Primitive Archer
Main Discussion Area => Bows => Topic started by: gfugal on December 22, 2016, 05:54:48 pm
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What's the purpose of a reflex deflex bow. I understand that if you induce reflex you get more energy storage earlier on. What I don't understand is the need for a deflex. That's like purposely putting string follow in your bow but with reflexed limbs. Doesn't that just undo the early energy storage in the limb? It seems counter intuitive to me unless its an attempt to reduce the stress but then why not just make a straight-limbed bow. In the attached drawing you can see the straight limbed and 1st R/D example have the same unstrung tip height. Wouldn't both of these have similar force curves or am I missing something. The only way it makes sense is if it was like example three where the reflex is greater than the deflex thus getting more energy storage. But then again why not just do a small reflex and forget the deflex.
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Here's what it says in TBB 1...
"The deflex-recurve, is probably the most efficient design for a woodbased
bow. Because of its deflex little of its ability to do work is used up bracing
the bow. Since little before-the-draw work is being done by the limbs, more
during-the-draw work can be done.
Being under little strain when braced, a deflex design would normally have
very low early-draw weight. This is overcome by using thicker, harder to bend
limbs. Such thick limbs would normally result in intolerably heavy draw weight
later in the draw, but after string lift-off this design's levers keep full-draw
weight down. Such a thick limb would normally be overstrained when fully
drawn, but these limbs do little work being braced, making this unused capacity
available during the draw."
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If tillered right I think it is less stress on the bow wood when strung. All you have to do to see/feel this is string and unstring one.
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Just to make sure. Are you sure you drew the string on the right side of your drawings? R/D bows are usually deflexed in the middle and reflexed at the tips. The way you drew it is referred to as "gullwing" I think. I may be wrong about the gullwing thing.
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DC, the second drawing would match the R/D design. But I've seen the tips above the line.
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The red line does not represent the string, he's just showing where the tips sit relative to the handle.
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My stupid, thanks Pat. Back on my head.
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Tim Baker followed up in TBB 3 with a four page explanation that I find a bit easier to follow than the explanation from TBB1 above. I am not sure if there is'nt more to it, that deserves a better explanation.
If someone has a digital version that they can cut and paste from, it would be helpful. It is in the "bows of the world" chapter.
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So the idea is that it saves the work for later? It doesn't have to bend as far to reach draw length and draw weight, therefore you can use a thicker stronder limb? I'm guessing thats beneficial because the wood is more structurally sound when it doesn't have to bend as much and you have less risk of damagining the wood and increasing its hysteresis when the limb is thicker and working less? I'm still a little confused, if somebody could link me to that quote in the TBB4 i would much appreciate it. Thanks for the info guys.
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That's pretty much it. The "thicker stronger limb" part is a bit meaningless though.
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it starts on page 75 of TBB 3. I could email a scan, if you sent me your email address via a PM. Might be a bit much to post here.
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it starts on page 75 of TBB 3. I could email a scan, if you sent me your email address via a PM. Might be a bit much to post here.
That description is good but it actually describes a somewhat different design than a simpler deflex/reflex.
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PM sent Willie
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b-but the 5 curves look nicer!! What would be the point of all the grip reflex in the hornbows, if it just makes them harder to string, etc? also in the gull wing bows, wouldn't it just make them really stacky?
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A horn bow can handle reflex and even needs it to stress the materials.
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I have experimented with these designs and agree, I cant see the purpose of putting in deflex in terms of efficiency....it does to appear to make a bow slightly more stable though and the limbs less inclined to twist, as they are prone to do with narrow highly reflexed bows..
I think if a bow is too reflexed it is prone to take a set and end up with a deflex because of set...these bows look attractive because of the curves, then people just copied this, thinking it was part of the design....just my ideas.... though from my own experience 2 otherwise equal bows, one with just reflex and the other with a reflex and deflex...the one with only reflex is the fastest
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I have an rd bow I made last year to stray strung and shoot many shots. It has more deflex then reflex so the tip are 1.5" behind the the handle at rest. I also have a shorter draw at 26" The limbs are heavy enough to get 50# at 26" Its not my fastest bow for sure but not bad either. Its accurate more then others Ive made and no noticeable string follow after shooting all day. I score higher at 3d shoots with it then recurves Ive tried.
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How I look at it...
Basically, you can only get so much out of the wood. You can have a fair bit of reflex and a short draw like in a flight bow, but if you want long draw as well the wood simply can't handle it. The deflex allows you to maintain the advantageous string andge and inproved endergy storage of the reflex whilst allowing a bit more draw adding stability and removing some of the stress that the just reflex design would have.
