Spine question

[JamesKerr]

I shoot a Tomahawk diamond series bow pulling 55@28 it pulls 54 at my 27.5" draw. I was wondering if I may be overspined. I am shooting a Easton Trad Only shaft 340 series cut to 30.25" with a 100 grain brass insert and a 175 grain point. Using O.L. Adcock's tuning method I appear to be in tune but I have a suspecting feeling that I am over spined after reading some post on here.

[bluntman]

The deciding factor is arrow flight, numbers and calculators are only guides, arrow flight tells the story

[JRY309]

A 340 spine is a stiff shaft for a 55# bow,but is they are flying good for you thats what really matters.I shoot a 340 spine on a couple bows,but they are 65# and 70# bows.

[gonefishing600]

There's only one way to find out. Get your self a dozen 200gr, 250gr, and 300gr.. By the time you get to 300gr if your still getting good arrow flight, then your overspined at 175gr.

[JamesKerr]

I had figured based on Easton's spine chart that with a 200 grain point and a dacron string I would need a 400 spine. But I am getting 275 grains total up front with a fastflight string which is suppose to equate to 5 more pounds, plus the 75 extra grains seems to bump me into a 340 spine on their chart.

[Workaholic1]

I tried to follow Easton's chart.  it told me that because I shoot 32 inch arrows, and my bow is 35@28, about 40ish at my draw, i should be using 400 spine arrows (at least I think I read it right).  I don't know what kind of assumptions they use for that chart, but, I found it typically put me a bit stiff.

stu's calculator says that in theory, with what you listed, you are about right.  my opinion:  if it bare shafts good, then you found what you need.

[lil red rooster]

Easton's chart generally will run stiff for traditional bows.  The Tomahawk is cut to center, but with the strike plate you will be about 1/16 or an 1/8 off center.  And that can make a big difference.  That is why longbows will normally need a slightly weaker arrow than a recurve.  The string material will make some difference, but the amount of strands will make more.  There is a bid difference between a 12 strand fast flight and an 18 strand.

I agree with the use of different field points.  When I get a new set of arrows I fletch them up and put different weight on them and throw them all in a quiver and do not pay attention to which one is which.  Takes all the prejudice out of it.  And when 2 arrows hit the center and the rest are right or left, it gives a clear answer.

I would much rather use Stu's spine calculator than Eastons spine chart any day. I have found Stu's calculator to get way closer initially. You have to make sure all the numbers you input are correct but if you do you will most likely have a tunable arrow your first try.

Here is a link to the calculator:
 
 http://heilakka.com/stumiller/

Bisch

[Stumpkiller]

Originally posted by JamesKerr:
 . . . I appear to be in tune but I have a suspecting feeling that I am over spined after reading some post on here.

You're not going to be able to tell if you are tuned by looking at a table or reading posts here.  Look at your arrow flight, better still, have an observer watch, and read the tears in a target paper or the position of nocks relative to the target.

Tables tell you where to start and the rest is determined by your shooting form and the bow/shaft compatability.

If you followed O.L. Adcock's excellent advice and the flight is good you're gold regardless what someone else's table says.

[Earl Jeff]

If you are getting good arrow flight I would stick with the setup. It is better to be over spined than under.