Hey guys. I've recently started making my own Flemish twist strings, but I've run into an issue with stretching. When I make a string, I usually make it just a bit short because I know that it will stretch. What I've found though after shooting a string and getting it to the desired brace height is that if I unstring the bow, then string it up in a few days, the string has shrunk back to the original length and the stretching process repeats itself. This is really frustrating since I can't get any consistency. Is there something that I'm doing wrong to cause this? Any help would be appreciated.
Are you prestretchjng the string after twisting it up? I make mine out of 8 strands D97 and 2 strands B50 and I get about 1" of stretch Initially then it stays put. I stretch mine by putting a hickory dowel through each loop. I'll put one dowel under my feet and depending on the string length, I'll barace my hands on either my shoulders or head. And use my legs to push and stretch the string before I put it in the now for the first time. Probably putting a couple hundred points of force on the string.
Kyle
Dacron, I'm guessing?
Leave the bow strung for a time, after shooting, if possible. Then check brace. Keep record. Check, adjust, if needed, shoot more. Until settles!
Dacron, I'm guessing?
Leave the bow strung for a time, after shooting, if possible. Then check brace. Keep record. Check, adjust, if needed, shoot more. Until settles!
I leave my shooting bows , 1 is B50, 1 is D97, strung all the time.
Once my brace is set ( adjust a couple times with B50) they never really change.
No reason to string and unstring your glass bow. Leave it strung
Also I make my B50 Flemish about 1/2 shorter than the usual 3-4 depending on bow to accommodate the stretch.
I also don't really prestretch my strings, just give a good pull to straighten everything out then string and adjust as needed.
That is the nature of polyester (dacron), and to a lesser degree other materials. I can put a dacron string on my stretcher and literally watch it contract once the load is removed (around 250#).
Easy solution, unless it's a self bow, is leave the bow strung. If it's a self bow, allow time for the bow to be strung a while and/or put several shots through it to let the string stretch back out.
I see the same thing a lot on the bow I have that I shoot B-50 on. I can shoot awhile, set the brace, shoot awhile and when finished, unstring. Several days later when I restring the bow, the brace is high again and it takes a few arrows through it to stretch back out to the correct brace height for the bow. I'm one of the guys who does not like to leave a bow strung when not shooting it every day. Just one of the downsides of B-50, but boy does it ever shoot quiet and smooth on my Martin/Howatt!
Thanks for the input guys. I am not sure what the string material is. It was given to me by a guy who builds self bows that I met while on a camping trip. There isn't a label on the spools and I never thought to ask. I will try pre stretching them to see if that works. I don't really like leaving my bows strung either, mainly for storage purposes, but if that's what it takes, that's what I'll do.
For a selfbow guy, most likely it was Dacron (B-55 or B-50).
How many strands are in the string and what draw weight? More strands may help a little. Low strand count 100% HMPE strings (Dynaflight, 8125, 8190, etc.) will stretch/contract more, as will Dacron.
I found it online and it's B50. The bow that I'm currently having issues with is a 62 pound longbow and the string has 14 strands.
On my bows with Dacron strings, I just press down on the limb tips after I string up and get the little bit of stretch out. I can actually feel it.
I've seen it happen. I like David Mitchell's suggestion.
After reading these posts over, possible this might be a spool of artificial sinew, nylon?
I never understood all these "Stretchy" statements, in reference to dacron/polyester strings.
QuoteOriginally posted by frank bullitt:
After reading these posts over, possible this might be a spool of artificial sinew, nylon?
I never understood all these "Stretchy" statements, in reference to dacron/polyester strings.
I figured out that it's B50.
I don't know if it's the string that stretches or the fact that I'm still new to making strings and possibly not doing it quite right.
It's the material. Polyester ("Dacron") stretches, and contracts. It stretches/creeps more in hot weather.
That was one of the main reasons for the invention of "Fast Flight". Less stretch/creep = better consistency and stability.
I shoot B50 and make my own strings. After reading Sagittarius and hearing about how Swinehart heated his bowstrings in the oven I got myself a little potpourri crock pot and melted my beeswax in it. When I make a new string I soak it in the hot beeswax for several minutes and then take it out of the wax and string up my bow hot. After rubbing excess wax away and after it cools I get very little / no stretch. Been doing it this way for several years now on quite a few strings. The wax really gets into the string and helps it last also.
