I had a customer, who just upgraded a b55 string to BCYX and he told me he thought the 'X' had made his bow gain a pounds as it was "noticeably heavier". I assured him that the bow didn't "gain poundage" and then got to thinking about the qualities of the two different strings. I know when i'm stretching the strings the B55 will "settle in" about 3" longer than my finished string length. For example, if I want a 56" B55, my finished string will be in the ball park of 53", where with X, it'll be 54.5". It got me to thinking, could the B55 actually be stretched while at full draw causing the limbs to not bend as much as the X does at the same draw length?
I am wondering if anyone else has experienced this when upgrading to a FF string.
P.S. this is just me thinking aloud and trying to rationalize a customers thoughts.
I've found that a bow feels noticeably heavier at a higher brace height. Could there have been a higher brace height when the customer tried the bow because the string hadn't settled in yet?
Dave,
I am not sure. But he said he has let it sit all night, etc. It just got my little mouse a running and thought i'd ask. In my opinion.. It COULD happen
Nope. Technically speaking, the string has the most load on it at rest (2 points of contact). At full draw (3 points of contact), supposedly that's when the string acts like two separate strings that share the load. At least that's been the explanation I've gotten...think O.L. Adcock was the first one I heard tell it like that.
So...if string material was that elastic, it would actually contract at full draw vs. stretching, and the draw weight would increase with the elastic material rather than vice-versa.
Of course that isn't happening either. Think about how much difference in string length there would have to be to feel a draw weight difference. To change the draw 2-3 pounds you are talking about he string changing a good inch or so in length. Not happening.
Very simple solution. Put it on a scale and check the draw weight. Brace is different, or someone said something that got in their head to the point that they are "feeling" something that isn't there. My guess is the latter.
Chad
To answer your question, yes, but not much IMO. Depends in large part on how well the string is made, how many twists it has, etc, but the B55 is slightly more elastic. Though the change may be measurable with sensitive equipment, I doubt it is great enough for someone to notice just by drawing the bow. He might be reacting to a different brace height, as McDave suggests.
LBR. Agree with your description of string load, contraction at full draw. But, though the lower stretch string may not contract as much at full draw as the B-55, I'm thinking it's reasonable to assume that it did not stretch as much during the draw as the B-55, and that it's still shorter than the B 55 string at full draw, thus placing marginally more force on the limbs, bending them ever so slightly more.
Thus, the additional performance derived from a low stretch string might be due not only to its lower stretch during the shot, which transfers more the the limbs' power to the arrow, but also to bending the limbs ever so slightly more. Makes sense to me. Keep in mind though that these differences would be very small, measurable, but probably not noticeable.
How's that for mental gymnastics? :bigsmyl:
B50 and B55 are more prone to stretch, I read that the best brace height of most bows is where the most force is exerted against the string. i also acknowledge that a Chad string makes a bow shooter better if it had any harsh qualities with a B50 string and in a case with one of my bows, it also allowed a stiffer arrows spine. this difference has to do with more than just the weight of the string, there are elastic things going on in the course of the draw and shot. How much? I don't know.
Quote...contraction at full draw
That would be "if" any string material were that elastic--it isn't. At least not to a degree where anyone could tell it. An amount that would be, at best, measured in 1/100's of an inch.
you guys lost me lol. Never knew there was so much to know about strings. Interesting
Daniel, If you are getting 3" of stretch, something is seriously wrong IMO. I agree that the highest tension on a string is at brace height position. And, I'll admit that I only use B50 and FF string material, BUT 3" is WAY too much stretch on a newly laid up string.
Arne
Arne,
what would be wrong with it, bud? (not asking sarcastically, seriously wondering your thoughts).
the b55(non FF) is like a rubber band. It is CRAZY how much it will stretch. Literally. I can put a string on the stretcher and stretch it almost 5-6" farther than what it is and then it will "settle" about 3" longer than when it was originally finished.
I usually put around #220 of pressure on it.
One interesting difference is that B55 will continue to stretch a significant amount when weight is added to it. BCY X will not really stretch more than 1.5-1.75". IF you put more pressure it will just hold it and eventually snap. Don't ask me how I know that! ;)
As I said, I don't (haven't) used B55. Just B50 and standard old Fast Flight. I've made my own strings for nearly 50 years and have never experienced that much stretch. I will also admit that I only place a new string on a braced bow overnight, then serve and then shoot. After a 100 or so shots, the brace height MAY need to be reset but then the string (for me) doesn't ever seem to change again.
That's just how I've always done it. I suppose many materials will stretch under 250# of tension, I just don't see the point.
