individually.  Problem is.....I'd rather shoot wood.