Arrow spine ?

[Mr. Longbeard]

Right now Im shooting a 50lb Bear Kodiak Mag... It doesent say what draw length I get the 50lb at... Im just guessing around 28in... I have around a 28-29in draw so I may be shooting a tad over 50 not sure... I'm shooting 2016 arrows that are 30.5in long with a 125gr head... Do you think this arrow is to light of spine and if so what spine arrow do you recomend??? I was thinking about trying some 2117 arrows...

[Night Wing]

In my opinion, with a long 30.5" arrow, you'd need around a 100 grain point weight because if your draw length is 29", you're pulling around 52# or slightly more. If you want to use a 125 grain point weight, you'd be almost spot on with a 30.5", 2114 aluminum. If you want to use a heavy 2117 at 30.5", it should fly well with a 175 grain point weight. This assumes you've got a 29" draw length. I'm also assuming your bowstring is dacron, not fast flight, your arrows are fletched with three, 5" feathers and you're shooting off the shelf. As you can see, there are lots of variable to take into account.

One variable is draw length. Draw length is very important. With a 28" draw length, you're pulling 50#. The difference of one inch makes a big difference point weight wise with different spined arrows. As an example, with a 28" draw length pulling 50# shooting a 30.5", 2117; you'd need a 205 grain point weight. I suggest you find out "exactly" what your draw length is.

You can play around with this free spine calculator known as the Dynamic Spine Calculator, but all the info put into the 14 boxes has to be "correct". Putting in the wrong info won't give you a tunable arrow. You're looking for a tunable arrow which means you might have to adjust your brace height and/or nock point height. You'll need Microsoft's Excell program to use it since Excell will open the calculator program for you. If you don't have Excell, then download the free Open Office program. Open Office is what I use to open and use the Dynamic Spine Calculator program. Some of the variables I spoke of are in my signature.

http://heilakka.com/stumiller/

http://www.openoffice.org/

[Mr. Longbeard]

WOW... Im sure after reading that, that Im all duked up lol... I see I've got a lot more to know!!!

[makkan]

Spine is one of those things that everyone talks about, but few completely understand. I'll try to provide some basic information and hopefully won't make too many mistakes.
Spine is basically a measure of the stiffness of an arrow shaft. More accurately, it is a measure of the deflection a shaft exhibits when a two pound weight is suspended from the middle of the shaft when the shaft is supported at two points 26 inches apart and the shaft is rotated so that the grain of the wood is vertical. This measurement is generally made with a device called, surprise, a spine tester. It is important that the grain of the shaft be oriented properly since a grained material exhibits different stiffness with and against the grain. Arrow shafts are measured to determine the greatest stiffness and that measurement is across the grain. Note that this is important because it tells you how to orient the fletching on the shaft.
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Internet Marketing Bedford

[LBR]

A spine chart might give you the right spine, or it might just get you in the ball park. There's gobs of variables to consider--bow performance, strings (how they are made, strand count,how heavy the silencers are, etc.), your release, nock fit, etc. etc. etc. Point being, if the chart tells you one thing but the arrow flight tells you something else, go with the arrow flight.