String breaks = Busted limbs

[HenrikBP]

I was out shooting in the back yard today, when suddenly on release, the limbs of my ILF bow are both flying down-range after my arrow.

The bow string had snapped right at the transition from the end of the loop taper to "main" part of the string. The sudden release of limb tension flung the tips forward and the inertia ripped the ILF "pins" right out of both limbs. The "pins" were still sitting in the ILF pockets on the riser.

The limbs look ok though. The holes where the ILF "pins" were mounted are still clean, with no crack or ripping as far as I can tell. It looks like the "active" part of the limbs survived as well - I don't see any cracks or other damage.

So I'm doing a debrief to see what I could've done to provoke and/or prevent this:

- the bow is in my sig line: Morrison carbon and foam recurve limbs - "D"/Long length on 17" wood riser. Limbs are 47# at 28" of draw. My draw length is 27" which gives me 45# draw weight. I shoot carbon arrows with weight ranging from 411 to ~500 grains. So no arrows lighter than 9.1 gpp.

- I got the bow about 1 year ago. I replaced the original bow string when the center serving started to separate - I would guess about 8 months ago. I bought both strings from Bob when I bought the bow. I believe those strings are 8-strand Flemish twist fast flight. I wax the bow string with Scorpion Venom Wax when I start to see dry spots or fibers peeking out - probably 3 times since I put the string on the bow. I store the bow lying flat on a padded shelf, so no hanging it from the string.

- I shoot about 5 times a week, probably at least 30 arrows per session. Since I shoot so often I never unstring the bow, so other than installing string silencers and adjusting brace height, the bow has been strung for a ~8 months with this string.

I'm thinking this was just a fluke with an unfortunate outcome. But it could've been worse I guess. I'll be sending the bow back to Bob to have him take a look and see if he can salvage the limbs. I'm hoping it's just a question of re-installing the ILF "pins" and checking that none of the other hardware is bent or otherwise damaged.

Now what do you all think - did I bugger something up that then caused this? Thoughts?

... and the real question - what do I shoot until I get this resolved? That Whip in the Classifieds is looking really tempting if a little too heavy for me  

Thanks,

Henrik

[xtrema312]

Not good. Hope it works out. I have had it happen twice. Once on a one piece recurve and no problem with the bow. String broke just like yours. I kind of suspect maybe a dry fire because of what the arrow did. Not sure. The second time was on a friends longbow. That time I still had part of the string in my hand. No problem with that bow. I can see where an ILF would trend to shed parts.

[Cyclic-Rivers]

Not sure what would cause it.  where the string broke is common when you talk to others that have had strings break.  

when you leave it strung, it makes it difficult to properly wax the loops.  Maybe that could have contributed.  

I would say look for a burr on the string groove that could wear the string  but that doesn't seem like the case since you have shot this for 8 months.  When you send it back, and the limbs are OK, I am sure bob will check that out.

Best of Luck, hope the limbs and riser are OK.

[ISP 5353]

I am sorry this happened, but glad no one was hurt.  I also hope your limbs are okay.  I had a string break at full draw and destroy a beloved longbow.  It was a pretty new string, but it failed at the lower loop.  It happens, just get up and keep shooting!

[S.C. Hunter]

Sorry to hear this happened. It happened to me once on a wheelie about 17 years ago. I have never had it happen on one of my trad bows.

Hope the bow will be okay and glad you were not injured.

[Ron Vought]

Henrik -

Where did the string break and did you find yourself having to adjust your brace height  often?

Ron

[Bjorn]

Sorry about your bow; I had a string break and bow explode at a 3D shooting from a ladder, at first had no idea what happened-stuff flying everywhere and my hands were empty!
One of my friends offered me a spare bow, but I was no longer in the mood. Clean shorts would have been welcome though.

[HenrikBP]

Thanks guys, I appreciate it.

