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

[Badger]

  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.

  Limb movement has nothing to do with it. I do it all the time and I build about 2 bows a week. Ignore limb movement just read the scale at where it reads on your tree just like it was braced. I do it on all styles of bows short and long heavy and light and it always works, not dead accurate but very close within a couple of pounds.

[Badger]

 You really have to think about 2 things when you are thinking about early draw weight. Your bow limb is like any spring it builds as a rate of so much per inch. The vast majority of the weight you gain is due to lack of leverage as your string angle changes, not the loading of the limbs, they don't load all that much as they build.

  The other thing you have to look at is how much of the lower limb is at a low string angle. So the unbraced profile has a lot to do with string tension. The longer the area of limb sitting at a low string angle the higher your weight will be.

[DC]

  Your bow limb is like any spring it builds as a rate of so much per inch.

Springs are linear so where does the hump in the lower end of an FD curve come from?

[Badger]

 DC, you did not read my post, you read like one line it sounds like. read it again. String angles and leverage.

[DC]

No, I read the post a few times and I knew I was taking this a bit out of context. I thought it might make it easier to understand if I took it one section at a time. I've done a little experimenting with bamboo sticks standing in for limbs and I did notice that the leverage dropped as I pulled the thing. I attributed this to the lever getting shorter as the limb bends. This accounted for the draw getting heavier toward full draw but I couldn't figure out what made the early draw weight hump.

[Badger]

  You really can't take one item and isolate it because they are all interacting. A hump in the force draw usually will have something to do with a sudden change of string angle or changing string angle that is not linear.

[meanewood]

I think the majority of the extra poundage created by a re flexed starting point will remain unused and so provide some extra speed but not as much as you think.

That's OK if you want to get the most out of your bow but you could get more by increasing the draw weight and reduce some of the shock to the bow and more importantly the string when the release comes to that sudden halt at brace height!

If you are building heavier bows and using natural material strings these things take on a different perspective.

[NorthHeart]

The other thing you have to look at is how much of the lower limb is at a low string angle. So the unbraced profile has a lot to do with string tension. The longer the area of limb sitting at a low string angle the higher your weight will be.

Regarding this explanation were you referring to the lower limb of the bow, as opposed to the upper bow limb.  Or by lower limb are you referring to the portion of a limb in relation to how far it is away from the handle?  Its hard for me to even state what im asking i hope it makes sense.  Things that would be simple when explaining and pointing to a bow in person are a bit harder for me to understand or explain online with just words.

Would you mind posting a pic or diagram of a "lower limb at a low string angle"?

Also, "string angle" and how it relates to the tips is a concept id like to understand better.  I get how a pulley system helps to lift a heavy object but my mind cant seem to apply leverage to a bow.

[Badger]

  I think you guys are looking at tip movement and the effort it took to get it to brace. You don't have any leverage when bracing a bow but when you first strt to pull a bow you have a huge leverage advantage. Tip movement is kind of meaningless if you don't include the leverage at a given spot. At full draw you have given up most of your leverage and that is why it pulls harder, not because the limbs are loading up.

[Springbuck]

" 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?"  To me, yes.  This is in some ways a primary goal.  Top three for sure. One other being low set.  I can't abide a mushy string.

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."  I believe you, but his surprises me.  In the TBB I, Baker did that experiment where a bow braced 3" out-shot (for speed) the same bow braced 6", despite landing at a lower full draw draw weight.  It was pretty darn close, though.

 "Simple it doesn't zero out,...."  Yeah, long string is loose, while braced string is quite tight.  The bow is stretching on that string.  That first inch of draw while braced may register only a few pounds, but that's down to geometry.

[Springbuck]

Certain principles that exist which make it hard to "cheat" the systems.  Stuff exactly like how a bow with lots of reflex should shoot faster, but reflex CAN cause extra set, instability, higher limb mass, and are harder to tiller properly.  Net gains may or may not be realized.  Likewise, recurves easily store more energy, but often have issues with tip weight and stability, thus net gains may or may not be realized.  As such, IMO, it comes down to how much you push the envelope, and whether your skills are up to the task.

  I have sketched out some RIDICULOUS designs I will probably never get around to trying, hoping to "cheat" these principles.  It would be great to achieve radical profiles that still manage to relieve strain on wood, increase early draw weight, counteract oscillation/vibration, dampen lateral wobbles, stiffen tips, create zero stack, etc...  Stuff like hollow bows,  Superlight limb tips, weightless recurves, two stage recurves, string bridges, inverted limbs (incredible F/D curve, but totally stupid in every other practical way), cable backs, string stoppers, bizarre limb and handle arrangements, etc..

  What WORKS for me tends to be; enough mass in the right places, MODERATE reflex or recurve, skinny tips, heat treating, Perry reflex, good workmanship, and knowing how much is too much to ask of your materials.

To the original post:  Baker covered a lot of this in the first TBB Design and Performance chapter, though sometimes he mentioned it in passing and didn't dwell on it.  Less set or even reflex increase performance.  Deflexed tips help bows survive to higher draw weights.  How do thickness, width, and length affect stiffness, set, and mass?  He stated that less or more of a limb's bending potential can be used up by high brace heights, short working sections, reflex or recurves, etc.  So, yeah, any given limb can only bend so far, and if much of that potential is used up before we get a string on it, less is left to get it to full draw.  It's a balancing act.

 I don't know how you add up the numbers exactly, though.   I don't think you can add one atop the other in a meaningful way.  I think you have what you have once you start pulling the braced string, and high early draw weight is good.  You just have to get there