tuning with a rigid button

[geoffretired]

Thanks for that, Rob. I would be grateful for any feedback.

[Chris B]

Originally Posted by LineCutter

I've always felt (no proof) that tuning like that was to the nth harmonic of the frequency of the oscillation. (I presume that means the arrow, although you should argue that it's the whole system)
If you think about the wavelength of the harmonics it explains why a "good" tune gives little spread, whereas a higher order harmonic has the potential to magnify the error you make hugely.

[/me waits for the physicists to get started )

There are quite alot of engineers or physicists on this forum actually; Rhys, sp220, Thunk, Moo-mop, to name only afew. I myself am on a physics masters.

I'm not sure that you can really get away with this sort of post in front of this crowd. Sorry.

Honestly, the science orientated people here will probably be the first to admit that they don't understand very much about the dynamics of a recurve bow, let alone how to squash a spring in such a way as to make the whole thing do as we say!

(Just as an aside, higher order is a phrase in maths for some terms in a differential equation, or in physics, for a perturbation of a system; higher order terms and perturbations are generally the least important, so are often, and rightly, ignored. I wouldn't want to attempt nth order degenerate perturbation theory calculations on my bow. I'd need a computer bigger than the moon, and i still wouldn't be able to decide between rigid button tuning and walk-back..)

[buzz lite beer]

Originally Posted by geoffretired

Lots of interesting ideas, so I am learning, thanks.
Perhaps I could pull things back on track a little. I'm only thinking of matching the arrows to the bow; or bow to arrows if they are close enough. Tuning for groups is another issue, although related.
Imagine I am helping a recurve archer to set up their bow. We decide to use the rigid button method and get as far as bare shafts in the fletched group at 15y say. The sight is then adjusted to get impact matching the aimed point. My guess is that if the arrows showed a good match, up to this point, the sight would be almost directly above the arrow. Perhaps off set a little depending on the archer's string picture. I'd assume the closer the string picture to the centre of the dot, the closer the sight would be to being directly above the arrow.
If the archer found the sight was well away from this, in line position, would that indicate some problem with the bare shaft results?

what is exactly a matched arrow? A one that flies straight, a one that has good clearance, or a one that hits close to another arrow with a completely different drag coefficient, different dynamic spine and however marginal a different weight?

[pHz]

dont quote me because [a] im no scientist (quite the opposite) and [b] i dont really care why it works i just know that for ME PERSONALLY the 'park' method seems to give better results quicker than other initial tuning / setup methods and [c] im just surmising without any techie evidence (according to marcus james park is actually pretty good at explaining the mechanics of all this) - but -

presumably the point of the short range stiff button / bareshaft method is to get arrows and bow 'matched' closely enough that in the first few yards of flight the fletchings have minimal work to do to get the arrow flying as and where it should therefore wasting minimum energy ?

slainte : rob

[geoffretired]

Hi Buzz,
The best answer I can give is an arrow that isn't needing a great deal of steering by the fletchings. An arrow that will fly straight ahead(more or less) without fletchings. Put fletchings on and it will fly even better, in the sense that it will impact in much the same place each time.
Perhaps a badly matched arrow will not clear the bow. Slightly better match will clear but fly off to one side or the other and require a sight that is well out of line.

[King Custard]

Originally Posted by buzz lite beer

what is exactly a matched arrow? A one that flies straight, a one that has good clearance, or a one that hits close to another arrow with a completely different drag coefficient, different dynamic spine and however marginal a different weight?

IMO a 'matched' arrow is one that will group together bare and fletched shafts, given the adjustments made to the bow and the archers particular technique..at the distance an archer chooses to perform the tests.

A 'tuned' arrow, or 'bow tuned to the arrow and archer combo- is the one that produces best groups and therefore scores - whilst aiding the archer to 'mask' small flaws in technique.

Bareshafting is the beginning not the end of tuning and a shaft that 'bareshafts well' for you may not necessarily be the one that produces the best results for you as an individual.
For instance, my 720's willbareshaft lovely to 80 yards- a great place to start microfiddling- but I achieve best groups with a fairly stiff button and bareshafts high and right.
This fairly stiff button, is not the best place for me to have it set- a bad release with 720's leaves me at 5oclock in the blue!...now if I were to shoot 670's ( which wouldn't bareshaft well on the same set up) I have the opportunity to soften the button tension a bit, nearer to its midrange, and a similar bad release should put me about 6oclock red.......possibly 2 points better!

