String angle and energy

[BowEd]

Good analogy.As good of a drawing to understand this as I've seen.
I agree with your final conclusion also.

[Allyn T]

"String Angle and Stack The angle made by the string and arrow is the important angle. The near-tip string angle is less significant. If limb and string are nearly parallel for a high percentage of limb length then braced string tension is greater, increasing early draw weight."

[simk]

"String Angle and Stack The angle made by the string and arrow is the important angle. The near-tip string angle is less significant. "

wrong. only the angles at the tip are relevant when we think about putting energy from string into the limbs.
I would even say, THE GREENER THE BETTER  regarding energy storage the first inches of draw are most efficient; the further the draw, the less efficient your draw becomes. Also that's why you are doing tricks with recurves etc. to keep good energy storage even on further draw.
this also (partly) could explain why a low braceheight makes a faster arrow.
but what do I know 

[Gimlis Ghost]

regarding energy storage the first inches of draw are most efficient; the further the draw, the less efficient your draw becomes. Also that's why you are doing tricks with recurves etc. to keep good energy storage even on further draw.
this also (partly) could explain why a low braceheight makes a faster arrow.
but what do I know 

Awhile back I lowered the brace height of my 60" recurve and found it did appear to increase velocity of the arrows. It also reduced a tendency for the arrows to buck to the left and they entered the target in a straighter line.
I overdid it then walked it back to what appears to be just right for my bow. Just a bit lower than recommended factory specs.

Its hard to compare the effects of limb length when discussing self bows and horn bows. According to authorities on the long bow quoted by Saxton Pope the average English war bow if drawn past 30" was "7/8ths broken".
The limit of safe draw length, to avoid limb damage and future failure, varied greatly according to length of the bow. The longer bows could be drawn further.

The long bows were intended for heavy hard hitting arrows rather than maximum range. The longer limbs helped accelerate the heavier arrows.

[RyanY]

Maybe a bit off topic from Arvin’s original question but I always reference this discussion when it comes to stacking. https://www.tapatalk.com/groups/paleoplanet69529/stack-and-string-angle-t6218.html

I think the relationship to arrow speed is more complicated and relates to limb mass as well as others have stated.

[Selfbowman]

So if the tips are flipped as in my pic . The flipped tip is adding some string tension at full draw? Would we figure the angle at full draw as if it was a straight limbed bow? I think I agree with Del.  Ryan Interesting info from days gone by thanks . That’s going to take some studying for me.

[George Tsoukalas]

Nice tiller, Arvin.
My understanding is that as 90 degrees is approached for  string angle, efficiency decreases.
String angle deceases for recurves  and  reflexed  bows.
As limb length increases for straight limbed bows string angle decreases but there arises another host of problems.
Then there is the issue of finger pinch on shorter bows which need to be reflexed.
Anyway, I don't really make myself short bows nor do I make myself recurves.
Great discussion!
Jawge

[simk]

So if the tips are flipped as in my pic . The flipped tip is adding some string tension at full draw? Would we figure the angle at full draw as if it was a straight limbed bow? I think I agree with Del.  Interesting info from days gone by thanks . That’s going to take some studying for me.

Arvin: With your flipped tips you are only cheating towards MORE GREEN and LESS RED. That's why you are doing them 

[Chumash]

I think string angle is not very important for the energy transformed to the arrow....

Stacking begins at high 80° angle and at 90° it is bad stacking....

The area below the force draw curve represented the stored energy...

[Selfbowman]

The bow above shot the broadhead arrow 260 yds. 50 pound bow. The recurve in the tips did work some toward full draw. I do think the pyramid does cut down on any unneeded mass in the limb.

[Selfbowman]

Question: If my bow in the pic is at say 60 degrees and I trap the back 25-30 percent decreasing mass and allowing the tension and compression to be the same at full draw is this a win win??? Just thinking here guys.🤠

[SDBurntStick]

The way I understand this is that the energy imparted to the arrow is the area under the F/D curve.  I think some knowledge of integrals would be needed to really calculate this but here is a way to show it.  After all a given weight at full draw is the same regardless of string angle.  If a bow stacks curve is steeper than say a longer bow with a linear force curve.  Mass and internal friction being equal the longer bow that stacks less would have more energy.  Hope this helps and a lot of this is explained in TBB 1. 

[George Tsoukalas]

"The way I understand this is that the energy imparted to the arrow is the area under the F/D curve."
Yes.
Flipped tips? Oh y'all mean recurved tips.
Jawge

[Morgan]

The limbs on a shorter bow has to travel further at a given draw length; does that come in to play? Or is that a false statement and an optical illusion? I’ve never done a comparative measurement, but it sure looks like they do.

[RyanY]

With respect to draw length I think they move the same distance. With regard to actual tip travel, they may travel further due to bending in a tighter radius curve.