weird tuning problem

[khardrunner]

I've been working on tuning and I cannot figure out why my arrows show stiff. Bareshafts consistently strike to the left and a touch low on the target indicating a stiff spine. I've used Stu's calculator, checked my draw length and have worked my way up significantly in point weight with no change. Currently I am using 250 grain points which put my dynamic spine (according to Stu) at about 10 lbs LESS than what I should be shooting at my draw length. I'm pretty good with excel and have also had my dad check it out to make sure that I am inputing the right numbers.

I am shooting a Kohannah Kurve 50 lbs at 28 inches, drawing approx 27 inches. CE predators (4560) full length with a 1 inch aluminum footing and currently 250 grain points.

Any ideas why no matter what point weight I use I am showing stiff spine?

[stevewills]

if your hitting left and shooting right that a sign of weak

[khardrunner]

I just looked at Adcock's bareshaft tuning guide and his picture for stiff spine has feathered in the center and the bare shafts to the left.

[Looper]

If a point change doesn't show a change in impact, something else is happening. It could be your release, or maybe you're torquing the bow. Or your arrow is bouncing off the shelf or riser. Try raising your nock point and see if that helps.

Also make sure you have 2 nock points installed. One above and one below. An arrow sliding down the string on release will be a nightmare to tune.

[Looper]

Originally posted by stevewills:
if your hitting left and shooting right that a sign of weak

You've got that backwards.

[khardrunner]

I'll try raising the nocking point, although once again according to adcock the fact that I'm hitting lower bare shafted means it could be high. I know that it's a bit nuts though with nocking point so I will try that.

I also shoot above, so sliding down isn't a problem. I did a little high speed camera action a couple years ago at lancaster archery with Blacky Schwartz and was able to see how much nocking above helped (I already did that as I shoot in the Hill style).

[lpcjon2]

Can you move your strike plate in or get a thinner one? And what kind of rest are you using?

[Looper]

You are right, a low impact point would indeed show a too high of a nock point, but you can also go so low that the arrow bounces off the shelf and gives you a false low. What is your nock set at now?

[mrjsl]

Forget the bow in Stu's Calculator and focus on the arrow - see what changes will make it weaker in dynamic spine.

I have two recurves, and both of them love an arrow that is 25-30 pounds weaker than what Stu's Calculator says they need. I have worked up an arrow that matched what my bow needed supposedly, and bareshafts hit three feet left, no joke.

If you are at full length arrows w/ 250 and you are only 10 lbs weak of what Stu says, then you are likely going to have to go down in spine. You will probably need a .500 spine or weaker shaft to start with.

[Blackhawk7204]

Some bows will need a much weaker spine than shown in any chart, some will need one far stiffer. The arrow being either to far from center or even too much past center.
My new Bear takedown needs a very weak arrow for its draw weight because the riser is farther from center than most of todays bows.
And the A&H longbow I had was cut so far past center that it took a 350 spine Heritage shaft cut to only 29" with a 125 point, it was only 51#. no other bow that weight I ever shot needed stiffer than a 150 shaft.

[xtrema312]

I have never gotten a bow tuned that was closer than 15# weaker than the  calculator says.  Often it is 20#.  That is with carbon and FOC around 20 or so.

My 50@28 ACS drawn to 29" shoots a 5575 30" with 100 gr. insert and 145 head just right with a bare shaft.  With a 125 point a bare shaft shoots like a bullet.

Another interesting thing I found is that with a 3555 shaft the calculator appears very close for me.  If it says the arrow is way weak it shoots way weak.  The GT 3555 comes about 30” so I shot them full length with as little point weight as I could to stay at a safe GPP.  Still calculated weak and shot weak.  When I go to the 5575 and calculate the same dynamic spice as the way weak 3555, the 5575 is much stiffer.  I have tried all kinds of combinations and just get right back to the same place.  I have no idea why this is.

When I have gotten an arrow to fly well using the calculator and the 5575 or a 340 shaft it has been a false tune as far as I could tell. I think the shaft was bounding off the riser.  It just didn’t act right to variations in points and it was not very forgiving at all.

[khardrunner]

Maybe I will try to get some weaker shafts and try that. I'm finding some very unforgiving flight and some wobble no matter how good my release is. Also, the arrow often will fly off of the outside of the arrow rest instead of staying in by the strike plate.