Spine variation with carbon shafts

[McDave]

The thread on spine/weight variations with wood shafts got me to thinking about the same issue with carbon shafts.

I know carbon shafts can be 10-15 grains different in weight, even though they might be marked +- 2 grains. This was explained to me that each batch was supposed to be within +- 2 grains, but shafts from a different batch could be outside that range. So if batches got mixed in the store, or if you mixed them yourself, you can't depend on the tolerance marked on the shaft.

I wonder if the same thing applies to spine?  I'm not even sure how to test the spine of a carbon arrow.  I know that VAP says their shafts come with nocks installed to match the spine grain, so evidently a carbon arrow's spine will change as you rotate the arrow, just like a wood arrow would.

I would imagine that by comparison with the variation in wood arrows, none of this makes much difference (I hope), but I wonder how much variation in spine and weight we're ignoring?

[katman]

Probably would vary with different manufacturers products and which grade of shaft you purchase.

Instead of purchasing a spine tester I will shoot all the shafts bare shaft after I have tuned and cull any oddballs(don't get very many) as stumpers with fluflu. Weight has been pretty close.

[bigbadjon]

Vast amounts in some cases even in the same dozen. I am right now shooting some Victory HVs that have in the best shaft 3# of variance from the stiff side to the weak side. The worst is 7#. The worst shaft I have is a CX with a baffling 11# variance. Easton and Carbon Tech have historically had the least variance by rotating the arrow for me. If you guys can wait til tonight I just got a brand spanking new set of Axis shafts that I will spine and weigh to show how matched... or usually mismatched your arrows will be.

[ISP 5353]

Interested in what you find out about the AXIS shafts.

[Sirius Black]

Most carbons are still made with the compound shooter (mech. release aid) in mind. I've done some tests when I was still shooting compounds,  and I could shoot a 400 or 340 spine arrow (340 was just slightly heavier)and couldn't really tell a difference. Most tuning that we have to go thru, they don't.

I shoot Gold Tip XT Hunter black shafts. These are the more expensive straighter shafts. I spine test every shaft I get and separate them into like groups of .010" deflection. These are the only shafts I have experience with, and there is a great variance in spine, even in the same dz shafts.

I shoot 55/75 shafts which are marked .400 spine on the shafts by the mfgr. I have tested probably 30dz or more, and have yet to have one single shaft spine out at .400. They are all stiffer, and the range is from in the .340's to the .390's, with most being in the .360 - .380 range.

I spine every shaft and mark the stiffest side and index my nocks to that mark. On my GT shafts, it is not uncommon to see .010" - .020" deflection difference between the weak and stiff side of the shaft.

What spine testing has done for me is to reduce the number of "flyers" to almost none. I now always have groups of like spine arrows, and never have a .340-something arrow in the same quiver with a bunch of .370-something arrows acting all wierd!

Like I said above, these GT's are the only shafts I have experience with, so I don't know if other brands are like that or not.

My spine tester is a high dollar one (can't remember the brand) that is set up at 28" with a 1.94# weight.

Bisch

[lt-m-grow]

Slight variation in spine and weight doesn't surprise me much.  

I am surprised that there is a weak and stiff side however.

I would think the process would be more uniform down the length of one shaft.

[bigbadjon]

It is not. They are usually rolled from a sheet and then ground round creating a stiff side. Easton, Carbon Tech, PSE, and W&W have some sort of seamless wrapping on their shafts that mitigate that feature some. Manufacturers try to sell you on weight and straightness becaused its easy and cheap for them to control but spine consistency is far and away the most important aspect of an arrow.

[Orion]

I have several dozen Axis shafts in 500, 400 and 340.  All are very close re physical weight, i.e. within two grains.  I can feel a stiffer orientation to the spine on most of them when I roll them in my palm with one end of the shaft angled onto a hard surface. Haven't measured all the spines, but those I did were closely matched as well.

[Matty]

I'm with BISCH. I bought a spine tester last year cause I want to shoot more wood arrows. I have about a thousand carbons. I've tested most of the unwrapped ones. It did explain "flyers" for sure. There is definately a stiff side, and they spined heavier than expected. I was amazed at how many 400s were closer to 340-350.  The weights were all close enough to not worry about within 3 grains I'd say on average.

[katman]

Shafts I have had to adjust nock position the most to get spines equal from the same dozen were tapered carbon shafts. Love the concept of tapered shafts but it must be difficult to get consistency in manufacturing.

[bigbadjon]

Ok guys, I just finished measuring a dozen Easton Axis 340s minty fresh and straight out of the tube. I was using a Flight Rite Pro set at 26" and I will list the spine in deflection rounded to .005 rather than poundage because in heavy weight shafts the scale is not correct. Again, I am using amo 26" with a 2 lb weight which will be different than what the factory uses.
Shaft 1 was .290, .300, and 326 grs.
Shaft 2 was .285, .290, and 327 grs.
Shaft 3 was .290, .290, and 327 grs.
Shaft 4 was .280, .290 and 324 grs.
Shaft 5 was .290, .300 and 326 grs.
Shaft 6 was .280, .290, and 326 grs.
Shaft 7 was .280, .285, and 326 grs.
Shaft 8 was .280, .290, and 327 grs.
Shaft 9 was .285, .290, and 326 grs
Shaft 10 was .290, .300, and 326 grs.
Shaft 11 was .280, .290, and 326 grs.
Shaft 12 was .290, .300, and 326 grs.

These readings are the stiff side, weak side, and weight.

[bigbadjon]

I am actually a little shocked... that is the most tightly matched factory set I have measured. Those might be able to be perfectly matched by indexing the nock.
I also have 3 remaining Bloodsport 55/75 and they measure:

Shaft 1 .305, .310, 279 grs.
Shaft 2 .275, .285,278 grs.
Shaft 3 .285, 290, and 278 grs.

Those were bought per shaft out of a bin and you can see why those won't group well.

Those axis are really close! My GT shafts are way wider than that! Just like my GT's though, there is not a single .340 on the group!

Bisch

[Grey Taylor]

So, the next time someone tells me he shoots carbon because he finds wood shafts to variable, I'm going to kick him in the shins.
   

Guy

[bigbadjon]

Bisch my Victory shafts were way wider than that to. Maybe somebody else has some axis shafts they can test to see if every batch is that close. I have never had carbons that close from a factory set.

[screamin]

[yth-mnstr]

Do you want the stiff side facing out or towards your rest?

[bigbadjon]

Ideally you wany the stiff side toward your riser. Sometimes though you will have to index the shaft to tweak the spine. Of course that doesn't always work either which is why it is important that they match.

[Jack Hoyt 75]

Originally posted by bigbadjon:

Shaft 1 was .290, .300, and 326 grs.
Shaft 2 was .285, .290, and 327 grs.
Shaft 3 was .290, .290, and 327 grs.
Shaft 4 was .280, .290 and 324 grs.
Shaft 5 was .290, .300 and 326 grs.
Shaft 6 was .280, .290, and 326 grs.
 

Great info guys!!  I shoot Axis 500 and 400 the most but don't have a spine tester yet.  May have to invest in one?

I have been looking at this and need to ask a dumb question.  Why two sets of decimal numbers ie: .290 , .300??