a fella i work with recently commented as to how quite my hoyt gamemaster was and asked what i had done to get that noisey (%^$#$ quiet
i told him that i had made a skinny ts-1 string for it
he then asked if the same princibles would work with b-50 dacron for the vintage bows he has
so i thought i would ask and see what the consensus was
thanks in advance
kevin
I'm no expert, but B50 has about 1/2 the strength of the modern materials...so I'd be careful.
ive used a skinny 6strand d97 with the loops padded out on my old tigercat with no ill affects.
Use a skinny padded 8125 or d97 on any bow. I wouldn't go with ts-1 though. 6 strands of 8125 is good up to a 73# bow. 4 is good up to a 49# bow 3 is good up to a 37# bow. If you pad to 14-16 strands in the loops an 8125 can be used on pretty much any bow. Don't go skinny with dacron B-50 and b-500 have only 37.6% the strength of 8125 and they are thicker so they're not great candidates for skinny strings. Now when using 8125 and old bows don't go higher than my recommendations in strand count because the low strand count makes the string act more like b-50 on the limbs but doesn't have the creep that b-50 has. The skinny 8125 will also reduce vibration in the limbs and riser and will actually be easier on the bow. What are the draw weights of the bows? Do you make 2 or 3 bundle strings?
thanks guys
jesse i make 2 bundle strings and the bows my coworker has are 40 @ 50# @ 28 and he draws 29
kevin
I have made quite a few skinny strings with low stretch materials like D97,450+ and 8125.But with dacron I see no advantage with a skinny dacron string,not strng enough.I use 14 strands up to 65# and 12 strands for under 50#.
I use skinny (six strand) on some vintage bows and they seem to be as bow friendly as dacron, as long as the loops are padded. Actually there is much less vibration for the bow limbs to cope with.
Skinny Dacron would creep too much and is not strong enough. Like George and others have experienced a skinny D97 (or similar) string with padded loops works great on my vintage bows too. I'm not recommending anything here just reporting my own results.
I'm not to the point yet where any non dacron string is going on any of my '59 Kodiaks but the test bows show no ill effects and shoot very nicely.
QuoteOriginally posted by Bjorn:
Skinny Dacron would creep too much and is not strong enough. ...
+1 :thumbsup:
hmpe fibers only, for skinny strings.
KHALVERSON I'd make a 4strand padded to 14 for the 40# bow and a 6strand padded to 14 for the 50# bow. The lighter one should be about 42-43# at his draw and the heavier one should be about 52-53#. The 4strand is good up to a 49# bow so it should work perfectly. The 6 strand will work fine for 52-53. It's good up to 73# so it's a little overkill but it will be fine. Please give us an update on performance changes in the bows speed, noise, handshock, etc. The bows will have a lot less vibration but he will need to retune them. You can only see the real benefits when the bows are tuned for the new strings.
jesse, you talkin bout dacron or hmpe 4 and 6 strand strings???
Those skinny D-97 will shoot on an old bow but padded loops or not you are gonna rattle those old bows apart. The real issue was the glues used back in the day. They were nothing like the glues today.
Sure if you pad the loops really well the tips should be fine but that is not the real issue with the low stretch string. Why do you think Bob Lee fought tooth and nail before they finally went to FF strings? Because the whole world was using them and they had to bite the bullet. 4 or 5 years ago Bob Lee would not warrant a bow that had FF on it.
Rob I'm talking about Hmpe. Specifically 8125. 4 strands of dacron could be used on bows under 20# in draw weight only. A padded skinny 8125 will actually be easier on an old because it will have less vibration than a dacron string therefore putting less stress on the glue joints. A skinny padded 8125 will put no more stress on the tips than a dacron. It'd be interesting to see the difference in stress cracks in a bow using a good fastflight vs a dacron string in the course of 30-40 years. I suspect the decrease in vibration from using 8125 would decrease the delamination rate and decrease the number of stress cracks.
