A crazy amount of time and a silly amount of money shows the following...

55# Bear 48 Mag Drawn to 26" = 29.5" XT 400 w/100 brass insert, 3/5" feathers, standard nock, 300 grain head.

65# Martin Mamba drawn to 26" + 27" XT 400 w/100 brass insert, 3/5" feathers, standard nock, 300 grain head.

Run those numbers on the calculator and you will see, you have to figure things out for yourselves.

;)

I feel your pain.

So that is the Stu Miller calculator and i was hoping it would help save me a lot of trial and error- not!

Before everyone says my inputs are wrong....i measured everything and weighed my bow at full draw....my inputs are perfect. now my form might be crap...but my inputs are good- grin

My 31" Centershot 400 with a 75gr insert and 145gr head shows 10# weak...but it bareshafts perfect at 5,10,20 and out to my PO at 30 yds.

OK...so following instructions....I put in my personal form factor of -10 to balance it out....but then another arrow I was checking was off by another 7# on the calculator.

Some guys say the chart works for them- surprising to me...or maybe my form is just baddddd.

i think stu did archery a great service attempting this and in no way am insulting him...just didn't work consistently for me.

The calculations given don't work for me either....I ignore them and just let the bow tell me

Im just glad I don't get into all those calculations, I just shoot a bare shaft into a bale, and shorten or add weight until it flies right. Have fun !

Lol! I had a popular compound bow builder/super tuner once tell me "never let a program tell you what arrow too shoot". I cannot see how traditional archery would be any different. Is that what you were wanting was the 400 grains up front?

R-griderX2. I don't cut to tune, but I don't use a calculator either. It really isn't that complicated. And, after you have at this a couple of years you should have test set put together to make your decision with any way.

I have the download from Stu on my desktop and it's dead on every time.

It works for me, but it wouldn't ever suprize me if it didn't get it wrong one of these days.

But on the flipside, rests can be different, form could set it off.

The good thing with calculators snd formulas is that they work on paper. Problem with that is that paper is not large scale with the diversification of the real world.

Funny, most people I know, including me, report Stu's calculator usually get's you, "in the ball park".

Bare shaft tune from there. Best free program available.

There are lot's of variables that can throw it off if not entered correctly.

Agree with firstlight

The downloadable Excel version has gotten me close enough, and once you have a good known tune, it's useful to mock up other arrow setups.

I tried using the 3rivers calculator and my bow isn't even listed.

Quote: Is that what you were wanting was the 400 grains up front?

Sure!

I tried the version on the 3Rivers page with my daily shooter recurve and an arrow setup that I proved correct through bare shaft tuning. The calculator's recommended arrow setup was pretty close to what I found through tuning, it was +/- about 50 grains (I don't remember which way) which in my opinion beats most internet guesses or some vague manufacturers chart.

I think the calculator is good for a lot of people who don't really know where to start. With accurate inputs it should get you close, but you will still want to tune.

It clearly doesn't work for everyone, but then look at the differences in arrow setup for people shooting similar bows and having similar draw lengths. There can literally be two static spine sizes between what works for archer A and archer B according to their tuning. That's why everybody needs to figure out what works for them, and it may be nowhere near what the guys on the internet tell them to use.

If you have been shooting for any length of time you probably know about where to start, and have several sizes of arrows to play with. The calculator really isn't for you.

I think it's awfully nice of Mr. Miller to go to all the work to develop the calculator and then offer it up for free to the public, along with frequent updates. For all the people criticizing and ripping on it why don't you come up with something better?

If your bow isn't listed in the drop down menu, use "generic recurve". When I played with the calculator it didn't list my Blacktail recurve so that's what I used and it worked well.

I continue to believe poor results are due to input errors. Always been true for me, but with EXTENSIVE testing with dozens of bows, I find reasons that can be very hard to uncover, and there are quite a few.

One is grip position. For example, my Howatt Super Diablo has a slope to the palm area of the grip. At draw, my bow hand would slide to the side a tiny amount. The result is the critical measurement of window/strikeplate, while correctly measured, wasn't the true depth from which the arrow was launching. The shift had the arrow launching off the riser window's forward edge vs. the strike plate. Solution was a leather grip patch built up to keep the riser from rotating in my hand.

I could have dismissed the Calculator as have others had I not made the correct assumption SOMETHING was wrong with my inputs and kept digging.

