Let-Off Question

[tremolo]

hey guys just wondering if let off on a bow has anything to do with speed.
will a bow that is set at 65% let off shoot faster then if the same bow was adjusted to 80% let off? If so about how much faster will it shoot?

thanks vince

[Dairy King]

65% will shoot faster, but Im not sure how much faster. I doubt its enough that you have to change your pins any.

[Arthur P]

It's very possible to get an 80% letoff that is faster than a 65% letoff, but the cams would have different force draw curves and the bows themselves would have different efficiency ratings. Assuming the two cams you're comparing have identical force draw curves except for the letoff, and identical efficiencies, the lower letoff would store more energy. The bow would have more stored energy to released into the arrow. More energy going into the arrow = more speed. Generally not more than 2-5 fps though.

[Rangeball]

In my experience it also depends on if let off adjustments affect draw length or not.

My 65% let off module is about 1/4" less draw length than my 80%. Basically, they just machined off the valley.

Due to this, the stored energy of both mods is identical, as verified by my chrony.

[KBacon]

Rangeball.. I agree with you on that. Take the Bowtech Infinity cam for instance. You adjust the letoff by adjusting the draw stop.. If you set it for 80% letoff.. the drawlength is a bit longer than the 65% setting.. and when the string is released.. the cam must spin past the 65% setting. I never tested to see if the 80% setting was actually faster or the same as the 65% setting.