If I have a carbon arrow that is tuned for a certain bow and that arrow is a few inches longer so that it tunes with a certain tip weight and I want to make the arrow an inch shorter, is there a formula that would show you how much more weight I would need to get the same tune? I could just cut an arrow and then just keep adding weight until I get it back in tune but I don't want to cut one and find out that I need an extra 300 gr. to get it to fly straight. Any idea?

What shaft/spine and point weight are working for you right now?

600 spine 30" with 145 gr points from a 40# recurve. It is kind of a hypothetical question though. If I wanted to use the same arrow from a 45# bow with the same tips I know that I could just cut the length until they tuned properly. I just thought that there may be some info. on how much stiffer the arrow would be at one inch shorter and then how much weight would be needed to overcome that.

C-

Ball park: 2" of length = 100 grains of point weight (or -50 grains of tail weight) = 10# of dynamic spine.

Viper out.

Candyman, what inserts are you using with those 145 grain points? Basic aluminum's that come in the pack, or ? Just my opinion, and others can disagree, I don't care. It seems carbon reacts VERY quickly, so you can get away with adding more weight on the nose of a carbon before affecting flight. As an example I have shot 600 spine GoldTip traditionals, with 100 grain brass inserts and 145 grain points out of the same 50@28 (I have a solid 27" Draw) Grizzly and a 500 Spine GoldTip Traditional only adding 1" to the length. Viper's formula may be accurate. I do not know. BUT I know what I have shot and watched in flight.

-Bones

Thanks. That's what I needed.

That's why I asked....

I ran it through Stu's calculator and (as usual!) Tony is dead- on....

According to Stu, the arrow should pick up #5-#6 if you cut it an inch, and you can get it back down to its original spine by bumping up to a 175 gr point.

Only thing not to like is that you end up with a slightly higher GPP number for the lighter bow, so it'll knock your velocity down a touch.

But if you're good enough to have to compensate, there's a good chance that you get all of your arrows for free anyway.... ;)

Too many factors at play to accurately predict. One factor is shaft diameter--- i have found skinnier carbons that move the arrow closer to center a bit more forgiving. Add in another bow ( the 45# bow referenced) and now you have other issues such as a difference in how close to center the bows are cut--- you might find the same arrow combination works in both.

The only way is to tune and go slowly with cutting.

The 3Rivers calculator is just one version of Stu's. Seems like he gave up doing updates.

DDave

Thanks. All good info.

What Stix said above.

Tony, that sound correct for the spine, I'm shooting. But would it be the same for a .800 or .340 shaft?

Bowmania

Todd -

It's a ball park figure, and should be "close enough" for either. But, yes, things like diameter and total weight do factor in, as does bow efficiency as you increase weight. How much of a difference they make, you have to tell me.

Basically, if you look at any spine chart, those numbers add up. T

The full equation is:

0.10" of deflection = 2" of length = 100 grains of point weight (or -50 grains of tail weight) = 10# of dynamic spine.

Viper out.

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