I am definitely a string know nothing but i thought the problem is the sudden instant stop of the limb travel with low stretch which lends to extreme instant high level shock. Dacron is like a rubber band and disperses some of that instantaneous shock and may even convert some of it to a little vibration. I didnt know a little vibration was bad for a bow. That pop noise of a ff string that makes them more noisey is when that instant force is released on the bow. Jim
As long as the tips are in good shape I just use d-97 on everything.I suspect most of the mishaps with modern strings on old bows is due more to the crappy way many of the string grooves were cut on them more than the string materials.Selfbows and all wood bows never have issues with modern skinny strings and I don't thing most any bow will if it does not have issues to start with.I don't own any bows that will ever be shot with a b-50 string.I think it is worse for a bow than the newer strings myself the way they add so much vibration and shock to a bow.It can't be good for one.jmho
Steve....no one has really studied that aspect of it, so I'm not too sure of that "rattle those old bows apart" thing. Anyone can say what they want about that, but the fact is, it hasn't been studied. That's why I'm doing it on some old bows. No 59' Bears by the way.
From what I see, there is less shock from a skinny string of 450+, than there is from from a sixteen strand dacron....going on feel now. The bow is also quieter and more dead in the hand with the skinny 450.
I'm not saying for anyone to put them on vintage bows, but since no one will take up the challenge of trying it, then I suppose I have to.
I'm not buying the "old glue isn't as good thing." Shock is shock, vibration is vibration, and the old linen strings were about as no stretch as any modern material.
I've now shot my old Shakespeare at least 2000 shots with the skinny 450+, and I'm betting I'll get another times that many more shots. I have a 61 Polar that has a TS-1 string on it, and it has more than 500 shots through it, and also is less shocky on the shot.
You know maybe down the road, the old Shakespeare will break, but it isn't showing any signs, and from what I'm seeing, it is having to endure less vibration than it did with a 14 strand dacron, endless loop. Go figure.
I'm certainly not an expert, and was also one of those guys who swore by the B50 only theory for old bows. Bottom line is you guys need to do what you do and not compromise your bows if you think you will by shooting modern strings on them. As for me, I'm not convinced, so I'll keep plugging along and see if I get an en-masse failure from using the strings. I don't know at this time, but I have a gut feeling these old bows will hold up just fine.
I'll keep you posted if I do have a failure....I'm not afraid to pass that along if it happens 8^). We will see, for as they say, "nothing ventured....nothing gained."
String shoulder rotator messed up last summer; can't pull the 55# widow so started experimenting with my old 45# Shakespeare X12 I got 30 years ago. Had it shootin half decent but alot of tinkering to find the sweet spot with a B50 string.
Right before Christmas I got the X12 an 8 strand D97 from SBD folks. What a fine string! Heavily padded loops tapering smoothly to the skinny.
WOW! Not so finicky about brace ht, more quiet that ever- super quiet, arrow trajectory obviously much flatter, and arrows sinking much deeper into the target. A totally different bow.
I got a Chrony for Christmas so plan to weigh both strings and compare speed and report back.
At 45# you could use a 4strand 8125 padded to 16. You'd see another increase in performance. BTW a 4strand 8125 is good up to a 49-50# bow
Jesse I want to build strings but not there yet. Anyplace a guy could buy one like you're describing? I think the SBD folks will build one with what strands you request.
Definitely want one for the 40# i am re-finishing.
What are you using for padding on those really skinny strings Jesse? I've been using 8125 for the padding on my 10 strand 8125 string (padded to 20 strands of 8125) but I don't think the loops come out big enough for the Dacron bows. I also tried some really outrageous levels of padding but it started to get a little tricky twisting the loops. I was thinking of slipping something over the loop before I close it.
I'm using 8125 for padding. 10strands in the body is your problem. 6strands is good up to a 73# bow. 20strands is more than enough padding. If you want you can use b-50 or artificial sinew for padding. It can get tricky with the padding what you want to do is cut your padding strands and stagger them 1/2 from each other. That way when you twist a string up the taper is already there. What do you mean by slipping something over the loop before you close it? Are you talking about serving it? Something you can do is serve the loop and neck of the string with wool. I do this for my recurves to quiet string slap. It also acts as padding.
FlintRiverKen, I don't know where to buy one like I make. It's not hard to make a string though. There's a tutorial here on how to make a jig out of a 2by4 about 30in long. You don't need a jig but it's nice if you make lots of strings so you don't have to measure out all the strands. Go ahead and get an $8 roll of 70# artificial sinew. Use one strand for 14# of draw weight. Artificial sinew is cheap and makes a good string. Once you get the hang of it get some 8125 and twist up some strings. I don't know the folks at SBD but go ahead an e-mail them and ask if they'll make one.
