Why spine difference wood vs. carbon

[SquareHead]

Hi Folks,

I have shot wood arrows for the last 20 years.  Nothing else.  I recently tried carbons and I must say I am very impressed.  Very flat shooting, quick recovery from archers paradox, etc.  Some of this could be because my wood arrows aren't as consistent due to age, wear, etc.  Nothing against wood, but those carbons sure shoot nice.

I am puzzled, though.  My wood arrows are spined between 46 and 50 lbs.  I have an arrow spine tester.  My bowyer, Dan Toelke, suggested I start with Carbon Express Heritage 150, and CE's website recommends same.  He also suggested a 145 gr. field point.  Like I said, they shoot wonderfully.

However, when I spine test the carbons, they come out to be almost exactly 65 lbs. on my tester.  How is it that my 48# bows can shoot a 65# spine carbons?  Is there something I am missing?  Shouldn't the carbon arrows spine at 45-50 lb?

My bows are the correct draw weight.

I am sure that I must be missing something about carbon vs. wood.

Thanks much,

Chris

[njloco]

Can't answer the spine question, but the draw weight  for the carbons are for coumpound bows.

[JRY309]

I find you can't really compare carbon and wood spines.They react differently and recover faster.Are they the same length?Usally wood was spined on 26" centers and aluminum and carbon are spined on 28" centers.With carbons for me I tune them to their dynamic spine and only go by their static spine in choosing which one to start with.

[Rob DiStefano]

what john just typed - carbons have very different static and dynamic spine ranges.  for the most part, all the carbon manufacturer's spine charts are waaaay too stiff (dynamically speaking).  no wonder carbons are sold in 15# spine ranges!

[Orion]

One reason you can shoot a heavier carbon is because they're thinner.  Your woodies are probably 11/32or 23/64.  The carbons are 5/16 or less.  That moves the center of the arrow closer to the side plate (and center) of the bow, and doing that requires more spine.

You're shooting a 145 grain field point.  Figure another20 grains for the aluminum insert, so you haves 175 grains up front.  My guess is you're shooting 125-135 grain heads on your woodies.  The heavier front end on the carbons weakens the dynamic spine.

The skinnier arrows requiring more spine and the heavier head softening the dynamic spine are two reasons the 65# spined carbons shoot like your 50# woodies.  If you've left the carbons longer than your woodies, that also decreases dynamic spine.

[moebow]

The spine rating method for the two materials is different.

For wood, the spine is measured by hanging a 2# weight on a shaft supported on rests that are exactly 26" apart.  This gives the spine for a 28 inch arrow.  The base point weight is 125 grains.

For carbon, the spine is measured by hanging a 1.94# weight on a shaft supported on rests that are 28" apart to give a spine for a 28 inch arrow. Not sure what the point weight starting point is for carbons.

So, simply, wood and carbon spines are determined under different conditions so a 50# wood spine is roughly .500 BUT a .500 spined carbon is not the same.  There are charts to show a conversion but I don't have them handy right now.

There are many stories out there as to why there is a different way of measuring spine but I sure don't know and have never understood  why it got changed.


Arne