Arne
well that explains why my Bear with B50 loses power after a few 14 target rounds. Have been told by another old guy the bow gets "squishy", at least his does. I knew it wasn't the bow! But to be serious I had a B55 string made for my Bear that "seemed" to improve its shooting qualities. I count that as a plus.
Something in the B55 allows for more hand shock with certain bows. That same thing allows the string to ride further ahead, which requires the need for an arm guard with certain bows. I don't know for sure if it is stretch or string weight.
Same here Daniel. The purpose is to try and get the string as close to settled as possible for the customer.
Polyester is elastic, to a degree. HMPE and HMPE blends are not. Most of the creep we get from them is air/dye/wax in the twist.
B-55 is a little higher grade of polyester (Dacron), but it still stretches like crazy.
Arne, the original FF formula is BCY's 652 Spectra. The founders of BCY (Ray Browne and Bob Destin) created the material when they worked for Brownell. Brownell owns the name, but doesn't have access to the original material. I have a few spools on hand if you would like to use the original.
Rick ****** wrote a post "on the wall" several years ago about low stretch strings and he described exactly what your customer is experiencing. The measured draw weight of a bow increased when he went from a B50 to low stretch string. He used the same brace and same drawlength for the comparison. I believe it was only a pound or so, not three.
He also made an opposite claim once that his string made his Black Widow pull something like 4# heavier than the 14 strand Dynaflight '97 that came with the bow. He said it was because his string contracted at full draw.
I questioned him about that--not his honesty, but his test methods, because to pick up that much draw weight his string would have to contract at least an inch. Dacron is the most elastic material and it doesn't contract anywhere near that, at least not on a bow and at full draw.
Long story short, he acted like he wanted to get physical over my questions. I just laughed.
Either way, he's mistaken in both cases. Even with a low strand count, you won't get nearly that much elasticity in a string.
So can someone explain why the string contracts at full draw?
That's just it. It doesn't, at least not to a degree that you could notice it without specialized equipment. Certainly not enough that it will affect draw weight to any degree.
I may be an idiot, but why(how) would the most pressure be put on a string at brace?
OK. Can someone explain why there is more tension on the string at resting brace than at full draw?
By the way, I am not a rocket surgeon, so keep it simple.
From Chad "Technically speaking, the string has the most load on it at rest (2 points of contact). At full draw (3 points of contact), supposedly that's when the string acts like two separate strings that share the load. At least that's been the explanation I've gotten...think O.L. Adcock was the first one I heard tell it like that."
Makes sense since each half of the string is pulling weight of one limb. The resistance of both limbs gives final draw weight.
But they can't be two separate strings if they are still connected, ie still one string and will share the load equally.
I understood what Chad said, just do not understand what it means or how that works. Still scratching.
I agree with lefty4. I see what you're saying, but theres not secret that when drawn, the bow gains poundage, so wouldn't it make the weight heavier at full draw?
either way, this is interesting. I have another question i'm going to post just to see what people think about it.
QuoteOriginally posted by DanielB89:
I agree with lefty4. I see what you're saying, but theres not secret that when drawn, the bow gains poundage, so wouldn't it make the weight heavier at full draw?
either way, this is interesting. I have another question i'm going to post just to see what people think about it.
Clearly, the bow's draw weight increases. String tension is different and is greatly influenced by string angle at the tips. I have access to a tensiometer, I'll see if I can measure the actual tension. Should be able to at least get relative comparisons.
In a March 1931 publication of "Sylvan Archer" (a magazine of the period) C. N. Hickman writes that (this is paraphrased folks) the tension of a bow string at brace height is at it's highest tension. then as you draw, the string tension decreases as you approach HALF draw the increases again until full draw is reached. AND, the tension in the string APPROACHES the tension of the string at brace height but doesn't quite reach it.
Now, in the article, he (Hickman) refers to mathematical results that predict this. And then goes on to show testing that confirms the math. In a quick review, I don't see that he addresses the WHY , just the results. For those of you that have an aversion to mathematics and physics this article and most all Hickman's writing are NOT for you. There are formulas and many graphs showing these results.
As a matter of interest, he also talks about the effect of brace height on the weight of the full draw. Basically, A bow's brace height (WITHIN REASON) does not affect the full draw weight of the bow significantly, if at all; but can greatly affect the stress in the limbs. This all was written in a period of time where all wood bows were the norm and linen strings were used. So things MAY have changed but again, maybe not.
A large set of articles written for archery magazines in the 1930s and 1940 are compiled in a book called "Archery _ The Technical Side" and has articles by Hickman, Klopsteg, Nagler and others. For those of you with a math and physics interest, MUCH can be learned from these writers.
There are many examples of things that would APPEAR to make sense that don't stand up to scientific study; I believe this is one of those.
