Wood arrows - spine help?

[kevgsp]

I have only shot carbons and want to give wood arrows a try.  Probably gonna get surewoods if that makes a difference.

Bow is a JK kanati LB highly R/D 55#@28 cut to center. FF string 10 strand.
 
I draw 29" so I'm guessing 57-58#ish, would like to shoot a 160 grain broadhead/point.

So what do you woody pros think??

My guess is 80-85...am I close?

[Don Stokes]

I would guess a little higher, closer to 90-95# for 160 g. broadheads. You could get by with a little less for field points or lighter heads.

[Orion]

I think you're about right.  Might even be able to shoot 5# lighter.  Don is also right.  Even if that is a little heavy, most bows will shoot overspined woodies quite well.  It's the underspined stuff that won't fly straight.  In that weight, you're likely going to have to go with 23/64 rather than 11/32 shafts.  The larger diameter shafts have the same effect as building out the side plate a little to weaken the shaft.  Might see if the folks at Surewood can supply you with a test kit of three shafts, one at 75-80, another at 80-85 and another at 90-95.  Good luck.

[Don Stokes]

Good advice from Orion. Many things can affect the spine, like diameter, bow quiver, heavy string silencers, and shooting style.

[Danny Rowan]

I think you will be right on the money with 85/90. You arrows will need to be at least 30" bop if you draw 29",that will add 10# to spine needed,add 5 for the ff,5 for the center shot,5 for the 160 head. So with the bow being 55# go up one spine=60# add in the others=85# spine. When I shoot woodies this works for me every time.

[griz#1]

try a test kit from 3rivers.

[kevgsp]

just looked and surewoods can be had in 11/32 85-90...thats probably what I'll get.  If the 85-90 end up a tad stiff I'll go to a 190 head I guess.

Thanks guys.

[Benny Nganabbarru]

A number of us tradbowhunters in Oz are kicking-butt using the formula Danny provided above.

[ChrisM]

use this site its spot on!!
 http://www.heilakka.com/stumiller/