Dynamic Spine Calculator

[JSimon]

I was just wondering if those that have used the dynamic spine calculator have found it to be pretty accurate?

I plugged my numbers in (CE250's, 31.7" long, 225grain point weight) and it gives me a dynamic spine of 52 lb. But, when I plug in my bow info (50 lb @ 28", 29.7" draw, fast flight) I get 72lb. My shelf is cut 5/16" past center and with the Bear Weatherest on, it looks like it is around 1/8" past center, maybe more.

I've been getting a lot of wear on my rest and some feather contact, and a few people suggested that my arrows were two stiff. According to the calculator, they are quite a bit too weak. I have been getting a weak spine indication when I bare shafted after the rest had a groove worn into it, but I've heard arrows that are too stiff can sometimes give a false weak also. Tapping a toothpick to the rest seemed to help, so maybe the calculator is pretty accurate.

I still need to replace the rest so I'll probably push it out a bit and play around with some different point weights to get it all figured out, but just wondering how much I can rely on the calculator from everyone else's experience.

[wingnut]

When I run your numbers, I get 50.7 on the arrow and 55.9 on the bow with the weatherrest installed.

Getting a slight weak on bareshaft and a slight weak on the calculator.  And building out the rest helps.  Hmmmm.  .well your shafts are weak.

Easiest way to tell would be to try 200 gr up front and see if they come around.

Mike

[JSimon]

I used 10 grains for the nock end since I use carbon express nocks and arrow wraps. That made the arrows 52.0 lb.

I used -1/8" for the center cut since my bow is cut 5/6" past center (-5/16"). With the Weatherest on, it still does not bring it out to zero. So, using -1/8", I get 72.9 lb for my bow setup.

It looks like moving the rest out is the way to go. I was just confused because I've had people suggest that my arrows should be too stiff.

[wingnut]

your correct.  I was using 1/8" outside of center not inside.

Heck take the heavy pts off and put 125 in and give it a go. You'll know right away if it's the right direction.

Mike

[shootarealbow]

I know that it has been posted before but
where do I find a dynamic spine calculator

[JSimon]

Originally posted by wingnut:
your correct.  I was using 1/8" outside of center not inside.

Heck take the heavy pts off and put 125 in and give it a go. You'll know right away if it's the right direction.

Mike

Yeah, I'll have to get some lighter points, maybe one of the test kits with various weights to keep around. I have 100 grain inserts glued in already and all I have right now are 125 grain field points and broadheads. I appreciate the replys

[wingnut]

email me and I'll send a copy to you.

Mike