String angle

[George Tsoukalas]

 
String angle is the angle between the string and the limb in the drawn bow. That's it.
Measure it close to the tip.
Other than that it doesn't matter.
In that right triangle from my last post, no matter where you measure, it is going to be 90 degrees from base to vertical line.
Where you measure is only limited by the size of your protractor.
Jawge

[PatM]

I don't think you're following the effect of the retro tip, Jawge.

[George Tsoukalas]

Pat, I don't know what a retro tip is. Never heard of it. Static recurve?

If there is a point where the string contacts the limb. String angle can be measured from there at full draw...from limb to string.

Jawge

[gfugal]

If you guys are talking about string angle I would have to agree with George. I measure it from nearest string contact point to the nearest section of limb that if practical to measure (if there isn't string let off it would be the bottom of the recurve where the string touches it). However, I am not as sure whether there is still benefit or not from a recurve if there is not string let off. Part of me says no, it's only where it last touches the limb. But part of me thinks there's more to it than that, so who knows.

[gfugal]

So going off the original photo I would say the string angle is the blue lined angle and not the red.

[George Tsoukalas]

gfugal, you have it.
One of the purposes of a recurve is to decrease the string angle making for a smoother draw.
Other possible decreases in string angle are deeflex out of the handle, designing the  bow longer, semi-recurving (reflexing the tips), etc.
Probably more bought I just woke up from a nap.
Jawge

[DC]

I tend to agree but my gut says there is more to this than just the angle. I'll just think some more.

[Springbuck]

would you say that the flipped tip applies a torque to the end of the limb?
[/quote]

Not exactly.  This is why I said it was hard to describe, but....  in a regular straight limb, obviously the string applies the force at the tip.  The most force is "felt" by the limb close to the handle due to higher leverage, right?  Halfway out, the limb "feels" less force/leverage, and even less right at the tips.  Everybody knows this.

Putting a recurve or reflex at the end of the limb changes the amounts (or probably more correctly, the proportions/percentages) of this "felt" applied leverage.  To my eye, it applies MORE during stringing and early draw to the limb close to the handle, then shifts as the draw progresses.

  With a contact recurve, the limb effectively lengthens later in the draw, right?  But, really that is proportional to the "original" limb length.  What I mean is, if I have a 64" straight bow and a 64" recurved bow, the recurve bow doesn't END it's draw longer, it begins the draw as a shorter bow.

So,  say the recurve takes effectively 2" out of the braced bow length.  As a proportion of the total, slightly shorter limb applies LESS leverage at the limb base than before, but the midlimb feels a LOT less.....at first.  Then, when the limb effectively lengthens later in the draw, the BOW is still getting shorter, but less dramatically because of the recurve.  The recurved tip thus continues to apply good leverage to the limb base, and BETTER leverage to the midlimb than early in the draw.  This is where the F/D benefits and lower "stacking" come in to play.  Non-contact recurves and R/D bows share this benefit, just less so and at lower angles.

The trade-off is of course then that the midlimbs need to be able to handle that extra strain, which is why I and most guys leave the limbs wider out past mid-limb.  The recurve can have excessive mass, too and vibration needs to be managed.  This is why (I believe) that my best recurves are short and stout.  I've seen a lot of new guys try to put huge recurves on a long bow and it's a really tough job.

My best shooting bows have always been R/D lam bows with skinny tips, and 64" or so deflex-recurves with pretty big recurves only extending a couple inches ahead of the handle at most, WITH string bridges.

[gfugal]

I think our confusion Is we don't have a universal reference point. Here are three potential reference points I drew out in a sketch.


PatM and a picture from one of the TBB say it's reference point #1 the average of the limbs or something. To be honest, this reference point makes the least sense to me, but as Badger was saying it might be the most accurate to what leverage the limb feels or something. Pretty sure I butchered that summary since I don't quite understand that yet. It just seems to me the angle change between a recurve and non-recurved limbs isn't that significant with this reference point. The 2nd reference point I just made up and hasn't been discussed here yet. The third is the reference point me Simon, and Geroge seem to be using. Maybe there's another reference point not illustrated.

[PatM]

Pat, I don't know what a retro tip is. Never heard of it. Static recurve?

If there is a point where the string contacts the limb. String angle can be measured from there at full draw...from limb to string.

Jawge

 I thought you had the BB series.

[PatM]

gfugal, you have it.
One of the purposes of a recurve is to decrease the string angle making for a smoother draw.

Jawge

  You seem conflicted.   How does it change the string angle if you don't measure string angle in that manner?

[George Tsoukalas]

Ah, gfugal, I thought you had it.
Like I said. Angles don't change according to where they are measured. Doesn't matter. Those angles are all the same in your last photo.
String angle is the angle between limb tip and string.
There is a huge difference in string angles between a  recurve and straight bow of the same length.
It's all about geometry.
Jawge

[PatM]

There is a huge difference in string angles between a  recurve and straight bow of the same length.
It's all about geometry.
Jawge

 Isn't that what people are trying to show in many of these diagrams?   You sound like your arguing against it and then agreeing in the next post.

[George Tsoukalas]

PatM, I don't understand what you think I said I am conflicted about.
I measure string angle from limb tip or point of contact to string.
Yes, I have the TBB's..all of them. In fact one of my bows is featured  in #4.
Jawge

[gfugal]

Ah, gfugal, I thought you had it.
Like I said. Angles don't change according to where they are measured. Doesn't matter. Those angles are all the same in your last photo.
String angle is the angle between limb tip and string.
There is a huge difference in string angles between a  recurve and straight bow of the same length.
It's all about geometry.
Jawge

Huh? true the position doesn't change. That stays the same regardless of the reference point but angle most certainly does. Angles are measurements just like distance. They both measure the difference between point A to point B. If you change point A the measurement changes. The angle measurements of each of those reference points I listed are different. The blue angle is probably around 135°, the orange angle is probably around 90°, and the purple 45°. Those are very different numbers. But yes, regarldess of reference point the position and effect are the same.