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Associate Member
Posts: 47
Reply with quote  #1 
I have a selfbow that is hickory backed with bamboo and 41# at my DL.  I have spent significant time tuning and figured out arrows that work. What I mean is that the arrows I ended up with hit point of aim consistently.  This is a very simple bow and I plan to use it at 15-yards. On a whim, I tried different arrows that I already had. They are 36 grains different overall, and different FOC percentage as well as one spine designation stiffer. At the 15- yards they seemed to be on-the-money. I moved back to 20-yards as my skills improved. My tuned arrows still go to point of aim but these other arrows (that work fine at 15-yards) fly significantly left at 20-yards. I was surprised that 5-yards made such a difference … about 20 inches to the left consistently. Is this typical?  

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Club Member
Posts: 1,661
Reply with quote  #2 
Not necessarily "typical".  Arrow/bow combinations that are not matched could behave in different ways.   One way to get a look at what is happening is to get in a place where you can safely launch an arrow against the background of the sky.  Without being focused on your point of aim, you might be able to actually observe what the arrow is doing.


TAS Upgrade Member
Posts: 97
Reply with quote  #3 
I guess your matched arrows may be borderline stiff, but it depends a lot on the out of center of the particular bow....
Remember, that in fall, when it gets cold, that your draw length may diminish and a borderline stiff arrow then will act stiff.
Another part is, how accurate your shafts are spined/sorted. Generally, 40-45 pounds for example is 6 spines.
It is recommended to spine them all and write the numbers on them, you may then find the best ones may be right between two regular groups or they were all on the lower or higher end of a spine group. Also, the accuracy of a spine tester is +/-1#, so you may get up to 8 spine numbers in a normal sorted group. This is of course for hand spined shafts. With machine spined shafts, you cannot really tune anything....
It also needs to be said, and a lot of people don't understand that: There is a huge difference in spine deflection in the lower spine ranges, that is how the correlation is set up. That can also be the reason for what you see.... Seeing your draw weight, you probably shoot either 30-35 or 35-40#.
Do the math: 26/x=30 ==> x=0.8667" and 26/x=40 x=.6500"
Assuming there is a +/-1# in spine tester accuracy:
26/x=29 x=0.8965"  and 26/x=41 x= 0.6341"

There could be a deflection difference of up to .2625" !!!!

Senior Member
Posts: 396
Reply with quote  #4 
There isn't any such thing as borderline stiff. Arrows are either too stiff, or not. A properly matched bow/arrow combination will shoot arrows into or very close to a vertical line as far back as you can shoot.

Arrows that are not properly matched to the bow won't. Even at 15 yards they were showing some form of spine issue, it just may not have been severe enough for you to recognize. If the arrow isn't spined correctly, it is effectively shooting at an angle from your line of sight. The longer your line of sight the more the angle opens there by making it easier for us to recognize.

40-45lbs. isn't 6 spines. 40-45lbs. is 6lbs. variation. The 2 terms are not interchangeable. Arrows should be spined 40-44, or 45-49lbs. That is a 5lb. spine range. 

Spine is affected by not only the bow and it's mechanics, but also the diamter of the arrow, as well as the dynamics/mechanics of the person shooting the bow.

Spine is one of the most misunderstood aspects of archery next to tiller.
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