Tuning / spine etc

nbuuifx

Member
Is there any obvious reason why my arrows are too stiff?

I tried following the Easton guide - did I get any of the settings wrong? Also do I go one step weaker or more?

My AMO Draw length is 30 7/8"

The poundage of the bow is currently measured at 34.3lbs

The way I read the arrow chart put me as a T7, with the poundage making it very close to a T8.

For ACC arrows the T7 box gives these two options:
3-18 560
3-28 500

For ACC arrows the T8 box gives these two options:
3-39 440
3-28 500

So I figured the 500 spine were a safe option.

However I tried a bareshaft tune.

I installed a matchstick to make the pressure button solid. I set the centre shot (as best as I could - using tape on the limbs with marks for alignment) and I set the rest height. I shot fletched arrows and set the sight until they were going into the gold (20 yards - 60cm target). Shooting the bareshaft goes to the left missing the 60cm target altogether (but hitting the boss).

I have 85gn and 100gn points. The 100gn points are a bit better but it isn't enough of a difference.

My limb bolts were nearly all the way in, I only had 3/4 of a turn left. I have tried winding that in (But haven't shot again yet) - however the poundage only went from 34.2 to 34.3lbs - so I don't think it will make a big difference.

Is it worth trying a bit more weight to weaken the arrow, or is my FOC going to go too far out?

I forgot to say my bow is on the maximum recommended bracing height.

Hoyt Horizon 25" Riser. SF Elite Fiber Foam limbs - Long rated at 28lbs @ 28".

Anything else to try?
 

Rik

Supporter
Supporter
Okay, so arrows about 30 inches and weight 34lbs... I see that as a T6 on the charts. If your shafts are over length, then it's more difficult to judge (an AMO draw length of 30 7/8 would mean a shaft length - as used by the charts - of 30 1/8).
You could get up to the lower end of T7 by increasing the weight over 36lb. Or by increasing draw length and shooting a longer shaft, but that's not so easy. A 500 spine basically looks too stiff, by a couple of grades. You can't compensate for that with point weights.
The simplest way to get a match would be to increase the draw weight, but you'd probably have to go up as much as 5 pounds.
 

messyhead

Member
I've got a set of 3-18, and the AMO length is 30". I've had trouble tuning them, and only got a tune by increasing the draw weight to 39lbs. They now shoot very slightly weak. I also tried 100gn points at 36lbs as that was the weight I was wanting to draw, but couldn't get a tune.

I had to do paper tuning to tune the centre shot, so it might be worth checking that. I ended up having to move it quite a lot further to the right from I initially set it.

Sent from my LG-H815 using Tapatalk
 

nbuuifx

Member
Shaft length if the acc arrows is 30.25" the point is level with the clicker extension bolt so it sits in from the edge of the riser.

I think I used amo rather than shaft length when looking at the chart. So that would explain it a little.

My only way to go up poundage wise would be to change the limbs.

I'm not sure that I'm ready for another poundage change yet.
 

Rik

Supporter
Supporter
Shaft length if the acc arrows is 30.25" the point is level with the clicker extension bolt so it sits in from the edge of the riser.

I think I used amo rather than shaft length when looking at the chart. So that would explain it a little.

My only way to go up poundage wise would be to change the limbs.

I'm not sure that I'm ready for another poundage change yet.
The charts assume a shaft length of 1 inch past the rest. Assuming that's about at the pressure point (which is a slightly dodgy assumption), it's AMO draw length minus 0.75 inches.
But the chart steps are an inch at a time. So "30" on the chart covers 29.5 to 30.5.
30.25 would be well into the "30" section. 34lbs is well under the border, so 34/30 is a good starting point. They're both in the upper part of the range, so it's possible that a weaker T7 might be made to work.

There are minor tweaks you could try - raising the bracing height, adding a lot of point weight (100 grains won't do it: 200 might give some movement). But I wouldn't hold out much hope of getting 500s to match.
On the plus side, stiff shafts might not behave too terribly even if they don't strictly work. Might not group as well as well matched shafts, though.
 

nbuuifx

Member
Thanks, I might try filling the points with solder to see what happens. Will that have any negative effect on FOC or distance they can travel etc.?

Bracing height is already max recommended.

The fletched are grouping OK at 20 yards - they were mostly going in the gold on a 60cm target. Only one or two went out of the gold and I would put that down to me rather than the arrows. That was shooting with the matchstick in the button too.

Luckily these were second hand so I haven't spent a huge amount out on these. I might just put them to one side and try and find another set if adding more weight doesn't help!

If it makes any difference, with 85gn points installed they miss the boss. With 100gn they miss a 60cm target (positioned in the center) but hit the boss. So the small increase of 15gn seemed to make a difference.

So what do you think the best spine to look out for in another set would be?

Thanks
 

jerryRTD

Well-known member
When you put your arrow length (30 inches) and draw weight (34 pounds)in to the Easton 2011 shaft selector app it gives a result for ACCs' of 620. Your mistake was using draw length instead Of arrow length.
there is a cheap way to tell if the recommendation you have for your shafts is correct and that is to buy two alloy arrows from the same group in this case 1916's ( 623 as opposed to the ACCs' 620) bare shaft tune with just the two alloy arrows. If you get a good tune then go ahead and buy a set of 620 spine arrows. Get another couple of alloy arrows and use the alloys indoors.
 

mbaker74

Supporter
Supporter
AIUK Saviour
personally I cant get on with the match in the plunger thing, so I always use the Simon Needham tuning method, which would be worth a try....

