String angle

[Springbuck]

   I have seen that before, I still believe every inch of that limb is responding according to its own relative string angle. But when you average it out I imagine that red line would be as close as you could get.

I do, too.  I believe Baker was right about the "net" string angle being most important, at least basically, but I did a lot of fooling around with basic limb shapes cut from slats early on, esp. the pyramid types (which really helped me visualize what was happening with different bow limb types).

 Anyway, it's hard to describe, but if you cut yourself out some little slats of wood you can watch this pretty easily.  make "pyramid" type half bow, bend the limb and watch how it acts.  Then flip a little recurve in the tip and watch how it changes.  The recurve not only changes how and where the the limb bends, but how and where it bends at various increments of draw.

[DC]

You need to draw your red line to the string nock. That drops the string angle a few more degrees.

  Overlay a straightened out version of the same bow to examine the difference.

So where the blue line is?

[DC]

ok how bout this

That's a string devil

[PatM]

I do think the blue line is more representative.  I think of  the limb like a  slightly flexible pry bar in your diagram. If you force down a flexible pry bar you run out of leverage when the tip hits the ground.   If you added a siyah to your pry bar and a slight outer limb recurve you can keep bearing down on it in a more advantageous manner.

[Badger]

    In the last picture the string has already lifted off the curves so the nock point would be correct. If it hasn't yet lifted off the curves it goes to the first point of string contact with the limb.

[Badger]

   Recurves give an improved string angle but more importantly they become longer as they lift off the curves keeping the draw weight from building so fast.

[DC]

So what I'm getting from this is that the recurves change the string angle but not by a lot. in the 2-4 degree range maybe. I think my confusion was in expecting a bigger change. I'm noticing that in a few things, a very small change can make a big difference.

[Badger]

  DC, a lot of thing affect string angle besides the tips, your tiller has a major affect on string angle, the close to the handle the bend better string angles, stiff outer limb better string angles. R/D bows have great string angles but don't have quite the benfits of the lift off which makes the bow effectively longer giving it lower pull weight gains as it lifts off.

[PatM]

So what I'm getting from this is that the recurves change the string angle but not by a lot. in the 2-4 degree range maybe. I think my confusion was in expecting a bigger change. I'm noticing that in a few things, a very small change can make a big difference.

 That will depend on length and angle/curve of the tip and draw length.  Draw some more extensive diagrams.

[George Tsoukalas]

I may be missing something in the discussion....

String angle has to be an angle. In the first photo, I see  the red line going to the drawn string. However, it is the angle between the string and that red line. It is darn close to 90 degrees so that bow will begin to stack badly. Not break...stack.

Picture the base of a right triangle and the vertical line. That angle is 90 degrees. That is what the first photo shows.

Jawge

[PatM]

The recurve diminishes the stack.

[gfugal]

http://www.primitivearcher.com/smf/index.php/topic,61791.0.html
This thread which I've been a part of also delves into string angle.

[gfugal]

I always thought string angle is the difference between the green angle and the orange angle. You can tell there is a huge difference between the angles when you draw it like this.

[simson]

+1
like Greg's sketch above

[willie]

Then flip a little recurve in the tip and watch how it changes.  The recurve not only changes how and where the the limb bends, but how and where it bends at various increments of draw.

would you say that the flipped tip applies a torque to the end of the limb?