So why don't I have 670's?
They'd be slightly too long for my bow / or I'd have to ruin my string picture/ or put tons of weight on the front end/ or shoot a faster string.

In short I'd need a second bow, and second set of arrows- swapping between ends with both painstakingly 'tuned' bows to prove what should happen, does......ie: the 670's group better- though they bareshaft awful.

And I can't afford two similar set-up's yet just to prove a point of maybe 2 points better on one of my crappy releases....I'm better off all round at this point of my 'career', to NOT make bad releases!!!

[geoffretired]

Hi KC, thanks for all the details.I was a bit confused over one aspect.

Bareshafting is the beginning not the end of tuning and a shaft that 'bareshafts well' for you may not necessarily be the one that produces the best results for you as an individual.
For instance, my 720's willbareshaft lovely to 80 yards- a great place to start microfiddling- but I achieve best groups with a fairly stiff button and bareshafts high and right.

With the720 bareshafts landing in the group of fletched arrows, do you then adjust the rest or nocking point to give a bare shaft in a high right position?
I wasn't sure whether the change of postion of the bare shaft gave better groups or changing the arrows for 670's.

[King Custard]

Originally Posted by geoffretired

Hi KC, thanks for all the details.I was a bit confused over one aspect.

With the720 bareshafts landing in the group of fletched arrows, do you then adjust the rest or nocking point to give a bare shaft in a high right position?
I wasn't sure whether the change of postion of the bare shaft gave better groups or changing the arrows for 670's.

Sorry Geoff, -I should have explained that..
But can't lol!

I'm still with 720's
After a 'perfect'ish bareshaft tune at 80 yards............

I 'nudged' the tiller to lessen the aftershot vibration duration until groups started to open up again
I 'played' with nock point height - a thread at a time til group height was more consistent at distance
Then I played with the tiller a touch more - as it 'felt' or was necessary.
Then I adjusted out the right/left of 'dead center' arrow drop on a walkback by fractions of a turn on the button body, only to find that I now needed a bit more tension on the spring...
and then, as if by magic - bareshafts go high and right up to 60yards and I didn't consider shooting longer than that, as I'd passed the bareshaft stage of my tuning.

The next week, a PB (and today would have ben close or better in awful weather, if I'd actually finished the round) - fletched groups around 12 inches across at 80 yards-groups around 7 ins at 50yards (ignoring of course the sloppy shots Im still prone to making).
If I shoot it right it goes in the middle- If I shoot it nearly right- it goes toward the middle. I'm happy with that at my level...I can ask no more of my bow.

But as for how I got to the point of bareshafts high and right- it's mostly mysterious to me!...a concoction of what worked or improved the group.
I'm sorry I can't be of more help there- truly I am!

[geoffretired]

Thanks for that KC.
It sounds to me like something I read in the days of Rick Mc Kinney, or was it Daryl Pace? One of them found that after the bare shaft set up, they tuned for better groups. Once they reached the best groups stage, they would see what had happened to the bare shafts. Which ever it was found that the bare shaft was at the bottom of the fletched group this time, not in the middle. He then said, next time he would set up his bare shafts to land at the bottom of the fletched groups, knowing that he could then cut out the next stage.

[King Custard]

Originally Posted by geoffretired

Thanks for that KC.
It sounds to me like something I read in the days of Rick Mc Kinney, or was it Daryl Pace? One of them found that after the bare shaft set up, they tuned for better groups. Once they reached the best groups stage, they would see what had happened to the bare shafts. Which ever it was found that the bare shaft was at the bottom of the fletched group this time, not in the middle. He then said, next time he would set up his bare shafts to land at the bottom of the fletched groups, knowing that he could then cut out the next stage.

I believe it was McKinney, where I read that, but both these guys probably have a better understanding of how each adjustment affects the other than I do.
Me?...I fiddle....and too often don't make a note of exactly what I've done.

Having found how meddling with one adjustment really can affect another- it leads me to wonder just how these guys would 'skew' things to achieve their desired bareshaft results- and still have any Certainty that groups would still be at optimum!!!
Can you imagine how frustrating it would be to set up a second bow for the precise bareshaft result you 'want'.....and find that it shoots poorly because you have a different 'mix' of settings??
Consider how many things can make an arrow go lower..... or lefter.....for example.

I'm going to stick my neck out and say that these guys STILL have to group test/tune.......but getting that bareshaft test in the 'right place for them' is a great place for them to start from.....and the end tune still won't necessarily be the same from one set-up to the next!