Spine variation with carbon shafts

[Matty]

I tested a bunch tonight. The average deflection of my GT 1535 were 470 the average deflection of my 3555 were 430. Now that's only a difference of 40! And notice I said average. The 1535 varied from 450-530 I measured 3 dozen!
The 3555 were much tighter tolerances. But all very close to 430 I measured 1 dozen all new all full length.
I can't measure FMJS on my scale as they are too thin.
Bottom line for me is. This whole program is really selling me on wood.

[LB_hntr]

Originally posted by Orion:
LB: A spine tester will work on made up arrows.  The results may be off just a little, but will help you identify any fliers.  Traditionally, spine was measured by measuring the deflection when a 2# weight is hung on the shaft suspended between two posts 26 inches apart.  The point and nock/fletches, represent a little weight on either end of the arrow, will affect the reading a little, but so little as to be of no practical significance.  

For some reason, I believe it was Easton that began testing shafts with a 1.94# weight with the posts spread 28 inches apart.  That became the standard used by most manufacturers of aluminum and carbon arrows. It does not give the same results as the previous  method.

Of course, each method gives consistent results for that method, but the two are not comparable with each other. For example, a 50# spine using the 2# method yields a deflection of .52 inches.  That same 50# gives a deflection of .61 using the 1.94# method, according to a conversion chart prepared by RangersArchery.com. When talking/comparing spine, it's important to know what measurement was used.

The most accurate testers give you the deflection in inches, hundredths of an inch actually.  Some display the result in poundage of spine, usually not quite as precise.

Thanks! Im very happy with my goldtips. I seldom shoot groups as I practice with broadheads mostly and shooting groups with broadheads is hard on the arrows. So im mostly shoot 1 or 2 arrows then pull em and repeat.
 But i am now curious and if buying a spine tester and taking a couple minutes to batch them up and cut a couple different to get them right can make them fly better im all in!
 Time to research testers!

[Hermon]

Originally posted by Matty:
I tested a bunch tonight. The average deflection of my GT 1535 were 470 the average deflection of my 3555 were 430. Now that's only a difference of 40! And notice I said average. The 1535 varied from 450-530 I measured 3 dozen!
The 3555 were much tighter tolerances. But all very close to 430 I measured 1 dozen all new all full length.
I can't measure FMJS on my scale as they are too thin.
Bottom line for me is. This whole program is really selling me on wood.

Matty, am I reading this right?  The 1535's (600 spine rated) basically averaged closer to 500 spine?

And the 3555's (500 spine rated) were closer to 400 spine rated?  I'm with you, think I will stick to my wood arrows.

Originally posted by Hermon:
   

Originally posted by Matty:
I tested a bunch tonight. The average deflection of my GT 1535 were 470 the average deflection of my 3555 were 430. Now that's only a difference of 40! And notice I said average. The 1535 varied from 450-530 I measured 3 dozen!
The 3555 were much tighter tolerances. But all very close to 430 I measured 1 dozen all new all full length.
I can't measure FMJS on my scale as they are too thin.
Bottom line for me is. This whole program is really selling me on wood.

Matty, am I reading this right?  The 1535's (600 spine rated) basically averaged closer to 500 spine?

And the 3555's (500 spine rated) were closer to 400 spine rated?  I'm with you, think I will stick to my wood arrows. [/b]

I'm not Matty, but I can tell you from my experiences with GT that you are reading correctly. Every GT shaft I have tested has been way stiffer than marked. I use 55/75's which are marked .400 on the shaft. I have done hundreds of them and NEVER yet had a single shaft spine out at .400. Most are in the .350's - .370's, which is closer to a .340 than a .400. But I get wacked ones in every group also, that might be as high as the high.380's, or as low as the .310's. Those shafts are trash!

For me, it really does not matter what they spine out to because they work, and I tuned to these shafts before I had a spine tester. The spine testing gets the oddballs out of the way so I don't have to deal with them.

