I can't help but think that if a limb profile was developed that shot an arrow better than those used by most olympic recurve shooters, there would be much more variety in what is seen used in those matches. I am surprised by how similar most of those bows are.
If more speed or range is desired, it seems to me that staying within the design and upping the draw weight, draw length and arrow weight would be the place to look for an increase in performance
I think you guys just have more faith in the world than me. It's easy for me to imagine it being more of a cultural thing. Like perhaps what was once innovation has calcified in to fashion, and there's just not much of a market for new and different. Then the incentive for companies would be toward incremental improvements. Just enough for the marketing team to sell each year. Also, (correct me if I'm wrong) isn't there a high degree of interchangeability between these bows? Swapping limbs and risers and such? If so, that would really stifle innovation in the interest of remaining compatible. But as you say, accuracy is of utmost importance for Olympic archers, and I fully believe that they've just about perfected that aspect. So, again, there may not be a lot of demand to try new and different.
https://www.ocf.berkeley.edu/~archery/wp-content/uploads/docs/recurve-fundamentals.pdf
That article was a good read on the points it covered, but I thought a few things were curiously omitted. Made me feel vindicated. Most notably... How're they going to not talk about the angle the limbs come off the riser? And the overall reflex or deflex? The distance the handle is in front of or behind the tips when unbraced. They just seem to start with the assumption that the industry has it perfect. Almost like it didn't occur to them that it's a variable they can play with. Maybe the industry does have it dialed in already, but their failure to mention it makes me think maybe they don't.
A bow limb gains very little weight because of bending it. The vast majority of the weight is gained because the string angles get higher and leverage is reduced.
I agree that string angle's contribution to draw weight is important and probably often underappreciated, but I think saying that bending causes "very little" weight gain has got to be overstating it. That would mean a reflexed bow's string tension at brace would be very marginally increased over a deflexed bow's, all else being equal. But in my experience, I wouldn't describe the difference as marginal.
Which is a nice segue in to... reflex. I will explain how I think of it. Probably this will be old news to some of you, but I haven't seen it explained quite this way before. Tell me if I'm way off base.
(This example is simplified to show the concept. And it will leave aside limitations of material, and efficiency issues. Don't take it as an indication that I'm unaware of these things, or that I don't think they're of utmost importance in design. But I also think understanding concepts is important, and distilling them in thought experiments is helpful. I'm picturing a modern material for the sake of this discussion anyway.)
Imagine 3 bows. All the same length, all circular tiller, and all 50lbs at 28". These bows look nearly identical. In use, their profile is identical. And in terms of nearly everything that article was concerned about, they are identical. They're all stable. They all have the same unideal string angles.
But these bows are really different. When you unstring them.
Bow A is deflexed, bow B is straight, and bow C is highly reflexed.
Let's call bows 0% bent when unbraced and 100% bent when at full draw. So I ask, how bent are these bows at brace?
I'm too lazy to try to measure my picture, so I will make up some numbers that seem reasonable to me. Bow A is about 10% bent at brace, B is 50%, and C is 80%.
So at brace, bow A barely has anywhere to be. Its position of perfect comfort is only like an inch away. It's feeling pretty good about things. The string isn't holding it back much. String tension will be low. Pluck it and get a low note, if anything.
Meanwhile, bow C is very far away from its unbraced profile, and is furiously trying to return to it. The straight string is holding back ~80% of the bow's might. The tension in the string is very high. Pluck it and hear a high note.
Bow B is in between.
So when drawing bow A you are making it move 90% its range of motion. From the bow's perspective, its state at brace is entirely different from its state at full draw. The bow is pretty comfy at brace, and furious at full draw:
Drawing bow C is only moves it 20% of its range of motion. The motion during the draw is not a huge change of state for this bow. It's furious at brace and still furious at full draw:
But they're all 50lbs at 28". So what does this mean in use?
For bow A, I picture getting ready to draw it, putting my fingers on the string, and finding it very easy to pull back. I'm like, "What is this? A kid's bow?" But the weight ramps up and by the time I'm at full draw, it's transformed to be much more difficult. In other words, bow A stacks a lot. It's f/d curve is hollow. It's not storing much energy.
For bow C I picture putting my fingers on the string, starting to draw, and immediately finding the string digging menacingly in to my fingers, resisting me. I think, "What is this? A war bow? Can I even fully draw a bow this heavy?" But then I continue and by the time I'm at full draw... surprisingly the last few inches felt not much more difficult than the first few. This is a smooth draw. It's f/d curve is full. It's storing far more energy.
Bow B, of course, will be in between.
Lots of talk about reflex gets caught up in geometry, but overall reflex or deflex isn't something you can see in a braced bow. Reflexed and deflexed bows can have just about any braced geometry you want.
So, that's how I think of it. I hope that's helpful.
