String angle and String angle.

[Buemaker]

To figure string angle I have always thought like in drawing A was the right way to do it. So when the angle approaches 90 degrees the bow start to stack.
Then again I have seen that some think that to measure like in drawing B is the way.
What say you?

[Stagmitis]

Hey bue I have always measured using the A angle. For me it’s about what the limb tip is doing.

[Crooked Stic]

A also.

[kennym]

To me A is stack, B is finger pinch

[Pat B]

A for me too.

[Kirkll]

Well…. I’m the odd man out on this discussion. Why? Because “B” angle  controls both stacking and finger pinch.

Think about this…. As the limb come back,  the distance between the top and bottom limb tip changes, and the string angle B  starts to close up. In a static tip recurve it actually maintains the string angle longer before the limb tipsstart getting closer to each other.   On a D shape long bow that bends full length of limb to the hand starts closing up as soon as you start drawing it back…. That’s why the stacking point and string angle is regulated more by the bows length. Once those limb tips quit moving straight back, and start moving towards each other the PPI starts increasing.

This can be mitigated in R/D longbows with faster taper rates and tip wedges that do not allow the tips to bend so much. It’s forcing the energy storage into a shorter section of the limb and helps maintain that string angle at a longer draw length.

I think the key to the whole performance thing is learning to manipulate the actual limb travel distance. The longer the limb travels, the more momentum it builds up with only the string tension at brace to stop the forward motion. If you are not stopping the limbs completely with the string tension or preload on the limbs, you are flushing energy storage down the toilet and it stays in the limbs.

For paper shooters and target archers who really don’t care about kinetic energy or arrow speed at all.  Most these guys stick with really long bow lengths to have a flatter string angle “B” that is easier to get off the string clean.

[onetone]

I am sticking with angle “A” which I learned to monitor early on.  With any trad bow as angle A opens, angle B closes. Angle B is a better indicator of potential pinch for finger shooters, but angle A is the better indicator of potential stacking.  Sorta depends on what you’re looking for …

[Kirkll]

My question is…. What exactly ARE you looking for? And what are you doing to achieve it?

[onetone]

Looking for to respond to Buemaker’s question … I thought my answer was clear.

[Kirkll]

Looking for to respond to Buemaker’s question … I thought my answer was clear.

You finished off your reply with "It sorta depends on what you are looking for" I was curious what you meant by that? 

To figure string angle I have always thought like in drawing A was the right way to do it. So when the angle approaches 90 degrees the bow start to stack.
Then again I have seen that some think that to measure like in drawing B is the way.
What say you?

Honestly.... I don't think actually measuring string angle at the tips or mid string is the best indicator for stacking points at all.  Those angles are the "result" based on limb travel, and where the limbs are bending, and the string length.... 

Measuring the angle on a radical static tip recurve at the tips is totally different than a D shape long bow.... How would you even measure the angle at the tips on a super hook recurve limb? You would be much better measuring PPI throughout the draw cycle and comparing your draw force curve results as you tweak your limb design and lengths..... 

Limb travel is something that is rarely discussed by bowyers , or factored into bow design. I've always wondered why? Its actually a really big factor.   

What i'm looking for is ....The shortest limb travel i can achieve and the flattest string angle i can get at the finger location....This typically produces a longer draw length potential with no stacking.      .02 cents worth...   Kirk

[onetone]

Ok. I favor angle A in part just because it is easy to see. Angle B is often blocked from view by the archer’s body or gear. I get a clearer sense, as an observer, of when a bow is stacking from watching the limb tip/string angle. You’re right, it is harder to read the angle with RCs, but I sorta draw a mental line to flatten the curve. As you indicated either angle is just a product of limb geometry, bow length and DL.

For sure DFCs are a more useful tool for fine tuning limb design than reading string angles. Your take on limb travel makes good sense to me, as does the limbs stopping dead when the string returns to the brace position, all factors in efficient bow design. Static curves help to keep the string tip angle smaller and they act as levers, easing the draw at the end of the cycle. All good counsel for bowyers to consider.

For some time now I have been experimenting with Ottoman style bows, which in my shop are made of traditional and synthetic materials. They are ridiculously reflexed and short, but finger pinch is not an issue because they are shot with a thumb ring. The limbs can’t help but bend sharply between a rigid grip and static limb tips … seems like something has gotta blow, yet some of the bows have shot more than 2,000 arrows (I count to convince myself of their durability) without failure so far. I had several delaminate at the beginning until I worked out some glitches. A bow that weighs only 13 or 14 oz. is an inch wide at the fades, draws 54# at 28” will shoot a 10 gpp arrow at 200+ fps or a 3.5 gpp arrow at 270 fps. I have gotten into flight shooting, so bow and arrow refinement are current priorities and how I plan to achieve that is just more than I want to get into tonight but I’ll post a couple of pix of a recent build. The string is on this bow is 37” long for a sense of scale.

[Mad Max]

A

[Kirkll]

Those type of bows always seem to defy physics to me. Just getting a string on one of those things without it flipping over has got to be pretty intense. Breaking  the 200 FPS barrier at 10 gpp is a tuff one to do. Congrats on that accomplishment.

But getting a bow to hold up to flight shooting arrow weights is a whole different ball game. I’ve never pursued that course. Never had the time….

Are you familiar with Allan Case? He’s been into flight shooting for many years and is a friend of mine I’ve kept in touch with over the years. Some of the foot bows he’s built are rocket launchers! 

The arrow building process for flight shooting is a huge part of it. Listening to Allan explain the process was fascinating. He’s a world class competitor.     Kirk

[onetone]

Kirk - I do know Alan Case, as a matter of fact he got me into flight archery. Rumor has it that his footbows have on occasion, put an arrow in low earth orbit which sorta nullifies getting any distance measurements! Kidding aside, finding his arrows is a big challenge for him. For example, this year at Bonneville while searching for arrows that were recently shot, he found one he had shot three years earlier!  Maybe it had just dropped out of a decaying orbit?  Arrow design is a major part of the endeavor for sure. A good amount of time and work goes into building each arrow. It really smarts when one can’t be found.

[Kirkll]

I used to tell Allan he should really look into putting an ultra light tacking chip in his flight arrows. Could you imagine being able to track a flight arrow in real time, and graph the trajectory? In this high tech day and age there has got to be a way to do this....Besides that... you could easily find your arrows.

Allan has tried to get me into the whole flight shooting thing off and on for years, but i never really have got into it. I sent him a seriously heavy set of limbs last year to play with on his foot bow. Unfortunately they didn't hold up long...... If i had more time, and wasn't so obsessed with salmon fishing. It would be a fun thing to get into, but i never could convince my wife to go to the Bonneville salt flats just to fling arrows...