Stu's measurement gathering of various bows was/IMO not a real improvement. True apples to apples speed testing reveals there is not enough difference between ANY similar bow design to justify using any specific bow versus the "generic" option. Even a 1/32" change in strike plate depth alters best spine stiffness. The point was to have a correct sight window depth onto which one adds strike plate thickness. The problem with that is the assumption EVERY specimen of a given model is exactly like the next one. With only one exception I can think of, riser's are still hand formed and each specimen isn't identical enough to trust yours being identical to the one Stu measured.

I'll bet another more common input error is TRUE draw weight/length. The easiest way to avoid errors is to draw to full, marking a spot on the arrow shaft; THEN scaling actual draw weight to YOUR draw length. Enter THAT weight ignoring what the distance really is and the need to enter any difference between the archer's DL and the 28" default.

Long enough note, but I could list more than a dozen "oops" of these types, string issues, true weight entries, parallax recovery of wood vs. aluminum vs. carbon, archer form, bow/arrow/archer idiosyncrasies etc. etc.

I stand by my opinion that poor results are due to poor inputs....someplace in the process what you think IS, isn't.

Rick

Here's the issue - YOU HAVE TO KNOW HOW TO TUNE. When I hear/read someone is 'bare shafting' they probably don't know how to tune. They're trying to read the tune by arrow kick out or angle in the target. I don't want to say it won't work, but it's very inaccurate.

Here's an example of why it's inaccurate. Next time you tune 'bare shafting' get your protractor out of your tool box and check the angle you're off so you know how much to add or subtract weight. You mean to tell me you don't have a protractor in your tool box? Well, if you did how accurate would reading the angle be? I'm not going to even get into the different angle of a bag target and foam.

Where as, if you tune by impacts you can get the distance your tune is off by a measuring it with a rule. Learning tuning (www.acsbows.com/bowtuning.html click on 'download printable version'.) and Stu will be in the ball park.

Bowmania

What Todd said ^^^^^^^^^.

You could have the perfect spine combo and get funky bare shaft flight with a less than perfect release, one arrow nock a little tighter or a bunch of other things. With the ACS/OL grouping method, they have a less dramatic effective and you can still see a pattern. Then fine tune from there.

Never like it never worked for me

Never used one. I do find it amazing that after sixty plus years of having access to spine knowledge, it's likely that well over 50% of the archers today have no clue how to go about setting up a bow without someone else's help. Just the term spine seems to bring out the most confusion in any archery forum.

I use the calculator for several things...determining dynamic spine is not one of them...that still makes it a useful tool

DDave

I also agree with Firstlight. Stu's calculator has always been a good tool for me to get in the ballpark. It's not the end all, nor was it even designed to be.

I have seen odd things happen when guys around here try to use full length shafts. Until an arrow is up to speed it is skating on the shelf. The distance the bow is out from center will greatly influence how far that arrow will bend into the bow at release. I know I know, we are always told that is caused by the string roll on the fingers, but it happens when a mechanical release is used as well, I have seen slow mo videos comparing the two on the same longbow. I will add that in out side of center shot bows, the amount of skate and whip can be greatly agitated by torque with full length heavily front loaded arrows. Minimum length wood and aluminum arrows can reduce that problem. In those cases the Stu Miller charts have been very close for the people that build arrows for. There have been a couple of cases where I opted stiff and had to change point weights from 125 grain heads to 145 grain heads.

I agree with Shawn. The calculator is too confusing as it is. A newbie would want to give up trying. For those that have several years experience WHY use the Stu? We have enough knowledge to figure things out on our own. Things in life CAN be oversimplified and overthought.

Ehh, I ran the numbers on one of my bows (the one listed) and it came out close enough.

IMO the brains at Big Jim justify dealing with them.

Point #1: In the example given by the OP?...

*******************************

"5# Bear 48 Mag Drawn to 26" = 29.5" XT 400 w/100 brass insert, 3/5" feathers, standard nock, 300 grain head.

65# Martin Mamba drawn to 26" + 27" XT 400 w/100 brass insert, 3/5" feathers, standard nock, 300 grain head."

********************************

The fact that the arrow length for the 65# Martin Mamba is a whopping 2 1/2"s SHORTER?...makes perfect sense.

Point #2: "Bare Shaft Tuning" has very little too NOTHING to do with observing the angularity of a bare3 shaft arrow that's already impacted a target...but has EVERYTHING to do with...

"Comparing Point Of Impact Differences Between Fletched and Bare Shafts"

In closing?...the calculators are rarely (if ever) "Spot-On"

They are there to "Suggest" good starting points which newer, less experienced archers need and are usually close enough that a decent state of tune can be achieved by adjusting "Point Weight"

In closing?...speak to any of the custom wood arrow makers who charge a premium for their arrows and you will find that even they?...with their wealth of knowledge and vast experience?....will more often than not attempt (if not "insist upon") you purchasing (or them sending you)....

