spine calculator

[nhbuck1]

how accurate are the dynamic spine calculators from 3 rivers and stu millers? both indicate that a 145 grain head will work on my bow and it seems to fly well,ive talked to a few people and said you cant go by that

[ranger 3]

Stu's is right on for me

[M60gunner]

They are a good reference tool in my opinion. I have got some screwed results but usually because of some bad info I entered. Of course you do need some starting points like your 145grain head. You need to read and follow the directions for inputting your bow info. If you do not know if your bow is center shot for instance you need to find out.
Where I believe people get in trouble is trying to get results using either to much spine because they want high FOC or not enough because they want a light, fast arrow.

[Sam McMichael]

Sometimes the published charts will be dead on, but, depending on the performance of both the bow and the archer, they are a good beginning point from which to experiment to find that "fine tune" point that works best for you.

For example, they never really work well for me, because I have a short draw length (25") and like a long arrow (29"). Consequently, I have to dink around a bit as I don't follow the general prescription. Still, they are useful starting points.

[nhbuck1]

so for this to be right on for me is nothing new? does each bow you type in that they have give you the centershot for that bow. why do people say it does not work?

[Sam McMichael]

nhbuck1, no it is not unusual for these figures to work just fine right out of the box. It is also common to need some tweaking to get the best results, as no product can take every single possible factor into account. As long as your equipment is shooting well, you are in good shape.

[bulldog18]

Usually spot on for me. I may have to do some tweaking with my brace height. It is only as good as the information that is put into it.

[AZ_Longbow]

Spine test kit is all I use now. The calculator rarely works. Unless it's a bow listed. It worked on on that one.

[slowbowjoe]

Ultimately, matching the dynamic poundage of your bow to the dynamic spine of the arrow seems pretty reliable.
Using the calculator to get that, however, opens up lots of room for error. Especially, as bulldog said, if your bow is not listed. Nor does it have any way of telling one when it's a form issue rather than a spine issue.

I do better, with less frustration, using the old reliable rules of thumb for spine, and trusting my eyes seeing the arrow flight.

It can be informative playing with the calculator to see how changes in your setup affect spine, at least in numbers.

[nhbuck1]

so you can get a completely different readying say  my 175s work it and its telling me to use 135s? but the 135s show stiff?

[slowbowjoe]

Not totally sure what you mean, but I think the answer is... yes.

False stiff or weak occurs often, and can be tricky to troubleshoot. I'm no expert, but my suggestion is: trust what you see more than what the "calculate" says. If you see your arrow flight is good... it's probably good. Shooting broad heads, as you've posted about, helps assess the tune.

Maybe try some paper tuning, if you're inclined, for some more feedback.