Bare shaft tuning

[Bruce M]

I've been bare-shaft tuning on a Bear Kodiak Mag 52" AMO and 40lbs @28". I have a 29-29,1/4" draw length so I guess that puts the bow around 43#

All arrows are 31.5 to BOP and have a 125g field point.
I have 40-45 spine full length shows week spine
I shoot 45-50 spine full length shows week spine
I shoot 50-55 spine full length shows week spine, but less so I'll be cutting down until I get it right on.

Question is doesn't it seem to be way over spined for a 43lb bow.

Also another question on edit. I assume but maybe it's wrongly assumed that the spine rating on wood arrows is in reference to the approximate poundage rating of the bow. if that is not correct please give me a clue.

[JohnV]

What is your point weight? Length of the arrows?

[Bruce M]

Just edited the OP to include that info but to answer it's 31.5" to BOP and 125g point glued on.

[the rifleman]

Bruce so much impacts the dynamic spine--- just to name a few: string material, how the bow is cut- before, to, or past center, your release, etc.
The best advice i can give you is to keep bareshafting and trust the results.  My process is to take this slow and verify before changing only one thing at a time.  In my experience, no one can tell me what arrow spine, length, tip weight will tune-- only my bow will tell me.  Good luck-- enjoy the process.

[the rifleman]

Just read your last post-- for every increment past 28" in arrow length you must go heavier in spine.  Wood, like other materials responds to length changes and in my experience, point weight changes.  Bet you'll see a difference as you trim them a bit.

[Bruce M]

Thanks for the response Rifleman. Guess that's what I need to do is just don't even look at the numbers and trust the process.

[Wudstix]

I always thought wood was spined at 26”, so 29-30” arrows would potentially be 10# above bow weight.  With 125 grain heads being zero gain.  Up the 160 grain heads plus 5 and over 160 grains 5-10.
 

[Bruce M]

So if I'm understanding you correctly these spine numbers are reflective of an arrow length of 26" and I can expect the need for even stiffer rated spines as my arrow length increases as compared to say aluminum where they are measured at 28"

[Pine]

So if I'm understanding you correctly these spine numbers are reflective of an arrow length of 26" and I can expect the need for even stiffer rated spines as my arrow length increases as compared to say aluminum where they are measured at 28"

Yep

[Wudstix]

That’s my understanding.  You’ll end up with about the same spine either way.  For example; my 66# D/R longbow with 190 grain BH would require 75# base spine, with 5-10 more for D/R, and 5-10 more for BH over 160 grains.  That’s 85-95#.   The bow shoots 2315 or 2219  very well at 29”+ and they spine 92-93# @28”.  YMMV depending on release, string, etc...  I’m guessing the 50/55 @30” should be close. 
 

[Bruce M]

Thanks for the insight, and I think you may be pretty darn close at your guess of the arrow spine and length, at least that’s where it’s headed to.

[Bruce M]

I’m also thinking, I know dangerous right, that if it does get cut down to 30” that doesn’t leave much in the way of clearance with my 29+” draw length. I may want to even go up one more spine to a 55-60 to get more room behind the broadhead

Of course I’ll tune what I have and see we’re I end up first, just thinking out loud.

[BAK]

It's  a delightfully simple process that seems to baffle almost everyone of us at one point or another.  I worked on a 47# BBO long bow yesterday and ended up with 30 inch 5/16" arrows with 125 grain heads spined 35/40.   

[Wudstix]

I usually have the head at least 1/2” in front of the riser window, but not always.

[Bruce M]

Well I worked it down to having the bare shafts flying straight out to 12 yards with a very slight nock left. My bare shafts are now cut down to 30,1/2"so yes I am closing in on Wudstix's prediction.
I developed a nock high situation and closed it down for the night, pretty sure it's a form thing. I may just be getting tired, I have been up and working since 4:30 this morning.
I'll resume this again tomorrow and once I am satisfied with the results I'll continue to shoot the bare shafts a couple days more just to be sure. I also think it's a pretty telling way to see issues with my form, if I start to get lazy in the shot.
Anyway thanks to all for the help so far, a good helpful bunch of guys/gals here.

[Wudstix]

With your permission I'll do a screenshot of your comments so I can show my wife that sometimes I do get it right.
 

[Wudstix]

The closer you get the less you trim off, better to have one shaft that isn’t quite right than a bunch.  1/4 or 1/8” if you can.
 

[Pat B]

Wood arrow shafting with indicated spine is for a 28" finished arrow with 125gr point. For each inch above or below 28" you subtract or add 5# from the indicated spine value. For each 25grs above or below 125gr point weight you can subtract or add 5# to the indicated spine value.
 ie. a 30", 50# spined finished arrow(minus 10#, 5# for each inch over 28") with a 150gr point(5# for each 25gr over 125gr) will shoot like a 35# spined arrow.

[Bruce M]

Well I thought I was getting close there for a minute but it wasn't to be. I was pulling my hair out trying to figure why the heck I'm still getting weak arrow flight.

I decided to start at the basics again in my numbers. When I derived my draw length at 28" last time I did it pulling backend holding where I THINK my full pull was/is and my wife marked the arrow and I let down.
I don't hold and aim on the target, I just release at what to me is a comfortable trigger point so there was no real way of getting my draw length correct using this hold method.
I then decided to take my 30.5 " arrow and put 1/4" graduations with a yellow paint marker and have the wife stand on the side of me to see how many marks appear  when I draw the arrow and this time release. She said the whole arrow, tip and all disappeared onto the shelf. I repeated this many times throughout the day and also did it with a full length 2315 aluminum arrow. I finally got a full draw measurement of 31"
BTW the full length 2315 bare shaft shows stiff spine so there is the other side of this up there in the distance.
I guess I expand a lot at the end of the draw. But this measurement explains a lot as to why I was still showing a very weak arrow even  after cutting a 50-55 spine to 30.5"
It also creates an issue in selecting the proper arrow spine in wood, which is what I really want to do is shoot wood arrows, But I will venture on and see where this takes me.
Just giving an update to those that have helped thus far.

Happy Fathers Day to all the Dads out there.

[Bruce M]

Other thoughts on this is the AMO of the Magnum at 52" with a 31" draw length really isn't ideal. I pulled a 1959 Kodiak Special with a 64" AMO and 52# off the wall that I have yet to set up to see where I am at on a draw length on that, IDK maybe for some reason it comes up different but no, I proves out to be the same.
It's unfortunate but I don't think the Magnum is going to be  a good candidate for what I had intended . That is I wanted a nice light weight nimble bow for spot and stalk hunting but the short AMO combined with the long draw just doesn't seem to be a good mix.
I think I may just go with the 64"  Kodiak Special.