Jessy,
Well when I look at some of the string nocs on my older bears, my 20 strand 8125 loop is considerably smaller than what was there in dacron. So I kind of wanted to get that loop up to the same size. I was thinking of slipping on a tube of something, but it would have to be just right to work, maybe some of that rubber heat shrink tubing would work. I like the idea of yarn or possibly fly tying floss. I also tried serving it by hand after the loop was done but I didn't like that either with the ribs of hard spectra thread.
Even at 6 strands there is still not going to be that much stretch in the dyneema string, either six or ten strand. About a half of a percent at 10% of the breaking strength (I got that off a rope web site). So there is very little difference in stretch between six and ten strands on bows up to 75lbs or more. But I don't deny your success with what your doing right now with your strings either. The stretch rates that I saw on the rope web site with dacron and nylon included were at 30% of breaking strength; .9 for SK-75 about 3.9 for dacron and 14% for nylon. Sk-75 was actually lower than wire rope. It is real popular for yacht rigging and winch ropes because when it breaks it just falls on the ground with no whiplash (no stretch).
The 10PD20 strand strings I make are for my modern bows, Morrisons, Pronghorns and Black Widows. You know I tried some 6 strand stings and I didn't like the way they shot. I went back and forth between 6 and 10 strand strings on the same bow in the same session and I really like the ten better. Maybe the slightly thicker string can transmit vibration to the cat whiskers better or something like that. And this was on fairly light bows too (36lb widow, 41lb pronghorn, 38lb Morrison longbow). My Morrisons came with a 10 strand 8125 so I just use that on most all of my modern bows. Maybe a twelve on the really heavy stuff.
This is interesting. My 16strand loops are about the same size as 14strands of dacron. Could you post a picture of the comparison? The difference you saw between 6 and 10strands was bow tuning. If you tune the bow specifically for 6 and specifically for 10 you'll probably like 6 better. On bows that light I'd try a 4strand and tune the bow to it to see how you like it. Thanks for the info on the stretch rates.
Well I can't post picks but the 8125 strand is very small. Just look at the size of the string grooves in an older bow. Maybe I got something mixed up, but I still think the major problem is the size of the loops.
You know there was very little performance difference between the six and the ten strand on those above mentioned bows. If anything they shot the same arrow better with the ten in my opinion (especially the Widows). I thought there was more vibration with the smaller string especially on a really long Morrison riser/limb combo. The arrows definitely weren't flagging high left with the smaller string. I came to the conclusion that there is very little difference between them, not enough to use such a small string.
But I still might use the six on older bows, even though if there is any more stretch it would be microscopic.
I forgot to add that for the tapering of the padding strands I added another row of nails on the jig. They have to be the exact same distance away from the center of the loop as the main set of nails in the other direction. Now when I have the main strands on the jig I start over with a color I don't like at the first nail and just wind around both groups of nails until I have five or whatever more strands of padding tapered on both ends. The ones for the second loop I just pull out and set aside and put them back in when I get ready to do the second loop. You do have to commit to where you want the center of your loop though with this setup. When you make your cut you have to cut in two places, about 14 inches apart if you start your loops at 7 1/2 that is.
It does work well for a lot of padding, with almost no trouble to add padding to a string.
SBD strings can provide 6 strand skinny see below:
------------------
Ken,
We do have a 6 strand string for bows 53# or less. It is called the SBD Ultra. Our web site is not quite finished but it is on there now. (http://www.sbdbowstrings.com/index.html) The Ultra cost is $24 and it makes difference on lighter poundage bows.
Hope this helps.
God bless, Pierre and Jean-Pierre
SBD Bows Strings >>>------------->
"Crafted for traditional bow hunters"
www.SBDBowStrings.com (http://www.sbdbowstrings.com)
724-323-2107
P.O. Box 193 Dunlevy, Pa. 15432
lucasintlltd@verizon.net
----- Original Message -----
From: Ken Garcia
To: Pierre Lucas
Sent: Tuesday, January 12, 2010 3:37 PM
Subject: Re:
Hi Pierre,
could you make a 6 or 4 strand SBD for a 40# bow ? Enjoying the 8 strand SBD I have on a 45# now. thanks, Ken
summa you guys are way braver than me - no way in heck i'd ever put hmpe on an old bow, i'd stick with dacron.
i remember the 70's and those poor folks that tried kevlar strings on their fita bows ... INCOMING! OUCH!
