The force required to brace a bow and how it affects things.

[NorthHeart]

All things equal(which they never are)...

Does a bow with more reflex at brace require more effort to string than one without, i think that most of us will agree so.  Must not the limbs move a greater distance from their original position, and thus start building energy(poundage) sooner? Will a given bow (reflexed or not) shoot an arrow with more speed and power over a bow requiring less effort to brace?  If you answer "yes", then isn't getting poundage at brace an important factor in bow building and one we should strive for to build faster and more powerful bows?

Onward....

Set is bad and robs bows of power, as well as puts more stress on the limbs, correct me if this is wrong.  I've been reading a lot of posts regarding "no set tillering" and not pulling your bow past the final intended draw weight throughout the entire process.  Here has been my experience so far.  I use a long string and tiller the bow to approximately where it would be at brace, sometimes ill even go a bit over.  Lets say i draw it to a max of 50# and it requires 40# to brace.  I remove the long string and brace it up with the short string, knowing that it took 40# to get there.  But when i put the scale back on it it starts back at zero pounds, not taking into account the 40# it took to get it to brace.  I tiller the bow to my draw length, lets say for this example this one ends up 55# @ 24".  I never pulled it past 55# on the scale, but in reality have i not put 95# of stress on the wood?

[Del the cat]

All that is fine except there is only a limited amount of movement you can get from a wooden limb, so if you use that movement to brace the bow you can't also use it as draw length.
So with 2" of reflex you may get a 26" draw before it starts to take set or pull out the reflex, but without the reflex you'd get 28"
To answer your question:-
You can't just add up the weights... well I s'pose you can, but your target draw weight was for the braced bow, so that is how you must measure it.
As an illustration of the argument by reductio ad absurdum (reducing to the absurd... I think Harry Potter uses this technique ):-
I expect any bow could take over 500# if it was clamped at one end pulled  at the other in line with it's length.
Of course this is irrelevant, but it shows how there is only one important weight.
As long as you can hit target weight and draw without taking set, you can add as much reflex as you like
Del

[Badger]

     The weight your pulling is more dependent on the leverage you have at the particular point you are pulling. When you have a bow on the long string and it is pulling 50# at 24" it will still be pulling 50# @24" if you brace it. Your string moves more than the limbs do so you have leverage. Stress is only relative to the radius of the bend and the thickness. If you have a lot of reflex it needs to be thinner in thickness because it is bending more and then wider to get the weight you  need, no design should be under any more or less stress than any other design if we do our jobs. Wood only handles so much and we need to stay below that number.

[Jim Davis]

If I  can  try to distill some of what Del said (I agree with him), if you have a bow that has 2" of reflex and you pull it to 24" beyond brace height, you have moved the limb tip 2"+6" for brace height, + 24". So the tip has moved 32" from its rest position. You stipulated 40# to get it to brace height and 55# at 24".

That means that it took 55# to move the limbs 32". You don't add any part of the force at some distance to the total at 24". The 40 and 55 numbers are pretty unlikely anyway. It might be more like 25 and 55.

My curiosity runs more to how much more speed is given to the arrow by a reflexed bow than by a bow of the same weight that is not reflexed?

[willie]

But when i put the scale back on it it starts back at zero pounds, not taking into account the 40# it took to get it to brace.

Yes, about half the energy put into the limbs is unused in the powerstroke (full draw  back to brace)

any ideas? utilizing some of this energy will take a very creative mind

[gfugal]

     When you have a bow on the long string and it is pulling 50# at 24" it will still be pulling 50# @24" if you brace it.

The zeroing out when you brace causes me to scratch my head with 240m3srt. Maybe once you draw it to 24" it might equal the weight on tge long string at 24" but that's at the later draw lengths for string travel, but the limbs aren't moving the same distances between those two examples. I've experienced where the bow pulls 40# when the limbs move brace distance (lets say that's 18 inches on the long string hypothetically) but after I brace it and pull it to 8 inches the limbs are moving more than the 18 inches on the long string, but the weight is far below the 40# you had before. You would think it would be 40+ lbs since the limbs are moving further, but that's not the case. You have to pull it to around 18 inches after brace to get similar poundage but that is much further limb movement.

So my question is if bracing zeros out that poundage from previous limb movement, how does reflex add additional weight? Whether the pre-brace limb movement is 6 inches or 8 inches what does it matter, if it is only going to be zeroed out anyway? I know there's something I'm not getting (probably something to do with leverage and string angle) since reflex does increase performance, but I can't wrap my head around what's going on.

[Badger]

If I  can  try to distill some of what Del said (I agree with him), if you have a bow that has 2" of reflex and you pull it to 24" beyond brace height, you have moved the limb tip 2"+6" for brace height, + 24". So the tip has moved 32" from its rest position. You stipulated 40# to get it to brace height and 55# at 24".

That means that it took 55# to move the limbs 32". You don't add any part of the force at some distance to the total at 24". The 40 and 55 numbers are pretty unlikely anyway. It might be more like 25 and 55.

My curiosity runs more to how much more speed is given to the arrow by a reflexed bow than by a bow of the same weight that is not reflexed?

   Jim, it just depends how much reflex 15 fps diff is not unusual. A well made straight bow will usually hit around 165 or so and a well made slightly reflexed bow ( 1" ) will usually hit around 172or so. Some straight bows do go over 170. I think the only way to tell is test a bow straight and then reflex it and lower the weight back down to the same or just test it at 10 grains a pound at its new weight.

