Bolt/Arrow Spine Optimization

[Significent]

As soon as the weather breaks and I have all of my bolts set up the way I'm going to hunt with them, I'm planning to take them out to the range and determine which vane orientation is best. (Which vane down).

I'm wondering if anyone has tried to measure spine consistency with a DIY jig? I was thinking I might be able to get a jump-start on the shooting process by setting up a contraption with a fulcrum between 1/2 and 2/3rds of the way back from the bolt tip, locking the nock in place and hanging a weight on the tip of the bolt that's just heavy enough to make the bolt flex a bit. In theory, I should be able to measure any slight difference in spine each time I rotate the bolt 180 degrees. If need be, I could take the field point out and screw in a coupler to another bolt or one of my vertical bow arrows to exaggerate and more easily measure the amount of flex.

Has anyone done anything like this? Is there a better way? If so, did determining the stiffest spine orientation in a jig actually correlate to tighter groups at the range?

[Boo]

I posted a picture of a jig a while ago.
I gave my home made one to Big John so if you want a picture maybe he's send you one with an explanation.

[Significent]

Don, I found your jig with an explanation here:

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http://www.excaliburcrossbow.com/phpBB2/viewtopic.php?f=1&t=46901&hilit=tester

I can see how it would work well. You and everyone else say's that the best place to put the cock feather is at the point of weakest spine (6 o'clock). Most of what I've read indicates that crossbows prefer more spine. If that's the case, wouldn't it be better to put the cock feather 180 degrees opposite the stiffest position that you call the "lump"?

Consistency is obviously the key, but I wonder if anyone has tried switching the cock feather from the point of weakest spine to 180 degrees from the point of strongest spine to see which produces the tightest groups.

I gotta run out and get me some bearings.

I appreciate the food for thought.

[Boo]

Don, I found your jig with an explanation here:

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http://www.excaliburcrossbow.com/phpBB2/viewtopic.php?f=1&t=46901&hilit=tester

I can see how it would work well. You and everyone else say's that the best place to put the cock feather is at the point of weakest spine (6 o'clock). Most of what I've read indicates that crossbows prefer more spine. If that's the case, wouldn't it be better to put the cock feather 180 degrees opposite the stiffest position that you call the "lump"?

Consistency is obviously the key, but I wonder if anyone has tried switching the cock feather from the point of weakest spine to 180 degrees from the point of strongest spine to see which produces the tightest groups.

I gotta run out and get me some bearings.

I appreciate the food for thought.

The problem comes when you run into a second spine. Some second spines are (as measured by the dial gauge of my Ram Tester) often close and sometimes identical to the other spine. So going to the softest spot seems logical to me because you are sort of averaging the effect of the spines. I might be wrong but I don't see it any other way of dealing with second spines and still be consistent with a shaft with a single spine.

[Significent]

I guess it boils down to how the bolt flexes in the rail channel (or whatever it's really called). I just ordered three of these ($8.85 total shipped) off of the bay:

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http://www.ebay.com/itm/629-2Z-Radial-Ball-Bearing-Double-Shielded-Bore-Dia-9mm-OD-26mm-Width-8mm-/360871645836?pt=BI_Heavy_Equipment_Parts&hash=item5405a0528c

They should do nicely with 9mm (0.354") hole diameters. My BEEs are 0.348" in diameter. 6 thousandths should be plenty of room.

Since my bolts are already fletched, I'll mark the weakest and the strongest spine and try the closest vane both ways. I have a couple dozen bolts so at least two or three should be on the button each way.

I still may have to build something to show relative spine between bolts so I can put them in order and see what difference more spine makes versus less. Hopefully, there will be so little difference that it won't matter.

Thanks again for your insights.

[Significent]

I got my three bearings in the mail today and proceeded to mark the weakest spine on each of my 2-dozen, non-custom, BEEs. As you would expect, there's no relationship between the weakest spine and the orientation of the vanes. Next step is to take them to the range and see how they shoot. The first session, I'll shoot each bolt three times, each time with a different vane down, measuring and recording POI for each. Then with a little time at the computer at home, I'll see what conclusions can be drawn. Should be fun.

Boo, your method of determining dynamic spine is almost mystical. It reminds me of using a divining rod to find water (only this works for an understandable reason).

One thing I did notice is that some bolts have two weak spines. They seem to be 180 degrees apart, but one is usually more pronounced. Did anyone else see that?

