Mando strings go sharp--why?

[Bill Cameron]

As others have said, higher humidity makes the strings go a bit sharp, and vice versa. Higher temperature makes them go a bit flat, and vice versa. This is normal! What is NOT NORMAL is that your strings snapped. This should not happen. The changes in pitch associated with usual humidity and temperature changes are not enough to move the strings more than about a semitone or two, and they should be able to handle that change with no problem! SO, if your strings snapped, you have a problem with (1) friction at the nut or bridge, causing the string to bind in the slot at one end or the other, OR (2) an edge or burr somewhere on your tuning posts (or possibly on the tailpiece) that is cutting into the string. Both items (1) and (2) are easily fixed. But you will never be able to do much about the weather, except complain (and re-tune)!

Thanks, Sblock, but...
You really believe that mando strings can go up a semi or full tone without snapping? Not in Bill's World of A440. But the incident of string breaking-in-case was an isolated occurrence. They always break at the bridge; I am reluctant to mess with it since the setup is otherwise perfect.
To make life easier, I decided to upgrade the tuners. Waiting on a set of Grovers now. Thanks for your input, everyone.

[sblock]

Thanks, Sblock, but...
You really believe that mando strings can go up a semi or full tone without snapping? Not in Bill's World of A440. But the incident of string breaking-in-case was an isolated occurrence. They always break at the bridge; I am reluctant to mess with it since the setup is otherwise perfect.
To make life easier, I decided to upgrade the tuners. Waiting on a set of Grovers now. Thanks for your input, everyone.

I hate to break it to you, but YES, any decent set of mandolin E strings should be able to handle being tuned to E (659.3 Hz), F (699.5 Hz) and even F# (740 Hz) without snapping! That's a 12% change in frequency.

Try using D'Addario's "String Tension Pro" web tool and see for yourself (go to www.stringtensionpro.com). Select a set of strings based on D'Addario J-74's, for example (the E is 0.011" diameter), and tell the tool that you plan to tune it to F, instead. See what string it recommends! It recommends sticking with the same 0.011" diameter, but increasing the tension from 23.25 lbs to about 26 lbs.

You'd have to go up quite a bit more than that to snap a decent E-string from a reputable manufacturer. Not that breaking an E-string (which tends to be the most fragile) this doesn't happen to a whole lot of people, mind you, but the root cause is almost invariably found to be that the string is binding along its path, or there is a burr on the tuner or tailpiece. Or, that they inadvertently tuned well past the desired note when first bringing it up to pitch. And if your string is always breaking in the same place, then THAT is your Big Clue!!

[Ivan Kelsall]

Mark - Your expansion figure for wood is 'across the grain'. The expansion experienced with the wood in a mandolin is ''longitudinal'' - 'along (or parallel) to the grain' which is 3 compared with that for stainless steel which is between 16 & 17,
Ivan

[Tobin]

I hate to break it to you, but YES, any decent set of mandolin E strings should be able to handle being tuned to E (659.3 Hz), F (699.5 Hz) and even F# (740 Hz) without snapping! That's a 12% change in frequency.

Try using D'Addario's "String Tension Pro" web tool and see for yourself (go to www.stringtensionpro.com). Select a set of strings based on D'Addario J-74's, for example (the E is 0.011" diameter), and tell the tool that you plan to tune it to F, instead. See what string it recommends! It recommends sticking with the same 0.011" diameter, but increasing the tension from 23.25 lbs to about 26 lbs.

You'd have to go up quite a bit more than that to snap a decent E-string from a reputable manufacturer.

I'm an engineer, so I decided to check the numbers. According to this site, music wire meeting ASTM 228 specifications has an ultimate tensile strength of between 230 KSI and 399 KSI. It's incredibly strong, considering that normal mild steel that you see every day for structural steel members like I-beams are typically in the 58-80 KSI range (again, we're talking ultimate tensile strength, not yield strength).

Keep in mind that there are only a couple of wire manufacturers that supply wire to the string companies. When you say "reputable manufacturer", it's important to note that companies like D'Addario and GHS and the others aren't actually manufacturing the wire. They buy spools of it and just cut it to length, then form the loops, do the winding, coating, etc., to make it their own special style. It's the wire manufacturers who are responsible for the quality and strength of the wire.