Take the match out of the plunger and set to a medium tension
Check centre shot,
align the sight pin directly above the centre of the arrow and don't touch it
Shoot fletched arrows and adjust button pressure to centre the arrow group on the target
Once the group is centred, shoot mixed fletched and unfletched arrows
Then the position of the groups will tell you the spine but taking into account the effect of the button.

I do agree though that you probably do need 620 spines. The Easton chart is very confusing that if you already have arrows you need to use the actual arrow length, not the AMO length.
 

$hock?eader

New member
Ironman
When doing my beginners course I was told that the arrow selection charts are only a guide, since then I have found that on occasions the "best" arrow can be in the next group down and possibly two groups down, I have yet to find anyone who went to a group stiffer. I have tried to fathom why this happens and can only surmise that the charts do not use enough factors to find out the correct arrow for each persons bow set up, and it would be more confusing if they did. The factors I am thinking of are things like limb length, limb recurve, limb speed, string diameter etc etc.

I would recommend that borrowing some arrows ( one fletched, and one unfletched) and shooting them to see for yourself how they group or even buy two alloy ones that match what you want and experiment with them is hell of a lot cheaper than buying a dozen composite arrows that are wrong. Some archery shops offer an arrow matching service which is well worth the money.
 

AdamD

New member
I have yet to find anyone who went to a group stiffer. I have tried to fathom why this happens and can only surmise that the charts do not use enough factors to find out the correct arrow for each persons bow set up, and it would be more confusing if they did.
I would (very politely) suggest that the factor for those people is a 'poor' release making a weaker spine shoot stiffer. Bow set-up is very overated and far too much time spent fiddling and tweaking when the main issue is normally the archer's execution of the shot.
 

jerryRTD

Well-known member
I would (very politely) suggest that the factor for those people is a 'poor' release making a weaker spine shoot stiffer. Bow set-up is very overated and far too much time spent fiddling and tweaking when the main issue is normally the archer's execution of the shot.
I would (very politely) suggest that your view does not change the fact that the shaft selector APP gives a softer spine result than the charts.
 

Rik

Supporter
Supporter
:melodrama you just have to make sure to wave the right sort of dead chicken over it (with appropriate incantations)
 

Aleatorian

Member
the shaft selector APP gives a softer spine result than the charts.
By app, you mean the Easton Shaft selector program for the PC?
Are you looking at the 2017 charts compared to the program, bearing in mind the program hasn't been updated since 2012, have the new charts been modified to reflect the advances in limb and cam designs that increase the speed for the given poundage that would warrant the need for a stiffer spine
 

AdamD

New member
I've found the app and charts to give pretty similar, accurate-ish results. Are we talking at cross purposes? I thought the OP was talking about recurve arrow selection.
 

Piasecznik

New member
Same thing different setup:
I have rather off charts setup.
SF Forged+ raiser set to zero tiller with SF Elite Carbon Foam limbs: Long rated #30 @28"
but my draw length is 33.5"
giving me whooping 43.3lbs draw weight
shooting uncut Easton AC Pro Field 470 with total length from nock groove to the tip of the arrow 34.5"
120gn point weight.
With such setup arrows should be on weak side maybe even very weak. However, bareshaft always lands to the left and it looks like arrow is traveling sideways - tip to the left, tail to the right which indicates stiff arrow.
Button stiffness have little effect. Any weaker than medium tears my XSwings off. Making button harder than medium seems to have close to no effect.
What I'm doing wrong? Could it be my poor release? Button bottoming up? I'm lost.
Walkback test (not full): if I hit X from 10m and without windage adjustment shoot at 70m I hit 3-4 ring to the left.
 

Rog600

Member
Shoot some bareshafts with centre shot dead centre, stiff button/matchstick and sight over the shaft. Adjust draw weight until the arrows hit dead centre*. Fletch some arrows, set centre shot so edge of point is just outside string. Medium button tension. Shoot, adjust sight so that fletched arrows hit centre of target. Bareshafts should be in there too. Look at angle of shafts, adjust centre shot 1/8 turn of button at a time either way until shafts land perpendicular to boss. Then you can tinker with button tension.

*If you can't get your bareshafts in the middle at this point cut your arrows down if they are behaving weak or reduce point weight (has a bigger effect if arrows are over length), or try a stiffer shaft. If they're behaving stiff, try more draw weight, might need some heavier limbs.

Not saying this is the right way to do things but it has worked for me (similar draw weight and length, not quite as long) and my son. Perhaps at extremes of draw length, he short, me long, the first step is most critical. Get that bit wrong and you might as well be peeing in the wind playing with button tension.

Also make sure your loose is in line and not away from your face; sends it left for a right hander.

FWIW and YMMV, I've always found the right arrows for me have been weaker than the chart of lies suggests 😀

I like to think that if I can shoot a bundle of bareshafts into a group with the sight and centre shot centre and button stiff, and them landing straight and parallel, no nock left/right or up/down, then I'm at a good starting point.
 

Piasecznik

New member
Thanks for reply. I'm definitely going to try solid button method. Probably end up having to cut my arrows. Ac Pro field are tapered (front s lighter than back) I wonder which end should I cut.
 

Whitehart

Well-known member
Thanks for reply. I'm definitely going to try solid button method.
Why? Even the person who resurrected and championed the idea these past few years now agrees with all who tried it years and years ago that it does not work as a reliable method for spine selection or bow tuning.

AC Pro Field - this is a specifically designed compound shaft. You cut from the front only, the back end is specifically stiffened for the energy delivery of a compound DFC.
 
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