B55 stretching at full draw?

[DanielB89]

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.

[McDave]

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?

[DanielB89]

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

[LBR]

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

[Orion]

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.

[Orion]

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?  

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.

[LBR]

 ...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.

[crazynate]

you guys lost me lol. Never knew there was so much to know about strings. Interesting

[moebow]

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

[DanielB89]

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!  

[moebow]

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

[M60gunner]

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.

[LBR]

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.

[lefty4]

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.

[LBR]

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.

[lefty4]

So can someone explain why the string contracts at full draw?

[LBR]

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.

[DanielB89]

I may be an idiot, but why(how) would the most pressure be put on a string at brace?