Guest bowhunter56 Posted November 5, 2005 Report Share Posted November 5, 2005 I see on some bow limbs, actual letoff and effective let off, what's the difference Quote Link to comment Share on other sites More sharing options...
VermontHunter Posted November 5, 2005 Report Share Posted November 5, 2005 Re: Bow letoff question [ QUOTE ] I DONT NOW THE DIFFERECE BUT IF UR OVER 75% I THINK U CANT PUT UR DEER IN THE RECORD BOOK [/ QUOTE ] Sure you can but it will be followed by an asterik ( showing what the letoff was..)..... Quote Link to comment Share on other sites More sharing options...
VermontHunter Posted November 5, 2005 Report Share Posted November 5, 2005 Re: Bow letoff question Oppps forgot to answer the question...sorry.. Here ya go...... If you've ever shot a heavy Recurve or Longbow, you've certainly noticed that it takes a lot of strength and skill. A traditional bow has the most draw weight when the bow is at full draw, so you must aim and release the arrow quickly before you run out of steam or begin to shake. Compound bows are designed to eliminate this problem, offering the shooter more time to aim and release the arrow. In contrast with the traditional bow, the draw weight of the compound bow decreases (sometimes dramatically) at the end of the drawstroke. This is known as Let-Off. Early compound bows featured a 35-50% let-off, a welcome relief. But today it is common for bows to have let-off in excess of 75%. A bow with a 70# draw weight and 80% let-off will require the shooter to hold back only 14 lbs. once the bow reaches full draw. Holding back such a small amount of weight, the shooter has the luxury to take more time aiming and releasing the arrow. Of course, you can have too much of a good thing. There is some concern that a bow can have too much let-off, making the bow feel "sloppy" at full draw. Maintaining some level of resistance at full draw is necessary to keep things in good natural alignment. However, the average archer will find the mid to high let-off bow to be more comfortable to shoot. Advanced archers and back-tension shooters often prefer a little less let-off. The only other disadvantage to a high (over 75%) let-off cam is a small reduction in arrow velocity vs. a lower let-off cam system. All other things being equal, a bow with 65% let-off will shoot faster than a bow with 80% let-off. However, the difference in speed is usually only a few fps. Fortunately, many cams use interchangeable modules which give you the option to easily switch between different available let-offs. Some cam systems, such as the High Country XD Cam, the Bowtech Infinity Cam, the Browning Cyber-Cam, and several others, offer adjustable let-off right on the cam without the need for additional modules. However, there's a bit of a technical snafu here too. Bear with us, this takes a little time to explain. Depending upon how you compute the let-off percentage, you can get two clearly different let-offs for the same bow, the "Effective" and "Actual" let-off. While you're drawing the bow back, friction in the bow's cables, cam bushings, cable slide, etc. adds a little draw weight to the cycle. Unfortunately, the extra energy you used to overcome that friction gets lost when you let the bow back down (or fire the bow). So basically, the bow doesn't put-out as much energy as you put-in. Some of the energy is stolen by friction (hysterisis). Bummer! So it would take more energy to draw the bow all the way back, than it would to hold it while slowly letting it back down from full draw. It's kind of an abstract concept, so imagine if we put a bow in a vice and then drew it back using a rope and winch. Now imagine we also had a spring scale hooked to our winch, so we would know exactly how much pressure was on the rope at all times. If we started drawing back the bow by cranking the winch, and watched the reading on the scale the whole time, the weight would go up and up until the bow reached it's peak weight (about 2/3 of the way back). As we keep cranking on back to full draw, the weight would drop-off as we arrived at the draw cycle's point of let-off (full draw). NOW! If we reverse our winch and slowly let the bow back down, we should expect the scale to read the same, just with the cycle in reverse, right? Nope! As soon as we begin letting the bow back down, all the readings will be slightly less than they were when we drew the bow back. This degradation or loss of effective draw weight due to friction forces is called hysterisis. SO......To compute our percent let-off, all we need to know is the bow's peak weight and it's minimum weight (at full let-off). But when you measure the peak and minimum weight, you'll get slightly different numbers depending on if you're in the process of drawing the bow back or letting down. Here's an example. Let's say you draw the bow back and the peak weight is 60# and the minimum weight at full let-off is 15#. But when you measure while letting the bow down, the peak is only 52# and the minimum at let-off is 13#. If you compute the let-off using either set of figures (15/60 or 13/52) it's easy to compute that at full let-off you're holding back 25% of the peak weight. So this bow must be a 75% let-off bow, right? AH-HA!!!!! Finally!!! Here's where the technical snafu comes in. Some manufacturers play a little trick when computing their let-off percentage. Instead of using the matching set of numbers, they choose the high figure from one test (drawing back) and the low figure from the other test (letting down). And if they use the 60 from one test compared to 13 from the other, the math comes out a little different. If we compute the let-off with 60 vs. 13, we get just over 78% let-off. And since let-off is usually listed in 5% increments, round-up and viola! 80% let-off! So in our example, the bow would have an advertised or "Effective" let-off of 80%, but it's "Actual" let-off would only be 75%. Tricky, eh? And of course, one could argue that the extra 5% really doesn't matter. But if that's the case, why fib about it in the first place? So be aware. You may not be ACTUALLY getting as much let-off as you think. Quote Link to comment Share on other sites More sharing options...
VermontHunter Posted November 5, 2005 Report Share Posted November 5, 2005 Re: Bow letoff question [ QUOTE ] VERMOUNTHUNTER THANKS FOR EXPLAINING THAT TO ME ALSO THAT IS GOOD TO NOW. VERY VERY NICE AND INFORMATIVE SPEECH, THANK U AGAIN WHO U WORK FOR HOYT,MATHEWS ETC. [/ QUOTE ] LOL... NOPE not that smart.... ,, I just love to do research,,, and I get to learn along with you guys with these questions as well... GLAD the info was useful to you as it was for me...Thankyou... And besides I shoot an ALPINE EXTREME... Quote Link to comment Share on other sites More sharing options...
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