Rob, the reason the skinny strings appear so scary is because they aren't the same as the strings most people use. I've found a skinny 8125 to be safer than dacron because the tips have no more stress but less shock means less stress on the riser, limbs, glue joints, etc. I've also found the numbers I listed earlier "6 strands of 8125 is good up to a 73# bow. 4 is good up to a 49# bow 3 is good up to a 37# bow" to be the safest strand count. More puts more stress on the tips. Less puts more stress on the string. I think that if the old bows had used skinny padded 8125 strings they would have a lot less delaminations, riser cracks, and stress cracks. A lot of things can appear scary or dangerous at first glance but when you look at the facts can be much safer.
FlintRiverKen, I think they use D-97. It's a bit different than 8125. 8125 is thinner in diameter and stronger. 8125 also creeps less. D-97 will still work you just won't see all the performance difference I described. 4strands of d-97 wouldn't be enough for a 45# bow but 4strands of 8125 is good up to a 49# bow.
QuoteOriginally posted by bearbowman:
Those skinny D-97 will shoot on an old bow but padded loops or not you are gonna rattle those old bows apart. The real issue was the glues used back in the day. They were nothing like the glues today.
Sure if you pad the loops really well the tips should be fine but that is not the real issue with the low stretch string. Why do you think Bob Lee fought tooth and nail before they finally went to FF strings? Because the whole world was using them and they had to bite the bullet. 4 or 5 years ago Bob Lee would not warrant a bow that had FF on it.
Actually, making a bow more efficient (like lowering string weight)reduces vibration. Less moving mass means less oscillating mass, which means less strain on the bow after the arrow has left.
Any of you guys who say the low stretch strings are quieter , have any data to back that up. I don't have the best ears but they are way noisier to me.
Not saying it is not true but would like someone to test it with a instrument used for measuring decibels to prove it once and for all with good unbiased data.
I think I already know the answer but will go with the data.
Jack
Jesse great idea about the artificial sinew. Like most folks wanting to learn to make strings the first thing I did was read and re-read all the how-tos and buildalongs. When moving to the hands on stage using a mtl that is inexpensive yet functional is ideal to train with. I have a couple kid's bows needing strings.
I haven't been able to find a buildalong for padded loops on flemish. It would be appreciated if you or Artifaker went into more detail. -thanks Ken
QuoteOriginally posted by Jesse Peltan:
Rob, the reason the skinny strings appear so scary is because they aren't the same as the strings most people use. ....
perhaps you missed my point - it's not the skinny string i have issues with, it's putting hmpe fiber bowstrings (dyneema, spectra, vectran, etc.) on old bows that far more than likely have limbs that can't handle the stress of a low stretch string.
putting a df'97 string on an old bear is just lighting the fuse on a bomb about to explode more sooner than later.
QuoteOriginally posted by Jeff Strubberg:
QuoteOriginally posted by bearbowman:
Those skinny D-97 will shoot on an old bow but padded loops or not you are gonna rattle those old bows apart. The real issue was the glues used back in the day. They were nothing like the glues today.
Sure if you pad the loops really well the tips should be fine but that is not the real issue with the low stretch string. Why do you think Bob Lee fought tooth and nail before they finally went to FF strings? Because the whole world was using them and they had to bite the bullet. 4 or 5 years ago Bob Lee would not warrant a bow that had FF on it.
Actually, making a bow more efficient (like lowering string weight)reduces vibration. Less moving mass means less oscillating mass, which means less strain on the bow after the arrow has left. [/b]
i don't think vibration, or lack thereof, is the issue - imo, it's the fact that hmpe strings just don't stretch/give anywhere near the stretch factor of dacron. if the limb tips on any bow can't absorb that shock, they'll blow off.
i saw that back in the 70's with kevlar low stretch strings - oooo, that was nasty!
My bet is, after a couple thousand strings built commercially over the past 30+ years Rob might have a pretty good idea of what's up with how older bows react to newer string materials/designs.
What JC just said.
My bet is he suffers from the same superstitions as everybody else, with tons of guys with more and different experience in their ranks as well.
