Pile weight vrs Spine Values

[Mistake]

Ok...

I know (as most archers do) that the heavier the pile you have in the arrow, the softer the arrow will act.

I was wondering if there is a direct colloralation between the pile weight and the softness of the spine (eg: a 100 gain pile will take the arrow spine down a group) or is it total guess work?

[LineCutter]

I tried asking in Quicks once - no helpful advice.

I have no idea what the relationship is, but given that I'm 2 spines & 25Gr off the table recommendation that may not be a surprise.

Get some heavier points & try for yourself I suppose: If you're not able to tune your current shafts with heavy enough points (i.e. they're too weak) then you need some stiffer ones.

HTH

[silver streak]

Originally Posted by Mistake

Ok...

I know (as most archers do) that the heavier the pile you have in the arrow, the softer the arrow will act.

I was wondering if there is a direct colloralation between the pile weight and the softness of the spine (eg: a 100 gain pile will take the arrow spine down a group) or is it total guess work?

depends what you are trying to do with your heavier pile. If your bare shaft is too far left of your group when you are tuning, then a heavier pile will make your arrows whippyer and bring the bare shaft back to the group.
All in all its really down to trial and error!
I always think that if you can shoot a bare shaft at 70m (after tuning at 30m) and get it somewhere near your fletched arrows, your tuning isnt too bad .

[Rik]

Hmmm.
I fed some figures into the old Easton Arrow Flight simulator.
It has the advantage of being based on real data, so the results are maybe more trustworthy than simple selection charts.

I kept the same setup and varied the point weight on the shafts being selected by 20grains. That's quite a lot - more than most people would consider altering their points by.

The resulting assessment of the spine match varied by 3%.
For comparison, the difference between an ACE 520 and 570 was 10%.

By that measure, to achieve about half a shaft size difference by fiddling with the point weights would need alterations on the order of 30+ grains. That's a heck of a lot.

Caveats: this was a very simplistic approach - I just took the defaults and made no attempts to check the extremes (long/short shafts light/heavy draw weights). YMMV. But in general I'd say you don't get far trying to alter spine with point weights.

I'd be interested if anyone could confirm this from personal experience...

[Mistake]

It's not to due with my tuneage issues atm, the thought was sparked off by STU's thread on indoor arrows

[pHz]

Originally Posted by Rik

But in general I'd say you don't get far trying to alter spine with point weights.
I'd be interested if anyone could confirm this from personal experience...

ive recently gone from 80gn piles in my x-perts to 110gn

they are acting SLIGHTLY weaker but not as much as id have thought from such a big change

the main difference (and the main reason for the change) was that they are WAY less affected by wind than they were - and as a bonus my 70m / 80yd sightmarks havent really changed either (still cant work that one out though with such an increase in arrow weight)

slainte : rob

[worthipa]

Originally Posted by Rik

Hmmm.
I fed some figures into the old Easton Arrow Flight simulator....

Presumably that's a software programme?

Is it available to download anywhere?

[robc]

I've recently increased my pile wt from 100 to 120gr, in nav 610, 30". The bare shaft test, with 120gr piles at 30m is about right, with the bare shaft grouping with the rest, or very slightly right, and at 70m, they were still in the group.
With the 100gr piles they were grouping just to the left at 30m. I used one shaft with 110gr pile, bareshaft it didn't behave any differently to the 120's. However, I have only had one session with them, & the day wasn't ideal for tuning.
RobC

[ASW1973]

as has been stated before:
poundage and arrow length alter spine
I would pick a point weight 100grain for upto 42lbs then 110 and 120 above that then pick an arrow and a spine that should tune (probably on the stiff side) and allow u to perform at distances required.
then cut it half to one inch to long and see how it tunes,
then alter arrow length or poundage accordingly

[DeeBee]

The effect of different pile/insert weights will vary depending on where you are on the arrow spine scale. A 20 grain change in point weight will have a different effect on the dynamic spine of an ACE 720 arrow to a 430 arrow. I am sure the poundage/speed of the bow will also cause variations in the effect of different point weights on the same arrow. There are too many variables for one simple formula to work in all cases.