Arne
PS. IF the above is true -- that the tension on the string is ABOUT the same at brace height as it is at full draw, you probably won't FEEL any "stretch". Maybe you are experiencing something else?
Arne
I'm assuming the tension in the string is different from the force required to pull the string, i.e., the force draw curve that we are familiar with. The force draw curve for most bows increases for each inch the bow is drawn within its usable range, so is at a maximum at maximum draw. The direction of the force vector is always at a right angle to the handle of the bow; i.e., the direction we would pull the string when we shoot it.
Tension in the string would be the force required to hold the bow at a given bend by pulling the string along its length. For example at brace height, if you took half a string with a loop in the end and pulled it toward the other nock, the tension would be the force required to pull the bow into its braced position. The direction of the force vector would be toward the other nock at brace height. As the bow is drawn, the force vector remains an extension of the string, and so changes direction as the bow is drawn. As the tension at any point could be measured by putting the bow in a vice and pulling with half a string in the angle the string would normally be at that point in the draw, the string does act like two strings for tension measurement purposes. Intuitively, it would appear that there should be some mechanical advantage in pulling the string at an increasing angle as the bow is drawn, which, unlike the normal force draw curve, might be enough to offset the increased force required to draw the bow as it is bent.
These are just my thoughts as I try to understand the physics of what's going here; please correct me if I'm wrong.
Thanks Arne for the references.
McDave, I agree with your assessment of the force vectors and angles and was thinking therein lies the answer. But I just can't see it in my head. I have been away from physics classes for a long long time.
I am anxious to see what Fletcher discovers.
Good discussion and thought provoer.
I'm not going to pretend I understand the physics behind it. I like to keep it simple.
Put the bow on a scale with two different strings of the same length (giving the same brace height). Measure the draw weight at a given draw length (or several) with both strings. Record the difference--if there is one, it will be minimal.
Immediately after letting the bow go back to brace (off a scale or shooting), measure the brace. I'm sure Daniel or anyone else who has put a string on a stretcher can verify, they contract very slowly. If the string stretched at full draw, you would be able to get a noticeable difference in the brace height.
I've seen some weird things blamed on strings, and it's come from people who had a reputation for knowing their stuff.
For instance...a claim that a string (high performance material) contracted so much at full draw that the bow gained 4# of draw weight; that a Flemish string caused the limbs to twist on a 72# longbow; that Flemish strings are less accurate and could be dangerous...
Not doubting the honesty of these people (not all of them anyway)...but however they came to these conclusions, there was a hiccup somewhere along the way during testing.
Your explanation appears sound to me McDave.
We know there are differences between dacron and modern low stretch materials, and we can see and have measured some of those differences. The disagreement seems to lie in how large those differences are.
As they say in scientific circles, more research is needed.
QuoteOriginally posted by LBR:
I'm not going to pretend I understand the physics behind it. I like to keep it simple.
Put the bow on a scale with two different strings of the same length (giving the same brace height). Measure the draw weight at a given draw length (or several) with both strings. Record the difference--if there is one, it will be minimal.
Immediately after letting the bow go back to brace (off a scale or shooting), measure the brace. I'm sure Daniel or anyone else who has put a string on a stretcher can verify, they contract very slowly. If the string stretched at full draw, you would be able to get a noticeable difference in the brace height.
I've seen some weird things blamed on strings, and it's come from people who had a reputation for knowing their stuff.
For instance...a claim that a string (high performance material) contracted so much at full draw that the bow gained 4# of draw weight; that a Flemish string caused the limbs to twist on a 72# longbow; that Flemish strings are less accurate and could be dangerous...
Not doubting the honesty of these people (not all of them anyway)...but however they came to these conclusions, there was a hiccup somewhere along the way during testing.
by "hiccup", you much mean bud light..
If I had to guess, something a good bit stronger...
I put a fresh, unstretched B50 on a 96 pound longbow and tested the weight. 20 minutes later my brace height was down to three inches from 6" nad the bow pulled less pounds. Once that string was in use for a couple of weeks, it was stable and bow remained at 96 pounds. I may be OCD, but that stability and nock fit for my 5/16 mercury nocks is a major deal, regardless of the lack of hand shock, faster arrow speed, and greater spine tolerance with the BCYs. I need to order a couple BCYs with a turn or two less in the loops than my standard narrow loops for a couple of tiny tip bows. Is there a minimum number of turns?
