Are they anything more than a tool of Satan to boggle your mind ? It may be my shooting ( style ) I can get good arrowflight but not with any its recommendations…

Works dead nuts for me.

But it’s only as good as the inputs. If things don’t weigh what you think they do, or your bow is not the poundage that it says it is or your draw length isn’t what you think it is, you’ll have issues.

And it helps to have a clean — and, more importantly, CONSISTENT— release.

The most common mistake is the centershot dimension & even appling it the wrong direction. >>>----> Ken

I agree. They are a start

Never used one, but have used spine charts. They will get you in the ballpark to start.

I have toyed with them, and to me they are a good starting point,but ot neccessarily perfect. Rick Barbee did some tutorials in the past explaining them a little better, which helped me. I like using brass inserts for added forward weight (just my preferance) but those also add stiffness further back in the shaft, so it acts like a footing as well. Once you learn how to add all the right informaiotn the results make more sense.

-Bones

The charts on 3 Rivers are what I use and they work. Their spine calculator shows a spine recommendation that is always too weak.

I have had good luck with the 3rivers one. It worked well for my Sage and A&H. One issue I found was for Black Eagle arrows - some come fletched and crested. The cresting changes the tune significantly so be aware. But When I used uncrested arrows the calculator was very good.

The 3 rivers one for me always shows spine stiff? 50# bow, 31" draw, 32" shaft, 175g point. All charts say 340 spine, that bow shoots a 400 spine the best, 10 gpp. Just got a R/D longbow, 45# @ 31", 32" shaft and the Calculator say's 400 spine, 175g up front. That 400 spine still shows stiff with 250g up front. I run a 500 spine with 175g up front and it show slightly weak. Then again, I always seem to be between spines and have to use too light of a point up front or heavier than I want.

I have found the Three Rivers spine calculator helpful; it is not 100% accurate but gets me in the ballpark close. I start by looking at a couple different spine charts then go to the spine calculator to get closer and then start shooting and tuning for optimal bare shaft flight. I also like knowing the FOC and total arrow weight at a glance.

I've never seen a spine chart or calculator that didn't recommend a shaft that was too stiff. Not just for me, but for most that come to me for help. Another reoccurring problem is many don't know when they are getting false readings and are moving their tune in the opposite direction of what it needs. BigJim

Jim, yes, false readings are a headache. I just ordered some 500 spines from you because I cannot get the 400's to bareshaft unless I go to 300 grains up front. The 500's are slight weak with bareshaft and should be good once fletching and wraps are on.

The best spine calculator that I have ever used is me and some test arrows.

Agree with BigJim and Livetohunt. Spine charts always come out too stiff for me.

The AMO spine standard it by far the most accurate for wood or aluminum arrows. You just have to learn how they work. That standard is 26" between centers with a 2# weight.

That deflection is then divided into 26 and will give you the spine for a 28" arrow, to be used in a bow cut 1/8" before (less than) center, and a Dacron string. For every 1/16" closer to center add one spine range (5#),further from center reduce spine one range. For an arrow cut longer than 28" (1") add one spine range. Arrows shorter than 28" reduce one spine range. For non- stretch strings add a spine range.

Example: The shaft deflection on spine tester says the shaft is .510. divide that number into 26= 50.9 bow. Use that shaft in bows from 50-55# weight and cut less than center 1/8" with a 28" arrow using Dacron string.

Add or subtract 1 spine range, from there depending on how the shelf is cut, the type of string being used or length of arrow.

A spine range is 5# i.e. 50-54, 65-69 30-34 35-39 etc.

Bob

Never accurate for me or guys I build strings for. Always end up Way to stiff for whatever reason. I just paper tune. Bare shafts can lie sometimes.

Most don't want to do the study or math. They just want to be told what spine to get.Which is impossible to do accurately. If you don't know their actual draw length, arrow length,draw weight at their draw length, center cut dimension & what point they want to use. The spine charts & calculators take the responsibility off the sales person. The suggested spine will shoot plenty good with 5" feathers. When you get into fine tuning you need an assortment of shafts,points,& a cutoff saw. You also need a good target that will hold the arrow at the angle it hit. Then you can experiment with brace height,string material,points, & spine until you get mite near perfect. If you have a consistent shot.;<) Isn't it fun? >>>----> Ken

Just like any calculator guessing at things ain't gonna work.

The best results with the calculators come from measuring everything, making sure those measurements are accurate, then entering them manually.

Select "generic" recurve, longbow, etc,

Measure the bow's draw weight at your draw, and measure an accurate center cut, then enter those manually.

Make sure of the arrow shaft weight in gpi, of it's static spine, and of it's diameter, then enter those manually.

Do that, and the calculated result will be close enough to work with if not spot on for most bows.

Some bows, especially the super curve designs are outside the spectrum of the calculators to work with. You can still use them, but only after you have learned the bow enough to know where to make the changes in the entries for it.

Rick

I use the 3rivers spine calculator. It's been spot on. As was said, the centershot measurement is the most critical and changes things the most.

Yea I agree with big Jim the Easton chart for carbon was way to stiff when I bought carbon.I went with a lower spine weight and it was perfect I went on past aluminum experience and my old friends advice .Had I bought what the chart said I would be adding all kind of weight to the front.As far as spine tester I made my own actually two different ones but with carbon or aluminum I really don't use it to much unless I want to make wood arrows

Long post.

You need repeatable form and a bow you can get to full draw for Stus calculator to work.

The 3R spine calculator (Stus) is on the money for me. I input accurate data for my bows. Centercut or centershot, the side plate thickness, my actual draw length, and since I shoot home made woods, the spine number off my ACE spine tool, gpi and shaft diameter.

I know my draw length from having my wife mark an arrow at full draw on my various bows.

If you really aren't drawing what you input, or collapse slightly from a less than clean release or whatever, then you're entering incorrect data. Releasing when expanding and pulling through is gonna be different draw length then a slow collapse or just short drawing. Etc. Form issues. Just one inch less draw then what you input will show up as a stiff arrow.

JME. YMMV.

“Their spine calculator shows a spine recommendation that is always too weak.”

First person I have EVER seen say that.

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