I was just wondering if the length of the broadhead has a direct affect in the dynamic spine of the arrow itself. Any thoughts or opinions?
                -Steve

No, I don't think so.  Spine is the bending of the shaft, the BH doesn't bend as part of the shaft
when the arrow is shot.  The shaft only sees the weight of the head, not it's shape.

By the way, BH length doesn't affect FOC much either.  A Majority of the weight of the BH is in the length of the ferrule. Very little mass or weight is out past the end of the ferrule.

I think the weight is what has the effect, the width of a BH could cause it to plane. I shoot Howard Hill heads(they are long 160gr) and see no difference in spine.

I don't believe so.  Nothing has seemed to change when I go from a shorter/fatter 125 VPA to a longer/wider 175gr Simmons.  I do believe it's just the weight also.

Broadhead length does change where the center of shaft is when calculating FOC. Other than that only the weight has an effect on spine.

I have never detected any differences due to broadhead length as long as the weight is the same, and I'm a bit of a tuning nut.

There is some effect; it's just very, very minor. Since the broad head is rigid, the effect come from its center of mass being moved further from the string because it is longer. With the center of mass further from the string (a lever effect) it weakens the dynamic spine minimally, but not enough to make a hill of beans.  

QuoteOriginally posted by CoilSpring:
There is some effect; it's just very, very minor. Since the broad head is rigid, the effect come from its center of mass being moved further from the string because it is longer. With the center of mass further from the string (a lever effect) it weakens the dynamic spine minimally, but not enough to make a hill of beans.    

boom

I say no as well. I have always shot fairly short bh's and just went to a long Grizzly. Fly's perfectly with no noticeable change.