Stack Attack...

[Shredd]

    In your opinion at what point does a bow start stacking??? When it starts gaining 1/10# , 1/3# or 1/2# per inch or do you base it on each individual bow design and average it out somehow by feel???

[Crooked Stic]

Each individual bow. Because a 30 lb. bow will be less per inch than a 60 lb. bow. The bow considered stacking when the lbs. per in. start to rise
. Most times the string angle will be close to 90 degrees.

[Flem]

I've never done force/draw curves. But I build walking sticks that look like Bows and have the cast of a turd compared to your guy's zippy R/D Bows. Don't want to set myself up for disappointment

I can say that I get no stacking sensation, even with a 64", short riser(12-13") Hill style drawn to 28" as long as they bend deep into the meat of the limbs.

[flntknp17]

I'd say there isn't one single point.....its all a very complex relationship of the angle of the string to the tip of the limb that would require higher maths to really work out.  The efficiency with which the string is able to move the limb tip changes constantly as the bow is drawn and this in turn changes the rate of "stacking".  Once the limb to to string angle exceeds 90 degrees.....then stacking really increases dramatically since the string is no longer bending the limb, but trying to just rip it off the riser!  All of this is why recurves are less prone to stack....a lower angle is maintained.  Really interesting stuff from a math standpoint.

Matt

[Shredd]

Good points on the string angle guys...

[flntknp17]

Just as an illustration, I ran a simplified geometric (as opposed to calculus-based) simulation in Excel that assumes a 56" bendy handled bow draw from brace to 28".  The results are that the simulated bow loses all draw efficiency (severe stack) at about 27" of draw.  I think it shows how the whole situation is a non-linear process and things become exponentially more severe as the string to limb angle nears 90 degrees.