Makes sense to me. I've always folded a small piece of leather and really burnished the heck out of my Flemish Twist strings (back when my hand cramps didn't preclude me from making them). Seems like your method of heating the wax in might well be easier on the hands, and less work.
Pure bee's wax is as hard as a rock when it cools. Bow string material comes pre-waxed. The materials go through heat when the color is cooked on. Too much heat will damage the material.
Chad, how much is too much heat? Is there any data / documented experience available on bowstring failure using this method? I'll admit it's new to me but I have not tested nor read / heard anything contrary. I have not read the reference from where this experience was obtained either.
Perhaps, back then they may have experienced some painful failures, eh?
I've been building bowstrings since the mid 1950's in both Flemish twist and endless styles, using linen initially before moving on to B36 and eventually on up to kevlar (bad stuff!!) and with today's HMPE.
"B50" is "Dacron". Both are trade names for "polyester" (i.e. - "polyET" or polyethylene terephthalate). Polyester and excessive heat are not things that go together well, and will change the properties of polyET. Saturating any bowstring material with any manner of "wax", be it natural (bees) or petro-chemical (oil resin) will do nothing to keep it from stretching under tension, which is the only way to get the material to take a "set".
Rob, if I understand you correctly, the Dacron will "take a set" either way? More important ly, is the "beeswax" method mentioned above detrimental to the string?
Tony, I don't know what temperature is the max, but I can probably find out. I have been told of instances where burnishing with leather has melted strands. You can contact BCY directly about this if you prefer. Normally I "could" be wrong, but in this instance saying Dacron can be damaged with heat is like saying gas can catch on fire. Not much chance of screwing that one up.
All current modern string materials are, basically, plastic fibers (some blended with LCP). Plastic melts when you get it too hot. The hotter it gets, the more pliable it becomes. That's why Dacron and 100% HMPE strings tend to "creep" in hot weather.
Rob is spot-on. String wax is a lubricant, and if anything saturating string material with wax will cause it to settle a bit more, as the excess gets squeezed out.
Bee's wax hardens when cooled. At best, it's going to get shot out of the string in short order, and heating may remove the factory "wax" (normally silicon based, so it absorbs better). If anything, the heating could cause the string to wear faster due to the silicon wax being melted out (much lower melting point than bee's wax).
I know the question was asked of Rob, but here's my input. When/where Dacron will "take a set" depends on a few variables. Under the right (wrong?) conditions, it can keep on stretching until it breaks (high temps, low strand count, heavy load). Or, under the "right" conditions, it can settle in (enough strands, light enough load, temps not too high).
a polyester bowstring will reach a limit of stretch when under tension (braced bow). relieve that tension (unbraced bow), and its rubber band effect will shorten its loop-to-loop length. brace the bow with it and it will come back close to its stretched out brace height, but will probably change yet again after a bit if shooting.
this is why a search for a more non-elastic string began back in the late 60's and the "answer" was kevlar (NOT!!), which had near zero stretch and as a result it shattered risers and busted limbs big time. the development of HMPE (polyethylene) bowstrings has been the biggest boon to trad bowhunters, where you get durability and low stretch that will, over time, take a true "set" but still offer a modicum of spring during the shot to protect the limbs.
rubbing in a bit of beeswax or paraffin wax or combination of both (i have my killer "secret sauce" string wax ;) ) with a piece of leather or paper is all that's needed to melt the wax into the string fibers. don't cook yer bowstrings!
left out of all of the above is strand count. a low strand count dacron string makes no practical bowhunting sense. in fact, low strand count of ANY type of string for a trad hunting bow offers no advantage to the bowhunter and IMHO is a disadvantage in durability. here we go, back to common sense traditional bowhunting. :)
I have 2 heavy duty shelf angle brackets mounted on a 2x4. One is adjustable for different lengths. When I make a new string I wax the strands before twisting it up. Then I put it on my jig and stretch it tighter than it would be on a bow. I let it set over night. The next day the excess wax is squeezed out of the string. It works great for me and my strings are stable when I put them on a bow.
I use D97, 452x, 8190, and FF. I don't think I'm stretching the fibers very much at all. I think it is tightening up all the twists and locking them in place.
X2 what David Mitchell said.
FWIW, the melting point of B-55 polyester is 500 degrees (the point where it becomes liquid). Not sure at what point it will start to damage the fibers, but I know it's much less than that. B-50 probably has a similar melting point.