Yeah, all in all if it had to happen, this was probably one of the better ways. Judging from the arrow flight, the string broke after most of the energy had been transferred to the arrow- it was a good shot and the arrow was in the target pretty much where I aimed. So only the energy stored in the strung bow - and not the full draw - was what "flung" the limbs off.

Also, because of how the ILF limbs mount, the pull on the ILF "pins" must have been an almost straight pull, which would explain why the pin holes in the limbs are still "clean" after the "pins" getting ripped out.

I was wondering why the string didn't hit me somewhere, but I guess I just got lucky.

[HenrikBP]

Ron: the string broke right at the transition where the taper of the bottom loop ends and the "regular" string begins.

I think I understand what you're hinting at with the brace height - if something was stretching or slipping I would be adjusting more frequently.  But no, the brace height has been rock solid for at least a month or more, and I check almost every time I shoot (yes, I really am that "particular"   )

When I first installed the string, I was adjusting brace height almost daily, but 1) the string was new and settling in and 2) I had installed cat whiskers by putting the whisker bundle between strands of the string. And as the whiskers compressed, and then started to break and fall out whisker by whisker, the brace height would change.

But like I said. No brace height changes in a while.

Bjorn: that had to be a scary experience. And up on a ladder at that. Yikes.

[FarmerMarley]

Wow, you got me rushing to inspect my strings right now...

[Ron Vought]

I was using the Scorpion Wax on my FF Flemish string and the brace height had to be adjusted very often....more than I had ever seen. I also had it twisted so much due to brace height adjustments that I couldn't see any twists on the upper part of the string.

I put a new string on and went back to regular bees wax and this string seems to be holding well after a few 100 shots. I still think the Scorpion Wax is a very good wax and not even sure this was causing the problem that I decribed.

Ron

[HenrikBP]

Originally posted by FarmerMarley:
Wow, you got me rushing to inspect my strings right now...

Well, if the thread helps someone else avoid this mess, then at least something good came of it  

Ron, I started using Scorpion Venom after seeing a Tradgang Sponsor string maker recommend it (I don't recall who though). I'm using the waxy version, not the fluid. I've heard of many compound shooters (i.e. much higher tension) using it, so I'd be surprised if the wax affected the string.

[trad_bowhunter1965]

Originally posted by FarmerMarley:
Wow, you got me rushing to inspect my strings right now...

DITTO

[LBR]

 8 months ago.
8-strand Flemish twist fast flight.  

First, I'd find out exactly what material was used in the strings.  Second, I'd contact the manufacturer of these materials--either BCY or Brownell in the U.S.

I can about guarantee they will tell you that's too few strands.

Even though modern materials are very strong and durable, they can only withstand so much.

The fibers get hammered with every shot, and can break down.  My best guess is this is what happened to you.

If you are going to shoot a low strand count string, I'd replace it on a regular basis.

If you find out more about what caused the failure, hope you post about it.  I'd like to know if my guess is right, or if there's something totally different to watch for.

[HenrikBP]

LBR:

I may not have explained well: I didn't switch to a thin string to gain a few fps. I've only used strings that I bought from Bob Morrison specifically for this bow. I can't imagine he'd spec and sell strings that he wouldn't consider appropriate for his bows.

So are you saying that thinner strings or strings in general may have an "expiration" date, either in terms of "time on the bow" or "arrows fired", even if the string doesn't show any wear as such? I guess it would make sense, but I haven't seen anything to that effect anywhere.

[LC]

Ok I'll put my feabile two cents in on this.
Qutoe" the string broke right at the transition where the taper of the bottom loop ends and the "regular" string begins."
...When I first installed the string, I was adjusting brace height almost daily"

So heres my theory. The material wasn't pre stretched and you had to constantly twist it up to make brace height or in fact make it the right length. The twists stop at beginning of the taper because they can't twist past there. See my point or theory of why where the stress point is on that string.

I make my own strings so that when they are stretched I only have ONLY a couple twists to make them all work together. If you buy a string and have to twist it up your lossing preformance and possibly making it weaker.

