Help: Bareshaft Tuning Recurve

[tovli]

Please look at this picture and help me interpret:

http://tinyurl.com/2w6jyc

This is 10y photo. At 20y bareshafts land in 1 ring at 9 o'clock.

Arrow: Easton Nav 710, 100gr bullet pt (no insert), 45mm kurly vanes, Easton G nocks (no insert), 14% FOC, 28" shaft only length

Bow: Hoyt Pro Medalist (1970) 69" 34#AMO Braced at 8.4", 10 strand B50 string, bottom of Nocking point up 13/32" from rest (makes bare shafts roughly same height as vaned), Hoyt Super rest cranked into center as far as possible (right side of point on centerline at draw). Arrows measured 177fps at bow. Cartel Magnetic clicker on sight bar.

Archer (me): DL 27.75"AMO, Leather finger tab.

OnTargetSFA says this arrow setup is exactly correct (although it says FOC is 15.7% and somewhere I read normal is 7 to 14%).

What does picture and 20yd data say to you?

At 10 yards I can put six in the 10 ring of indoor target (once or twice), but when I move back to 20y the group opens up to include some 7s and 8s and at most three in 10 ring.

[Aechmea]

Please look at this picture and help me interpret:

At 20y bareshafts land in 1 ring at 9 o'clock.



Hi Tovli

Righthanded?

Bareshafts at 9 o'clock suggests that the shafts are a little too stiff. Also if you look at the direction of entry of the bare shafts on your 10m picture, the nock end is out to the right, (and the point end is a bit left of centre as well). Signs of stiffness.

Had a quick look at the Easton charts. 28" at 34 lb. gives group T4 which suggests Nav 660-710, which is what you have, so no help there.

Still, the evidence says too stiff; maybe the Easton charts are on the conservative side.

[The One]

Still, the evidence says too stiff; maybe the Easton charts are on the conservative side.

Way too many variables to discern still. Have you tuned the bow using brace height yet? Is the centreshot done correctly? Does the string have a suitable number of strands/serving? Are you releasing the bow properly? The Easton charts are merely a guide, and different people's techniques can manufacture results either way of what is recommended. Assuming you have gone through the process of tuning correctly and in the correct order, then yes, a little stiff for a right hander. Best to do the bareshaft tuning a little further back, though.

I would suggest either increase bow poundage, or put heavier points in.

[tovli]

Have you tuned the bow using brace height yet? No - have been assuming that is fine tuning group size after arrow is tuned close. What is process and when? (My bow is old one piece and string length is standard for 69AMO bow giving 8.25-8.5" - I've been shooting it a little low to get the most out of the bow.)

Is the centreshot done correctly? Don't have a plunger and the bow cannot go true centershot...rest with flexible tab "plunger" is in as far as possible. What is "done correctly"?

Does the string have a suitable number of strands/serving? 34 lbs Dacron 10 strands should be plenty.

Are you releasing the bow properly? Good enough to sometimes put six in the x ring.

Best to do the bareshaft tuning a little further back, though.

I would suggest either increase bow poundage, or put heavier points in. Can't increase bow weight. I'm at 100 gr which is 14-15%FOC. If I increase the point weight I think the FOC will be too high, no?

I'm thinking of buying two Nav 880s with 50gr points, fletch one and leave one bare. With insert and pin nock this will be slightly weaker than current and I may pick up 10-14 fps. Without the insert, using "G" nocks will be even weaker. If that doesn't match, I'll move up to the 60-80gr breakoffs.

I'm a little concerned that the weight of arrow will be too low. SFA says it will be 6.3gr/lb. The Nav 710s with 100gr points give 7.9gr/lb so perhaps I need to go with Nav 810 with 70-80 gr points as a compromise - a little more speed and a little weaker spined.

Thanks for looking and suggestions.

Tovli

[The One]

If you can't get proper centreshot due to the nature of the bow and thickness of the sight window, interpreting the results from bare shaft testing may be misleading. Just because the bare shafts are impacting left does not necessarily mean the arrows are stiff - could just be that the arrow is situated too far to the left of centre.

Without getting proper arrow alignment, I'm not certain that it is possible to get the bow tuned perfectly. I am also not sure whether treating the arrows as being stiff will prove useful. Most of the steps in the Easton tuning guide are reliant on the intial set up of centreshot being correct.

Perhaps someone else can suggest something? My opinion is get it as close as possible and shoot it. If you're worried about getting a good tune, you can always buy a more modern bow which allows good arrow alignment.

[Sandy Hancock]

Am I right in guessing B50 is Dacron? Changing string material to BCY 8125 or similar should weaken your arrow reaction.

I would strongly recommend getting a plunger, if your bow accepts one.

[Jazza]

My advice, get a plunger.

[Sandy Hancock]

On second thoughts, on a 1970 vintage bow, 8125 might be a bit harsh :silly:

Time for a new bow?

[The One]

My advice, get a plunger.

On the sort of bow he has, I doubt a plunger will be useful, as to get it out far enough to give, it would push the arrow even further out of centreshot.

[Jazza]

On the sort of bow he has, I doubt a plunger will be useful, as to get it out far enough to give, it would push the arrow even further out of centreshot.

This is true.

[Robhenry]

On the sort of bow he has, I doubt a plunger will be useful, as to get it out far enough to give, it would push the arrow even further out of centreshot.

I have one of these bows - I ended up cutting into the riser and reducing the thickness so that a plunger could be used.

It worked very well - these are a very tough riser as you will find when you try to cut it - also you don't have a high bow weight.

[frommy]

On second thoughts, on a 1970 vintage bow, 8125 might be a bit harsh :silly:

Time for a new bow?

Lucky I read the whole thread before replying to your initial comment, Sandy. :rolleyes:

On steel cabled bows anything but Dacron will blow the teardrops off them. Been there, done that. :(