Reflex-Deflex Design Question

[Badger]

   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.

[PatM]

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.

[gfugal]

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

[upstatenybowyer]

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 .
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.

[PatM]

DEFLEX/reflex is probably the most accepted term. Of course people argue that just to cause trouble. 

[Traxx]

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.

[PatM]

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.

 

[gfugal]

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.   

[Emmet]

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.

[willie]

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.

[mikekeswick]

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

[Springbuck]

  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.