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Main Boards => The Shooters FORM Board => Topic started by: toolmaker on July 28, 2010, 06:16:00 PM

Title: Stu Miller's spine calculator
Post by: toolmaker on July 28, 2010, 06:16:00 PM
Just got my arrows properly spined.  Wow!  I didn't believe spine was the issue because my arrows were coming off the shelf dart straight, left to right, but I couldn't tune out the porpoising.  The best I could do was a 3/4- 1" tear. almost straight up and down.  Normal nock point adjustments just made it worse.  I softened up the spine with heavier heads after checking my setup against Stu Miller's spine calculator.  Problem solved.  

 
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Title: Re: Stu Miller's spine calculator
Post by: Old York on August 09, 2010, 09:03:00 AM
Now that is very interesting!

Solving a  porpoising  problem by changing dynamic spine. I take it you were shooting through paper?
If so, what distance? What kind of arrow shafts? Were they fletched? Bare? Split or 3-under? Off the shelf or elevated rest? More details please! Thanks
Title: Re: Stu Miller's spine calculator
Post by: House on August 10, 2010, 07:55:00 PM
How much of a cant were you shooting with?

Travis
Title: Re: Stu Miller's spine calculator
Post by: toolmaker on August 11, 2010, 08:36:00 PM
Yeah, I didn't believe it either.  After adding fifty grains to my arrow heads I am now getting about a half inch tear straight up and down, with almost nothing left to right.  My knocking point is about 5/8 above square.  I shoot three under with about a fifteen degree cant.  The arrows are 2216.  I was not bare shafting, and my paper screen was about 6 ft away.