3Rivers Dynamic Spine Calculator ?? UPDATED

[DHOWARD]

Have you used this and how accurate did it work for you?  Did it prove to show your arrows weak or stiff with your current setup?

Both bows are setup with the following:

Thunderchild:
GT Nugent 500 Blems
30"
100gr. Insert
100gr. Point
3) 5" Feathers

Bob Lee:
GT Nugent 500 Blems
30"
13gr. Insert
125gr. Point
3) 5" Feathers


Results:

     
Big Jim Thunderchild =

3River Results:
 

Arrow Setup Total Weight:
 

Chronograph:
 

Results:

     
Bob Lee =


3River Results:
 

Arrow Setup Total Weight:
 

Chronograph:
 

Congratulations to 3Rivers for having a great product to assist with arrow setup.

Overall I wish I had more total weight and FOC with my Bob Lee but both bows shoot great.

[meatCKR]

I have used it a lot.  It has always gotten me close.  Carbons seem to show just a tad stiffer than what the calculator says but it's pretty close.

Steve

[Haydenj7]

I have a big Jim buffalo 49@28, but I draw 29.
The dynamic spine calc was spot on for me.
Axis trads 400 spine cut to 30inches Carbon to carbon. 2inch 2018 footing, 50gr insert, 200gr tip, 9 inch wrap 3x5 shield cut. From memory it works out to about 60 on the calc which put bow and arrow within 1-2 or each other. Arrows weigh 615gr. I think flying around 170ish. I use the blue hot melt to hold it all together.

A buddy of mine shoots the exact identical setup drawing 53@28 out of his bow. Both came out the same on the calc.

I use the Stu Miller calculator, which is basically the same thing. It was never all that close for me till the Personal Form Factor was added. Now, with the PFF set for me, It always gets me pretty close to what I need.

Bisch

[AZ_Longbow]

Never had it work right. To many variables.

[M60gunner]

Funny you should ask. Until the other day I usually had to "work" with the numbers to see what would get me into the park. But I wanted to see how close I was with a setup I tried from my Bear TD. I had less than a pound difference between bow and arrow, I quit there. So now I am off to get the makin's for another doz or two.

[Bobaru]

It's worked well for all my recurves with the exception of my Blacktail Elite.  With my blacktail, even the form factor doesn't provide enough adjustment for me.  However, I tune my arrow to the Blacktail, then jury rig the side plate with an intentionally false number to match up.

Why do this?  Simple.  Once I've got one arrow figured to my bow, I can figure any other arrow for my bow.

I have Stu's calculator downloaded to my computer and use it continually.  

I even fiddle with the weight per inch if I added a weight tube.  And, I have added momentum to the other calculations results that Stu had.  

Finally, I save my results from each bow, so that a couple years later, I can go back and figure how to get good tune without having to reinvent the wheel.

Terrific tool.  Wouldn't want to be without it.

[Msturm]

Bisch told me about the personal form factor on a post I had with a similar question. after I got that dialed in it is pretty spot on.  also be very accurate with your strike plate measurement. that rchanges things a quite a bit.

[Ontario Longbow]

I found it bang on for all my bows from an ACS to a Hill. Perfect arrow

[Ontario Longbow]

I found it bang on for all my bows from an ACS to a Hill. Perfect arrow

I tried it for wood shafts and got a wacko negative number, I am not sure what I did wrong.  On my PC the Stu Miller chart agrred with me as long as I added a 6 for the pff.  On this imac the Stu Miller uses a completely different program and is a pain.

[M60gunner]

OK, I do not understand the form factor thing. Is this a "fudge factor" to make up for sloppy shooting form? Or?

[COMPOUNDLESS IN CONCRETE]

If your bow is listed in the drop down menu, it's much more accurate than if you use generic recurve or generic longbow.  If you enter your exact draw length and the exact draw weight of the bow at your draw length, in my experience it will be either dead on or very close.  When I bought my new long bow, after running several different arrow setups through the calculator, I found that with full length 2216's, the dynamic spine of the arrow and the dynamic spine of the bow were exactly the same.  When I got the arrows built, bare shafts and fletched shafts were grouping together out to 30 yards with a few nocking point adjustments.  I tested broadheads and they were hitting right with field points out to 30.  

So in a nutshell, the more accurate the info is that you enter, the more accurate the calculator will be.

[DHOWARD]

TTT

Results included with Photos.