Verify spine calcs for me please

[swampdrummer]

Staring to doubt myself a bit here.
Playing with Stu's calculator.
First bow stats
Super shrew 58"
53" @28"
drawing 28"
center cut is -1/16"
fastflight string

Shooting easton XX75 2117
cut to 28.25
200 grain field points
25 grain insert
14 grain nock
3 5" right hand helical fletch

If I'm inputting everything correctly I should be really close.
I'm coming up with a dynamic spine of 66.8
required spine of 67.9
Now.
These bareshaft well. Hitting the bag target just a hair nock right at 18-20 yards
Bareshaft and fletched are hitting in the same spot.

I just refletched a few of these with bright lime fletch and now I'm seeing what seems to be a wobble, or a spiral as these fly. They are still hitting well but this wobble or spiral has me a bit concerned.
I hunted with these arrows all season thinking I was tuned up pretty good and the last two animals I shot I was a bit less than impressed with the penetration.
Shooting at game with aboyer javalina lights with a 75 gr insert for a total weight of 215 gr plus the 25 gr insert etc etc.

First was a little 6 point at 17 yards. Got the arrow thru him but not a pass thru. He broke the arrow off quickly busting thru the palmettos. He made it a hundred yards with a psarse blood trail but was an easy recovery in open woods

Second was a small boar hog, about a hundred pounds. 12 yard shot.Hit him a a couple inches too high but not into the shoulder blade. Same scenario. Got hole on both sides but not a pass thru. Arrow stayed in him until he was out of sight and after a 600 yard very sparse blood trail I lost him.

At any rate, This wobble or spiral I'm seeing has me worried and doubting my tuning.Has me thinking that I'm not getting the penetration I should be.

The numbers look right. I thought the arrows were flying well until I put this bright fletching on them and can now see whats going on.

Any ideas?
Thanks
Brad

[mmgrode]

Has your brace height remained constant?  I periodically need to add a couple twists to my string when it stretches a bit.  I can tell it needs it when the arrows start to spiral as you described.   You may want to try increasing brace height a bit.

Matt

[mmgrode]

[xtrema312]

Left or right handed?  Have you tried to rotate you nocks to see if you are getting a feather contact issue?  How is the hock height?  Did you go up higher than needed then work down to make sure you are not a little low and getting a little bouncy off the shelf?  You can also shoot some paper to see if you can see what the issues is.

[xtrema312]

It does look good on the calculator.

What about silencers, or bow quiver?  Are you sure you are -1/16" and not +1/16"?  If you have that mixed up and silencers you could be off 10# in spine.  Do you have any 225 points to try just to see if that helps?  Nock right if you are right handed could be a stiff arrow.  Bare shaft maybe slides by so so, but feathers make more of a kick? Try that bare shaft at 25 and 30 yd. and see where it goes.

[swampdrummer]

Thanks guys,
I'll check my brace height this evening but I think its good.
extrema, I'm shooting right handed. I do have bow hush and hush puppies on the string. Never thought about that.

The center cut. It is cut past center for sure. If I read the directions correctly that would be a negative measurement?

I've tried rotating the nock and it doesn't seem to make a difference. I'm also pretty confident in the nock placement. Started way high and brought it down until I was getting level flight out of the bareshafts.

Don't have any heavier points on hand but can pick some more up without to much trouble. May have to do that. I do have some 100 gr brass inserts but that throws things WAY out.

I'll try and shoot thru paper this weekend and see if it shows anything. I've shot out to 25-30 yards bareshaft and fletched and I'm getting about the same results as closer. Bigger groups but still in the same area and the bareshafts are still hitting just barely nock right.

I'll keep playing with it. Any other ideas are for sure welcome.
Thanks!
Brad

[inn8hunter]

How much does silencers change the dynamic spine of the bow? It must lower it?

Tim

[onewhohasfun]

So many variables involved when taking an animal. Were the animals moving at the moment of impact? You did not list total arrow weight. What is your %FOC? What BH? How many blades? How sharp? Wood arrows dampen 6 times faster than alum. Carbon faster still and easier to acheive a higher %FOC with same overall weight. Cat whiskers noticeably slowed down my super shrew versus lighter fox fur I am now using. Lots of things to ponder here in the trad world. Keep it simple and enjoy your tinkering. Ain't it fun? Tom

[Guru]

I haven't read everyone's response..

You say your bare shaft is hitting a little nock right...that means your too stiff....

My experience with that is a small,lazy spiral wobble in my arrows when shot....a stiff arrow is not very forgiving...

 What you want is an bare shaft that shoots a bit weak(nock left)...that will give you a very forgiving set-up...and a better penetrating arrow.

Add some point weight and try it out...

[xtrema312]

Originally posted by inn8hunter:
How much does silencers change the dynamic spine of the bow? It must lower it?

Tim

It varies by type and amount.  Last fall I had a mouse run off with one of my fur silencers when I had it off over night in the barn to adjust the locations on the string.  I then went to whiskers and a couple other types.  I was all over the place.  I was missing a bag target at 25 yd. with a bare shaft with one set-up.

[Clay Hills Bill]

I have 2 super shrews and they are cut 1/8th inch out from center so the calculator needs an input of +1/8th.  You can call Ron but I think all Super Shrews are crafted with the goal of 1/8th out from center.  Ron told me that many longbow competitions required that, so it was part of the design.

HOpe that helps,

Bill