I'm fiddling with the 'dynamic spine calculator' and am a bit surprised by the results I'm getting.  

I'm plugging in the specs for my Bob Lee Hunter TD (55@29 and 3/16 past center, at least I think it's 3/16 past center) and I'm getting a dynamic spine of 78.1.  Sounds a bit high to me.

I know 2018's will fly fine from this bow, but on the calculator they're not even close ...

Is your bow a longbow or recurve?

recurve ....

The calculator's 3/16 is FROM centershot not PAST centershot....could that be your issue?

If the bow is cut to 3/16 past center then you need to subtract the strike plate thickness. If it is 1/16 then you put on -1/8 if it 1/8 thick then you put in -1/16. Their is always the human factor also

Now im interested!
does that mean if i have a bow that is 1/16 thicker build than the center, i substract the 1/16 of the strike plate and get to pu 0,0 in to the calc?

Forget the riser cut.  It doesn't matter unless you don't have anything on the riser.  If the strike plate material face is 1/16" outside the string center or that much farther away from the riser then the center of the string it is +1/16.  If it is 1/16" inside the center of the string or closer to the riser than the center of the string it is -1/16".  I don't know anything about Bob Lee bows, but -3/16" sounds like a lot cut past center to a strike plate.

From using the calculator, IMO it's darned accurate.

I use a piece of rug rest rather than a leather strike plate  on my Lee TD Hunter, and it's -1/16".  It's 52#@28", I draw 28.8", use FF string, and it has a calculated dynamic draw weight of 69.6.  I built several test arrows based on that draw weight to a calculated spine within 1#, and they shoot beautifully.

Based on that, and assuming you draw at least 28" & use FF, you might well be in the mid 70's, but I agree 78 & change seems high...


The calculator drop down box has both +/- center cut settings, BTW.


Hope that helps...

QuoteOriginally posted by saumensch:
Now im interested!
does that mean if i have a bow that is 1/16 thicker build than the center, i substract the 1/16 of the strike plate and get to pu 0,0 in to the calc?

If your bow is cut past center you subtract side plate thickness if it is cut to center or thicker then you add side plate thickness.

If you bow is cut 1/16' before center and you have a 1/16" side plate you put in 1/8. The main thing is to put in actual center mesurement, dont forget to add or subtract side plate thinkness

Thx guys.  I have a weatherest on the bow I'm monkeying with so I probably have the wrong center shot variable plugged-in.

Overall, I think it is a very accurate tool to use.  I tried it out a few months ago on some new CE carbons for one specific bow. Fletched arrows were spot on.  Bare shafts grouped spot on as well, but were nock right, indicating stiff.  Had some folks tell me to ignore the nock right since they grouped tightly with the fletched shafts.  Fletched up the bare shafts and never looked back.

I've also recommended the calc to another guy and provided my own suggestions.  This guy had been having fits trying to match carbons to his very short draw BW.  He used it and had a bow shop put the arrows together to the calc's specs.  Spot on right out of the box.......another convert!

I was playing with it the other day and put in all the specs including the arrow I found flies best out of my bow. It nailed it, and the amazing thing is it hit the speed to within 3fps!

I think it is more accurate than my form.  It needs a few bad form boxes for me.

Just finished tuning a new to me bow. After deciding on my shaft and point weight went and plugged all the info in. My arrow combo was within .1 of requred spine. Pretty dang close!! 66.4 required and 66.5 the arrow I put together.    

up

I shot a indoor tournament last night and tried a specific arrow and had the best scores ever never shot the arrows before    Went home plugged in the # and I was .5 difference in spine deflection can't get much better than that!
I like thae calc. just so I can play around and fine the best set up with enough FOC to my likeing.

Where can a guy find this calculator?

Here's the link to Stu's page where you can download it.  http://heilakka.com/stumiller/
I, too, think it is pretty darned accurate.
-Z

Thanks alot "z".

Just weighed my components, my is dead nuts.