Centreshot for Aluminium/Carbon Arrows

[MikeD]

"The Heretic Archer" arrived on my doorstep yesterday and when I got back from shooting I started reading... There are going to be a few questions I can see. To start with:

Position the cushion plunger so that your arrow point is only slightly outside of said axes (string in line with centre of limbs). The relative image should be around half millimetre for all arrows, or a little more for X10s

I can see that this would exacerbate clearance issues if the arrows are not well matched to the bow weight. Assuming however there are no clearance issues what are the advantages of a centreshot closer to the centreline and how do you set your centreshot?

[Big Boy Blue]

When I started I was told to set centreshot an arrow diameter outside the string. This works for Ali's but when I got my ACE's I was advised to change it to 1/2 arrow outside the string. These are just starting points before you start the tuning process, but they are a good place to start.

[disbloke]

As with all things to do with recurve tuning it's a case of trial and error until you get the set up right for you shooting the bow. The arrow being set just outside the bow string on a recurve is all to do with the archers paradox, someone much more able than me can explain that one. Basically it's the effect that on release the arrow wraps itself around the riser then ends up flying in a straight line to the target. No idea how it works but it does.

Think it's something to do with the string being wrapped around your fingers flicking one way and the solid "bar" of the riser causing the arrow to bend round it the other way resulting in the two effects cancelling each other out. Hence the need to have correctly spined arrows. If the centreshot position is set on the wrong side of the string I think that the arrow then continues on its bent path around the riser rather than straightening it self out.

I think......

[geoffretired]

Centre shot is much talked about. In theory the arrow would be set on the centre line of the bow if the arrow didn't flex and if the string returned on a perfectly straight line. Fingers cause the string to return in a wave and the arrow flexes for similar reasons.The flexing causes the arrow to push into the bow/button then gets pushed away. If the button was set for centre shot, the arrow would press against it and go inside the centre line. Setting the button so the arrow is slightly outside centre means when the arrow presses against the button it moves closer to the centre line. Adjusting the button is about getting that pressure to put the arrow close to the centre line so the arrow follows the straight ahead direction. From your reading, it would seem to suggest that those who have tested different arrow types have found that in general, alli's will eventually have to be set closer to the centre line than X10's so you may as well start the process with those results in mind. Where you start is a guide, not a strict rule. If there was one correct place for all bows etc. then button tuning would not be necessary.
Clearance is really more to do with the cut away of the riser and size of fletchings. If the riser is cut well way from the centre line, the button still protrudes far enough for clearance to be good.

[Jerry Tee]

Down load the Easton tuning guide. In there is a section on 'Node alignment' and setting the center shot which will explain it all. Then get your copy of the Quicks catalogue and on page 68 you will find an extract from 'simple art of winning'. There you will find picture of the bear shaft and walk up tests showing results and corrective actions. And good luck.

[joetapley]

The recommended centreshot position is (IMO) mainly related to having a good button spring pressure (nothing to do with lining up arrows). If you increase centreshot you have to reduce spring pressure which can give clearance issues; if you decrease centreshot you have to increase spring pressure which makes the system less forgiving or at the extreme results in unpredictable arrow behaviour.

As for setting centreshot there are two approaches. One is set it and forget it (for basic setup) - the Frangilli approach. In this case you move the fletched arrow into the centre with the button spring prior to nocking point tuning. My suggested alternative is set the centreshot in the normal way with the spring at 60% and then adjust centreshot (within reason) to move the fletched arrow to the centre of target prior to nocking point tuning.

[MikeD]

Originally Posted by joetapley

If you decrease centreshot you have to increase spring pressure which makes the system less forgiving or at the extreme results in unpredictable arrow behaviour.

Sorry I wasn't clear in my post. I know how to tune for a vertical walkback. I believe there is not just one combination of sight setting, button pressure and button position that will result in a vertical, straight walkback.

My point was why is Frangilli suggesting such a small offset, and what is the result of a small offset?

Joetapley has suggested it will be less forgiving/unpredictable. That was my suspicion too, so why is it suggested in the book?

I can only guess that better grouping can result, provided your technique is good. Perhaps the results due to a bad loose are counteracted by the better scores of the good arrows??

[geoffretired]

I haven't read the book and there are no clues in the quote. However, setting the arrow so close to centre, is only a starting point;or is there something in the text that says this is how you will set the button permanently?If it is simply a starting point, it is not a suggestion that you should shoot so close to centre.

[joetapley]

or is there something in the text that says this is how you will set the button permanently

Exactly. The "THA" method is to set the centreshot with a marginal offset and thats it. The tuning variables are the button spring setting and the draw weight. Centreshot is only adjusted as part of a fine (group) tuning process not as part of basic tuning.

My point was why is Frangilli suggesting such a small offset, and what is the result of a small offset?

A sensible spring setting.

[MikeD]

Originally Posted by geoffretired

I haven't read the book and there are no clues in the quote. However, setting the arrow so close to centre, is only a starting point;or is there something in the text that says this is how you will set the button permanently?If it is simply a starting point, it is not a suggestion that you should shoot so close to centre.

Hi Geoff, I won't quote the whole section, it is too long and there are copyright issues to consider. However, I can summarise as the steps stated:

1. Position sight w.r.t. string, centre of limbs.
2. Position button so arrow point is .5mm left of the string when string is aligned to centre of limbs
3. Shoot fletched arrows at 30m and adjust spring tension to bring arrow to centre of target.
4. Shoot bareshafts and fletched arrows and adjust nocking point
5. Shoot bareshafts and fletched arrows and fine adjust pressure to bring bare shafts into the group. If that is not possible adjust bow weight and try again.

Fast tuning is considered complete only when you can move the bareshaft from left of the fletched arrows to right of them by adjusting button pressure only.

That completes the basic tuning.

He then goes one to say that for fine tuning to improve groups at 70m it may be necessary to make small changes to the centreshot, nocking point and button pressure, though I havn't found anything in the book yet that suggest a plan to achieve the best combination other than trial and error.