To put it another way, and elk don't know how many legs a horse have. So, if we make a 4 strand string with essentially the same elasticity as another of different material but say 14 strands. And the first 4 strand string has a mass of say 70 grains, the 2nd 14 strand 200 grains but we compensate by using heavier arrows with the first, light, 4 strand string, and we fashion the loops to be the same diameter and shape (perhaps tricky with an endless but certainly possible), does the bow know or care what the string material is?
Not to sound grumpy here, it's not my purpose, but a false argument knows no personalities regardless of how renowned the speaker or subject. No point in guessing, show me the math, show me the experiment, show me the broken bows (not antecdotes, but properly tested using a control group). We didn't get to the moon, etc. by guessing how much thrust a rocket engine will make.
Flintriverken. Flintriver sounds like my kind of place. I need to get back to being able to post pics so I can show how I modified the jig for string padding. It is probably kind of hard to picture it from just words.
Maybe the hot setup for older bows would be to file off the tip material and glue on a tip of micarta with heat set epoxy. That is all a lot of modern bowyers use for FF.
This subject seems to be all sewed up but there is still the messy detail of a surprising number of people who have come forward and claimed to be using FF on older bows. I'm not at all convinced that a lack of stretch in strings (increases performance) is really bad for the limbs, it might be, but "were" using FF on all these modern bows and many just simply have a layer of tougher material on the tip. That is why I feel that the key is in not having the loops (bigger loops, micarta tips) cut into the string groove and get the whole process of tearing up the limb tips started.
But there ain't no way I'm going to put a six strand 8125 string on my 73lb Bear/Chastain limbs. Heck I was afraid to shoot them with a 20 strand Dacron string, LOL.
Well, DCM, I guess we'll just have to agree to disagree. My personal experience, first hand coincides with Rob's advice: many older bows simply will not stand up to FF material either from tips or limb/glue failure. I found out the hard way on two different bows that previously worked beautifully with B50. I firmly believe the bow DOES care what string material is.
So why would you believe that 4 strands of FF have the same elasticity as 14 strands of B50 (or even FF)? Show me your math, show me the experiment, show me the bows that did not break under experimental conditions.
And as far as the moon analogy, don't assume to tell someone what it takes to get to the moon if they have already been there....
Wow.
Now I'm really confused. :help: :biglaugh:
What jc just said. Again
while perhaps, maybe, there is some merit, on some bows, for using hmpe bowstrings, to me it's worse than playing russian roulette, and for me and my family's sake i don't wanna take a chance that i'm not feelin' lucky.
i'm just saying that there have been countless reports of old(er) bows failing with hmpe bpwstrings. these aren't bad bows either, they were good, well functioning bows to begin with and the introduction of a dyneema string blew off limb tips.
so i'm saying this to all - be really care if you feel the urge to test out hmpe bowstrings on bows that are not at all rated for low stretch, low creep bowstrings.
i see a lotta mentioning here of bcy formula 8125 string fiber. that's the same dyneema blend fiber as dynflight'97 and dyneema'02, only half the diameter. why? it was made specifically for use with recurves for a higher strand count to allow the string to be better 'rounded off'. a strand of that f8125 is still gonna be around 50% stronger than b50 or b500 dacron. btw, the median diameter of b50/b500 is the same as df'97 and d'02.
JC, I have a lot of respect for Rob, and many others here. However, there has been no meaningful tests on older bows, so the point is moot until that happens. We can opine all day, all week, all year, and it doesn't get past the opinion stage. I've been at this going on 46 years and have opinions also....and they are just like everyone elses opinions.
That said, I'm doing my own tests, at my own direction, to prove one way or another that there is merit...or there isn't...as to the fragility of old bows versus new strings. No one has shown by doing that there will be dire straits ahead.
Confusion is a product of the lack of legitimate information. My old Shakespeare, for one, has only Wenge overlays on the tips, and has shoot over 2000 arrows with a 6 strand 450+ string. What I'm finding...so far...is a mild mannered bow that is shooting better than ever...less vibration, quicker on the shot, and as quiet as any string material I ever used.
I have a 61' Bear Polar, that has three layer fiberglass tip overlays....it is shooting the same string material and is much quieter and better behaved than with a 12 strand dacron. Enough of the guesstimates on old versus new...show me the numbers..show me the tests done to prove/disprove.