[Badger]

     When you have a bow on the long string and it is pulling 50# at 24" it will still be pulling 50# @24" if you brace it.

The zeroing out when you brace, causes me to scratch my head with 240m3srt. Maybe once you draw it to 24" it might equal the long string at 24" bit that's at the later draw lengths for string travel, but the limbs aren't moving the same distances between those two examples. I've experienced where the bow pulls 40# when ththe limbs move brace distance (lets say that's 18 inches on the long string hypothetically) but after I brace it and pull it to 8 inches the limbs are moving more than the 18 inches on long string, but the weight is far below the 40# you had before, when you would think it would be 40+ lbs since the limbs are moving further.

So my question is if bracing zeros out that poundage from that early limb movement how does reflex add additional weight, if what it adds is only zeroed out. I know there's something I'm not getting since reflex does increase performance, but I can't wrap my head around what's going on.

  Simple it doesn't zero out, as soon as you start pulling it starts at a higher number. All the stress is going a different direction toward the limb tips until you start pulling it back toward the shooter.

[George Tsoukalas]

The whole key is to not brace a bow that is more than 20# heavier (10-15# is better) than potent draw weight.

Some bowyers can do it at floor tiller. They are more talented than I am.

I use the long string.

For a straight limbed bow, I long string tiller out to ten inches looking for good limb movement and target weight or a little over.  Then I string it. This puts the bow at 10# over target. Plenty for me to tiller it.

If the limbs are reflexed 2 inches then I long string tiller out to 12".

Never mind increasing set, which you will of the  bow is too heavy a t bracing, I broke some bows at the first stringing before I mended my ways.

Jawge

[NorthHeart]

     When you have a bow on the long string and it is pulling 50# at 24" it will still be pulling 50# @24" if you brace it.

The zeroing out when you brace, causes me to scratch my head with 240m3srt. Maybe once you draw it to 24" it might equal the long string at 24" bit that's at the later draw lengths for string travel, but the limbs aren't moving the same distances between those two examples. I've experienced where the bow pulls 40# when ththe limbs move brace distance (lets say that's 18 inches on the long string hypothetically) but after I brace it and pull it to 8 inches the limbs are moving more than the 18 inches on long string, but the weight is far below the 40# you had before, when you would think it would be 40+ lbs since the limbs are moving further.

So my question is if bracing zeros out that poundage from that early limb movement how does reflex add additional weight, if what it adds is only zeroed out. I know there's something I'm not getting since reflex does increase performance, but I can't wrap my head around what's going on.

  Simple it doesn't zero out, as soon as you start pulling it starts at a higher number. All the stress is going a different direction toward the limb tips until you start pulling it back toward the shooter.

In my experience it does not register the higher number.  When braced, i pull it one inch the scale registers 3# for example, not 43#.

[gfugal]

  Simple it doesn't zero out, as soon as you start pulling it starts at a higher number. All the stress is going a different direction toward the limb tips until you start pulling it back toward the shooter.

Not entirely no, but there is a good amount of zeroing going on. The limb movement at 28" on the long string is not the same as if it is at 28" after brace. If you were to continue to pull the long string to where you get similar limb movement (maybe more then 34") you would have a much heavier draw than 40#. So where does that extra poundage go? It's lost somewhat in bracing, (hence why lower brace heights store more energy). This is why i think it has a zeroing effect of sorts. Although not all of it is zeroed since extra reflex does increase the stored energy, especially during early draw.

[willie]

So where does that extra poundage go

[Jim Davis]

  Simple it doesn't zero out, as soon as you start pulling it starts at a higher number. All the stress is going a different direction toward the limb tips until you start pulling it back toward the shooter.

Not entirely no, but there is a good amount of zeroing going on. The limb movement at 28" on the long string is not the same as if it is at 28" after brace. If you were to continue to pull the long string to where you get similar limb movement (maybe more then 34") you would have a much heavier draw than 40#. So where does that extra poundage go? It's lost somewhat in bracing, (hence why lower brace heights store more energy). This is why i think it has a zeroing effect of sorts. Although not all of it is zeroed since extra reflex does increase the stored energy, especially during early draw.

You also have to recognize the different angle. Even a 100# bow only takes a little bit to move the string 1"  from brace. There is a huge mechanical advantage to a deflecting a string or cable only a tiny bit from straight. At straight, a scale reads zero, at one inch maybe a pound, at two inches maybe three pounds, at four inches maybe 10 pounds. The first few inches do not produce a linear result in force required for deflection. After that the force line becomes straighter for a while, then  turns upward when the bow begins to "stack."

Willie's useful chart above uses a constant weight at different angles. For bows, it's more useful to recognize the different "weights" of pull at each angle to produce particular forces at the bow tips.

[DC]

In my experience it does not register the higher number.  When braced, i pull it one inch the scale registers 3# for example, not 43#.

 this is what I think, may not be true. The first inch is important. A straight bow of 40# will pull roughly 2# in the first inch. A reflexed bow of the same weight will pull a little more, maybe 2 1/4# or so in the first inch. It's not much but it adds up to that 5-10 fps.

[DC]

Yes, about half the energy put into the limbs is unused in the powerstroke (full draw  back to brace)

any ideas? utilizing some of this energy will take a very creative mind

I'm thinking this is what deflex does. The deflex/reflex bows I've been making lately are very easy to brace but don't seem to suffer for speed like you'd think they would. But there seems to be a limit.