Arrow Spine Consistency, Tuning for Tighter Groups.
There are three debates amongst archers on the spine stiffness area on an arrow.
1) Is the stiffest part of the arrows static spine under the manufacturer label?
2) Do all arrow manufacturers place the cock vane over the stiffest (spine) part of the arrow?
3) Do rotating the nocks determine the stiffest part of the arrows spine, when the arrow is in dynamic motion?
Answer, No, No and Yes in that order!
This test will show you various arrows I will use and where the nock location will indicate on the arrow surface area which gives the best arrow groups out to 40 meters. This test will also indicate the most consistent spine stiffness from arrow to arrow manufacturer in which to affix your cock vane.
Don't Nock it, until you tried it!
All arrows will be using an adhesive Bohning Nock Position Indicator with gradient adjustments from 1 to 4 to show me the exact location of the nock in relation to the arrow in order to see where the consistency of the spine is finally located. By turning the nock a ¼ turn on each arrow should eventually see me getting a tight arrow group at 40 meters, thus concluding this is the best spine consistency from arrow to arrow!
Nocks from most manufacturers have a raised line on the shank which I will correspond with the Bohning Nock Marked Gradients located on the end of the arrow.
The Nocks raised line can then be lined up with the Nock Indicator Gradients and used to consistently to determine where to affix your cock vane on the end of the arrow later on with the help of marking the arrow shaft with a black sharpie.
The Arrows and Spine Range
I will shoot a set of four arrows with each set from different arrow manufacturers at 40 meters and adjust the nock a quarter turn at a time thereby rotating the arrow and shooting the arrow to see which nock location indicates the best group, thus indicate the most consistent spine from each arrow.
All arrows used in this test will be within the same spine (350-400) range for a 60 pound bow, though some arrows will be longer by a few inches and or heavier by up to 100 grains.
The test will use the most popular arrows such as the Easton Powerflight, Easton Fatboys, Gold Tip Hunters, PSEX-Weave, Bemans, Victory Arrows, as well as the Victory Nanos (Now calledVAPs).
All arrows will be tipped with Martin Archery 100 grain screw in field points.
Vanes and Feathers
The test will be based on the more popular used Vanes and Feathers such as Bohning Blazers, Bohning X Vanes, Duravane, AAE Vanes,TrueFlight and Gateway Feathers.
This way everyone's favorite vane or feather is included so compound and recurve bow, release and finger shooters can benefit.
Keep in mind this test is not to determine the best arrow, vane, feather or point. This test is to find the most consistent part of the spine which will give the best arrow grouping.
Since these arrows are all of varying manufacturers, design, length and vanes, I will be using my 40 meter pin sight and not all arrows will be hitting the gold. For me to adjust my sight for each arrow set of varying size and weight arrows to hit the gold I would have to spend two days doing this test.
Again, we are going for best group, for accuracy into the gold I leave that up to you fellow archers to adjust your pin sights to do that!
(It is assumed all arrow manufacturers (with the exception of PSE's X-Weave carbon arrows) are consistent in their manufacturing process in placing the stiffest or consistent part of the spine in the same location for every arrow to date).
The Issue of Nock Tuning
The problem with nock tuning is vane clearance when you rotate the nock in which the vane may contact any rest that is not a full dropaway, hence the popularity of dropaways.
For this test, I replaced my Spott Hogg Infinity Blade Rest to a Dropaway rest which offers total vane clearance and no vane contact. This is especially critical when rotating nocks at varying degrees when trying to determine the stiffest part of the spine while getting no contact vane clearance. Once I get consistently tight groups, I strip off the vanes and put new vanes to correspond where the spine on the arrow is consistent. I then takeoff my Dropaway rest and put my Spot Hogg Infinity Blade Rest back on.
This test will allow archers whether they use a trigger release or fingers to fletch their vanes to their arrows and tune for best performance. If all things being equal this test should show the location where to place your cock vane over the stiffest or most consistent part of the arrows spine, without having to resort to changing their arrow rest like I have done to gain total vane clearance.
While you could use a spine tester and you can also take up badminton and wear lacy pink socks too!
I noted a few things that spine testers "Bless their cotton socks" do not or cannot determine, though no fault of their own, they measure static spine, not dynamic spine.
Spine can vary along the shaft, so I took a few carbon arrows into my lab and cut them into exact 1 inch increments and weighed each 1 inch section to determine if all equal lengths weighed the same. The answer, out of 30 sections of cut 1 inch carbons measured end to end with a digital micrometers 3 sections weighed the same out of 30 sections the rest of the sections weighed up to 3 grain more than the others. So you can see why field testing for dynamic spine is the better way to judge an aggregate stiffness of the entire arrow.
Spine testers I have used in the past do not determine best arrow grouping, only field testing will determine that. Some spine testers I've found have inaccuracies in which I will not go into, let's just say spine testers are good for wood arrows and leave it at that!!
You should know carbon arrow spine can have various spine differences in a dozen arrows of the same set, even Easton X-10s may have one or two arrows in a set of a dozen arrows that are not matched. So there is nothing like true field conditions to see how arrows group at 40 meters when dealing with these carbon spine consistency anomalies. After all isn't great groups what it's all about, followed by sighting adjustments for great accuracy?
Once I attained the best arrow group possible using the Bohning Nock Position Locator, I let another archer shoot all the "newly tuned arrows" to determine if he would also get all arrows to group good and tight.