whats this section mean for the dynamic spine and how do you know what to enter for it -15 to 15? any help would be great thanks

I'm sure you will get a lot of replies, but the way I use it is to sort of "reverse engineer" it. I tune my bow, starting with what is recommended and varying length and point weight as necessary. Once it is shooting right, I put the specs into the calculator and then use the form factor (-15, +15) to get the bow dynamic spec s to match the arrow dynamic specs. At that point, I can use the calculator to check out different brands, spines, etc and know they will be spot on, or VERY close to it.

^^^perfect explanation^^^ I always wondered the same!

That's how I use it.

X3 Bladepeek

Excuse my ignorance but how do you determine the form factor? Maybe I missed the explanation somewhere

There is an entry for form factor at the end of the calculator...in the end form differences can trump all the other factors so Stu allows for adjusting things to personal form...by the time one gets good at figuring out their form factor they are likely already good at determining appropriate spine from experience...I use the calculator for several things but never for determining a starting point for spine...I do that from experience and by having a whole bunch of bareshaft arrows and point weights kicking around

DDave

I only use the spine calculator as a start. See if shaft will work or not. That form thing at the bottom I do not use. It seems I could use any arrow just by tweaking it plus or minus. Maybe if I used it after the fact like suggested above but I do not see the point.

With the form factor it always you to 'tune' the spine calculator to your shooting style. So if you have a bow and arrow combo that is working perfectly for you you would put that combo into the calculator. If, according to the calculator, it wasn't a good match, you then would use the form factor to tweak the results until they were right. Then, you would make a note of what your form factor is and can use that when considering other arrow combinations.

wcdurand, May I try to explain? We are bad about taking for granted that others know ever thing. Use the calculator to find your combination to start with, using 0 as your form factor. Then fine tune your bow/arrow combination to your satisfaction. If the calculation was perfect and your bow is tuned great. If you had to adjust point weight or what ever,enter that in the calculator then adjust the form number in the calculator up or down until the calculator agrees with your actual findings. The number that gets it to come out right is your form number for future calculations. Next time enter your form number and you will be spot on. It is a simple way for the calculator to adjust for the little differences in all of our shooting styles/forms. Hope this helps.

Really appreciate everyone!