Pinwheel et al, a word problem if you're up to it

[Rangeball]

Suppose a guy wants to shoot an finished arrow weighing 275 grains and get most speed safely possible from his bow. His draw length is 28".

What is the minimum poundage he should shoot? And if it is between the standard limb poundages of 70, 60 and 50, such as say 55#, does the decreased efficiency of the bow (because the limbs aren't tightened to their maximum) factor into the equation at all?

And if you're still with me, assume the bow has an achievable IBO of 318 and only a standard brass nock on the string, what would you suspect the fps to be for the 275 grain arrow shot from the minimum poundage you came up with?

I have too much time on my hands

If the answer is 60#, never mind, I think I figured it out.

Ok, so because I went off half cocked and posted this before doing my own math and figuring out it was a stupid question, let's change it

Assume two identical bows rated at 318 IBO. One has 60# limbs set at 60#, the other 70# limbs backed down to 60#. Each is set at a 28" draw length. How much difference in speed would you assume there would be when shooting the same arrow, of say 275 grain finished weight? Would you expect the 70# limb bow to be considerably louder than the 60# limb bow?

Edited by - Rangeball on 09/09/2002 15:53:47

Edited by - Rangeball on 09/09/2002 16:42:54

[Pinwheel 12]

The 70lb bow would be "looser" by being backed down to 60lbs, and the limbs would lose alot of efficiency due to:

1) Lesser travel of the limbtips at the given draw-weight of 60lbs instead of the 70.


2) The additional mass weight that the 70lb limbs have over the 60, (they will be thicker and heavier to take the extra poundage, of course)


The exact amount depends upon each individual configuration, cam efficiency, ATA, Brace, and overall geometry of each setup. Very hard to pinpoint unless you get an overall speed from one setup, then deduct or add mass weight and efficiency levels of the greater or lesser limbtip travel and mass weight of the opposing limbs and their relative differentials.

You're absolutely right, you have too much time on your hands my friend!<img src=icon_smile_wink.gif border=0 align=middle> Shouldn't you be out flying broadheads and comparing them? LOL.

I apologize for only giving this a half-hearted answer, but it is my busiest time of year, and the old &quot;noggin&quot; is overloaded! <img src=icon_smile_shock.gif border=0 align=middle> <img src=icon_smile_wink.gif border=0 align=middle> Good shooting, Pinwheel 12