"A TEST KIT"

first. ;)

All I know is this:

Probably a dozen, or more times I tuned my rig the old fashion way. You know, the one where you shoot bare shafts until you get good groups & accuracy, then you mix in some fletched shafts, and fletched broadheads, and tweak until you get them all, including the bare shafts accurately grouping together.

I then took those arrow configs, and entered them into Stu's calculator along with my bow specs. Every time the calculations were within an acceptable tolerance, and often were spot on.

I don't know about the 3R's calculator, but have heard it is a stripped down version of Stu's calculator. Maybe it gives different results from Stu's version.

Rick

I have never used it until I have the bow arrow combo tuned to my liking. Then I check and see if my setup is close to what the chart says. MP

I already see the defenders coming up to close the hole in the gate but trust me, this is not a 3rivers bash. I am a registered customer and do like them very much BUT...

The calculator could never have served me or (maybe) anyone who doesn't fit a mold. I started with a very shallow grip and now have a crazy deep hold. I could never shoot now, what I shot then.

Some people will obviously fit but not all. This is the reason for this thread (I guess) in which I hope to speak to all the threads I have seen (started) on the topic of starting spine.

I love 3R's.

I'm just wondering if their version of the calculator gives the same results as Stu's unmodified version.

Rick

I recently bought and tuned some carbon arrows for a 55# recurve. Just for kicks I checked the 3 rivers calculator and it was EXACTLY on.

3 Rivers calculator has worked for me for aluminum shafts.

My wife used the calculator and it was as close as you can get. I think she had to add 50 grains to the arrow to get perfect but that is still great IMO. As long as it kicks out the correct spine, that in and of itself saves time and potentially money. It just didnt come close for me.

I am not sure how any calculator could be expected to work on all finger shooters since the variables are so great. If we all fitted the string in our hands the same way it still wouldn't eliminate the variable of finger width and length which has a great effect on how the string comes around the obstruction.

As I said... Just putting this out here so that others will take calculators and advise with the grain of salt that is needed, before diving into the process of arrow selection.

Rick, Yorktown5, is right on the money. There are lots of subtle variables that can cause big differences. The ones I see most frequently tripping folks up is amount of centershot and strike plate thickness.

But at the end of the day I also wonder why folks complain about a complex tool that has been developed and presented free to anyone who wants to use it. If you cannot get results that are helpful to you, why not ask for help vs. generating all the negative comments?

I still don't get the original point it seemed the OP was trying to present where he compared two different bows that were 10#s apart from each other with arrows that were configured exactly the same except for?...

The arrow on the bow of 65#s was a whopping 2 1/2"s shorter than the arrow on the 55# bow.

which makes perfect sense of why that would be and should be as?...

Juts a 1/2" difference in "arrow length" affects the dynamic spine in a huge way and can easily make the difference between an arrow that will hit tune and one that won't so?...

I just don't see "The Issue" here.

Sorry for the blank post I got ahead of myself. I didn't run the calculations, don't need to. Others have given the answer. 2 1/2 inches on a carbon arrow makes a giant difference in spine stiffness. The calculator is a great tool if you use it instead of trying to prove it wrong all the time. Ken

The Stu Calculator matches what I shoot very well.

I personally have no need for it. But some folk find it a help .Before these caculaters we all got by OK.I suppose the time put into the calculator is a great thing and it being free is great too..Its has always been regarded as a guide only by most folk.From experience I can make all necessary adjustments and tweaks and get good shooting arrows.If it ain't no good for you come up with something better yourself.Stop whining no body makes you use it.Find your own way it worked that way for thousands of years Why not now? OSR

A couple posts here sure as hell aren't gonna doesn't make the calculator worthless garbage. lol Yet more strongly opinionated silliness.

I find it 'spot on'. No calculator is gonna be 'the arrow spine bible' but it is very close ime, and not only that the calculator has helped untold numbers of archers, including this one, find a good arrow match for their bow.

This was not a post to prove anything other than the fact that I saw what (it seems like) maybe 30% of other people here have seen. It is not a fit all. I even pointed out that it works great for my wife.

I guess nobody ran the numbers on the calculator themselves or they would have clearly saw what I was speaking to. The bows/arrows I listed come up (as much as) 40 off and that is no where near the recommended 2. Yet they show a perfect tune in walk back as well as with paper.

Dont get your panties in a wad fellas :D

Chris, have you tried tuning with bare shafts? The reference I used had three bare shafts and three fletched shafts grouping together at 27-28 yards. I'm just curious since I don't paper tune or walk back tune.

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