Confused - Arrow spine weirdness

Hi, perhaps someone can unravel this. Compound bow set at 45lbs, 32" long 550 spine Skylon Paragon arrows with 120gr points. 3 x fletched arrows and 2 x bare shaft arrows. Paper tuning gives bullet holes. Bare shaft tuning the arrows land together at 10m. At 20m the bare shafts land well left of the fletched arrows, at 30m the bare shafts miss the target to the left. Fletched arrows all landing accurately. Bare shafts landing left means the spine too stiff as per Easton tuning manual. OK, using John Dudley's mantra of tuning the bow to the arrows I increased the poundage by half a turn until it has been increased by 2.5 turns on the limbs. Still landing well left. It appears the fishtailing is increasing although one would have thought that they would land left and right if it was that much. So I backed off the poundage by the 2.5 turns and then another half a turn - same result. Can't really back off that much more as not enough thread left if I do. The Skylon spine chart suggests 550 at 31" for 40-45 lbs compound bows. So, any ideas ? Thanks
 

KidCurry

Well-known member
I would probably bin the paper tune for a while. Apart from nock hi/lo I find it tends to be more useful for detecting torque. Note torque can also bullet hole a badly out of spec arrow.
Are you certain about the spine, it sounds weak to me, especially with a 120 point. I would have started at about 500 spine. The chart is below if I'm reading it correctly.
If it is a weak arrow you may have contact in the system somewhere or torque or both. If you use a longrod take the weight off the end plus any other weights and shoot watching the longrod tip to see if it kicks to one side due to torque. I would also be tempted to try a Carbon 1 450 to see what results you get. You cannot go too stiff on a compound as the arrow doesn't respond like a recurve arrow. Only disadvantage I found was a slower arrow and very slightly larger groups. Also make sure your centre shot is truly on centre as well as the sight pin. It's not always obvious but modified french tune will show it .
1593533872573.png
 
Last edited:

jerryRTD

Well-known member
Hi, perhaps someone can unravel this. Compound bow set at 45lbs, 32" long 550 spine Skylon Paragon arrows with 120gr points. 3 x fletched arrows and 2 x bare shaft arrows. Paper tuning gives bullet holes. Bare shaft tuning the arrows land together at 10m. At 20m the bare shafts land well left of the fletched arrows, at 30m the bare shafts miss the target to the left. Fletched arrows all landing accurately. Bare shafts landing left means the spine too stiff as per Easton tuning manual. OK,
Not if you are using a release aid. The stiff bare shaft only applies only if you are tuning a finger loose compound
 

jerryRTD

Well-known member
Just had a look at the Easton shaft selector and that comes back with a spine of around 400 but I am inclined to follow KidCurry and suggest a 450 spine arrow
 
Thank you. Of course, you are absolutely right. I had just been tuning a recurve and was in that mindset and forgot that of course that all is set using the arrow rest for left and right walk back tuning. Stupid mistake. The Skylons are really for my barebow but was trying to see if I could make them work for the compound. They are too weak whereas my Victory VAP's at 350 are too stiff. Do I fork out for a set of 450 Skylons????? I'll have to look in the piggy bank.
 

mbaker74

Supporter
Supporter
I would try tuning the 350 VAP's and see how you get on.... I think the normal response is you can't really go too stiff on a compound arrow?
 

Shirt

Active member
First question would be do you really need a 32" arrow for qa compound? Implies a 33-34" draw length.
Can you cut them down, as that will make them stiffer and possibly help the bareshaft thing - although that is also influenced by way more factors than just spine (think about cable guard torque, whether the cams move in a perfectly straight line, whether the limb deflections are consistent, if your draw length is wrong...)
 
Top