Bow design and development

[Halfbow]

I'm with DC here. Reflex should decrease stack, deflex should increase it.

In general. the higher the early draw weight, the less stack a bow should have. Said another way, the closer the weight at partial draw is to the full draw weight, the less stack. This is almost by definition, as a bow that stacks can be described as a bow with a partial draw weight that's considerably less than its full draw weight.

To illustrate:



(Pic from https://horsebackarchery.wordpress.com/2012/11/04/bow-mechanics-energy-storage/ I hope they don't mind)

The farther the tips are in front of the handle, the higher the early draw weight, because the bow is already more stressed at brace. This means that the farther the tips are in front of the handle, the less stack. So reflex, whether in the handle, through the limbs, or in recurves at the ends, should reduce stack. (Of course this is not the only factor, but it's a big one. String angle matters too.) Conversely, deflex makes a bow less stressed at brace, and thus should decrease early draw weight, and thus will increase stack. Reflex/deflex bows balance two factors to get pleasantly straight draw curves.

Deflex is useful for materials like wood because it reduces strain. It allows for recurved limbs and the beneficial string angle that comes with them without stressing the wood too much. But if your materials can take more stress, it seems to me that more reflex would result in more energy storage, smoother draw, and more speed.

If you look at the draw curves of highly reflexed bows, they're excellent. Better than the curve you posted Stick Bender.

These bows which are not deflexed in the handle:



have a draw curve like:



(Bows and data from http://www.atarn.org/islamic/Performance/Performance_of_Turkish_bows.htm)

However the deflex part of deflex/reflex bows has a lot of other benefits. Less vibration (though highly reflexed vibration free bows are possible, just finicky to get right). They're less effected by sloppy releases. And highly reflexed bows are difficult to string and require more care to make sure they stay well aligned. I think that's the real answer to why companies don't usually make highly reflexed modern material bows.

[Stick Bender]

Do it Brad you might be surprised I'm going to be sending you a highly natural reflexed  osage stave shortly when I can get to the post office in a couple weeks I cut 2 years ago that would be perfect for the designed or one of your native bows !

[leonwood]

My last five selfbows have been deflexed reflex/recurve bows. The first one I made just shot so extremely smooth and really fast that I had to try a few more. Now I am not a calculations kind of guy. I just grab a stave and start building totally by feel with a general design in my head. But the deflex reflex bows are my best shooters for sure. Almost no handshock, no set and really fast. So I am guessing those fg bow designers sure knew what they where doing when they started designing rd bows!

[Halfbow]

Leonwood, there is absolutely no doubt that reflex/deflex bows are excellent, both in performance and in shooting characteristics. They are likely legitimately the best design for many people. But when you say they're really fast, I'm curious what you're comparing them to. It's a claim I hear a lot, but I expect many people's impressions come after comparing them to longbows, and not highly reflexed bows. Have you tried a highly reflexed bow? (Not an attack, just curious. I haven't tried any extreme examples myself.)

If you read that article I linked about the Turkish bows (http://www.atarn.org/islamic/Performance/Performance_of_Turkish_bows.htm) I think you'll be impressed by the performance. All three of those bows pictured are made of natural materials and are toying with 200fps at 10 grains per pound.

[bradsmith2010]

well its got me thinking for sure,, sure wont hurt to try one,,

[bradsmith2010]

halfbow you are right,, 170fps seems fast till ,, well 200 fps,,,and like we talk about all the time,, its not all about speed,,
but it is very interesting to see what certain designs will do,, my hunting bow is slow by most standards,, but I shoot it very well,, but if I had a faster bow I shot as well,, I would shoot that,, etc etc etc,,

[Halfbow]

Absolutely, I'm not trying to put speed on a pedestal. It's smart to be more concerned about other things, and that's why I say reflex/deflex is such a great design. My point here was really just to say, deflex doesn't reduce stack.

[bradsmith2010]

wow, I really didnt understand that,, 

[DC]

I'm with DC here. In general. the higher the early draw weight, the less stack a bow should have. Said another way, the closer the weight at partial draw is to the full draw weight, the less stack. This is almost by definition, as a bow that stacks can be described as a bow with a partial draw weight that's considerably less than its full draw weight.

I'm not sure if this is semantics or not but I kinda thought it was the other way around. It sounds to me that you're saying that a bow with high early draw weight won't stack. Correct me if I'm wrong . I think that if you have a bow that doesn't stack it will have a fatter F/D. If the bow doesn't stack it allows you to make the bow heavier. It may sound like we're saying the same thing but my cause is your effect and vice versa.

[DC]

I'm a little different. I put speed on a pedestal . Cast has been the measure of a bow for thousands of years. (I think, I wasn't there for all of them) It isn't the complete measure of a bow, though. If a super fast bow is so shocky that it's unshootable it's not much use. Or if it sprays arrows all over the shed. It is a major part of most of the good things and it's the easiest to measure though.

[Halfbow]

Hm I think it is semantics. I am indeed saying a bow with high early draw weight won't stack (with some qualifications, but that's the gist of it). A fat f/d curve shows that the bow has a high early draw weight. So to saying a bow has high early draw weight is the same statement as saying a bow has a fat f/d curve.

These are all just descriptions. Fat f/d curve, high early draw weight, non-stacking. All equivalent descriptions, and you can say them in any order you like. A bow that stacks less will have a fatter f/d curve. A bow with a fatter f/d curve will stack less. It works fine either way.

Let me know if I misunderstood you.

[DC]

I think we're on the same page.

[Badger]

 This was an experiential bow I built several years ago. In the pic the bow was knocked down to about 28# so the lady could shoot it in the 50# class. She did get a record with it. But on this bow I tried out some theories. It had about 12" reflex to start, and 12" static hooks as well as a very short working limb area. the theory was that the short working limbs would keep it stable at brace and prevent it from vibrating and loosing power at the end of the power stroke. It worked extremely well but the wood broke down badly within a dozen shots and the performance fell off to nothing extraordinary. One the first shot it was well over the 200 fps mark, I think about 208 if I remember correctly each shot continued to drop off as did the bow weight. It leveled off after about a dozen shots to 38# starting at 50#. I made 2 of these, this was the slightly lighter of the two.

[DC]

Do you think that if you had let the hooks work a bit it would have been unstable?

[Badger]

  i think it would have been unstable and defeated the whole purpose of a rigid limb test. I call these hinge bows. I n the pic it is not as clear because I tillered it down for a lday to shoot so it has a bit more working limb than when originally made.