Stu Mullins Spine Calculator

[dragon rider]

I'd appreciate hearing from anyone who has used this.  Hayslope recommended it on a recent hunt, but the results I'm getting keep surprising me.  With almost all of my bows it says I need stiffer arrows than I'm shooting.

I draw 29".  I generally shoot bows between 45 and 50.  I generally shoot carbon - Beman, Gold Tip, Whitetail or Carbon Express.  I don't cut them, because at full draw the back of my broadhead is generally against my index finger.  My heads are generally 175 gr.

I've been shooting ICS Bowhunter 500's and Whitetail 35/55's - but according to the calculator I should be shooting ICS 400's of 55/75's.  

Does that make sense?

Thanks.

[Rob DiStefano]

ALL of the charts, guides, calculators are ballpark at best.  if any of 'em hit the nail on the head for ya, that's just great, but in truth there is MUCH to figuring out what arrow will work best for what bow and what archer.  take all of these "aids" with a pound of salt.

fwiw, all  my bows are between 48 and 55 pounds holding weight at 29" of draw length and after spending a ton of time and money what works best for me are ics 500's.  interesting, eh?

carbon shafts are VERY different than any other shafting material in that their static and dynamic spines are poles apart ... at least that's what i reckon after doing the testing.  

and of course, ymmv.

[Rob DiStefano]

lemme please add - if yer arrows are flying real well, don't start second guessing ... no matter what anyone sez, either human or machine or software.

[FerretWYO]

Originally posted by Rob DiStefano:
lemme please add - if yer arrows are flying real well, don't start second guessing ... no matter what anyone sez, either human or machine or software.

 So True

The Calc said the same to me. I tried it and it was close but I was closer with what I had before I started messing with things. I have seen you shoot Paul you have a well done setup.

[Rob W.]

I use it as another tool for a complete setup. It allows me to get close on "what if" kinda tuning,total weight, speed difference questions. I usually end up with a 6-7# weaker spine than it calls for.

Not a set in stone automatic arrow tuning miracle but a great tool to have at ones disposal.


Rob

[Swamp Yankee]

The centercut measurements are critical to get right for the calculator to work correctly.   The most common error seems to be not adding arrow plate thickness to the centercut number.

[SAVIOUR68]

Paul the arrows your shootin should be right on with a 175/200 point weight, as Rob said the charts and calculators are just a starting place and I find with Stu"s calculator i have a 15-20 # differance and thats why i bare shaft. by the way i will see ya next weekend in south texas for some pig stickin. Scott

[reddogge]

RobW has the right idea. Use it to get in the ballpark when selecting a new set up, not checking what already flies nice.

[Bladepeek]

What I didn't see in your post was how they are flying for you. I'm shooting 30.5" 5575s from my 50# recurve, drawing 29.5", so it's probably close to 53 - 54#. My bare shaft and fletched arrows fly to the same point with 175gr and the normal insert. May be a difference in center cut.

[Hatrick]

Stu's calculator is an interesting and well thought out tool. If you pay attention to the variables, and as Swamp Yankee said, the centercut and strikeplate measurements, it can get you in the "ballpark". Although there are also personal variables to consider such as release and inconsistent draw that are individual, I find that I can get real close to what works for me.

[Swamp Yankee]

The centercut measurements are critical to get right for the calculator to work correctly.   The most common error seems to be not adding arrow plate thickness to the centercut number.

[SAVIOUR68]

Swamp yankee you are right about the centercut measurements but how do you calculate the personal variables to determine a close spine measurement with out shooting a arrow from the bow with your personal form/release. Just my opinion and there are different strokes for different folks so to each there own.

[Night Wing]

I don't look at the Personal Form Factor until "after" my arrows are tuned.

Example. Both of my 42# and 37# Blacktail TD recurves shoot the same 2212 arrow with the same 75 grain point weight. The arrow dynamic spine and dynamic spine for both bow setups is the same which is 57#.

But, the Personal Form Factor for my 42# bow is at (0) and for my 37# bow, the Personal Form Factor is at (+9).

For some reason, my 37# Blacktail likes a very stiff arrow.

[Joeabowhunter]

Stu's calculator has been real close for me.  I use it as a starting point and to get a good estimation of my total arrow weight and FOC.  Then starting with long shafts and a few point weight combos paper and bareshaft tune.

[JamesKerr]

Originally posted by Rob DiStefano:
lemme please add - if yer arrows are flying real well, don't start second guessing ... no matter what anyone sez, either human or machine or software.

X 2

[Bowwild]

I've been a paper and then broadhead tuner all my archery life (when I learned that fine-tuning mattered in August of 1977 after blaming "it" on the broadhead).

I learned about Stu's calculator here on Trad Gang in the spring of 2010.  It is an amazing tool for me.  

If I enter all the specs correctly (foot length, centershut, actual draw weight, etc.) I've found it extremely accurate for me.

I alternately shoot Beman Carbon MFX 500's and 600's by changing point weights in bows from 40-48# at my 26" draw weight. I proof every set-up at three paper distances and then broadheads at 20 and 30 yards.

Like others have said though, the proof is out front of YOU and your bow.

[dragon rider]

Thanks guys. Much appreciated.  Notwithstanding the calculator the ICS 500s with 175 up front are hitting right where I want them, assuming I don't screw up the shot.  I think I just won't tell my bow that it's supposed to need a stiffer arrow and maybe it'll continue to be happy with what it has.

[frank bullitt]

Rob is speaking my language!