effect of let off on performance

[spoiled one]

MNViking's recent thread got me thinking about about what effect the percent let off has on overall performance of a bow. I know what it does for the shooter and accuracy (I think), but what does it do to the speed of the arrow, if anything.

 

[Marc Taylor]

I don't know, but perceived letoff is drastically increased with the use of FOBs. (See thread: Draw weight)

Taylor

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[AKDoug]

Here's a good article that should answer all your questions.. without a single FOB plug

http://www.huntersfriend.com/bowselection.htm

 

[6XLeech]

Shooting from the valley - effects on performance

Shooting from the valley - effects on performance

Good link, AKDoug. The Hunter’s Friend website is worth bookmarking for the information alone. Their explaination of force-draw curves shows the 3 phases of compound bow function. Looks like the effects of letoff are all about the cams?

Under the Cam Aggression section, HF graphs the energies of a round wheel bow (a), medium cam bow (b), and hard cam bow (c). As I understand it, the beauty of hard cam bows is greater stored energy. But as Larry Wise (Tuning Your Compound Bow 4th ed, Target Communications, 2006) says, "...you never get anything for nothing in this sport, and so it is with the cam". Then the HF section on The Valley explains what it’s like to shoot bows with softer vs harder cams – the good and the bad. Generally, harder cams store more energy but have a narrower valley/letoff. The Archery Evolution website, ( http://www.archeryevolution.com/reports.php) has test reports that use these graphs, showing the actual graphs for tested bows.

Wider valleys are more forgiving. Wise explains in some detail the effects/hazards of shooting from different parts of the valley, emphasizing how important it is to shoot from the middle of the valley. If you anchor and shoot from the “front slope” (draw weight measured as you move into the letoff/valley) instead of the middle of the valley, it causes a harsh arrow start - jamming the arrow and adversely affecting accuracy. Other contributors to front slope/ inconsistent shooting can come from a tendency to creep forward at release and the tendency to underdraw when shooting uphill or downhill. All these factors can make it more likely to anchor/release from the front wall, especially in hard cam bows with narrow valleys. Overdrawing past midpoint in the valley causes the weight to go up quickly and is called the wall. The problems in the wall are worse than shooting from the front slope.

 

[spoiled one]

Thanks for the info guys. Great link, Doug. Now I just need to render it into a form that 3rd grader can comprehend. Lots of new terminology for me.

 

[AKDoug]

Let me make this simple for you Go to your local shop and let them help you. If you want to order a bow online, then I cannot think of any mid priced bow out there that isn't good. In fact, there are a lot of $300 new bows out there that are better than the $800 bows from 5 years ago. Don't sweat the details like force draw curves, valleys and letoff. Go shoot some bows and see what feels right to you. The industry is so competitive that there really isn't a bad bow out there.

 

[spoiled one]

A bit more info. I have been shooting a Kodiak Outdoors 36 inch bow since 2003. I purchased it from Tim at the old Full Draw in ER. I shot multiple bows and this one felt right for me. I am 6' 6" with very long arms. I have never had my draw length measured, per say. The bow is set at the longest possible draw length and I shoot with a loop. It is rated from 60-70 pounds. It actually draws at 72 pounds. The let off is set at the minimum which I believe is 65%. I think that the max let off is 80%. I have never run an arrow through a chronograph. I guess this info would help answer my original question. It makes more sense to set the bow at maximum let off if performance does not suffer.

 

[AKDoug]

The only bow I have had that had two positions for letoff actually lost very little speed when going to the higher letoff. I wish I had a solid number, but I remember it was less than 5 fps.