If I have issues with any of these bows, I will post such outcomes....my skin is pretty thick and I can admit failure if it comes. As of this point, 1/15/2010, I'm not expecting the need to report failure. Your mileage may vary of course, but at this point talk is only talk...we must have proper findings...that's what I'm doing. And remember, I was a hard-headed, dacron-only, kind of guy for decades.
And a final disclaimer for those who don't read complete posts/threads: This is not a suggestion for you to start putting low stretch strings on your old bows....So don't do it unless you are satisfied you want to try it. It's a personal decision to try something new; I don't have a lot invested in those old bows and feel it is worth the effort.
QuoteOriginally posted by kybowman:
Wow.
Now I'm really confused. :help: :biglaugh:
Yes it can be. Unfortunately it is ever increasing the néed to separate the wheat from the chaff on Internet forums. You need to ask more specific questions and pay attention to decifer the Truly knowledgable and experienced from the keyboard cowboys with their bandwidth rodeos.
8125 is 92% SK75 and 8% SK65 for some reason. It is rated at nearly the same strength as D97 (latest I seen; 120lbs for 8125) and is noticeably smaller than D97.
And once again the stretch rates for SK75 off of the rope web sites show very small rates in my above posts. Virtually none. It is an anti stretch material for sure.
George, I get where you are coming from. Actually, I'm really surprised to hear you trying it out...kudos to you for experimenting, always something to learn. First carbon arrows, now skinny strings...before you know it you'll have carbon/foam limbs and be wearing synthetic camo ;)
My point is, you can experiment all day, you can "prove" something up one side and down the other, and one instance of "anecdotal evidence" can totally disprove to an individual all your "proof". There is no way to accurately test to the point where you can be assured it will not hurt older bows...just as there is no way to prove it will hurt old bows. But it doesn't matter one bit either way if it's my bow that blows up because I took someone's advice and tried a string that at best, has had a substantial history of breaking other vintage bows. That's all I'm trying to prevent and I believe Rob's intention as well. 6 million guys shooting ff on vintage bows does not erase the two I lost. Knowing what I know now, the potential gain, in my opinion, was not worth the risk of me losing the bow. It's as simple as that for me but as you said, your mileage may vary.
The opposite side of the coin is skinny strings on modern bows. Ron LaClair and others have used them for quite some time with great longevity in bows. I switched some time ago when it first started to grow in popularity but only through my own testing and proof. So far, with no failures I'm very happy with the benefits, mainly reduced noise. The increased speed was a nice side benefit but not enough to really make a difference outside of a chronograph. But I changed only because the risk of permanent bow damage due to string failure is greatly reduced because it's a "modern bow." If I thought for one second it would hurt my beloved Morrison in any fashion, I'd go back to whatever string was historically "safe" simply because the proven (minimal) gain would not be worth risking the loss.
QuoteOriginally posted by Rob DiStefano:
QuoteOriginally posted by Jeff Strubberg:
QuoteOriginally posted by bearbowman:
Those skinny D-97 will shoot on an old bow but padded loops or not you are gonna rattle those old bows apart. The real issue was the glues used back in the day. They were nothing like the glues today.
Sure if you pad the loops really well the tips should be fine but that is not the real issue with the low stretch string. Why do you think Bob Lee fought tooth and nail before they finally went to FF strings? Because the whole world was using them and they had to bite the bullet. 4 or 5 years ago Bob Lee would not warrant a bow that had FF on it.
Actually, making a bow more efficient (like lowering string weight)reduces vibration. Less moving mass means less oscillating mass, which means less strain on the bow after the arrow has left. [/b]
i don't think vibration, or lack thereof, is the issue - imo, it's the fact that hmpe strings just don't stretch/give anywhere near the stretch factor of dacron. if the limb tips on any bow can't absorb that shock, they'll blow off.
i saw that back in the 70's with kevlar low stretch strings - oooo, that was nasty! [/b]
Agreed. That wasn't the misconception I was trying to correct, though...
Quoteyou are gonna rattle those old bows apartQuote
Vibration isn't the problem with old bows using modern materials, because vibration is actually reduced with fast flight materials. It's that really quick stop at the end that gets 'em!
