Wood Arrow Spine

[Burnsie]

When wood arrows are said to spine at 55-60#, or 70-75#....etc.  What weight field point/broadhead is assumed.  If you throw a 315 grn Ashby head on an arrow that is said to spine at 50-55# and shoot it out of a 50-55 lb bow it is going to show weak every time.

[lpcjon2]

I dont think any head weight is calculated in. The spine weight is that of the shaft, if you want to add a heavy head you would calculate that and up the spine you want.

[Grey Taylor]

Those spine numbers are just arbitrary labels. They do not mean that 55/59 shafts are suitable for all or any 55/59 lb bows.
Perhaps it would make more sense to label shafts with their deflection as they used to do.

Guy

[moebow]

I've always used and assumed the static spine for 125 grain points.  Using the 5# per 30/40 grains rule (old rule of thumb and starting with 125 points) your 315 grain points would reduce the effective spine of 50-55 down to about 20#.  In my experience, wood shafts and extremely heavy points don't go well together.

The static spine rating for woods (like other materials) is just a starting point.  Again, in my experience, the 5# rule helps get you close.

[Rufus]

In my learning days, around 40 yrs. ago, of such as arrow spines for wooden shafts, we pretty much figured the spine weight for use with 125 gr. points. Then we would play with point weights to weaken spine if necessary. Men for the greater part shot a minimum of 125 gr. Common field tips/blunts/broadhead weights at that time were 125/145/160 gr. Of course one could find others but these were the norm. The common denominator for spine to a bow was + 5 lbs. for a bow with a shelf and - 5 lbs. for shooting off the hand. Like people say, every bow and every shooter differ. I always had better luck with +5-10 lb. Keeping your hand to your face when you shoot make a lot of different spines shoot better I learned.
 We used to play the weight and FOC game some by using a stiffer spine and then use a heavier point, mainly we were thinking about the total weight gain, not FOC. I guess when I tapered my shafts I was kinda doing some FOC but never thought about it. Tapered shafts were supposed to clear the bow better but.......
 So there ya go, just my tad bit of info., Ralph

[Rufus]

Sorry, that is +5 to +10lbs.
 R2

[Burnsie]

Thanks guys.  I used the heavy 315 grn as an example of something out on the far extreme, but the same would hold true for anything in between and on the far light weight side as well.  I too have always used 125 grn as the starting point.  Then there is the lenght of the arrow,  is it full length, cut way down?...etc.  Lot of combinations and permutations to think about , I guess a guy just needs to make an educated guess for a starting point and tune from there.

[WESTBROOK]

The spine rating is for a 28" BOP arrow with a 125g pt. You loose about 5# of spine for every inch over 28".

Eric

[BAK]

As Westbrook said.  There is an AMO standard and it was just as he said.  We're not reinventing anything here.

[Burnsie]

Thanks, Westbrook and BAK, kinda thought there had to be some kind of standard for it.

[BrownA5]

I also appreciate the input.  Have been thinking of moving from carbons to wood arrows.