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.
The deciding factor is arrow flight, numbers and calculators are only guides, arrow flight tells the story
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.
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.
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.
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.
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
QuoteOriginally 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.
If you are getting good arrow flight I would stick with the setup. It is better to be over spined than under.