POC Shafts and Stu Miller's Calculator

[LV2HUNT]

Considering shooting wood from new Longbow. Have had great luck with Stu's calculator and carbons.

A couple of questions for those who know:

1) What is average GPI for 11/32 POC shafts?

2) If Stu's Calc says 50 is good weight is it best to go 45-50 or 50-55? If I use 50# spine with my bow specs the spine values are identical. When I vary them (increase or lower shaft spine) it seems that I deviate less by lowering the spine as opposed to increasing it (hope that makes sense)

3) A long time ago I made some tapered 23/64 and am surprised how well they have stayed straight over time. Would 11/32 shafts exhibit more, less, or the same "persistence" characteristics?

Thanks in advance!

[Bjorn]

Cedar can vary quite a bit; but an average 32" shaft weighs 430 gn.
As far as staying straight cedar does that very well and the diam will have little effect.
I only shoot wood and have never visited that calculator.
It is easier to tame a slightly stiff shaft than a weak one.

[Buckeye Trad Hunter]

This is from TBM tip of the week, it may be of some help.

Wood Arrow Spine

 
 By T. J. Conrads
from The Traditional
Bowhunter's Handbook

 
To get arrows with the correct spine for your bow you first need to know your exact draw length and the weight that you are pulling from your bow. The standard measurement for a bow is based on 28", but many of us fail to draw to that length; most of the time we draw less. A rule of thumb is to add five pounds of spine for each inch over 28" as well as an additional five pounds for the broadhead. For each inch under 28", you will subtract five pounds. For example, if you are drawing 65 pounds at 29" you would add five pounds for the inch over 28" and another five pounds for the broadhead, ending up needing an arrow spined at 75#. I would also err on the high side, adding another five pounds. In this case, I would opt for shafting that is spined 75# to 80#.

 

A recurve bow will generally accept a wider range of spine in its arrows because of the near centershot design of the bow. A longbow, on the other hand, will require a tighter tolerance due to the arrow having to bend farther around the bow's riser when shot. But this is not true for all archers.  Bow weight, bow design, release, and numerous other individual shooting characteristics will all play a part in what spine arrow will work best for you.

[hkmp5]

Hello LV2HUNT,
This is Stu.  I totally agree with Bjorn on the fact that wood by it's nature can vary quite a bit in GPI.  That said, I have put together some averages for popular wood types based on my past experience.  This chart is included in the DSC instruction sheet and is meant to be a reference or good starting point if you haven't weighed you actual shafts yet:
2.   Average GPI for 11/32" Diameter Wood Shafts  
   
Spine Range       Sitka      POC      D. Fir    
  30-35         10.3       11.1
  35-40        10.0      10.6       11.3
  40-45        10.2      10.9       11.7
  45-50         10.5      11.3       12.0
  50-55         10.8      11.7       12.4
  55-60         11.1      12.1       12.7
  60-65       11.5      12.6       13.2    
  65-70        11.9      13.0       13.6   
  70-75      12.3      13.3       14.2
  75-80       12.6      13.7       14.8
  80-85        12.9      14.0       15.5
  85-90        13.3      14.4       15.8
  90-95         13.7                 16.3
  95-100                 16.6
   
NOTE:
   1.  For 5/16" diameter shafts multiply number above by 0.826
   2.  Typical wood shaft finish adds 0.7 ~ 1.0 GPI
 
Regarding a weak or stiff shaft, I always try to shoot right in the middle.  You can add point weigh to decrease the dynamic or add a little thickness behind the strike plate if you end up weak.
I also agree that a well sealed woodie wil stay straight regardless of diameter.  I have fir shafts that I made years ago that have never needed a re-straighten.
-Stu