I'd also submit that the way bow tips are cut and shaped is as much of a problem as what materials and glues are used. I've seen self bows shoot fast flight with no problems when the string grooves and tip mass were cut to allow it.
http://www.answers.com/topic/rope-stretch
I sincerely hope folks will invest the time it takes to at least entertain this argument. It's not practical to test bows to failure, obviously, so the practical way is to at least test the argument that FastFlight can be used in a way that is indistinquishable from Dacron in terms of the strings working properties. One must accept the premise that laws of physics apply the same in each case, which would be hard to argue against in my view. I'm paraphrasing from the URL above for clarity.
The argument hinges upon this factor:
"Nylon stretches about 10 to 15 percent under a load equal to 30 percent its breaking strength..."
It stretchs as a constant factor (30%) of it's breaking strenght.
"Dacron... stretches only about 3.5 to 5 percent under the same conditions... Spectra stretch about 1 to 2 percent"
They all stretch 30% of breaking strenght.
http://en.wikipedia.org/wiki/Bow_string
So if Dacron has roughly 1/2 the strenght per strand of FastFlight then the strand count comparison would be about 10:5. So a 10 strand B50 would stretch roughly the same as a 5 strand FF. Honestly I don't trust Wiki here, I can only cite from memory but I think it's more like 40# for Dacron and 100# for FF.
I'm not suggesting these numbers can't be argued one way or the other. Only that given this premise: both materials stretch as a constant factor (30%) of it's breaking strenght, comparable strings can be fashioned.
Now, if you compensate string mass difference by increasing arrow mass, and make the loops the same diameter, how is the bow going to know any different?
You may ask, why would you want this? My answer is, it means I can shoot a heavier arrow with ZERO penalty.
Also, lower mass string on a bow is actually better for the bow than a heavier one, if no extra engery is left in the bow by compensating with arrow mass as described above. What makes bow limbs flex at the bottom of the power stroke is the energy left in the bow, by ITS moving parts, both limbs and string. When you have low mass limbs and string, you have less energy and so less stress on the bow as it has to vibrate off this energy.
I'm not trying to be butthead here. I know I use provocative language. But I think if folks would just stop and think this through some would see it differently. I honestly don't care what kind of strings you use, I just think it's important to be faithful to the underlying science in ones advocacy, in all things. And the burden generally is accepted to fall upon the declarer, in this case the supposition that "FF will break yer bow." Absolutely it CAN, but not if applied to the task in an all else equal ratio. And I also agree bow limb/string groove design is a factor. But only in the sense some designs are stronger than others. If you have a weak design (like an old Ben Pearon with no overlays at all), then apply a weaker (FastFlight) string, and compensate with much higher arrow mass.
dcm, i know from whence you come, and i believe i understand where yer going.
the one common denominator in all cases is the string fiber and its associated empirical data. them's the hard facts.
the loose canon in all of this is the bow and the archer.
i do believe there are instances where hmpe will work on bows that don't have the 'fast flight certificate of approval'. the question then becomes, 'you feelin' lucky?' umm, no thanx, not a chance i wanna take. ymmv.
I will remain neutral in this discussion. But if you have ever removed the tips on an old bear as per Bowdocs Restoration 101 thread, You will be able to see that the lack of glue on these tips certainly does not help the situation. 20% of surface contact with glue is not uncommon. Bow doc recommends replacing tips even when using a dacron string.
Rob I'd hoped we'd achieve just about what you spoke. I reget only the part of that concept that includes from my pov an element of randomness or luck. And admittedly in some cases the most practical choice is B50, absolutely.
Most issues with the old Bear's you speak of are with the old micarta tips, not the fiberglass overlays more common after 1959.
As I said, everything we talk about here is just talk. It's good fodder for getting the hair-covered computer going, but it's like running with paper scissors.....doesn't mean too much.
Rather than waste any more brain cells, and having to ingest more Omega 3's, I'm finding out myself. That said, I still can't give you a definitive answer for another couple thousand shots, and that will take awhile 8^).
As far as feelin' lucky Rob, I don't do well on lottery tickets; probably more like the little guy in Peanuts who has the cloud over him all the time 8^). But I digress......on with the program...tune in for future information. I will post photos of the limb tips imbedded in my navel or other body part if and when my old bows bite the dust. Heck....maybe I am feelin' lucky.
No use doing something stupid if you don't let everyone in on it. :thumbsup:
give 'em heck, george! :D
Bringing this back from the grave against my better judgement. Since everyone ahs an opinion and no one wants to hear mine, I'll just give a status update on my situation.
