How accurate is STU calculator

[marsniper27]

Ok I know most people here suggest to use the STU calculator to help select arrows. I used it to find the right shafts for my bow. I did a couple searches but didn't find anything like this on here.

My question is how accurate do you find the calculator to be? Do you usually get good flight with what you find with the calculator or does it take a significant amount of tunning after using the info as a starting point?

I just got my GT 1535 blems from big jim and the calculator says if i use 105gr points i have perfect spined arrows. I do not have any points yet and was wondering if i should trust this and order a dozen 100 gr heads or wait and get the test kit before ordering points and heads?

Thanks

[acadian archer]

From what I have read it's a good calculator but while it may get you close you likely are better off trying a real world solution instead of the theorectical one.

[COMPOUNDLESS IN CONCRETE]

Not very with my setup, but very accurate for other people's.  I think it is like factory arrow charts, they work for some, and not for others.

[K. Mogensen]

It's pretty close with mine. I usually just go up one group in point weight I.E. if it says I'll need 175's I'll go to 200's.

[marsniper27]

thanks for the info so far guys i was planning on ordering 3rivers point test kit either way. I just want to start shooting asap.

[calgarychef]

I love that calculator, and it's right in the ballpark for three of my bows.  I'ts not perfect I still do a little tweeking but not very much.

have fun with it!

[Pack]

It seems to be very accurate for the bows I used to select woods with.  It is interesting to play around with different parameters to see what else might work.

[MSwickard]

From my experience, for a normal FoC arrow the calculator is spot on when relating the dynamic spine of the arrow to what your bow needs.  However, in my quest for Extreme FoC (EFoC) arrow, the dynamic spine on the arrow in relation to the bow is way off.  Here is an example:

My 53@28 60" Griffin called for 59.6# of dynamic spine using a 6 strand 450+ flemmish string.  Shooting a normal FoC arrow I was getting great arrow flight (dynamic spine 59.5#, but arrow was only 498 grs. 18% FoC with 188 gr head and stock inserts. 30.1" BOP using a CX Terminator Select 45/60 shaft.

My EFoC arrow (same shaft), 29-7/16" BOP, 285 gr head, 100 gr brass insert, 678 gr arrow.  The Dynamic spine on the calculator is 33.8#.  The EFoC is 27.2%.

So you can see the Dynamic spine is off 25.8#'s, but I'm still getting lazer arrow flight.  Granted the EFoC arrow is not going to shoot as flat but the gains in other areas is well worth it.  

The bow is whisper quite (no string silencers)and those EFoC arrows hit with authority.  Basically, I have a Ashby EFoC arrow and all the attributes for penetration.

Use Stu's Calc as a guide and if you want a EFoC arrow you just have to load the shaft up and use the planing method to see what works in your bow.  The Calc will help in selecting the correct shaft.  BTW, the calc. is spot on when it calculates the total arrow weight.

Mike

[dbishop]

It's way off for me.  I shoot a 500 spine arrow (Easton axis)out of my Toelke whip with a 75 gr insert and 125gr head.  Arrow is around 30.75" long.  The calculator shows a difference of 23lbs(underspined) but the arrows shoot like lasers.  I emailed Dan about the arrows of choice and the above is what he recommended for my bow.  My bow is 54lbs @ 30".  I also have good luck with the AD trads.

Dave

[Hud]

Spine charts and calculators are a good starting point, but it is still important to tune & make adjustments for your individul setup. I find some bows are much easier to tune than others. It is very much an individual because there are so many different shafts available and mfgr quality and standards differ some.

[smokin joe]

I just tuned some carbon arrows and then compared the tune to Stu's calculator. The calculator prediction and the arrows I tuned were identical. I looked it over for some wood arrows I have tuned for another bow and the calculator was right on for that too.
I think the calculator is pretty good for me so far. But, as President Reagan used to say, "Trust, but verify." I think that is a pretty good plan. I think the calculator can save me a lot of time and get me a lot closer than guesswork.
Joe

[BCWV]

I use it and for me I always need a little stiffer arrow than the calculator calls for. That works great as I can cut it back to get the flight I need.

 I have a friend that used it for the first time with a new bow and it was dead on. I don't know for sure but think it may be the differences in our form and the way we each shoot.

 However it is, I love it and think it's a great tool.
 Thanks Stu!

[marsniper27]

From the sounds of it if you are going for more of a target arrow it works out great. If you want hunting, High FOC, arrows you are going to be off on the calculator.  So i guess for my current needs (practice and training) i can most likely count on the calculator. for my hunting setup i will need to tune.

[CEO]

Not even in the ball park for me.

[xtrema312]

What I am reading sounds like my experiences.  I think with wood and aluminum it works well.  I am using all carbon now and have had some problems.  High FOC usually makes me need a little weaker arrow.  I am on the line with 500 vs. 400 shafts so I often find myself using 400’s and heavier points or real long shafts.  I almost always need a little weaker arrow than the calculator says.  A long overhang on a carbon like 1.5” or more also throws a wrinkle into things for me with the higher FOC because of the way that weight way out front of the riser causes it to flex, I think.  Another problem for me is insert length and weight.  I can’t get the same thing using a 50 gr. insert and 175 point as I do a 100 gr. insert and 125 point; The weight moves forward and flex length of the shaft changes.  

So what I have done now is work with shafts ¾” to 1 ¼” more than my draw.  That helps with the odd flex I get with long carbons.  I insert shaft length as true flex length by deducting the actual length of the insert.  With this approach I am a lot closer.  I can get a lot more accurate on arrow variations with different insert weights and lengths as long as the arrow length says in the ¾” to 1 ¼” more than my draw length range.  I also get real close to matching spine of arrow to bow spine in the calculator because this gives me a stiffer number.

Even with all that I still have one bow cut to center and one 3/16” out.  Both confirmed within .5# draw weight.  Both are R/D LB’s.  My 3/16” out needs more spine than the cut to center and both shoot within about 2 fps.  I can’t say why other than bow design.  I also get a little different spine requirement for shooting split vs. 3 under so form and release plays a role.

[Dean Lintz]

For me the calculator runs 5 to 10 pounds under spine compared to bare shaft tuning. But I believe a persons release will effect the arrow flight that being said as long as it is done the same every time should not make a difference.

[Flying Dutchman]

I calculated five different bows for different people with Stu for different arrows, carbon and wood. Even with EFOC (I shoot 20% carbon EFOC's) Stu is right on.

You have to remember a few things though:

- Garbage in = garbage out. Especially the center-cut option has to be filled in accurate, otherwise your spine is way off!

- The values of Stu are based upon a shooting-machine. We are no machines, and each archer has his own way of shooting, releasing and canting the bow. Stu will get you pretty good in the ballpark, but afterwards I would go and bareshaft your arrows to be sure.

[Earl Jeff]

I don't use it Much. Sorry  

[Arrow4Christ]

I have only used it for matching wood arrows, and for my setup it's been pretty spot on so far. However, I think it's important to look at it as a reference and do the fine tuning yourself. You're probably going to have to make small adjustments to your setup to get perfect arrow flight.

Craig

[Doug in MN]

Sure has been very close to spot on for me out of several bows.

The thing that seems to be very critical is the amount of center shot. If you are on with this spec you will be very close.