Originally posted by Rob DiStefano:
imho ... NO "spine calculator" can ever consistently predict a good arrow spine as there are far too many factors involved, starting with the archer and ending with the arrow's flight past the bow's riser.
i know, i know - many of you are gonna chime in and praise these shaft selection systems as they've nailed for you what you consider the perfect shaft spine for a specific bow and its tasks. consider yerself lucky - maybe. you might think otherwise if other shaft brands and spines are tested out. not all arrows and their spine labels are alike.
in my experience with all manner of shaft materials, over the last 60 years of messing with all things trad archery/bowhunting, personal testing trumps computer based "smarts" every time. there simply is no substitute, sorry. yep, there will usually be both monetary and time costs involved.
carbon shafts have a far higher ratio of static to dynamic spine stiffness. this ratio is apparent as all carbon shafts list a very wide range of static spine, typically 15 to 20 pounds - you don't see that with wood, alum, alum hybrid or glass shafting.
that fact alone - the large STATIC spine range - can easily become even wider when DYNAMIC spine is considered. hence, it's very plausible that a 29" 500 static spine carbon arrow with 350 grains up front can fly very well out of a 55# holding weight bow ... or a 45# holding weight bow.
how you shoot a bow, how that bow is set up, all the parameters of the bowstring, and how your arrow is built, will all play MAJOR roles in how any arrow shaft will react upon your release of the bowstring, and how it will subsequently fly.
at best, shaft selection software is a third party tool that might get you into the ballpark for the arrow criteria you might need for a specific bow and task. just don't rule out the benefits of seat-of-the-pants testing. you may be surprised at your results.
Read this...maybe read it two or three times because this is the correct answer. I've never, ever been able to tune a bow with a spine calculator. You have to actually shoot the bow with the arrows you are trying to tune.
I changed the string on my bow and had to start over recently. I had to either reduce point weight or cut the shaft to get them tuned. I like all the FOC I can get and at least 10 grains per pound of draw, so I started cutting. Half an inch later, I was back in tune. Carbons are very touchy that way. On my setup, half an inch in length equated to 50 grains in weight. I don't worry about the length as long as I can draw to full draw without hitting the back of the riser. Preferably, I have just enough length to have the back of the broadhead touch my index finger at full draw, but I can't always make that happen.
Good advice, Rob!
Topic: Dynamic Spine matching bow? (Read 484 times)
