O.K. Chad, here goes. Please bear with me 'cause this gets a little complicated. Perhaps JRW or some of the others could explain it a little better. Static spine refers to the arrow while suspended between two points with a weight in the middle. Wood arrows are traditionally spined over 26" centers with a 2# weight suspended in the middle and the amount the arrow deflects or bends in the middle (deflection) is measured to determine spine. On the other hand, metal arrows are spined over 28" centers with a 1.94# weight suspended in the middle. So really you are comparing apples to oranges if you only look at static spine. Dynamic spine refers to the way the arrow actually flexes under stress, i.e. the way it operates when shot from a bow. Thus when we say a 2512 has a dynamic spine of 57#-62#, we are really saying that it flexes the way a #57-62# wood arrow would if shot from the same bow, even tho if it were spined on the same 26" centers as a wood arrow it would measure a deflection equal to a 95# woody. With a center shot bow (one cut exactly to the center of the riser) or true center shot bow (one cut 1/2 the diameter of the arrow past center) you can use a considerably stiffer arrow than in a longbow which is typically cut 1/8" before center. For this same reason compound shooters can use extremely stiff arrows with light point weights compared to comparable poundage traditional bows. So while the static spine of your 2512s may be #95 when measured on 26" centers like your woodies, it is not unreasonable to see them act like 57#-62# woodies when cut to 32". Remember, for every 2" of draw over 28" you need to increase aluminum arrows by one size (5#) or 10# in your case.

Jack

Edited by - Floxter on 01/06/2002 22:00:51

Thanks Jack--you explained it perfectly. I knew a good bit of it, but didn't know what static and dynamic spines were. Have just wondered why a bow that would shoot a 150# (static) spined aluminum would also shoot a 80-85# wood.

What are your opinions on going way heavy on spine with centershot bows? Any advantage to it? I can shoot my 105-110# spine cedars on a recurve I have, but it also shoots 75-80# and 80-85# just fine (to my eye--haven't paper tuned).

Chad

Actually, the static spine numbers that I was refering to were done by people with spine testers on the LW and measured with the standard 2# weight hung in the middle of the shaft suspended by points 26" apart.

Jack, I think you're right, it should spine the same as a 2419.

Dynamic spine is how an arrow "reacts". For every 1" difference in length, or 35 grain difference in point weight, they arrow will "act" 5# heavier or lighter. For example, if a 32" 70# spine POC with a 125 grain tip will shoot well, so will a 31" 65# spine with a 125 grain tip, or a 32" 75# spine with a 160 grain tip.

JRW

Chad, I don't really think there is any advantage to shooting overspined arrows other than it might allow you to interchange different bows with the same arrow or allow you to shoot a heavier arrow. However, you can accomplish the goal of heavier arrows thru other means, such as point weight or shaft material. Using an overly spined arrow will reduce the forgiveness of the arrow and accuracy will suffer unless you have a perfect release every time. That's why I feel bare shaft testing is so valuable. It will show that while different spines will all shoot out of the same bow, one particular spine will be consistently more accurate in terms of right and lefts (windage) than the others and will allow for an occasional imperfect release. For this reason I don't papertune, because I've found that while I can shoot bullet holes thru paper, if my release is slightly off it will give me an tear rather than a bullet hole, even tho the arrow will impact to point of aim. Thus I don't think papertuning is a reliable method of tuning with fingers off the shelf. Just my opinion. Others may feel differently.

Jack

Y'all think Easton uses different centers to throw a monkey wrench in the works? I've always wondered why static spine was calculated (mainly) using 26" centers & draw weight on "off the shelf" tradbows used 28" as standard. Easton using 29" centers & AMO using a 30" draw only complicates matters further. If everyone was on the same page this would all be much simpler, but obviously that ain't about to happen. Go figure, huh?

Arrowsmit, I don't mean to be picky, but AMO uses 28" as the standard for measuring draw weight. Actually, they measure draw at 26.25" to the pivot point of the riser and then add 1.75" for arrow clearance to the back of the riser for a total of 28". But you're sooo right; why not one measurement for everything, whether 26", 28", or 30"???

Jack

Edited by - Floxter on 01/06/2002 22:02:33

Hmmm, my bad. I thought AMO rating had been "standardized" as 60# @ 30"/540 gr arrow?

Jeez, this is way overcomplicated.

Arrowsmit, you are right! That is the way AMO measures to determine arrow speed. However, to measure draw weight they use the 28". Just another of the inconsistencies you pointed out.

Jack

Huh? I'm RIGHT?? Hmmm...you sure about that? <img src=icon_smile_big.gif border=0 align=middle> Hehe. Didn't Bowhunting Worlds technical editor, engineer Norb Mullaney (sp) come up w/that index in the late 70's/early 80's? Heck WHO KNOWS??? Oouuw, my heads a hurt'n. <img src=icon_smile_wink.gif border=0 align=middle>

Edited by - Arrowsmit on 01/06/2002 14:03:20

dang guys..and they say this trad crap is easy! <img src=icon_smile_big.gif border=0 align=middle>!