Arrow spine conundrum

StevoNilo

StevoNilo

Member
Here's a good one if you're bored.

My wife and I have shot, in total for 55 years. Lots of experience, both trainers, shoot regular Landesmeisterschaft and Deutschemeisterschaften here in Germany. In Flint, 3D and Fita Target. We set up our own kit. Have done since year dot.
Now.. my wife, she uses the set up bow for target and 3D. However because you can easily trash/lose arrows in 3D we opted for a cheaper arrow.
The arrow for target is an ACE 920, however for the same set up bow, everything the same she has used 1300 spine Aurel Carbon for 3D. Both tune smack on. Bare shaft couldn't be more central at 18/30/70m. Walk back tune perfect. Same string compositions. Podium places very often with both bows. I still cannot understand why the 1300 flies just as straight as the 920s. The weight of each arrow is nearly the same. The ACE being the heaviest arrow. Both arrows the same length. Beiter nocks. Point weights aren't unusual. I believe 90 grains or so. This spine difference has baffled me. How do we get away with that? If someone has experienced the same I'd like to hear from you. And if there is someone clever enough to explain it then please do. Have a good weekend.
 
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Timid Toad

Timid Toad

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It'll be down to the archer. Barrelled shafts react differently to things like loose, torqued string, canted bow. And of course diameter on the ACEs is the same as the Auriels....measured where? At the point where they kick off the bow or at the maximum barrel?
 
StevoNilo

StevoNilo

Member
Hi TT.. diameters are the same. For the ACE thats taken at max belly of the shaft. I'm not convinced its the diameter.. or where the ace arrow comes off the button. Both arrows fly so straight. She's a very accomplished shooter. Very consistent release. No cant. Better than me :( its a weird one. Well if it ain't broke, don't fix it I'd say.. :)
 
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Timid Toad

Timid Toad

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Absolutely.
But static spine isn't dynamic spine and as we all know...it's *always* the archer, for good or ill.
 
A

AndyS

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Hi Steve, my wife and I have both experienced the same thing shooting target recurve, i.e. needing to go significantly weaker for pure carbon, compared to AC arrows.
It clearly wasn't just us either, because the first time I went into our local retailer to buy some cheap carbon shafts, I was intending to buy from the Easton charts that worked pretty well for our ACEs & ACGs, but was advised to go weaker.
I can't remember the specifics now, but I bought a few of what I'd intended, plus some of the weaker spine the retailer recommended, and they were right, the weaker spine were the ones that would tune. We've since found that any pure carbon arrows we've shot have needed to be weaker than the charts suggest, whereas for ACs the charts have been about right.

I've never found an explanation for it, but wonder if maybe the natural frequency of oscillation is higher for a carbon shaft than an AC with the same static spine.
If that was the case, then perhaps it would make sense to need a weaker carbon shaft to get a frequency of oscillation that would tune the same as the 'stiffer' AC equivalent?
 
M

mhenschel

New member
Greetings from Germany. If you get the chance try recording a slow motion video of both arrows leaving the bow. You'd need a camera that record at 1000fps.
I assume your wife has also tried the Aurel in a stiffer spine and they showed stiff?
In some of my setups I don't get a clear weak/stiff bareshaft reaction when going up or down a spine.
 
G

geoffretired

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I've never found an explanation for it, but wonder if maybe the natural frequency of oscillation is higher for a carbon shaft than an AC with the same static spine.
If that was the case, then perhaps it would make sense to need a weaker carbon shaft to get a frequency of oscillation that would tune the same as the 'stiffer' AC equivalent?
I would expect that to be the reason, too. Matching must be about getting the arrow to be at a certain stage in its flex/oscillation cycle. That stage will happen at a different time if the weights are the same but flex rates are different. Like you, I guess the weaker all carbon shaft will have a similar flex rate to the stiffer AC
 
StevoNilo

StevoNilo

Member
Thanks guy's. Yes I've done lots of slow mo. I had thought the carbons would go through a few more oscillations before clearing the bow, but i must admit it is an interesting phenomena. This is why I always recommend newbies to shoot out arrows first as Charts can be misleading for the inexperienced. With my own arrows , they're not that different. My 3D aurels are 600s, my Fita ACEs are 520. The 600s do show weak, they've gotten me on the podium however, I really should get 500s this Summer. Maybe this quirk is more apparent at weaker spines. Thanks for your reflections.
 
G

Geophys2

Active member
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Have you actually tested the static spine of these arrows on an accurate spine tester? I regularly test various arrow makers' arrows for spine using my Bearpaw electronic spine tester, it's amazing the difference in reading you get from different manufacturers, especially between US makers and those from other countries. This is especially true with the higher spine arrows. They are usually within the same ballpark up to about 500 spine, though one makers 500 might be another's 450, or 550, but the gap often widens with the higher spine arrows.
 
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