[jbw59]

According to a chart, and the chart is correct, I've shot these arrows before, I'm supposed to have 100grain point on a 28" shaft for it to be spined correctly. Now, this new arrow I'm looking at has a stock length of 29 1/2". The NIB point that is available is only 60 grains.

QUESTION: Will an inch and a half in length compensate for a 40 grain drop in tip weight so that it is spined correctly? Someone out here has had to have put this formula together. You guys are that smart.

If you need to know, these are aluminum shafts at 8.6 grains per inch. Oops, did I just answer my own question?
Thanks

 

[Viper1]

j -

0.05" of deflection (static spine) = 1" of draw length = 50 grains of head weight = 5# of dynamic spine. (all numbers approximate)

Short answer, it should be fine - but all charts have a built in error factor and tuning gets the final say.

Viper1 out.

 

[Bowmania]

What chart is that? I want it. Even Stu's Calculator isn't that accurate. What kind of archery are to doing? I'd never shoot an arrow with that low of an FOC.

Bowmania

 

[BarneySlayer]

It has been suggested to me that Stu's calculator, while it may not predict precisely what will work for you, is very effective, once you know what works, in finding alternatives. I.e., plug in your information, find your dynamic spine, and use that dynamic spine as a target when messing with variables. In your case, enter the arrow information, decrease the point weight ( and remember to account for the insert weight, and then increase the arrow length until you've got what you need. It is unlikely that you'll end up with exactly the same arrow weight. I would guess that it's going to be lighter.

Ultimately, though, I have to agree with Viper and Mr. Mania. Got to try and see.

Also, I have noticed that some components are interchangeable between lines. I.e., the Power flight, Red Line, X-Weave, ICS bow hunters, can all take the same inserts and nocks, so you can do some fine tuning if you want to shift the weight forward or backwards to adjust the spine while keeping the weight biased in a given direction.

You might also be able to find inserts that simply fit the shaft, in which case you can simply try to get closer to the original point weight. I'd try Lancaster and see if they can recommend something.

 

[Sanford]

Tuning check is the ultimate answer, but if playing with the calculator, and using those NIBBS, don't forget to plug-in some for footing effect for those extra long shanks on those NIBBS. Your FOC is probably going to come out to around 6% with that NIBB on aluminum, which is what my 1814's are set up at.

 

[Arrowwood]

The Easton NIBB ("new improved balance bullet") point is designed to give 7% f.o.c, with a few exceptions (8%). They used to sell a "heavy weight" nibb that was 9%.
edit: Like Sanford says, the foc could vary somewhat

I love nibbs. Easy to install, easy to pull, never had one come out that I can remember..

http://www.lancasterarchery.com/media/cms_files/downloads/Target_Comp_2011.pdf

 

[Sanford]

Yeah, it seems that with aluminum, running low FOC was/is more the norm for these points. For my arrow, it's only one point option, so 60gr was it. Shot them for 900 Round, though, and never noticed an issue.

 

[Sanford]

Now, this new arrow I'm looking at has a stock length of 29 1/2". The NIB point that is available is only 60 grains.
Thanks

Here's another issue to consider. That stock length is a variance of 1", so it can come to you 29" or 30". Call LAS and they will measure their stock before shipping.

As example, I had dropped to ~32# on the fingers for my Oly bow and needed X7 Eclipse in 1814 and 30" clicker length. At 30", 60gr NIBB, they tuned in perfect. You might plug in 30" for your calculator as well and order 30" shafts. That's 2" more than your old set up.

 

[Viper1]

Todd -

NIBB points or variants have been around for the better part of 1/2 a century, and provide an FOC of 7- 9% on the arrows they are specified for.
It worked then and works now.
I do recall on Olympic Coach telling his students that FOC just meant Freakin' Over Complicated (or words to that effect).
I kinda go along with that theory.

Viper1 out.

 

[gr4vitas]

I only use charts as a rough estimate, just something to pick the spine of the arrow you want. There are a thousand ways you can setup your arrow for a particular draw weight, you could get a really stiff spine but put a heavy point on (200+ grains) or a lighter spine with a lighter tip etc.

Just get a spine that should be in the range you want, then play with different weighted tips.

I know for my self for example with my bow a .400 spine with 125 grains up front at full length should have been perfect but it was actually a little stiff with those specs according to my bare shafting. Ended up just needed a little heavier head.