stu miller: 100g insert + external footing

[boznarras]

I just got the Stu Miller program downloaded today and am using it for the first time. I copied the recent thread with new instructions and am using those.

All seems clear except for the parts (box 5) where you enter for footings weight and length, which is also a correction area for long & heavy inserts which would normally be in box 4.

Specs for me:
My arrow is a GT5575, BOP 29.75, 3x5 fletch, 175g point. I have a wrap and the standard GT nock, which I guessed to be 20g together.
I am using both a 100g insert and a 1 inch 2216 (2216 are 12gpi)footing. The 100g. insert is 1.22inch internal with a .22inch external shoulder.
The bow is a Predator classic, 59@28, my draw length is 28.75, SBD 8 strand, 1/16" sealskin strikeplate.
Okay then:
The instructions say to subtract 0.9" from the internal part of the insert and put that in the footing length box, and then put the insert weight in the footing weight box, and shows leaving insert weight box 4 at zero. This example assumes no external footing. I would come out with 1.22-0.9=.32, and 100grains.

If there is an external footing with a standard insert, I see I put in box 5 values for the footing length and weight. The example assumes there is a standard length insert. I would come out with 1.0inch and 12grains this time, and put 100g in box 4 for insert weight.

There is not a clear instruction (to me anyway) about what to do when I have both a long heavy insert and an external footing. Can somebody tell me what to do here?

This set up is shooting real well for me but works out to be way too low spined (about 30 lbs off)with the 175g point, no matter how I massage the numbers for the insert and footing, or the form factor correction. So I am curious to see if I am doing the calculator right or not. I can see it is a great tool, I want to learn how to use it correctly.
Thanks for any advice you can give.

Walt

[metsastaja]

Your numbers are correct before getting into the footing question. The arrow is under spined for the bow even though it shoots well for you.  I think if you did a bareshaft test you would see under spine.

For now don't mess with the form factor.  Most of us can leave it a 0. The insert shoulder becomes part of the BOP so do not worry about it.

In the case of "double footing" put yes in the box. If footing is greater then .5 put in the total length and the total weight of the footing.  

If you want more details you can email Stu direct.

STUART MILLER [email protected]

[AKCrazyhorse]

I asked stu this same exact question about a week ago. Would it depend in the particulr arrow? I ask because shooting an axis shaft with the 100 grain Insert and a 2 " 2016 external footing, weighing 20 grains... This is what I was told: " enter 100 for the insert, enter yes in the firing box, 1.1 in the length ( 2" - .9") and 20 grains fir the weight. Hope this helps.

[boznarras]

Thanks for the help, Les. Sounds like I was not too far off in understanding the program.
 
I have some 30" GT7595s that work out almost perfect with the 100g insert and a 125g point,if I am figuring it right; only 0.3 lbs difference between the bow and the arrow values. And I will still have 17.5%FOC.
 
I will give that a try...should be fun to compare.

Curious, do folks who shoot EFOC often go underspined to do it? I know good flight trumps EFOC, I just wonder if it often requires choosing to ignore this calculator's recommendations to get EFOC? Some of the arrow set ups I have seen described would be interesting to cook thru the calculator now...

[boznarras]

AKCrazyhorse,
Now that I read your post I see I forgot to subtract the 0.9 on the footing in my new arrow set up. I can redo the footings to 2" instead of 1" and get close again....or something.
Well it is easier to do it on the computer than in the shop.
I bet in Fairbanks your arrows are good and stiff right now, along with everything else.
Thanks,
Walt

[metsastaja]

I know of one other guy that has some arrows that are "off the chart" regarding spine by about 30# due to heavy front end loading and they fly great too.

Fun thing to try would be to find a bow that matched the spine and see how the arrow shot .

[boznarras]

Originally posted by metsastaja:


....Fun thing to try would be to find a bow that matched the spine and see how the arrow shot .....

I might need your help selling this idea to my wife, Les. But I like the way you think.