What makes a bow more efficient than another with light arrows given the same energy storage? Are carbon foam limbs far better than regular wood glass limbs? How about narrow longbow limbs vs wide recurve limbs?
I've got to try and answer this question even though we are drifting out on the tangent a bit here. :p
What makes a bow more efficient using light weight arrows over the next bow, is typically being able to stop the mass weight of the limb moving forward clean and transfer more energy to the shaft.
Carbon /foam limbs are much more desirable to some discriminating archers.... they can feel the difference and they do perform very well. but to say that they are "far better than regular wood glass limbs." would be a stretch.... A great comparison would be a bamboo fly rod vs a top of the line graphite rod.... both catch fish, but there is a world of difference in the feel, and the actual performance..... but by golly you'll always have guys that swear by those old bamboo buggy whips.
A guy could write a book or two on LB vs RC limbs comparisons, so i'm not going there. The highest performing bow in the world is going to be a very narrow limb static tip recurve bow. IMO
There is a large difference in measuring the "efficiency of the bow itself" and "How efficient the arrow cast is compared to the stored energy in the draw cycle." you can increase any bows efficiency by shooting heavier shafts. but some of these, heaven forbid "Faster bows" will shoot those heavier shafts a lot with a lot flatter trajectory, and hit a lot harder..... THAT is good stuff for any archery hunter....it's still your responsibility to put the arrow where it needs to go.... But the straightest distance between two points is.... A flat line.... or is that one word as in "Flatliner"
For those of you that are not interested in exploring the details regarding the complex nature of what a bow is really doing, or care about the advanced physics involved.... that's cool... but keep in mind here.....there are many Trad bowhunter's out there there that find it fascinating and are interested in guys willing to do the prototyping and raise the bar a bit in terms of performance.....
Some of these sarcastic remarks about arrow speed being unimportant get old.... but those same guys are probably saying the same thing about arrow speed threads...LOL! Gotta love it!