Reflex-Deflex Design Question

[gfugal]

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.

[upstatenybowyer]

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."

[mullet]

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.

[DC]

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.

[mullet]

DC, the second drawing would match the R/D design. But I've seen the tips above the line.

[PatM]

The red line does not represent the string, he's just showing  where the tips sit relative to the handle.

[DC]

My stupid, thanks Pat. Back on my head.

[willie]

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.

[gfugal]

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.

[PatM]

That's pretty much it. The "thicker stronger limb" part is a bit meaningless though.

[willie]

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.

[PatM]

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.

[gfugal]

PM sent Willie

[loon]

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?

[PatM]

A horn bow can handle reflex and even needs it to stress the materials.