Yeah you can make a heavilly reflexed design, pull a long draw and cause a load of set spoiling the performance... if you design the "set" already in there as deflex... you get your performance and draw length without ruining the wood.
Ok not very technical, but it is my gut feel approach to trying to understand it... better than a shed load of maths and physics which is only an aproximation anyway ::) >:D.
Del
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Some good replies here being posted. It might be useful to know, how much more performance is commonly realized with this design. I have read many claims for the theory, but have also built a few bows that were not so fast, after a while.....
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My Take on this design.
I think most today,that put performance numbers as a first criteria,have a hard time,understanding the benefits of this design,that would have been beneficial to those that utilized it under the conditions that they required.
While they were used from the ground as well,it was primarily designed for a mounted archery bow.The ease of brace would be a bonus in a n impromptu situation.The early softer draw would also be easier to manage,from the back of a running horse,over uneven terrain and still maintain a proper grip,shaft control and ease of partial draw,at the ready for a quick snap shot,when it presented itself.With the augmented pinch style that many used to grip the string and nock and the draw style used with this style of bow,it resulted in softer early draw that gained as it was drawn and often resulted in stack,toward the rear of the draw,with the result being the release being ripped from the fingers at a pre designed draw length.Think about the benefit of easy partial draw and only having to hold high draw weight,for a small percentage of the late draw,in a fast moving,high stress quick action shot with a small window of opportunity a hunting and mounted warfare situation,would often present.If there wast benefit to the design,i wouldnt think that so many people from such a broad range of territory,would have utilized it to feed and protect their people,when other designs could have just as easily been made.
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If I understand you correctly, Traxx, the low early draw weight (that comes with deflex) is the primary feature, and the reflex is added to bring the weight up to a usable range within a short draw?
We often forget that form follows function in this day and age.
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Exactly Willie.....
I much prefer your shorter winded version to mine and may adapt your version,in future discussions of the subject.
with your permission of course.
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of course you can adapt it any way you wish, Traxx.
I have often suspected that many of the designs we appreciate from the past, were designed the way they were, for practical reasons not realized now a days.
I was intrigued by this description of the shooting style... possibly even utilizing stacking by design?
with the result being the release being ripped from the fingers at a pre designed draw length
perhaps a subject for another thread, or has it been discussed before?
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Switching the topic to gull wing bows might be throwing some people off the original topic a bit.
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One problem I see with bows that reflex out of the handle is that they don't come around right when drawing and will tend to stack. A bow deflexed out of the handle will come around much smoother. A horn bow can get away with it because of its long static area and large hooks. A wood bow needs more working limb and cannot be designed like a horn bow and expected to act the same way.
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Switching the topic to gull wing bows might be throwing some people off the original topic a bit.
Based on the description of the original post,i thought gull wing bows,were what he was trying to convey,or was i mistaken?
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Switching the topic to gull wing bows might be throwing some people off the original topic a bit.
Based on the description of the original post,i thought gull wing bows,were what he was trying to convey,or was i mistaken?
That's what I thought until Pat pointed out that the red line is not a string.
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I think,that in the first 2 examples,that it was to show the correlation of tip to handle,but in the 3rd example,i thought it to show the braced example.
What say you gfugal
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If i am mistaken,then i just wasted peoples time and some of my own,with senseless typing. :-[ :-[
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I think all three were to show the correlation of tip to handle but I'm willing to be wrong ;)
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I think you are right Traxx, I was kind of tired and just read some of the text thinking they were talking about reflexing right off the handle.
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The top straight example has the handle on the bottom. so logically the examples underneath follow that. This confusion partially rises from where people consider the naming of a bow to start., the handle or the working limbs.
I am 99.9% sure the intention was to show the modern style of bow.
I thought the 5 curve reference was maybe branching off from loon mentioning it. If that bow type was ONLY mentioned as five curved or double curved or gull winged there would be less confusion.
deflex/reflex or reflex/deflex is the problem definition.
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Sorry if it looked like a string. Its supossed to show tip height. But its good to know that the reverse is also a bow. Didn't know about gull wing bows. My bad i just realized the topic was called reflex reflex and not reflex deflex
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How I look at it...
Basically, you can only get so much out of the wood. You can have a fair bit of reflex and a short draw like in a flight bow, but if you want long draw as well the wood simply can't handle it. The deflex allows you to maintain the advantageous string andge and inproved endergy storage of the reflex whilst allowing a bit more draw adding stability and removing some of the stress that the just reflex design would have.
Yeah you can make a heavilly reflexed design, pull a long draw and cause a load of set spoiling the performance... if you design the "set" already in there as deflex... you get your performance and draw length without ruining the wood.
