Wood Spine Charts, my bows and me?

[anatone hunter]

I am getting more focused on tuning bow and arrow for best flight. BUT, can someone suggest my "issues" are not unusual, or perhaps something else could be wrong.
Here's the deal. Both my bows, a Slick Stick 60", 45# and my Maddog Moutaineer, 63", 43# shoot very much the same. I draw 27 inches and the arrow length is 28 inches. For both bows the wood spine charts suggest that with a typical 125 grain point the shafts should be in the 40-45# range.
Fletched arrows display good flight, however when bareshafting or papertuning with these same shafts, they suggest a very underspined shaft in each of the bows! When tuning with a shaft that is rated at 50-55# the results are much much better. So one would conclude that going with a much heavier spine rating is the better choice.
So that begs the question, wood spine charts, my bows and me are sure not on the same page. Why?
I shoot with a draw check clicker on each bow and my results are based on many, many arrows being shot. (same results with either Douglas fir, or cedar shafts.)
Guess I am a bit confused about the differences In other words, the charts are not even close for me to go by. Is this normal, and not for me to worry and just go with what works and stop trying to figure out why?
Thanks for some input.

[moebow]

The charts or associated arithmetic are STARTING points.  If they recommend 40-45# spine you THEN must apply what I call the 5# rule.  Add 5# to required spine for fast flight string, add 5# if bow is center cut, etc.  

So I suggest that your "results" are in line with that, not knowing the bow's setup.  The 5# rule has been around a LONG time but many have forgotten it or never new about it.  There's more to it but that is the idea.

Good luck with it.
I'd also suggest that you may get more answers in the Pow Wow, this isn't really a shooting FORM question.

Arne

[nek4me]

The wood spine charts are based on the older bow setups that don't have the higher performance designs of today's models and the low stretch strings which apply more energy to the arrow requiring a stiffer shaft. Also risers cut to centershot or beyond require a stiffer shaft than the same weight bow not cut to centershot as the arrow doesn't have to flex as much to clear the riser on release. The results you got with the higher spine is what would have been expected with your setups.

I see Arne answered while I was typing. His suggestion to search on the Pow Wow is a good one as I had recently gone through the process you are in and found so much useful information that allowed me to start off with good results.

[McDave]

Maybe they have been updated recently, but wood spine charts for many years did not reflect modern bowmaking methods that result in bows that are much more efficient than they were in the past.  Black Widow had a section in the instruction manual that comes with their bows that gave “fudge factors” that need to be added to wood arrow charts for wood arrows shot with modern bows.  The effect of this is that a stiffer arrow should be shot from a modern bow than the old charts recommend.

Bare shaft tuning doesn't lie, which is why I haven't checked in the last 10 years or so to see if the charts have been updated.  If I have a bare shaft that flies well, the fletched arrow is going to fly well.  I have had a few strange things happen with bare shafts from time to time that I don't understand, but nothing that would cause me to doubt my overall confidence in bare shaft tuning.

One has to be aware that false weak readings are possible, where the shaft rebounds off the strike plate and shows nock left when it is really too stiff, but I don't think that's what's happening in your case.  Also, bare shaft tuning reflects the state of your own shooting skill and form at the time you make a particular shot, which is why I keep all my bare shafts and go back and retune from time to time as things change in my shot, I get older, etc.

If I observed a case where bare shaft tuning did not reflect the best arrow to use, I would suspect that the shooting skill of the person doing the tuning had not yet developed to the point where bare shaft tuning would produce meaningful results.

[McDave]

Evidently both of us need to learn to type faster if we're going to be able to keep up with Arne!

[nek4me]

I might be able to improve my typing speed a bit but could never even think of contributing what you two have to this this forum.
         

[anatone hunter]

So sorry if I posted this on the wrong forum but after seeing other spine questions here, I did.
Thanks Arne for your response.
Believe me that I have read til blue in the face about this tuning stuff, but there are just times when one has to ask a question specifically about his own results.
The math that you suggested does add up with my  more centershot bows and fast flight strings. So that is why the 50-55# spines are best. It is a forum like this that present more polite reminders of what I should have already known.
Hmmm, now back to having fun!