Bisch

[Matty]

Yep you read that correct, thanks BISCH...
Now that's not to say I won't use them. I'll still use them but I can weed some out for sure.  Get them close like BISCH does. And save the random odd balls for stumping or 3d targets with water or the Grand Canyon behind them. Regardless of how they spine...the thing that really sells me in carbon is its durability. It's an incredible material from this stand point. And for as much as I miss. I need durable!    
keep it going

[Hermon]

Guess this explains (partly)  why so many folks shoot leave their carbons full length.   They think that they are shooting one spine arrow, but in reality are shooting  a step stiffer than what the arrow is marked.

Since 2020s are gone, 28&1/4" 2020s is the only shaft my son will shoot and he cannot find any, I read this thread very carefully. He is considering going to carbons and I wanted to give him some advice on which carbon he could cut to that length and shoot out of his favorite Robertson longbow.  I must say that I am as confused and skeptical as ever about carbon arrows.  Since we use the arrow as a draw length check with tagging the broadhead to the finger, full length is not going to happen. I shoot tapered carbons that I tag at 27", they fly perfect out of one of my bows, not the one I wanted them to, but that is okay as it happens to be the best right hand longbow that I ever shot. He wanted to do the same with carbons for his 60 pound Robertson, but if there are big enough spine variances that he will be able to see, I would never hear the end of it if I told him anything wrong.

[Tedd]

Three Rivers Trad .300 are pretty consistent all the way around. I just checked a bunch. Almost no change in spine from shaft to shaft. And batch to batch they seem to always be the same.
I have the wall hang type spine tester. I can spin the shaft and check for a stiff side easily. The needle doesn't move much. While the tester is precise, it's scale doesn't correspond to the big ones. So I don't know how close they are to .300
They say .250 on my tester.
Tedd

[Pheonixarcher]

Something to keep in mind when spine testing your arrows; any change from a full length bare shaft will affect the results. Manufacturers test their shafts before labeling or printing and without nocks installed. A fletching wrap, feathers, and cutting the shafts and installing inserts will all affect the reading. Also, very few shafts (if any) are perfectly straight. Depending on where the bow of the shaft is located, can also show a variance in spine deflection. The true stiff side may or may not be the stiffest reading side if the bow of the shaft does not line up with the manufactured stiff side. So before you trash a shaft that does not read close to the rest, be sure to shoot it to make sure you are not being misled by other variables.

[olddogrib]

Okay,
Somebody who is not even a proper redneck "technoweenie" has probably already devised a cheap, rigged device that is perfectly sufficient for at least comparing how close a set of arrows is, regardless of whether it agrees with stated values or not. That's what most of us want to know, whether we've got a "wildcard" in the bunch. I already have such a device for measuring draw weight from a $12 modified digital luggage scale that's scary accurate and an el cheapo Harbor Freight cut-off saw that works great. Okay, whatcha got....let's see it?

[Matty]

Originally posted by olddogrib:
Okay,
Somebody who is not even a proper redneck "technoweenie" has probably already devised a cheap, rigged device that is perfectly sufficient for at least comparing how close a set of arrows is, regardless of whether it agrees with stated values or not. That's what most of us want to know, whether we've got a "wildcard" in the bunch. I already have such a device for measuring draw weight from a $12 modified digital luggage scale that's scary accurate and an el cheapo Harbor Freight cut-off saw that works great. Okay, whatcha got....let's see it?

There's a bunch out therein the "inter webs" some of my favorites are sam harpers, with a tuna can and fishing weights. And I think tenbrook did one with a bunch of bananas!
   

[Matty]

Oops double post

[olddogrib]

Okay chilluns, stumbled across this link that looks entirely doable, even for the mechanically challenged. Wonder if you could chuck the dial indicator in a drill press and lock it at he right height and simple use the arrow mount?


 http://www.fieldandstream.com/articles/hunting/2013/10/step-step-boost-accuracy-your-diy-spine-tester