Have you ever been in a situation where the bowyer tells you to use +15# with the bow you just bought.  And you want to use carbons but haven't a clue how to tell what +15 means.

Here's a dynamic spine calculator that lets you set up your arrow with the FOC you want and calculate that spine the bowyer was talking about.

I was turned on too this today and spent some time working with it and my bows.  Our Orion curve is a +15 bow.  Meaning that you will find that the dynamic spine is 15#s heavier then the weight onthe side of the bow.

I spent the afternoon working on bareshafting my 45 @ 28" Orion recurve. I decided to try a string with less mass. And notice that my arrows that were tuned were now flying a little weak.

So out came the bareshaft. Ended up having to drop my point weight from 200 to 160. This gave me a dynamic spined arrow of 60#. After we were done I was working with the dynamic spine calculator and ran some 2016 shafts. Ended up with a 29" arrow with 125 gr point and 60# dynamic spine. Took a 2016 bare shaft out and shot the 3 D course at the house. I was holding kill zones out to 25 yds.

So now I have two arrows that shoot the same out of the same bow and the means to design many more combos.

Here's the download link to the calculator. It's pretty easy too use and seems to be dang accurate.

 http://briefcase.yahoo.com/bc/hkg3sg1@sbcglobal.net/vwp2?.tok=bceRJecBj15UbCko&.dir=/Public&.dnm=Dynamic+Spine+Calculator+Rev1.xls&.src=bc  


Mike

This is great!

I agree with Focusource. Sure is easier than hunting through a chart and guessing about various factors.

From a few test calculations I've done the result seem to be quite good.

awesome but it showed me that i cut my two dozen arrows a half inch to short.if i had'nt they would of have been within 0.2 bummer

Wingnut,
can you tell who the author of the calculator is and or its source?

I just played a little with it, using numbers for alums I have every parts specs in mind - and it was quite a bit off as far as total mass goes. It was more accurate though, when I added the weight of the insert to the weight of the actual point. This is not mentioned per se in the manual but is maybe intended this way?!

Yes you have to add in insert weight and nock adapters ect if you use them.It is very close if you enter everything right.I havw tried it with several combos of bows and arrows I shoot and it works for all of them.A great tool for guys that want to play with the heavy points,inserts and footing on there arrows.Nothing can be perfect for everyone because we all have that unknow factor that we can't add it.Us and the way we shoot.

Yep I figured the adapters and inserts in because they have such a large variance.

The other thing I recomend is get the arrow you shoot the best and that bareshafts great.  Use it as your dynamic spine standard for that bow.  Now play away.

Like I said, my 45 @ 28 bow likes 60# dynamic spine.


Mike

QuoteOriginally posted by Falk:
Wingnut,
can you tell who the author of the calculator is and or its source?

I just played a little with it, using numbers for alums I have every parts specs in mind - and it was quite a bit off as far as total mass goes. It was more accurate though, when I added the weight of the insert to the weight of the actual point. This is not mentioned per se in the manual but is maybe intended this way?!

I think Stu Miller on the wall.

I'm not sure on the author.  Rusty sent me the link yesterday morning.

Mike

I can't open it

You have to download it and then open it in Excell.

Yep Stu is the author from what I've been told.  He has it out for free download.

Mike

Is the center cut + xx distance past center or less than center? Does that make any sense to anybody?

QuoteOriginally posted by Andy Diggs:
Is the center cut + xx distance past center or less than center? Does that make any sense to anybody?

The number is the distance out from center.  If it is cut past center then you need to enter - . If you get access and scroll down you can read all the variables and instructions for use.  I have been playing with it as I tune some arrows to my new bow.  I am working my way down to the calculator numbers to see how it works out.

Thanks. I should have read the instructions.

Thanks Mike    

This is a cool tool. question--how do I find the amo static spine of the arrow dynamics?? does anyone know ?? thanks

good stuff!

What number should I use for the AMO static spine on a CX Heritage 250.  The spine is listed at .373 on carbon express' website.  I've tried everything I can think of and can't get results that make sense.

I believe the static spine for the CX 250 is 84#.

You can divide 31.5 by .373 to get the spine weight. You can do this with any deflection. Butchie is right on of course!