Help with calculating arrow speed/energy
 

I'm trying to figure out the speed and energy that my bow is producing on bowjackson. I would rather toss an arrow through a chronograph, but don't have access to one. Here's my hold ups on figuring out speed.

1) SE/PDF Ratio (~0.5-2)

2) Bow Efficiency in % Is this the let off of the bow? It is rated at 70% let off, but meets the 65% let off requirement for P&Y. What number do I use there?

3) Virtual Mass (grains) Is this arrow weight? It asks for that already, so I figure it must mean something else.

Here's my full set up.

Mathews Q2XL set at 65 pounds with 29" draw length. SL2 cam with 70% let off.
string silencers, loop and peep sight all weighing roughly 15 grains.
Beman ICS 340, 29" with 125 grain tips, total weight of 452.8-454 grains

Thanks in advance

RE: Help with calculating arrow speed/energy
 

Arctic-

I just ran all your info through "The Archery Program" I got the following results:

Speed 246.7 f/s
K.E bow = 61 ft/pnds
K.E @ 20 yards ~ 56 ft pounds

You didn't mention fletches etc so I guessed 4" vanes.

Happy Shooting!



>>>------Tony Virnoche------>>>
>>>---The Archery Program--->>>

RE: Help with calculating arrow speed/energy
 

I use calc speed method 2

Eff 100

se/pdf 1

I gave me the same number is got at the crono.

RE: Help with calculating arrow speed/energy
 

Thanks TAP. Do these numbers factor into a certain type of bow? I know some bows get a lot more speed than others at the same draw length, draw weight and arrow weight.

What makes a Bowtech shoot nearly 300+fps when a similarly set up Mathews would only shoot ~247?

Oh yea, I'm shooting 4" vanes like you presumed.

RE: Help with calculating arrow speed/energy
 

Arctic-

It mostly has to do with draw length, arrow weight and draw weight. Example: That bowtech you mention will not shoot your arrow @ 300 f/s with a draw of 29" and 65 pounds. Depending on the bowtech model it may infact be a little faster than your mathews because they have good BPF numbers in my program. (its an efficiency rating....my own proprietrary thingy)

I hope this answered your question,

Happy Shooting!



>>>------Tony Virnoche------>>>
>>>---The Archery Program--->>>