Question about spine charts

[TroyH]

I have a couple of spine charts for trad bows using the 26" span, unlike the one in the Easton catalog that uses 28".
My question is, is the correct spine based upon a certain point weight, and how will that spine change if a point/broadhead weight changes?
I know this has been discussed many times, but alas, I must not have been paying attention.

I am making some cane arrows and trying to determine the correct spine.  I usually shoot 2016's which are supposed to spine at .531 on Easton's 28" chart, but actually spine at around .420 on a traditional 26" spine meter.  I'm using my current arrows as a basis to go from but may change length or head weight on these homemade arrows.

[Rob DiStefano]

add front end weight = weaker spine
add rear end weight = stiffer spine

if you change a glue-on 125gr point for a 175gr, technically the spine will weaken, but how that translates to both bare and feather shafting flight for you could be another story.

if you have a spine meter, measure the deflection of a 2016 then try to get close with the cane shafts.  though i prefer spining at 26" apart with a 2# weight, if yer comparing same or different shafts, all that matters is comparing the deflection distance, the rest don't matter.

imho, in the long run yer gonna hafta see what'll work best for you and just use the commercial spine charts as a guide of sorts.

would love to see yer finished cane shafts!

[TroyH]

Oops, the arrow pics weren't resized small enough.
Here they are in smaller size.

 

 

[Rob DiStefano]

way cool, they look great!

[TroyH]

Here is a pic of my spine tester (modeled after the James Hill type).

 

[aromakr]

How point weight effects an arrow depends on a couple of factors. Point weight is usually assumed to be 125 grains in the spine standard.
1. what that bows usable spine range is and where those shafts fall within that range. Lets say your usable range is 60-70#@28" and the shafts spine 70# you could go up in point weight to probably 160-175 grs with no ill effect, however if that shaft spines 60# it would probably be too weak with that much weight.
2. How deep the shelf of the bow is cut will effect how much usuable spine range you have, the more center shot the greater the range. The less center shot the narrower the range.
The only effect the points you have pictured is probably not enough weight forward. I think I would try loading up the front end by putting something inside the cane to increase the front of center. If the cane spines the same as your 2016's you should be fine.
Bob

[TroyH]

Those points are actually very light weight.  I am making some small game points out of 1/4 all thread and nuts (not very traditional I know) that weigh just over 160.
BTW, those two steel points fly quite well.  The stone point is so nice, I haven't brought myself to shoot it yet.  I may just set it up for looks.

[Don Stokes]

When you add weight to the arrow by increasing point weight, it takes more energy to overcome the inertia of the arrow and move it, so the arrow has to be stiffer to handle the additional energy input before the arrow moves. And vice versa. For most of my bows, it seems to take a change of about 25 grains to make a spine difference. Your results may vary.