HELP! - Spine question

[TSchirm]

I am newly back to trad archery and am wondering how you determine the spine of an arrow of a certain length.  I am wondering about 2117's cut to 27 1/2" BOP.  Thanks for any help.

[TSchirm]

TTT

[Shaun]

Easton has a spine chart for their shafting. Maybe someone will post the link or you can use a search engine to find it.

Spine is "relative" and only a starting point from which you will need to tune for proper arrow flight. In general, a 2117 cut that short is going to be pretty stiff (high spine) and you will need a stout bow or heavy point to get clean flight.

With aluminum, I usually start with the bow and point weight and a full length shaft. Then cut 1/4" off at a time and test until it flies right. Or, try different points weights on the fixed length shaft until if flies.

[Bowferd]

TShirm, I don't know the answer but would think that at 27 1/2 they shouldn't be much heavier spined than at 28. The 2117 is still a pretty heavy spine that would compare to a wood arrow in the 75-80# range and a carbon in around 400 spine.
I'm thinking if you shoot a bow in the 60-80# range they may work depending on your actual draw and point weight used.
I used to shoot them out of 55# longbows but they were left longer.
One of the aluminum gurus will come around and give you a much better analysis.

[metsastaja]

I just ran that arrow through Stu Miller Dynamic spine calculator. using 125 bh 100 g insert 4"feather the spine came out at about 74.6


  Calculator download