How do you?

[wildschwein]

#4730

I was just wondering how you folks come up with the best starting point when you are putting so much wieght on the nose of your carbon arrows?

For example if I were to mount 360 grains on a carbon arrow, and get it to fly well out of my 35# at 28 inch (my draw)longbow (centercut, shoots 40-45# cedars at 29 inches), what spine of carbon would I need? And how would I figure it out for future knowledge?

[Troy Breeding]

#33811

To be honest, when I started it was a guessing game. I knew I wanted heavy point weight so I took acouple shafts of different spines, put the same weight on each shaft and started shooting.

It doesn’t take that much shooting and trimming to quickly find out which shafts will weed themselves out by being too weak.

Since I already knew the 400’s with 175gr up front shot great at 1″ longer than my draw length I was able to weed those out right off the bat because I knew adding another 125grs up front was going to require shortening the shafts too much for me to use.

The 340’s started out like they were going to do the job, but as they started getting close to the same length as my draw I could see they were going to come up short.

I then started working with the 300’s. So far they havn’t let me down. I’ve even put in internial footing to allow me to exceed the standard point weight most can get with standard adpts. and fieldpoints.

One other thing to consider is if the shaft you choose is ever so slightly showing weak when it starts to get close to your draw length is building out the sight window.

I had to do this with my recurve. Since it was cut 3/16″ past center I found that even the 300’s had problems carrying a lot of weight up front. By building out the sight window to 1/8″ before center (and adding interinal footings) I’ve been able to carry as much as 900+grs up front.

Troy

[wildschwein]

#33841

Thanks for the reply Troy.

So it mostly a trail and error thing then. Did you find a rough correlation between grains added and spine lost (example 25 grains causes 5# loss of spine) or did it vary to much to keep track of?

[ChumpMcgee]

#33994

I don’t know if I am the person to be giving advice, but I just ordered some carbons and went with the term 10 grains for each pound the bow is. I have an overall arrow weight of about 500 grains with 125 field point on. I hope that it works or else I just spent 100 bucks for nonworking arrows.

[Troy Breeding]

#34039

Justin,

There’s just so little info on this subject it’s more try and see at this point.

You have to remember, what works for one fellow may or may not work for another. Bows, draw lengths, how much the sight window is cut, even your release makes things change from one shooter to the next.

I never checked the ratio myself. I do know that once you work your way into UEFOC any added weight to the point doesn’t effect the spine as bad as it does in EFOC or FOC.

Troy

[apfarmer]

#44843

Stu Miller’s Dynamic Spine Calculator can be downloaded online for free. This is simply an Excel spreadhseet set up to allow you to put in your arrow and bow details. It compares a given arrow shaft, length, point weight, etc to your bow (including #, draw length, center shot, etc). Use of this program will get you in the ball park initially.

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