Spine Calculators vs Real World Shooting

Mud_Slide_Slim · January 13, 2014, 05:52:00 PM

Hello Gang! First, let me say how much I enjoy this forum and the way everyone shares their knowledge. I have lurked for quite a while; absorbing as much info as I can and have learned quite a bit...and I thank you. I am trying to grasp how arrow spine works and have been playing around with a spine calculator. I guess my question is how do you shoot heavier heads and keep everything spined correctly or are most of you not too concerned with what the calculator says?

For example..I am shooting a Bear AuSable, 64", 60# @ 28" and I draw 30". I am shooting Heritage 250 cut to 31", 4x4 feathers and standard inserts with a 16 strand D97 flemish twist string. With this setup the calculator suggests a 125gr point. Which fly great, but what if I want a heavier point with more FOC? Do I need a new arrow setup?

I have tried heavier points which makes the bow quieter, but I can see where the arrow leaves the bow with a bit of fish tailing. I'd like a heavier FOC with arrows that fly like darts...suggestions are welcome. Thanks.

Manitoba Stickflinger · January 13, 2014, 05:57:00 PM

Yep...you'll need a stiffer arrow to handle the point weight. Since you draw to 30"s then the bow is more like #66....plus a heavy point you'll need a pretty stiff arrow.

Onehair · January 13, 2014, 06:00:00 PM

That's the beauty of the spine calculator. Once you know the bows numbers you build what ever arrow set up you like, just hit that number. Heavy head, heavy spine.

Submarinokotbw · January 13, 2014, 06:11:00 PM

Are you using stu miller's dynamic spine calculator? I find that one is the best. It seems to do a good job compensating for a lot of different factors, and has been really accurate for me. Google it.

longbow fanatic 1 · January 13, 2014, 06:18:00 PM

Ive used Stu's calculator and have found it to be accurate and effective in shaft selection and head weight.

Mud_Slide_Slim · January 13, 2014, 06:27:00 PM

Thanks for the replies. I was using 3 Rivers but will try Stu's to see how close they are.

Bowwild · January 13, 2014, 06:41:00 PM

I rate Stu's Calculator one of the greatest new tools in archery for me. I don't start setting up any new bow or change in arrow dynamics without gaming with the calculator.

I can vary a carbon shaft from 600, 500 or 400 spine by simply varying the different weights of broadheads and inserts. Usually I'm at the 500's.

TxAg · January 13, 2014, 06:46:00 PM

QuoteOriginally posted by longbow fanatic 1:
Ive used Stu's calculator and have found it to be accurate and effective in shaft selection and head weight.

Same here

January 13, 2014, 07:01:00 PM

I have found that Stu's calculator can be a bit off. You need to enter a bow and arrow setup into the calculator that you know is right (by other tuning methods) and then set the "personal form facor" to make them match.

Once that is done, you can enter just about any other arrow and come out with a result that is real close to what you need.

As far as changing point weight goes, you will need to change the shaft length to make the spine stay correct. If you go up in point weight, you will need to shorten the shaft length and if you go down in point weight you will need to lengthen the shaft length.

Bisch

M60gunner · January 13, 2014, 07:21:00 PM

Stu's calculator is a great tool. It does give me some answers that surprise me once in awhile.
I just wish it would work on my I pad and I phone. I am not allowed to shoot in my backyard and there is no "hot spot" at the range.

damascusdave · January 13, 2014, 08:54:00 PM

If you look at the top of the 3 Rivers calculator you will see it gives credit to Stu Miller...many seem to miss the notation near the bottom about a personal form factor...like any tool it needs to be used with discretion...the 3 Rivers version works with my Android tablet

DDave

TxAg · January 13, 2014, 09:35:00 PM

QuoteOriginally posted by M60gunner:
Stu's calculator is a great tool. It does give me some answers that surprise me once in awhile.
I just wish it would work on my I pad and I phone. I am not allowed to shoot in my backyard and there is no "hot spot" at the range.

Post above mentioned it, but you can use the 3Rivers site to take advantage of the calculator on an apple device

GrisMunkyNinja · January 13, 2014, 11:29:00 PM

Not perfect but a lot better than those charts.

Friend · January 14, 2014, 01:19:00 AM

You may consider giving a 200 gn point a go at your current 31" arrow length.

Provided the 200 gn point was to work, there would be a significant increase in FOC, yet not enough to improve penetration.

A viable option may be:
Victory HV300...~31"s...100 gn insert...225 gn pt...~568 total..~27% EFOC

threeunder · January 14, 2014, 06:47:00 AM

Friend is onto something. I've spent a lot of time recently shooting the V Force HV. This is the first time I've done any shooting with a setup that was EFOC. All I can say is wow!

threeunder · January 14, 2014, 06:51:00 AM

Oh! Forgot to mention, I'm a Stu Miller calculator junkie. As said above, get your personal form factor adjusted and it is stunningly accurate (for me at least).

January 14, 2014, 12:13:00 PM

The personal form number has always had me a bit confused. Using aluminum arrows, when having someone to watch to make sure that I am really paying attention to my own form and then applying the Miller formula, I find that my pf number is different with different bows and it does not match the spine requirements in the listed generic bows. If I were to use one bow that I have as my standard, my pf number would be a minus 4, but on another bow it would be a plus 8, and that is adding the center shot variance accurately as well. One other minor point, my 1918 aluminums do not match the stated weight on the Miller chart. My grain scales are accurate. Still, it is a fun thing to play with.

JamesKerr · January 14, 2014, 12:19:00 PM

It sounds like your arrow setup is really shooting good and sounds right to me as far as having the right spined arrow for the bow. If you wanted to move up in point weight the only way you could do it with your draw weight and draw length would be to go to a 300 spine shaft or the CX Heritage 350's.

Mud_Slide_Slim · January 14, 2014, 04:14:00 PM

I appreciate all the responses. I will be playing around a bit more with the calculator too see what I can come up with...this is all new to me. The learning curve is steep as I have absent from traditional archery for about 12 years and now returning to it. I forgot how much I enjoy shooting!

With regards to the bow I am shooting...a buddy of mine is letting me borrow it as he prefers his compound. So, admittedly I will say, I believe I am a little over-bowed. I believe I should be somewhere in the low 50's lb range for real comfortable shooting. I shoot til I am almost exhausted and my groupings really spread out...then I know I've shot too long. But, I do enjoy it so much! Thanks again for all the advice.

Friend · January 14, 2014, 04:45:00 PM

Approximately 17#s under spine is working quite well for me on front loaded carbons.

Note: have successfully tuned EFOC and Ultra EFOC arrows utilizing Carbon Express, Beman, Gold Tip and Victory....did not maintain records of the AD Trads.

Have discussed the phenomena with Stu in the past. He is quite aware of it, yet is unable to explain this occurrence.