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Discussion Starter · #1 ·
Was just playing with the "shaft selector" part of my AA program.

I've noticed this before, but never was on the internet at the moment to ask the question.

If all other conditions are the same, spine, weight, length, draw weight and length, etc., etc. Why does a shaft show weaker (softer) if an overdraw is used?

And, by the way, if Perry is looking, what constitutes an overdraw anyway?? How is the length of an overdraw measured? Is it just the distance behind the back of the riser? Or is it from the Berger Button hole, or what??

Curious.

DDD
 

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Because if you had a 30" draw with a 4" overdraw. You use a 26" arrow but the the draw isn't 26". Your storing more energy so you need an arrow stiff enough for the energy stored at 30" rather than 26".
 

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Discussion Starter · #3 ·
Everything is the SAME!!!!

With all due respect Ian, I did say that everything stays the same, arrow length, etc., etc., etc.

The pounds stay the same, the energy stays the same, the ONLY thing that changes is the point where the rest contacts the arrow.

Why does the spine show differently??

DDD
 

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The rest should be your AMO draw length minus 1.75" with no overdraw.

Your arrow spine is used to determine how the arrow is bent when the feathers pass the rest.

As you're moving the rest closer to the string, the arrow has to bend more rapidly (i.e., a higher natural frequency), hence the spine should go up....

I haven't thought about this but am just throwing this out, so don't believe me.

kgk
 

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DDD,

I've always used the distance from the center of the "berger button" hole. This usually corresponds to 1.75" back from the AMO draw length.

Most probably, the reason is that it's what the Easton Charts say is the effect of an overdraw. I know that's a lousy answer, but in looking through the charts, it says to multiply the draw weight by a certain amount for each inch of overdraw...1.03, 1.06, 1.10, 1.17, and 1.25...for 1-5" of od, respectively. (1994 Easton Catalog)

The explanation in the catalog is: "The energy stored in a #70 bow with an overdraw that shoots a 27" arrow will be greater that the energy stored in a #70 bow that is drawn only 27" and shoots the same length arrow(27")." Ovbiously, the assumption is that there is a difference in draw length.

Logically, adding draw weight because an overdraw is attached doesn't make much sense, especially if nothing else in the system changes. It's not like the overdraw is causing the bow to store more energy or something.

That being said, my program, OnTarget!, adjusts (increases) the draw weight as per the Easton Catalog suggests, which resluts in "showing weaker (softer) if an overdraw is used".

If Perry is doing his calculation in the same manner, that would explain what you are seeing.
 
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