converting draw wt from crossbow to vert bow

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hunter with MS
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converting draw wt from crossbow to vert bow

Post by hunter with MS »

I am trying to figure out how to convert the draw wt from crossbow to vert bow and visa versa . Like if I have a crossbow that is 200 pound draw wt. what is that with a vert bow ?
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XB I GO
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Re: converting draw wt from crossbow to vert bow

Post by XB I GO »

You have to know the FPS and work backwards.
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Species8472
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Re: converting draw wt from crossbow to vert bow

Post by Species8472 »

hunter with MS wrote:
Wed Apr 24, 2019 7:35 am
I am trying to figure out how to convert the draw wt from crossbow to vert bow and visa versa . Like if I have a crossbow that is 200 pound draw wt. what is that with a vert bow ?
You take the draw length you use on vertical bow - say 29 or 30 inches and divide that by the powerstroke on the crosswbow to come up with a factor. So say 30 inch draw on a vertical bow divided by by a powerstroke of 12 inches. That gives you a factor of 2.5. Than you take the 200 lb draw weight of the vertical bow and divide it 2.5 to come up with the equivalent draw weight for the vertical bow. So in this example:

30/12 = 2.5 factor
200 lb/2.5 = 80lb

So a 200 lb crossbow with a 12 inch powerstroke roughly equals an 80 lb vertical with a 30 inch draw length.
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papa bear1
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Re: converting draw wt from crossbow to vert bow

Post by papa bear1 »

Species8472 wrote:
Wed Apr 24, 2019 10:56 pm
hunter with MS wrote:
Wed Apr 24, 2019 7:35 am
I am trying to figure out how to convert the draw wt from crossbow to vert bow and visa versa . Like if I have a crossbow that is 200 pound draw wt. what is that with a vert bow ?
You take the draw length you use on vertical bow - say 29 or 30 inches and divide that by the powerstroke on the crosswbow to come up with a factor. So say 30 inch draw on a vertical bow divided by by a powerstroke of 12 inches. That gives you a factor of 2.5. Than you take the 200 lb draw weight of the vertical bow and divide it 2.5 to come up with the equivalent draw weight for the vertical bow. So in this example:

30/12 = 2.5 factor
200 lb/2.5 = 80lb

So a 200 lb crossbow with a 12 inch powerstroke roughly equals an 80 lb vertical with a 30 inch draw length.

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paulaboutform
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Re: converting draw wt from crossbow to vert bow

Post by paulaboutform »

Brilliant!!! I love it, thanks. :thumbup:

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CBRon
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Re: converting draw wt from crossbow to vert bow

Post by CBRon »

A vertical bow with a draw of 30'' and a 7'' brace hight has a powerstroke of 23''.... I'm mixed up..
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Species8472
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Re: converting draw wt from crossbow to vert bow

Post by Species8472 »

CBRon wrote:
Thu Apr 25, 2019 10:38 am
A vertical bow with a draw of 30'' and a 7'' brace hight has a powerstroke of 23''.... I'm mixed up..
Sorry for the typo. To get the factor use powerstroke/powerstroke or drawlength/drawlength. Otherwise the process is the same.

The one caveat with this methodology is that it assumes that the efficiency of both bows is the same. This is not usually the case. Verticals tend to be 5 to 10% more efficient. The result is the calculated draw weight for the equivalent vertical is overestimated by 5 to 10 lbs.
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XB I GO
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Re: converting draw wt from crossbow to vert bow

Post by XB I GO »

With all due respect Sir, that is not working out for me. Maybe I have the #'s messed up.

My Dad's bow is 28" DL
My Axiom is 14.5 DL
That's 1.93
My Axiom is 175 DW
Divided by 1.93
That's a 90 pound bow?
The Axiom get around 288 FPS. With the same weight arrow my Dad's bow is faster and its 50 DL.
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Species8472
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Re: converting draw wt from crossbow to vert bow

Post by Species8472 »

XB I GO wrote:
Thu Apr 25, 2019 2:58 pm
With all due respect Sir, that is not working out for me. Maybe I have the #'s messed up.

My Dad's bow is 28" DL
My Axiom is 14.5 DL
That's 1.93
My Axiom is 175 DW
Divided by 1.93
That's a 90 pound bow?
The Axiom get around 288 FPS. With the same weight arrow my Dad's bow is faster and its 50 DL.
Is the speed from your dad's bow an actual number from a chrony? Published IBO speeds are usually overstated by 30 or 40 fps once the bow is set up the way the user prefers. If that is an actual chrony speed than your Dad's bow is super efficient.
Never violate a woman, nor harm a child. Do not lie, cheat or steal. These things are for lesser men. Protect the weak against the evil strong. And never allow thoughts of gain to lead you into the pursuit of evil.

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XB I GO
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Re: converting draw wt from crossbow to vert bow

Post by XB I GO »

My Dad's bow is getting 291 FPS. Is it more efficient because it has cams?
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XB I GO
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Re: converting draw wt from crossbow to vert bow

Post by XB I GO »

BTW that is with my chronograph, not the IBO speeds
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Re: converting draw wt from crossbow to vert bow

Post by flightattendant100 »

Species8472 wrote:
Thu Apr 25, 2019 3:19 pm
XB I GO wrote:
Thu Apr 25, 2019 2:58 pm
With all due respect Sir, that is not working out for me. Maybe I have the #'s messed up.

My Dad's bow is 28" DL
My Axiom is 14.5 DL
That's 1.93
My Axiom is 175 DW
Divided by 1.93
That's a 90 pound bow?
The Axiom get around 288 FPS. With the same weight arrow my Dad's bow is faster and its 50 DL.
Is the speed from your dad's bow an actual number from a chrony? Published IBO speeds are usually overstated by 30 or 40 fps once the bow is set up the way the user prefers. If that is an actual chrony speed than your Dad's bow is super efficient.
Joe, you forgot to figure the sine of the hypotenuse. Silly you. It also depends if bow has a flux capacitor. TI C.😎
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