Just a few questions: why is it that an underspined bare shaft will strike nock left, and if overspined nock right? Also, why do we set our nocking point on the string higher than the arrow rest on the riser? Wasn't able to figure these out for myself. Thanks.[
When an underspined arrow is shot, it bends around the riser as it leaves the string, because it is not stiff enough it bends too much and the point goes right so the nock strikes left. With an overspined arrow the arrow does not flex enough, so does not bend round the riser enough and goes left, with the nock striking right.
The nocking point is higher than horizontal because of tiller. This causes the bow to tip up slightly when drawn, so is actually now in line.
As, with a good setup, you can easily move the bare shaft either side of the fletched arrow with just a small change of button spring tension it's clear that bare shaft going left or right has nothing to do with "spine". The left/right result comes from the net lateral force (actually torque) on the arrow from the string and button spring being to the left or right.Hi All,
Just a few questions: why is it that an underspined bare shaft will strike nock left, and if overspined nock right? Also, why do we set our nocking point on the string higher than the arrow rest on the riser? Wasn't able to figure these out for myself. Thanks.
Is this not all assuming that the arrows are the correct spine? If the spine is incorrect then surely by definition, the flex rate will be INcorrect?As bow set up relates to matching the arrow flex rate to the bow this by definition is correct so bare shaft going left/right has nothing to do with arrow flex rate either.
When you go through a bow set up process what you are doing is adjusting the bow so that all (spine) arrows do shoot the same. By this I mean that the flex rate of the arrow matches the bow geometry. The arrow goes through 0.75 of a cycle on the string and 0.25 of a cycle between the nock leaving the string and passing the riser. So overall the arrow goes through one flex cycle between full draw and riser and this takes 1.25 the arrow free free vibration time. Established/verified for last 60 years and forms the basis of all these arrow selection systems.Hi Joe, You have confused me yet again.
If it is nothing to do with spine or flex rate, why don't all spine arrows shoot the same?
If you cannot sensibly match the arrow flex to bow geometry then you have the wrong arrow. As for saying the spine is incorrect you could just as well say that the draw weight is incorrect or the archers arms are too longIs this not all assuming that the arrows are the correct spine? If the spine is incorrect then surely by definition, the flex rate will be INcorrect?
Hi Joe, I follow what you say this time. The bit I am having problems with is quoted above.All spine arrows shoot the same.
If the arrow was too stiff then during the set up you would increase the draw weight to get the bow to match the arrow.Hi Joe, I follow what you say this time. The bit I am having problems with is quoted above.
I feel that you are saying that in a way that I am not "seeing".
I imagine a stiffer arrow and a weaker one, being shot from the same bow by the same archer, and one going through more flex cycles than the other, because of the flex rate differences between them. So, in that sense, they don't fly the same.
Hi Joe,When you go through a bow set up process what you are doing is adjusting the bow so that all (spine) arrows do shoot the same.....
Thanks, that makes a lot of sense to me.It isn't just the size of the bend, but the rate at which the bend changes from side to side. Stiff arrows bend from side to side at a faster rate than softer ones. A stiff arrow can bend one way and the opposite way and then back again, by the time it reaches the launch position. If it bends too quickly for the speed of the bow, it will exit the bow facing left. If the arrow is too soft, it will bend too slowly and still have a bend in it that is facing the front end over to the right.
OK - also established at set up is the arrow launch alignmentHi Joe,
Would it be a gross oversimplification to then say that:
adjusting limb weight/braceheight tunes the bow to the arrows flexing rate/cycle
Better put as spring button pressure (and nock point) are used to control arrow rotation at launchspring button pressure effects the arrow rotation
This is the tricky one. Center shot affects both the lateral string force on the arrow (launch rotation) and probably the arrow launch alignment.spring button in/outness (left rate) effects the arrow direction