dynamic spine calculator - accurate?

RUTANDSTRUT · June 11, 2009, 12:46:00 PM

how accurate is a dynamic spine calculator? i have two black widow psa im setting up and need to buy arrow!
thnx, ron

snag · June 11, 2009, 12:49:00 PM

I have found it to be very accurate with wood and carbon. It will get you right on or at least in the ball park. What is the poundage of your bow and your draw length. What point weight are you wanting to shoot?

Matty · June 11, 2009, 01:52:00 PM

I was wondering the same thing myself. I did a set up according to it got with in "1". decided to leave the arrow 1" long just in case and so if it was weak I could trim at 1/4" increments down to the 29" I wanted and the arrow flight tests came up STIFF at 30" with bothe bare and fletched arrows...SO I'm skeptical now, I wont give up..

snag · June 11, 2009, 02:01:00 PM

Just like any calculator you have to make sure you put in the right info. or it will be off. That includes the nock weight and on the bow side the shelf location and string material...?

lilbobby · June 11, 2009, 02:17:00 PM

A repeat of what "snag" said, I have found very accurate.

xtrema312 · June 11, 2009, 03:21:00 PM

I found it to be close and a great tool. Almost right on for one bow. I found that really long full length arrow with light point and close to my draw length with high FOC don't quite match up with each other for spine on the calculator.

I would still start long and work down with different point weight to verify bare shaft group shooting as you cut. I am using about a 5# cushion when setting up an arrow then I work down. So far I have been safe with that. It is sure better than cutting little sections off when I need to cut of 2" to even get in the ball park.

There are too many variable to get right on for everyone. There is no input for form, and that is a big one. There is no input for feather variation, wraps, exactly what you have on your string, quiver, bow efficiency, or a lot of other little stuff that can add up. It is best to put in everything you can, and tweak it a little for some of your variables. That should get you close so you can figure what shaft you need to be using. Just being able to see if you can even get close to what you want is a big help I think.

It is great if you have an arrow that works and just want to make some changes. Then you can input the arrow that works and use it for a base.

Oregon Okie · June 11, 2009, 03:27:00 PM

I found it to be way too addictive and I spend too much time playing with it. It has worked pretty well on my bows.

snag · June 11, 2009, 04:43:00 PM

Oregon Okie, maybe it should have a warning on it! "Beware! With frequent use this calculator may become additive!" There's a lot of archery items like this!!!!!!

metsastaja · June 11, 2009, 05:02:00 PM

One of the better tools to come along in a long time and Stu is still working on revisions and fine tuning. I have tuned 4 different recurves.

Even Mikey likes it.

metsastaja · June 11, 2009, 08:15:00 PM

for those interested and with Mr. Miller's permission I set up a permanent home for the Dynamic Spine calculator. It has three versions of the calculator. the rev 6-10-09 is his latest.

DYNAMIC SPINE CALCULATOR DOWNLOAD PAGE
http://www.heilakka.com/dynamic.htm

snag · June 12, 2009, 01:37:00 PM

I'm getting different readings when plugging in figures into the NEW one. Anyone else notice this? I am still going to use the old one because it matches up to my bareshafting results for the Carbon Express Heritage shafts.....? I was getting a difference of 50gr. on tip weight for the same specs on the arrows and bow....?

snag · June 12, 2009, 04:57:00 PM

Stu made some adjustment and it is right on the money once again! Thanks Stu!

metsastaja · June 12, 2009, 09:09:00 PM

Snag was getting the same. There is a new release rev 6-12-09. I am hosting a page and will continue to update as Stu sends me info.

Anyone can download it at Stu Miller Dynamic Spine Calculator

the address is http://www.heilakka.com/stumiller if you want to bookmark it.

June 13, 2009, 12:56:00 AM

As stated above, it will get you real close, if not right on. I have found carbons are the hardest arrows to get tuned just right, I guess because of the wide spine ranges. I can use the calculator and go but some arrows that I know will work. It may still take a little tinkering with length and front end weight, but a lot less headache than starting blind without it.

Bisch