I tried a 14 strand 8125 string on a ~1969 york tunderbolt that had walnut and hard maple overlays. The string began literally chewing and splintering the bottom limb tip overlays within 10 shots. The top limb tip remained fine. I believe the issue was a poorly cut string groove that created unnecessary pressure points; the string wasn't sitting in the groove well.
Those overlays got filed off and replaced with 2 layers of 1/16" phenolic, and string grooves cut in properly.
No problems for ~2-300 shots. I don't anticipate issues. Bow tuned to same arrows at a brace height of 7.5" instead of 8.5".
Thats all the data so I'll stop there.
littleben, what style of string - flemish or endless? ....
flemish, I lack an endless string jig.
Just to add to the fun, I have another nearly identical (49# vs 50#) 1973 york thunderbolt that is in the process of being refinished with phenolic overlays also, and will get a 6 or 8 strang 8125 string ... haven't decided yet.
Maybe if I get fiesty I will do the actual math on some of this string stretch guesswork and try to estimate the %elongation of each string type under normal shooting conditions.
as i suspected. adding to the gamble of hmpe on such an old bow, with its old glass, i suspect the lack of dacron served loops did you in ... or rather, did your bow's limb in. almost ALL commercial trad bows of those 50's 60's 70's and even 80's eras used endless bowstrings. flemish strings weren't the norm at all, and scarce as hen's teeth. :D
I got that feeling too Rob. Actually, I used to have a dacron flemish string on the later bow (the 1973) and had not problems. But as anyone who's used it knows, when HMPE is under alot of tension it gets ridiculously hard, like wire. I think it was that really hard lumpy surface of the flemish string which added to the problem of bad nock grooves and cause extreme pressure points ... I mean, what's the shear strength of hard maple? it's alot of force I can tell you that, and little pieces of grain were literally getting sheared off.
Anyone, I got some quick info on the modulus (stiffness) of dacron (polyethylene terepthalate) and dyneems (UHMWPE or HMPE).
The tensile modulus of Polyethylene terephthalate is roughly 2.8-3.1 GPa according to wikipedia.
The tensile modulus of HMPE is above 116GPa according to EuroFibers supply.
That means that for two strings of equal diameter, one dacron, and one HMPE, the HMPE string will only stretch 1/40th as much as the dacron string (we're not talking about creep but just the elastic stretching of the string)
So in order to have the same amount of stretch (i.e. % elongation) the HMPE string would have to be roughly 1/6th the diameter of the dacron string.
Lets do the same math assuming the stiffness of dacron is actually 5x the number given by wikipedia. In this case, the HMPE string of equal diameter stretches 1/8th as much as the dacron string, and a HMPE string would ahve to be slightly bigger than 1/3rd (~1/2.8) the diameter of the dacron string to equal the stretch at a given load.
Long story short, unless the numbers I've got for the dacron are way off, even a skinny string of HMPE is much stiffer than a dacron string.
Thats not to say there's no merit to the position that a skinny string is safer than a full diameter strign of HMPE, it's just the math. Take it for what it's worth.
Ben It is interesting that you bring up the change in brace height. Jay St. Charles told me to expect lowering the BH about an inch on one of his bows when switching to an FF type string.
I tested the braking strength of single strands several years ago and found it was about half of what the manufacturer was reporting in every case. More recently some manufacturers have stopped publishing those numbers altogether. :dunno:
Breaking strength is a risky game when it comes to threads. Since a single "strand" of bowstring is actually a single ply bundle of many many strands, alot of factors can influence the results. Not the least of which being test methods .. also twist, temperature, elongation rate, history of elongation of the material.
It is interesting to note that the published numbers may not be what you see in real life. I think I heard someone also say that the strength can be reduced by as much as 40% when the fibers are bent, or in any way loaded other than perfectly in tension.
Just calculated the diameter of 8125 and dacron and determined that according the the numbers I have for modulus, a 6 strand 8125 string is approximately 4.5x stiffer than a 12 strand B-50 string, meaning the dacron stretches by 4.5x as much.
So long story short, if skinny strings are safe on old bows, it's got to do with more than just the stiffness.
(dacron vs FF, dacron vs 8125, skinny strings on old bows, skinny strings on vintage bows, B50 vs 8125, stiffness of skinny string, stretch of skinny string)