# 65% letoff Vs 80% letoff and the effect on speed?



## petev (Jun 7, 2008)

I don't think you will see much difference in speed with the newer bows. If you look at the draw force curves on the newer bows (especially the speed bows), they drop into the valley fairly quickly. So the difference in the area under the curve (energy stored during draw) is very small between 65% and 80% let off. I certainly don't think it's worth the time twisting strings/cables.

~petev


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## A Mess (May 21, 2005)

simple math and physics.

If you achieve the 65% letoff by moving a draw stop, you shorten draw length, and LOOSE speed

If you have two cam systems that yield the exact same draw length, then 65% letoff has higher holding weight (than one with 80%), and therefore more speed.

More draw weight means more speed
More draw length means more speed

(all else being equal)


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## swwiff (Oct 9, 2008)

A Mess said:


> *simple math and physics.*
> 
> If you achieve the 65% letoff by moving a draw stop, you shorten draw length, and LOOSE speed
> 
> ...


Well that's what made me start this thread.


I would think higher draw wt for a longer percentage of the stroke of the string would also equate to significant gains as well.

I'm shooting a tribute so I'll use the binary cams for example. 

I built a draw board and have used it to time the bow so that the cable stops on the cams just kiss the cables and set the ATA,BT to factory specs.

My thinking is that with this system let off is dependent on where the cam rotation stops, therefore I can set my letoff to 65% with the hard stop (shortens draw), then re set the timing and draw length on the bow by untwisting the cables such that again the cable stops just kiss the cables and the draw length , ATA and brace ht are back where they should be.

Now if this is sound logic, (and it may not be), what would kind of efficiency can be achieved by a compound with zero let off?

100% pull all the way back to the wall on say an Airborn, Gt500, Firecat or whichever speed bow you prefer. Is it even possible?

Now I wouldn't want to pull a 70lb bow this way, but say a 50lb max bow.

Just curious .
SWWIFF


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