SpineDeflection, Wood vs. Carbons

[Stephen Graf]

#61132

You are not missing anything much. The bottom line is that there is no standard system for expressing arrow spine any more.

Back when it was just wood, then the “weight method” was pretty much standard.

When aluminum’s came out, it was “chart time”. I never really got that. Look up your bow weight, cross reference the length you wanted, and then you’d get a selection of possible shafts. Ug.

When Carbons came out, each manufacturer had their own way to determine spine. Now, it’s bubbled down to just listing deflection, or bow weight.

A gold tip 3555 is spined to work with arrows from 35 to 55 lbs.

A Beamon 350 has a deflection of 0.350 inches when put on a spine tester. (how spine testers are calibrated / set up is another an of worms).

Now, most arrows seem to hold to one of these 2 methods.

Is that what you were asking? I hope it helps. I like the way gold tip does it. Keeps it simple.

[Leo Carrisalez]

#62716

and here i thought it would all be standardized. either way i still start off with a full length shaft and the field point id like to shoot. I stop cutting once it flies nice and pretty. lots for me to learn here from all the experience. thanks for the reply.

[David Petersen]

#62779

S. Tex — The problem with all spine ratings, then and now, is that they presuppose a given head weight. That was fine when almost everyone in the universe shot 125, but now that we’re (a growing number of us) are liberated from that antique model, spine means little to nothing … unless we have one of the charts that annoy Steve. 😛 Rather like Ashby’s FOC calculation chart, the ideal spine chart for every shaft model and brand would include bow poundage (which also means less and less these days), arrow length and head weight, to offer a spine or code-number range. I have found out by trial and error that, say, CE Heritage 350s at my draw length will shoot nicely with anything from around 225 to at least 450 up front. Wood shafts for the same 52# longbow with 225-300 up front need 85# spine! While it would not be easy, I’d love to see a standardized method for spinning carbons, so that a meaningful spine chart could be used. I don’t know that there’s any hope for woods … I just spent $60 for a dozen spruce shafts in three different spine rates to determine what I needed for my selfbow, then had to spend that much again for a dozen more shafts once I got it figured out. I guess we should look at it as part of the fun. 😀

[Etter1]

#63723

The other issue with this is that it depends how the bow is cut. I was shocked to see how different arrows reacted between my (cut past center) black widow to my other recurves (cut to center).

Shooting 200 grains up front, my black widow requires a 28″ 5575, while my other bows of similar draw weight are maxed out at 190 grains up front on a 30″ 3555.

I surely wish it were easier to decide. As Dave said…it gets pricey tuning a new bow.

[James Harvey]

#63731

Etter1 wrote: As Dave said…it gets pricey tuning a new bow.

A great resource an organisation like an archery club could develop would be a collection of unfletched shafts of different materials, spines, lengths etc so members could use them for tuning before making a purchase. It’s fun to play around but it’s not necessarily cheap 😕

[parthur]

#21735

I hope this is relevant to the thread, but I am considering building a new set of woodies. I’ve done this before with not so good results, so I am hoping to improve.

I downloaded Stu Miller’s arrow calculator and found that, for my bow, draw length and point weight I need an arrow spined at 55lbs. I plugged in a BOP length of 29.5 inches to get my numbers to add up correctly.

Now for the question- Should I buy cedar shafts spined at 40-45 lbs knowing I am going to cut them back, or how do you guys do that so that they aren’t over spined once cut to length?

[Jason Wesbrock]

#21907

South Texas wrote: and here i thought it would all be standardized.

Actually, arrow spine is very standardized. There is a very specific method by which static spine is determined. For aluminum and carbon shafts, it is the deflection created by hanging a 1.9# weight on the shaft while it’s being supported by two points 28” apart. For wood shafts it’s a 2# weight and supports 26” apart. When a wood shaft is said to spine at 52#, all that means it is has a deflection of .500” (26 divided by .500 equals 52).

The part where things can get confusing is the model designations used by manufacturers. Some like Beman, Easton, and Victory occasionally use the spine deflection as the model number. Beman ICS 340s have a deflection of .340. Victory VAP 600s have a deflection of .600. Others use numbers that may or may not have any real relevance, like Gold Tip 5575s or Carbon Express 150s. Thankfully, I have yet to find a manufacturer that doesn’t have their shaft specs online, so finding their actual spine deflection is simply a matter of a few clicks of the mouse. You can also compare Easton aluminums to carbons the same way. It’s not confusing, but it does occasionally require a little research.

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