I can't be that unlucky

[tomsm44]

I put a new flemish string on my bow about 3 weeks ago.  I had been shooting for a few minutes this evening when all of a sudden, a shot made a funny sound and the arrow flew about 2 ft. to the right of where I was aiming.  I inspected my bow and found this.
 

Now for a little background.  I was given this bow last year around July:  Red Wing Hunter, 58" 53#@28, along with a 70# Super Kodiak.  I put a brand new string on it last year when I got it all the way up to opening day on October 1st.  After hunting that morning, I was getting a few shots in after lunch before heading back to the woods when my string broke about 4" from the end.  I didn't think it was normal for a string to break that soon, but thought I may have just gotten one with a defect.  I quickly tied some silencers on the Super Kodiak and hunted with it the rest of the season.  I got busy with other things and didn't get around to buying another string until the one in the picture a few weeks back.  This is only the second string that has been on this bow since I got it and both failed within a few weeks to a few months.  It seems that there has to be something causing this.  I'm realitively new to trad archery, but I have one theory.  Any input would be appreciated so that I can hopefully avoid this in the future.  By the way, I was smart enough to get two strings this time, so I do have a spare.

Here's my theory.  When I started shooting trad, I had never heard that I should have an arrow around 10 grains/pound of pull.  The arrows that I had been shooting on my compound shot ok off of my recurve so I used them last year.  They were a little stiff, but I was grouping about 4-6" at 15 yards, plus I didn't have the funds at the time to buy all new broadheads/field points.  The arrows were about 440-445 gr including a 100 gr point.  I shot them for about a week this summer before going to a 125 gr. point which would put me at about 470 gr.  The bow shot the best with a couple of old 145 gr. broadheads that I borrowed from my dad, but I haven't had a chance to get any heavier field points, so I've been practicing with the 125s.  Could this arrow be light enough to be causing the strings to fail prematurely, similar to dry firing?  If not, what else could be causing my strings to break.

I've learned a lot in the last couple of months from this site.  I hope you guys are able to come through again.

Thanks, Matt

[Igor]

I'd check the nock to see if it is rough/exposed glass -if it is then I'd take some 220grit paper (wrappped around a small round file) and round/smooth the nock out. Seal it with a little true oil and that should eliminate the issue. If we could see a pic(s) of the nock area that would help us help you?

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Glenn

[Cool Springer]

I think what Igor is referring to is the string groove on your bow.
It seems logical that there could be a rough spot on the groove that's causing wear.

Good luck.

[tomsm44]

Thanks guys.  I checked that when I took the string off and it looked smooth.  Also, the first string broke about 4" from the end, about where it made contact with the limb.  I may try sanding the string grooves a little just to make sure though.

[limbolt]

When you get a new string check and see if the string is tracking straight in the string groove,you might have a slight twist and be rubbing the sides causing wear.  

[threeunder]

Agree.  Check that string groove. I'd bet there's a rough spot there.
Ken

[tomsm44]

I just put my spare string on.  Drew and let it down slowly several times.  It appears to be tracking perfectly.  Nobody has ever heard of shooting arrows that are too light causing this?  The ones I was shooting were around 8 gr/# of pull.  If I go with the 160 gr zwickeys, it would put me at 9.5 gr/# of pull.

[tomsm44]

Here are some pictures of the string groove.  I'm going to try to sand it a little smoother just to be sure.  I'll also wait until I get my heavier points in before I shoot anymore in case the lighter arrows were part of the problem.

 
 
 

[Killdeer]

Strings are typically overbuilt. The stress is mostly transferred to your bow limbs when you shoot underweight arrows, and it will be the bow that blows first. You are shooting about 8 grains per pound, which is minimum for most bows. But I still suspect your string groove, or your cat is chewing the string in the middle of the night.    

Does somebody here remember the trick for finding itty bitty roughness in bow surfaces? Nylon hose? I don't own any. Maybe a cotton ball?

Killdeer

[Sharpend60]

Rub a cotton ball on the suspect area.
Any burrs and it will stick to em a wee bit.

[AWPForester]

I am pretty sure your arrow weight is not the culprit.  It might be a good idea to run some cotton balls along the limb tips like killdeer said.  Other than that you might have gotten 2 defective strings,  That is more probable than arrow weight.  Remember, for as many people that swear 10 gpp f draw weight is the only way there are just as many that shoot less that are just as successful.

Everybow is going to have a perfect setup and that might be 8.5 or 12 gpp.  The 8-10 gpp is what bowyers have adopted as it considered the best balance of performance all the way around.  Get the proper arrows, get it braced correctly, and unless something is wrong with the bows tips or string grooves, chalk it up as bad luck.

One more piece of advice, watch your string around anything that can nick it.  They have so much pressure on them, a ever so faint tuch from a sharp blade or anything else will ultimately lead to a failure.  God Bless

[tomsm44]

Don't have a cat.  Maybe a preschooler?  

I'll try the cotton ball and try to take care of any rough spots.  

Trad gang members never fail to deliver.

Thanks guys.

[Eric Krewson]

It is your arrow weight.

Years ago (early 90s) I was shooting light 2114s out of a 60# Bighorn. I kept breaking strings on a regular basis so I asked the same question as you on one of the popular bow sites.

Dan Quillan answered on the thread and said I was dry firing my bow with the light arrows and needed to go up at least 100gr on my arrow weight.

Being bullheaded I thought "you old rascal, that can't possibly be the cause of the problem", kept shooting my 2114s and breaking strings.

About 6 months later I was making up some much heavier 2018s to hunt with. I put my 2114s off to the side and practiced with my 2018s, strangely, my strings stopped breaking.

Old Dan was a lot sharper than I gave him credit for. I never shot my light 2114s again and never broke another string.

[Orion]

Light arrows can certainly exacerbate the problem.  Nearing dry firing results in the tips moving forward faster, putting more stress on the string at the end of the shot.  That would lead to failure faster, but it also could occur anywhere along the length of the string at it's weakest point, perhaps under a squeezed on metal nock, where the string was abraded and/or where dirt got into it, etc.

Does the wear you show occur on both loops?  If it's the bottom loop, it's possible that dirt and grit worked into the string from leaning the bow against various objects with the lower tip on the ground.  The grit will work on the string and cause the type of fraying you picture.  But, as others have already noted, so will minor roughness in the nocks.  If it's the top limb, that's what I'd look for.

BTW, light arrow weight and roughness in the nock area can work together.  It doesn't have to be one or the other.  Can be both.

[V I Archer]

I have a PSE longbow modeled after an Earl Hoyt design.  The strings would break after only a few hundred shots.  Took it to a local bowyer who suggested the srting angle was too severe creating a sharp angle, prematurely weraring through the string.  His suggestion, wrap the loops (sort of like an endless loop string), with dacron and soak in bees wax.  Problem solved.

[JamesKerr]

It could be your arrow is a little light, but I think the most likely problem is that there is a rough spot somewhere around the nock.

[tomsm44]

Eric/Orion.  Both of your opinions are in line with what I suspected.  I don't think it is a problem with a rough spot because I've had two strings on this bow and both failed prematurely, but only one failed at the string loop.  The other failed about 4 inches from the end.  

Hopefully I've fixed the problem.  I couldn't find any rough spots, but I went ahead and sanded the string grooves then sealed with true oil.  I also picked up some 145 gr points today.  That's the weight that seemed to shoot best with this bow when I tried some borrowed broadheads earlier, but I didn't have any field points on hand for practice.  This gets my arrow weight to around 9.5 gr/# of pull.