Ok not very technical, but it is my gut feel approach to trying to understand it... better than a shed load of maths and physics which is only an aproximation anyway ::) >:D.
Del
Assuming were still talking about a bow with deflex in the handle and the outer limbs curving back into reflex I think Del's thinking makes a lot of sense.
I like the name Tim Baker gives it in TBB 1- Deflex recurve, it seems to conjure the best image of what the design looks like.
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DEFLEX/reflex is probably the most accepted term. Of course people argue that just to cause trouble. ;)
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Actually in my Experience,R/D is the most accepted term,regarding the style prevalent in the modern Laminates,but it is used incorrectly.Even the guys like Earl Hoyt and Tim Meigs who brought the style into the more modern Traditional archery world,defined them as Deflex/Reflex and termed them as duoflex.
The true Reflex/Deflex as it applies,is the style popular among Native people in America,from the southwest region north through the mid west and great plains,northern plateau,great basin on in to Canada.It reflexes off the grip and deflexes in the outer limbs. The common term,for this style being,Gull wing or double curve.
Based on the wording of the op,the later is what i interpreted as being described.
What's the purpose of a reflex deflex bow. I understand that if you induce reflex you get more energy storage earlier on. What I don't understand is the need for a deflex. That's like purposely putting string follow in your bow but with reflexed limbs.
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But then one bow (the double curve) is being named from the handle out and then the other generally modern bow from the limbs in. That's the source of the confusion.
Even a duoflex and a modern deflex /reflex or reflex/deflex (whichever makes you happy) are different bows. One is two essentially two big recurved limbs that are essentially straightened achieving brace height and the duoflex saves some bend that isn't unrolled until it is drawn.
In a wood based bow the design saves the wood from bending stress to achieve brace and full draw and eliminates residual energy that contributes to handshock and in a glassed based bow mostly the latter.
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There must be something to inducing deflex early on. Posted are two pictures of compound bows. The first is an older design and the the second is a more efficient modern design. The reason I say it's more efficient is because the latter bow can reportedly shoot an arrow faster than 300 fps with a 70 lb draw. If you are like me you find compound bows ugly, and am ashamed of even posting a picture. However, it's hard to ignore speeds like that and makes you wonder what about the design might be better, other than the material and cams/pullies. The first thing I notice is the angle of the working limbs. The first is more recognizable limb while the second is almost horizontal. To me it seems like as if they are trying to get it to flex as little as possible hence why it's so short and deflex looking. I think the Idea is that the less the limb bends the less energy is lost to friction and hysteresis, and in order to get the draw weight with such little bend the limbs are incredibly strong and stiff. granted they also have their cams that make it so they can translate a little bend into a large draw length. Its possible its only benefit is from its much larger cams than the other but i'm not sure. We can't use cams but if I'm correct in this theory (which I very while might not be) than the more deflex there is the less the limb has to bend thus the less energy lost to friction. However, in order to get a decent energy curve the bow limbs would have to be much stronger than a bow that has to bend much further to get draw length.
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A compound is just un winding the string off a large wheel to get the draw length. The limbs don't need but a little movement. I think deflexing at the handle comes from getting a short bow to reach a reasonable brace height on compounds.
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the Idea is that the less the limb bends the less energy is lost to friction and hysteresis
I agree, short stiff limbs must help with limb efficiency.
so they can translate a little bend into a large draw length
that and the max energy available to accelerate the arrow coming into play at the end of the powerstroke rather than at the beginning. Well designed and tillered conventional limbs are of most benefit to arrow speed if they can continue to impart accelerating force to the arrow for as long as possible, hence high early draw weight being useful. The reflex gives the high early draw weight while the deflex allows for a longer powerstroke with limbs that would be otherwise overworked.
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Del explained a r/d bow perfectly. My fastest wooden bows have all been r/d recurves. I've made plenty of pure reflexed bows and to a certain point you will always get set with them if you push the amount of reflex. Wood doesn't like a lot of reflex. The best hornbows aren't reflexed out of the handle - Turkish = straight handle into the limbs (or not much handle reflex).
Compounds make use of the same design principle of a true duoflex. Very heavy weight gain because of extremely stiff, short travel limbs = leverage of the cams to bend the heavy limb far enough without huge weight gain on the fingers mid to late draw. Remember though that compounds are shooting light arrows to get those 300fps speeds. Put a 10gpp arrow through them and you quickly see they aren't all that :)
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One problem I see with bows that reflex out of the handle is that they don't come around right when drawing and will tend to stack. A bow deflexed out of the handle will come around much smoother.
The opposite of stacking is...........? High energy storage! Stacking and lousy F/D curves go together. Smoothness and fat F/D curves go together.