# Any physics nerds in here?



## rehatch (Jan 4, 2017)

Ok, I decided this target season that I am going to drop bow weight in order to focus more on form and accurracy. However, as much as possible, I want to attempt to set my new bow up to shoot at the same speed as my hunting bow so as not to have a major adjustment in brain and muscle memory for aiming between the two bows. In other words, I am trying to set up so both bows shoot the same at the same distances if at all possible. To me, this would require that both bows are shooting at as close to the same speed as possible. 
So, my question for the physics/math nerds out there: if my hunting bow is 58# and shooting at 187 fps, what arrow weight range do I need to be in to have a 43# bow shoot at about 187 fps?
I know most folks on here pay little attention to arrow speed in trad archery, however, I am trying to figure out what arrow to start with that would allow the two bows to shoot as equally as possible.


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## Clipper (Jan 4, 2017)

The general consensus is that trad bows should be shooting arrows that weigh about 10 grains per pound of bow weight.  This will give you close to the same velocity and point of impact provided both bows are of similar design.  Limb length, limb design, and type string(Dacron vs fast flight) will affect arrow velocity as well as the weight of the arrow.

If you are having accuracy problems you are wise to drop down in bow weight.  You will also enjoy shooting much more with the lighter bow and may never go back as high as 58#.  Provided your arrow hits where it is supposed to 43# will kill any animal in GA and 50# will kill an elk.


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## Philbow (Jan 5, 2017)

Divide the weight of your 58# arrow by 58, multiply the result times 43. This will give you a starting point for the 43# arrow. Add or subtract weight until it reaches the 58# bow speed. The problem will be that the 58#bow and the 43# bow will probably not be identical in efficiency/effectiveness (and unless you are very careful you will have a longer draw length with the lighter bow). But this should be fairly close.


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## Todd Cook (Jan 5, 2017)

The 10 grain per pound rule Clipper talked about is usually pretty close. The 43 pound bow with the 10 grain ratio may actually be faster. As draw weight increases, bows tend to become less efficient. It's all about how much of a limbs stored energy it can apply to the arrow in the time it's still attached to the string. You see the same thing with guns. More powder makes the bullet faster but makes the powder to speed ratio less efficient.

Also, you may increase your draw length a little bit with the lighter bow( most people do whether they realize it or not). That will also pick up some speed.


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## Barry Duggan (Jan 5, 2017)

I think your main obstacle might be best I recall you normally shoot a light arrow out your heavy bow, to realize your current velocity, so finding an arrow light enough to give you the same velocity out of a much lighter bow might become a problem.  However, seeing how I am more of a redneck than a physics nerd, I could be wrong. Have fun.


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## Jake Allen (Jan 5, 2017)

I ain't no physics expert, but my 44# set up shooting a 440 grain arrow is every bit of 187 fps, might be a little faster.
My advice, shoot a well tuned bow with a quality limb that returns the string to brace quickly, and efficiently.


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## Mudfeather (Jan 6, 2017)

I think you are way overthinking this thing. I doubt you shoot well enough(or anyone else) to tell a difference at normal killing range of traditional equipment. The type of handle and center shot of the bow will have much more to do with it than speed of the arrow varying ....say 20fps...


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## rehatch (Jan 10, 2017)

Thanks for ya'lls input.  Will be deciding on some arrows soon so I can break the new bow in.  Hopefully I can find a set up that will allow minimal adjustments between the two bows at any distance.  Looking forward to a great 3-D season!


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