Quote "Judging from the arrow flight, the string broke after most of the energy had been transferred to the arrow- it was a good shot and the arrow was in the target pretty much where I aimed. So only the energy stored in the strung bow - and not the full draw"

I've read numerous times and still find it hard to believe but alot of intellegent folks say the string is at it's most stress level at brace height!    :confused:   Makes sense then thats when it would break during a shot.

Finally I never ever wax my strings. Like I said I make my own but even boughten strings are really cheap. If they even look wore I replace, I don't believe "waxing" down fuss helps the string to be stronger. And I come from along line of folks that think wax, grease etc exposed to dust or grit just picks it up and then effectively becomes like sandpaper.

Now all my thoughts are my humble opinion only  your mileage may vary!

[Orion]

I agree with LBR.  8 strands is just a very thin string.  It's bound to give out quicker than 10 or 12 or 14.  If there's a weak spot anywhere for any reason, there's just not much in reserve to back it up.  Folks haven't been using ultra skinny strings for very long.  Most less than a few years.  I think we'll hear of more of this happening if it becomes more popular.  Glad you weren't hurt.

[HenrikBP]

Thanks for the feed-back guys.

LC - I don't know about the string not being pre-stretched. Again, Morrison is well known for the quality of his bows, and I can't imagine he'd work with a string maker, who would leave out such an important step.

I do see your point about the stress of over-twisting the string would focus at the loop tapers.

As for waxing, my understanding is that the wax helps lube the strands and fibers in the string, to keep down wear within the string. Of course if that wax is filled with abrasive dust it's a different story. But it seems that newer types of wax is a lot less "sticky" than some of the older stuff I've used, and as such would attract and hold less dirt. But then I'm no expert by any stretch.

Orion: my previous archery experience is from ~25 years ago, where thick Dacron strings were the norm. So I just go by what the experts advice. I don't think though that Morrison is the only bowyer using thin strings. I've also seen a string maker offering 6 strand strings for bows up to 53# draw weight. Maybe the material is different from what my string was made of.

I'll see what I can find out and report back if anything interesting pops up.

[dragonheart]

Why push the envelope?  Shoot more strands in a bowstring.

[LBR]

I may not have explained well: I didn't switch to a thin string to gain a few fps. I've only used strings that I bought from Bob Morrison specifically for this bow. I can't imagine he'd spec and sell strings that he wouldn't consider appropriate for his bows.

No idea what testing Bob has done with string durability.  I do keep in close contact with BCY though.  Don't take my word for it--ask the manufacturer what they think.

 

So are you saying that thinner strings or strings in general may have an "expiration" date, either in terms of "time on the bow" or "arrows fired", even if the string doesn't show any wear as such? I guess it would make sense, but I haven't seen anything to that effect anywhere.

That might be a way to look at it.  I don't push the envelope with my personal strings.  I don't use a minimal strand count, and if it's a bow I'm shooting much I'll replace the string every 6 months or so.  You can break down the fibers by using too much tension to pre-stretch.  The reason strings fuzz up is do to the strands breaking down.  It's normal wear and tear.  Less strands, more stress on each strand, more/faster wear and tear.  At least that's my thoughts--I could be wrong.

Fewer strands will also stretch/creep more, and have less elasticity, which may also affect wear.

Again, I have no idea what kind of tests Bob does to decide on a string.  I do know I have seen some pretty wild things from other bowyers concerning strings...for example:

A string (the one sent with a bow) cause the limbs on a longbow to twist.

A bowyer who voided the warranty on his bows if you used a flemish string, or a dacron string.

A bowyer who said in his warranty that "flemish strings are less accurate, and can be dangerous".

A bowyer that recommended against one type "FF" material because it didn't have enough stretch...but suggested another material that has even less stretch.

I've seen some of the nicest looking, better shooting bows I've had my hands on with some of the most awful looking strings ever on them.

The string seems to be a part of the equation that is often overlooked, taken for granted, etc.

Again, I suggest finding out exactly what the material is, then contact the manufacturer for more insight.

Chad