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For every inch of draw length I get how many fps? (Assuming draw specific cams)

For every lb of draw weight I get how many fps?

For every 5grains of arrow weight I get how many fps?

I'm curious. Thank you.

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Joined

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8,359 Posts

For every inch of draw length I get how many fps? (Assuming draw specific cams)

For every lb of draw weight I get how many fps?

For every 5grains of arrow weight I get how many fps?

I'm curious. Thank you.

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3,139 Posts

In my experience those approximates are generally pretty accurate.So...what's the theory here.

For every inch of draw length I get how many fps? (Assuming draw specific cams)

Approximately 10fps per inch of draw length.

For every lb of draw weight I get how many fps?

Approximately 2fps per 1lbs of draw weight.

For every 5grains of arrow weight I get how many fps?

Approximately 1fps per 3 grains of arrow weight.

I'm curious. Thank you.

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8,359 Posts

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8,659 Posts

Not necessarily.

The estimates are general rules of thumb, and not always exact. Take the Hoyt spiral cams for instance, since they are DL specific, and since they do not use modules for the DL they do not loose the estimated 10 fps, as a rule of thumb.

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47,473 Posts

On my spiralled bows I'd say they lose 6-7fps per inch. It's why so many people post speeds that are adjusted to well above IBO.

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here's a calculator for ya. http://backcountrybowhunting.com/articles/calc/

......That is fun to play with, and see how it matches up with real world , but most Hoyt's will be off that chart....I punched in the specs for my Son's CRX 32, and it is off by a large margin...At the charted specs I entered,, it should be 270 f.p.s., but we are getting over 280 f.p.s., and havent tweeked the bow yet....it is pretty close on my new PSE Dominator Pro....But still a few f.p.s. slow....Thanks for the link, that is pretty cool to play with.......Take care!..........Harpermanhere's a calculator for ya. http://backcountrybowhunting.com/articles/calc/

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Start with the IBO numbers. Subtract 30fps for DL, subtract 25-30 for arrow weight over IBO (275 for 55#), and subtract 1fps for every 3gr of weight added to the string. Then subtract 10-29 from that since you're running such a large cam and have it turned down shorter (DL specific cams would save a lot here).

So if the IBO rating is 330fps, you'd be at 255fps if you're lucky.

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Send me an email to [email protected] and I will send you a copy of Excell spreadsheet for calculating bow speed based on IBO rated speed of your bow.

For every inch of draw length I get how many fps? (Assuming draw specific cams)

For every lb of draw weight I get how many fps?

For every 5grains of arrow weight I get how many fps?

I'm curious. Thank you.

Joined

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23,576 Posts

I gained...... Wait on it...... Here it comes..... NOTHING. The bow is much more comfortable but I did not gain any speed. I may bump it up another 1/2 inch this weekend just to see what happens.

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