String angle and energy

[Selfbowman]

Question: string angle is often talked about on here and my related math holds me back on understanding. Does an arrow take on more energy from a longbow or a short bow? The string is longer on a longbow and the angle is lower but does it stay on the string longer creating more energy? Even though the draw is the same? I’ll listen or try to. Thanks in advance. Arvin

[Digital Caveman]

The idea is that the string pushes harder for longer. 

Think of it this way, how does a #50 @28" longbow feel at half draw?  What about a 50# @28" short bow? 

Because the longbow pushes harder over more of the stroke it accelerates the arrow more.

[Morgan]

The idea is that the string pushes harder for longer. 

Think of it this way, how does a #50 @28" longbow feel at half draw?  What about a 50# @28" short bow? 

Because the longbow pushes harder over more of the stroke it accelerates the arrow more.

I need to work up a fdc on a 60” vs 66” bow all things else being equal. I do not think that the weight or tension at half draw will be higher on the longer bow. I think where you get into a performance loss with short bows is when the string angle gets to the point that you start to stack. If you have a fluid build to full draw without stacking, I cannot see how or why the shorter bow would not out perform the longer one. Shorter bow limbs has less mass, and if the fdc is equal or near, then performance should go to the shorter limbed bow. One doesn’t push the arrow longer than the other, unless one is drawn further. At least that’s the way my thinking works.. looking forward to following this thread.

[Del the cat]

I think that as long as the string angle doesn't get past 90 degrees you are not wasing energy.
As it gets past 90 you are starting to pull slightly along the length of the limb, trying to stretch it rather than bend it.
E.G. Imagine a skinny limb growing straight out from a tree at shoulder height.
Tie a yard or string to the end and pull down (string angle 90 )... it bends the limb. Now try pulling directly outwards in line with the limb (string angle 180), it won't bend at all! This shows that "feel" can be deceptive.
Del

[bownarra]

It isn't that when it hits 90 degs you lose all advantage. Every inch pulled from brace loses the advantage over the limb. The longer bow stores more energy as drawn because the string angle is proportionately lower through the whole draw. People talk about the stack when a bow string hits 90degs because you can't ignore it then! If you get to the point your bow is actually hitting 90 degs it is likely a bit short for the draw anyway.
Force draw curves are plotted from brace for a reason

[simk]

 Arvin: when it comes to the string angle topic my thinking never was focussed on the the arrow side but the drawing side: how much of your drawforce actually gets stored in the bow and how much of it is just lost in space? the higher the angle of attack of the string, the less energy finally is stored in the bow; vice versa: the lower the angle the more efficient the energy you put into the bow really gets stored.
to understand this its best to visualize with the force vectors operating at the tips. maybe somebody has a pic of it... similar to Del's explanation.
this also greatly helps to understand the term of "stacking"
cheers

I'm not claiming full understanding in this topic. But other than Del I think its relevant even beyond a 90 degree angle. Like bownarra said its a gradual loss of efficiency with increasing draw and angle.

[Morgan]

It isn't that when it hits 90 degs you lose all advantage. Every inch pulled from brace loses the advantage over the limb. The longer bow stores more energy as drawn because the string angle is proportionately lower through the whole draw. People talk about the stack when a bow string hits 90degs because you can't ignore it then! If you get to the point your bow is actually hitting 90 degs it is likely a bit short for the draw anyway.
Force draw curves are plotted from brace for a reason

How is it storing more energy unless the force it takes to draw it is greater? Why does string angle alone play into how much energy is stored?

[BowEd]

Not sure it's just a string angle thing here.Talking only about performance wise.
The weight of the arrows makes a difference between short to long bows.Shorter bows shoot lighter arrows more efficiently.
Longer bows shoot heavier arrows more efficiently.That's a limb mass difference thing.
All bows shoot heavier arrows more efficiently really.
Accuracy wise at least for me a smoother draw/lower string angle helps.

[Selfbowman]

Ed that’s what I’m seeing happen in flight bows. Sleek made impressive shots in flight arrows with his short bows. I seem to be shooting arrows farther than him in broadhead class with a longer bow. I would like for everyone to think about this some. My force draw curves usually come up in the first third of the draw and then a short flat spot and tail off at twenty eight inches or so. Arvin

[Selfbowman]

Morgan what does the average 60 inch bow weigh vs say a 67” bow. My 50 pound bows come in at 21-24 oz usually. Depends on width at fades. That’s with a 9-10” handle weighing close to 7 oz.

[bjrogg]

String angle has always confused me to Arvin. I never read the Bible. Seems like I need things explained in simple ways.

I don’t know if it’s right, or if it makes since to anyone else.

The way I understand it now. As the string angle increases a certain angle. It starts to cause the bow limb to push out more than ahead. I can imagine how that could be less efficient.

Bjrogg

[Morgan]

Morgan what does the average 60 inch bow weigh vs say a 67” bow. My 50 pound bows come in at 21-24 oz usually. Depends on width at fades. That’s with a 9-10” handle weighing close to 7 oz.

Arvin, I just weighed one that is 59” long and 55 lb draw @ 27”. Closest one I have at the house to what you have.  Minimal handle section that has just a hair of bend only @ full draw I can’t see the bend but can feel it. It is 15.4 oz overall, no idea what the handle weighs.

[Morgan]

String angle has always confused me to Arvin. I never read the Bible. Seems like I need things explained in simple ways.

I don’t know if it’s right, or if it makes since to anyone else.

The way I understand it now. As the string angle increases a certain angle. It starts to cause the bow limb to push out more than ahead. I can imagine how that could be less efficient.

Bjrogg

I like the way you explained that. I can see where that could be a factor.

[Selfbowman]

Morgan that draw weight and that mass weight sounds like you ended up with not having to much extra unneeded mass and good distribution. Seems like most bend in the handle bows come in around 15-16 oz. if I remember right.

[Morgan]

Been thinking about this. So if you bend a short bow to 28” the limb tips have to move further than if you bend a long bow the same. Does that come into play in the performance? If the stroke is carrying the weight of  the limbs further it would kill performance. Or am I off base?  Most all of y’all posting are far more knowledgeable than myself, I’m just trying to wrap my head around performance factors.