Pavan,
what do you mean by minimum turns? Are you referring to the number of twists in the loops? if so, no. That is how you adjust the size of the loop. A few less twists would make the loops smaller(assuming that is what you're wanting)
When I made my B50 strings, I would twist them much harder than normal, resulting in an apparent thinner string. When I made strings for heavy bows with 18 or 21 strand strings, it took a lot of pressure in the twist to keep the loop small enough for bows like Schulz longbows. I was kidding about the number of twists, but I do need a couple of strings that have a couple less twists, I need to count the urns on the strings I have on my current bows. Some longbows do not kick all that hard, but when I put a Chad string on them, I can still see what I was missing with the B50s. Chad seems to put a graduated twist towards the loops in the main string, I imagine it does more than just look cool.
I am not sure what you mean by "graduated twists", excuse my ignorance. I have seen several of Chad's strings and he definitely knows what he is doing!
I can see what you're talking about about needing the loops smaller, but also needing a high count of strands.
On my Chad strings about five inches or so from the area where the loop strands begin, the twist is about twice as tight as the middle section. i tried duplicating this on a B50 string for an old bow and as soon the bow is strung they start going away and are gone with the first shot. I have been shooting the Chad strings for many thousands of shots and that tight twist prior to the loop doubling remains. I don't know he does that.
Here we go! I borrowed a tensiometer from work. This is an accurate and calibrated tool that is used to measure the tension of aircraft flight control cables. Test bow is a Great Northern Field Bow, 41 lb at 28". I chose it for its lower draw weight, making the test easier to perform and its nice round string which leads to consistent readings with the tensiometer. With the bow at brace height, the meter indicates a 34, which translates to about 55 lb actual string tension. At 28" draw the meter shows a 24, which translates to about 36 lb actual string tension. Watching the meter as I drew the bow, the tension dropped steadily to about 1/3 draw the held steady for another 1/3 then slowy started to climb approaching 28" draw. This matches Hickman's findings mentioned in Arne's post above and pretty much settles it for me. Interesting and fun.
Tensiometer at brace height:
(http://img.photobucket.com/albums/v450/Fletcher610/Bow%20pics/20170205_090402.jpg) (http://smg.photobucket.com/user/Fletcher610/media/Bow%20pics/20170205_090402.jpg.html)
Tensiometer at 28" draw:
(http://img.photobucket.com/albums/v450/Fletcher610/Bow%20pics/20170205_090513.jpg) (http://smg.photobucket.com/user/Fletcher610/media/Bow%20pics/20170205_090513.jpg.html)
Thanks Fletcher for doing the "test". This is not what I would have guessed at the beginning of this thread. Glad you could show some "proof" that concurs with Hickman's findings.
Very cool--thanks for the info.!
At least we know that the load on the string is greatest at brace, and drops noticeably at full draw...but the fact remains that if the string contracts at all at full draw, it's nowhere near enough to make any noticeable difference in draw weight.
Agreed. Also throws my theory out the window about the lower stretch string potentially exerting more force on bending the limbs at full draw.
If the strings start out the same length, any contraction as it approaches full draw would be greater with the stretchier string. In short, the lower stretch string wouldn't contract as much and would be longer at the shot vis-a-vis the B55 so if anything, it would be flexing the limbs a tad less.
In other words, its effect on increased arrow speed is due to its low stretch properties during the shot, not aided by an additional incremental bending of the limbs.
Of course, we're talking small fractions of an inch here. Stuff that would not be practically significant.
Woah!! That's cool!!!
Thank you for that Fletcher!
I'll just stop talking false theories now! ;)
Amazes me at the "old wive's tales" that get told about strings...even from people that are supposed to know their stuff. I love threads like this though--helps to quell some of the fables.
Chad
Saxton Pope, also tells of the high tension of the string at the nock, of a braced bow!
Hunting with the Bow and Arrow.
Brace height might not effect the measured draw weight much at all but your bow will stack more with a higher brace height making it much more difficult and uncomfortable to draw.
As for string material the non stretch stuff is indoubtly much better on laminated bows because they can handle it. B55, B50 and so on is better on all wooden bows in my opinion since it put's less of a strain on the bow.
I use a low stretch BCYX string and sure it is very fast but I can feel the strain it put's on my fingers and the bow compared to a softer not as high stretch material.
Stretch on some bows can be a good thing since as the string stretches throughout a shooting session it allows the bow to relax (through string stretch) slightly without losing any cast by slightly lowering the brace height over time.
This is probably best for all wooden bows.
I disagree, John forestdweller.
I have shot selfbows and backed all natural material bows, with high performance strings since 1991. They are a compliment to the bows and their performance!
String materials are not created for certain types of bows, nor are bows designed for specific types of string matetials! As time goes on, each has been created to be the best!
That is what we strive for, performance at its best!
The best in tune, arrow flight, gentle on release, and as a hunter, true penetration for a clean, quick kill!