[offshore]

I find this a very interesting thread, and often pondered this idea myself. I have built many types of custom offshore fishing rods and depending on the application is where you want the spine to be located (top or bottom) for your optimal performance. I too, have checked (just by hand) many brands of vertical and x-bow "store bought" fletched arrows and found the cock vanes to be located all over the place. I wounder if the "custom" guys do the same thing and just lay them up in jigs and glue on the fletching and components of your choice, or if they take the extra time to go through these steps. . .and if so, what their consensus is? Keep us posted on your findings.

[Oppie]

My good friend Diesel made up his own spline tester.
I'm thinking Diesel & Boo have forgotten more about arrow splines and arrow building than I'll ever know
Here ya go.

http://www.excaliburcrossbow.com/phpBB2 ... e&start=15

[PSEWOOD]

Aluminum arrows are the same 360 around.May not be as durable as carbon for target shooting, but from one arrow to the other there the same.Be hard pressed to find straighter, more consistent arrows than xx78 or xx75 2216 arrows.Cheaper to!

[xcaliber]

I used to stress a lot about this, then started trying this, and that to see where it took my accuracy. I found that this exercise really does not yield a whole lot for me. I use all the same colored vanes, and really put the emphasis on my ability to shoot, and the equipment, my ability to fletch good bolts, etc. I have said this before, and I live this philosophy, you can only shoot in hunting situations as well as you can in practice situations. There is a university of arrows section on Hunters Friend's website that goes into great detail the many facets of carbon arrows, and their function. It is geared more toward the longer arrows used on verticals, but the principals overlap. One aspect that might have more of an impact than spine locating is head weight. The flexing of the arrow, or bolt is a victim of action / reaction where as the weight pushed is the resistance. This imparts the greatest flexing in the arrow at shot!
I say practice like you hunt for this reason, no game harvested by me ever set up in range where I could use sticks, etc. from my stand! It seems that they always approach from behind me, or off to my weak side, etc. Unless you can take these shots with confidence, you will most likely make a shot that does not represent your best shooting abilities!
I encourage you to spend more time practicing the hard shots than you do chasing the spine of a bolt!
The more you wrestle a hog in mud, the more he likes it!

[diesel]

Ok I got this from a post on crossbow nation Made by Southshore Rat Hope it all post it is just a copy and paste. The pic really tells and explains a lot. In the end to have arrows that shoot the same every time you need them First to be quality shafts next they all need to be Fletch in the same place they all need to be as close to the same as you can make them in every way. JMO.
Now how much difference can you have between your arrows and not see any effect at 30 yrds is a lot different than what you can have at 100 yrds .
I'm not a pro and I'm sure there are a lot of people that have forgot more about arrow building than I will ever know . Here is that post made by Jerry at South Shore Archery.


" Disclaimer! Much of what I'm about to say is theory and my opinion only because there hasn't been enough testing or real life application to prove the ideas as 100% valid.

Grims discovery of FLO testing opened the door to a very interesting testing process that IMO is going to change how some of us look at arrows and how are tested when spine matching arrows.

For as long as I remember we have used a RAM or similar tester to identify the Static Spine Deflection of arrows. We have also used it to identify the stiff side also sometimes referred to as back bone of shafts in order to index them for consistency. We have known this improves arrows for some time but what we haven't known is it appears that the static spine weak point does not come into play at the Dynamic Spine level.

Dynamically speaking the Stiff Plane and the Static Spine Stiff side are very similar. When testing shafts on a spine tester we see a deflection readying at the stiffest point then if we rotate the arrow 180 degrees we will see a very similar reading but it may not deflect as quite as much. In comparison when looking at an arrows Dynamic Spine Stiff Plane using a Frequency Analyzer we find the shaft actually produces the same Frequency Reading 180 degrees out. Likewise the Neutral Plane is always 90 degrees out from the Stiff Plane. This breaks the arrow into 4 quadrants, two stiff and two neutral.

I believe the force applied to an arrow when shot is funneled by the Stiff Plane to and though the Neutral Plane causing the arrow to flex along the Neutral Plane during flight.





What does all this mean!

After testing a number of shafts IMO arrows, during flight, do not flex along the weak side identified by a spine tester, I believe they flex along the Neutral Plane at a Dynamic Spine level.

IMO the Frequency Analyzer is going to shine when spine matched arrows are needed. Our plan is over the next 6 months to a year when we sell crossbow arrows that are to be spine matched we are going to use the Frequency Analyzer to identify the Neutral Plane Frequency and document the findings. Our goal is to compare the readings taken from a RAM spine tester to the Frequency readings taken from the Frequency Analyzer and develop a testing process that will produce a more consistent set of arrows. "