Dynamic Spine Calculator issues ???

[Msturm]

Any one else have a set up they shoot pretty well come up way off on 3rivers dynamic spine calculator? I did the little adjustment for form on the bottom and it took +12 to get the set up I bare shaft tuned pretty darn good to come up within the 2# difference.

Current set up:
50lb bear grizzly (newest bow I own)
b50 string. 2 wool silencers
Brace height 8.5
Draw 28.5
3 under

Shooting a traditional only carbon with three 5 in fletch
500 spine
29.5 in
standard alum. insert.
250 grain up front.

Bare shaft tunes real nice out out to 20 yards. Fletched arrows seem to hit where I want them to ...  I guess  if it ain't broke....

[TIM B]

Sounds like you have it tuned.  Check out the thread "tuning help please" as we are talking about the same issues

Just go with the +12 and you will be good. My PFF is -15, which is as far as you can go on the minus side! As long as I have the PFF set at -15, I can put any arrow combo in I want, and the result will be real close to what I need to tune well off my bow.

That's what the PFF is for; to make the calculator "fit" you better.

Bisch

[Arctic Hunter]

It was way off for me too. I think part of it is the difference in string silencers and how they effect the bow. In my experience, cat whiskers don't slow the string down as much as yarn balls. Silencers farther down the string will slow it down and cause your arrow to appear stiffer, and so on.

[Mint]

Yeah, sometimes I think they are off. Stu's calculator works very well with me except when I plug in GT 1535's. Then it is way off for some reason.

[Msturm]

Nice. Thanks guys.   Also thanks for the heads up, Tim B.  I don't mean to beat a dead horse.

[damascusdave]

The calculator is a tool I use for a number of things, but I long ago stopped using it for tuning...after having tuned enough bows one has a pretty good idea what will work...for me the most important factor in dynamic tuning is the string and there is no way Stu could build all the combinations into his calculator

DDave

[lt-m-grow]

I think making this about the "calculator" is wrong.

My first take -without the calculator- is that your setup would be weak.  It is a weak, long shaft,  a lot of weight up front, and a longish draw.  Yet, obviously they work for you so your personal form factor is different...nothing wrong with that.

I personally think the calculator rocks, if for no other reason,  it teaches a lot about how shaft variables can effect spine with change.

[9 Shocks]

Originally posted by Bisch:
Just go with the +12 and you will be good. My PFF is -15, which is as far as you can go on the minus side! As long as I have the PFF set at -15, I can put any arrow combo in I want, and the result will be real close to what I need to tune well off my bow.

That's what the PFF is for; to make the calculator "fit" you better.

Bisch

Me too! -14,-15 is where I'm at!

[Brock]

Stu's Calculator is great but the way you draw bow, your release, your grip...all play a part and that is what makes it important to update your PFF so that you dont have to figure it out every time....well unless you fix your crappy release and pluck like I have been trying to no avail...hahahha

Sounds like you got it figured out and that is exactly how yo are suppose to use it....get you close enough to fine tune and once it is as good as you can get or want....adjust PFF to line it up in calculator and save the profile for next time.

Good luck.

[AkDan]

Welcome to dynamic.    Not static!

[Msturm]

Just for the record, this was not intended to question the validity or reliability of the tool. I was just wondering if it was really abnormal to get numbers like that. Thanks for all the input folks. It has eased my mind.

Thanks.

Sturm

[smokin joe]

Nope, I don't think it is abnormal -- depending on the bow.

However, it is really consistent in that my 50# at 29" R/D bow needs an arrow that is 68-70 pounds dynamic spine. Every shaft that I have built with a 68-70 dynamic spine on the calculator shoots great out of that bow. So, once you find the shaft that shoots, then put its specs through the calculator and if you switch types of shafts you can get your arrow flying right much faster by building it to match the dynamic spine you had before. Thats how I built some heavy aluminum arrows to match the tune of some lighter carbon arrows. It's easy -- that is, if you don't forget what dynamic spine that particular bow likes.