Carbons - spine weakening

[R H Clark]

The statement that all you're shafts are 1/4" longer than you're draw gives me a clue into your thinking.

In my experience it is nearly impossible, without extreme luck or the ability to adjust the bow and tip weight in small ammounts,to cut carbons to an exact length and get them to tune.I always tune a set of arrows to a bow by shaving length in small ammounts untill I reach an acceptable degree of tune.A set of arrows may be any length from 1" to 3" longer than my draw.

It is possible that during tuning a slight variation in form caused your shafts to look tuned.Later your form changed and changed the shafts.

They may or may not shoot weaker over time.Without an accurate spine tester and repeated testing there are just too many variables to say for certin.

[Ragnarok Forge]

I am an engineer and have done quite a bit of work with matrix materials ( carbon is one ).  Degredation of spine on a carbon arrows would be very tough if not almost impossible to achieve.  Carbon does not degrade over time, and neither does the resins.  Both are inert materials.  Constant flexion stresses on the arrows can cause degredation over time. Heres the catch.  It wouldn't change the arrow spine for very long.  Degredation always comes from a hard hit and a crack along the carbon fiber - resin interface.  Once a microscopic crack is formed the arrows life is going to be short.  An extreme failure will come along shortly, and you will be buying a new arrow to replace the broken one.

I would look to changing form, such as slightly changing draw length due to regular shooting and your arms getting stronger, or perhaps that you are pulling further at the shot for the same reason.  A good buddy and mentor of mine in traditional archery says it is the ground connections causing the problem.  i.e.  I am the reason things are off.

[freefeet]

One also has to consider that modern Formula 1 cars are built from carbon fibre and have far more stresses put through them than an arrow and they do not lose strength or rigidity at all.

The Ducati MotoGP bike has carbon fibre sub frames holding it together, and like the F1 car does not lose strength or rigidity the more Casey Stoner hammers it around the track hour after hour - it's the same corner after corner after corner.

Aircraft have been using modern composite materials for a long time, and i'm not aware of any that have fallen out of the sky due to carbon fibre losing rigidity.  If it did it would be banned from aircraft use.

Why should a carbon fibre arrow be any different?

[Morning Star]

 In my experience it is nearly impossible, without extreme luck or the ability to adjust the bow and tip weight in small ammounts,to cut carbons to an exact length and get them to tune.I always tune a set of arrows to a bow by shaving length in small ammounts untill I reach an acceptable degree of tune.A set of arrows may be any length from 1" to 3" longer than my draw.

I used various brass insert and tip weights.   I also added weight (inserts) to the rear of the shafts to get them to spine correctly at that length.


I feel I'm a pretty consistent shooter as far as form, never have much problem reading my bareshaft results to select arrow combinations. I do agree there are plenty variables that can happen.  

As far as my draw length increasing, that did happen a few years back when I changed to a different anchor style.  But, I sincerely doubt that has any issue here at this time regarding this issue.

I can take this group of 7 arrows (bareshaft now) that are a bit over a year old and they are all shooting weak to some degree.  
A new batch (same brand, model and spine) that I made up to the exact specs as my old ones will shoot correctly (bareshaft).  

I dropped the point weight down 25 grains and the older shafts are now shooting appropriately.

The spine tester would be the best judgement.  But, looking at it from consistent results, common sense says there's a little degredation in the spine.

This thread has definitely got me interested in getting them on a spine tester.  I will post the info back up when I get that chance.