Perry reflex question

[DC]

If you leave a wooden bow braced for a year or so it will take a permanent set. Do the internal stresses of a Perry reflex take a set and lose their effect after a while?

[bushboy]

I dought many folks have tried that on wooden bows?

[Badger]

   I don't believe the internal stresses are doing much to begin with. Very little stress is applied when laminating. I think a big part of it is simply a superior reflex condition. In a self bow that takes no set there is very little difference in performance. 

[Bayou Ben]

   I don't believe the internal stresses are doing much to begin with. Very little stress is applied when laminating.

Can you explain this a little more Badger?

I've been trying to get my head around the forces involved with glued in reflex.  The way I grasp it at this point is that there's a certain amount of forces that the glue itself it holding therefore "freezing" the fibers in their reflexed position.  At some point during the tiller process the glue force is exceeded by the internal forces of the wood and some of the glued in reflex is lost.  It's not necessarily set of the wood fibers but set of the glue. 
This may be totally wrong as I haven't experimented with this theory, just my gut. 

[DC]

There has to be something going on. I think it's so cool to gain reflex as you tiller. I've got about a 1/2" gain in reflex but then when I get to about 20" draw it usually starts to go away. I assumed this was just set. Steve, do you think the "internal stresses" are relieving themselves about then?

[Badger]

  The bottom line in a bow is stored energy and efficiency which starts with early draw weight. Backed bows tend to have slightly more early draw weight in most cases and also tend to have slightly more efficiency. I think most of the difference simply boils down to backed bows tending to have less damaged wood cells when finished. Glueing them into reflex is less stress on a bow than heating them into reflex. The belly fibers are already wanting to go back to their natural position but the back is holding them away. Maybe we are putting more work on the back where it should be.

[Bayou Ben]

  The bottom line in a bow is stored energy and efficiency which starts with early draw weight. Backed bows tend to have slightly more early draw weight in most cases and also tend to have slightly more efficiency. I think most of the difference simply boils down to backed bows tending to have less damaged wood cells when finished. Glueing them into reflex is less stress on a bow than heating them into reflex. The belly fibers are already wanting to go back to their natural position but the back is holding them away. Maybe we are putting more work on the back where it should be.

Thanks.  I totally agree with this.  Gluing in the reflex leaves the wood "fresher" than heating in reflex which permanently deforms the wood fibers to it's cooled down profile. There's only so much that wood fiber can be tampered with before it goes.  And I think there's something to the fibers wanting to spring back to their natural position.....Well put. 

The phenomenon of gaining reflex during tiller goes hand in hand with my reasoning.  The wood was set during glue up with the force that it took to hold that stiffness of wood in that position.  When you tiller and remove wood the force to hold it in it's current reflex position now is less, but the force that the glue is holding remains the same.  The wood has no choice but to reflex more till the forces balance.

[BowEd]

Related here but what I've noticed is that natural reflex is probably the best scenario.Heat treating a naturally reflexed bow after taking set not clamped to a caul will often times increase the reflex back to close to it's original profile too.Glued in reflex like laminated bows is next in holding that shape and then heated in reflex other than it's original profile is the last in holding the best.
Tillering a heavily sinewed bow will show the same gains in reflex many times too,but negated some after pulling closer to the full draw.I see that happen on lesser dense woods more so that are sinewed.

[willie]

Heat treating a naturally reflexed bow after taking set not clamped to a caul will often times increase the reflex back to close to it's original profile too

Ed, I had always imagined heat treating as a way to bake in hardness or increase stiffness, but your example shows that fibers and matrix can be reset? possibly a reflowing/rehardening of the lignins?

[Stick Bender]

Ok let me throw this wrench in the mix, Ed are you talking natural reflex in terms of the reflex in the stave at time of splitting or natural reflex as the stave dries ? Or both the reason I'm asking almost every stave I have after a couple years of drying all have varying degrees of natural reflex ? Some more then others particularly Osage !

[PatM]

Lignin does start to flow at a certain temp.

 I think a reflexed bow holds reflex because you have effectively put a shorter piece of wood on the back.  I don't think it really saves the belly from stress.  The cut apart bow test  shows this.

[DC]

Lignin does start to flow at a certain temp.

 I think a reflexed bow holds reflex because you have effectively put a shorter piece of wood on the back.  I don't think it really saves the belly from stress.  The cut apart bow test  shows this.

Trust PatM to throw logic into the discussion That seems too simple but maybe it's saying the same thing with different words. I'll have a nap and think about it.

[willie]

Lignin does start to flow at a certain temp.

I have often thought that lignin might have a long curing time. dry vs seasoned etc.........

maybe heat bending works better on less "seasoned" wood?

[BowEd]

Ok let me throw this wrench in the mix, Ed are you talking natural reflex in terms of the reflex in the stave at time of splitting or natural reflex as the stave dries ? Or both the reason I'm asking almost every stave I have after a couple years of drying all have varying degrees of natural reflex ? Some more then others particularly Osage !

Rich....I'm saying a stave that gets totally dry into a reflex are ones I like the best as far as holding reflex good after good tillering.I've seen them dry deflexed too.I know and believe too much heat does weaken wood to a certain degree too.Just because it looks reflexed at the time of splitting does'nt always mean it will be a reflexed stave.There not near all the same.At least with osage.Hickory has a tendency to dry into the most reflex overall I've seen.Hackberry can act that way too.Black cherry for some reason for me likes to dry into a deflex more so.Many times for some reason some winged elm wants to dry into deflex too.Black locust is pretty mild either way when drying for me.

Heat treating a naturally reflexed bow after taking set not clamped to a caul will often times increase the reflex back to close to it's original profile too

Ed, I had always imagined heat treating as a way to bake in hardness or increase stiffness, but your example shows that fibers and matrix can be reset? possibly a reflowing/rehardening of the lignins?

Willie...I don't know about your reflowing lignin statement but heating a bow into a different profile is changing the cells the way I see it.What I said is that it resets itself from memory naturally with heat to it's original profile of reflex to a large degree.I've seen it.Just like it has'nt forgot where it came from in a way.Dry heating too wet of wood will dry check for sure,but steam bending is good and not near as detremental.

[PatM]

If lignin flows then it does allow the cellulose fibers to move and slide I would presume.  Basically the same idea as glass fibers in Epoxy moving in the matrix and setting in a new position.