So, with that said, let's look at an 0.011" E string from your example. At that diameter, it has a cross-sectional area of 0.000095 in^2. So at the low end of the tensile strength range (230 KSI), it will break at 21.86 lbs. At the high end (399 KSI), it will break at 37.91 lbs. One would typically expect wire that meets this specification to fall right in the middle of the range, or around 315 KSI, giving it a break strength of 29.93 lbs.

Now that we know that, we can go back and look at tuning pitches from the D'Addario link you provided. You can see that wire which falls in the low end of the acceptable ASTM 228 range would break somewhere between Eb (20.71 lbs.) and E (23.25 lbs.)! On the strong side of the curve, an E string should be able to go all the way up to G# (36.90 lbs.), almost to a high A (41.42 lbs.) before it breaks. But the "average" music wire that's in the middle of the acceptable range will break somewhere around F# (29.29 lbs.).

Another way to look at it is this: A typical 0.011" E string that is of average quality (i.e. having strength in the middle of the acceptable range) is tuned up to 23.25 lbs., with a break strength of 29.93 lbs., so it's expected to perform at around 78% of its ultimate strength. Or, we could say that it has a safety factor of about 1.29. That's not a huge safety factor, especially considering that this average-quality string will break when tuned up a whole step.

[Mark Gunter]

Mark - Your expansion figure for wood is 'across the grain'. The expansion experienced with the wood in a mandolin is ''longitudinal'' - 'along (or parallel) to the grain' which is 3 compared with that for stainless steel which is between 16 & 17,
Ivan

Ivan, if you read all of my post you'll see that I understand that, and that is why I say that the change comes from the swelling of the top and perhaps to a degree the bridge itself across the grain. As a woodworker, I have never for a moment ever consider that strings were being lengthened by a mandolin getting longer. There is so little movement of wood in the direction of the grain as to be negligible in comparison with movement across the grain. This is also why I originally thought that the strings were causing the differences through expansion and contraction.

In reality, I noticed time and again that the strings would go flat in the cold, and sharp in the heat. This experience flies in the face of string expansion. So I reason that the more likely culprit is humidity, not temperature per se. Once you realize this, and knowing that the mandolin is not getting any longer through wood expansion, you look at the box end of the instrument, not the neck. What might show significant expansion across the grain? Answer: the ribs (sides), the top and back plates, the bridge.

Expansion of the ribs will move the top upward and the back downward a bit. Expansion across the top from side to side will cause the top to bulge upward. Expansion of the bridge will be in an upward direction away from the top. All this movement will affect the pitch of the strings significantly.

The coefficient for SS ranges from 10 - 17, while the expansion for wood across the grain is around 30. So where we would disagree is in your statement, "The expansion experienced with the wood in a mandolin is ''longitudinal'' - 'along (or parallel) to the grain'". I couldn't disagree more with this. In my thinking, longitudinal expansion of the wood is pretty negligible, and in no way could any engineer say that longitudinal is "the expansion experienced with the wood in a mandolin" or with any piece of wood. To the contrary, notable expansion in wood is perpendicular to the grain, and any woodworker worth his salt knows this.

The same principle I've described is in effect on flat top guitars which have an induced arch. Changes in humidity will effect a swelling across the grain of the guitar top (side to side) which causes an upward bulge in the top.

I haven't conducted any measurements on these instruments, but like you and other musicians I've noted the changes in pitch in numerous instruments through the years that I've owned, as well as noting the changes in dozens of instrument at a time in a guitar shop that I frequent regularly. For a very long time, I thought exactly the same thing as you wrote in your post and illustrated with a diagram, but the data didn't always bear that out: Often strings go sharp when climate is warm, and flat when cold. Therefore, temperature acting on steel cannot be the most significant feature. Humidity acting on wood is likely the more significant cause.

[Stevo75]

I have a hygrometer in my house (two actually) and always pay attention to the relative humidity. Things are usually pretty consistent here in Colorado (i.e. dry), but last spring there were a few weeks where the temperature would drop over night and the RH would go WAY up ~75% or so in the house. Then as it warmed up over the day the RH would drop down to around 25% or so. I can't imagine this is good for the mandolin, but I was keeping it out on the stand anyway.

When I'd wake up in the morning and get some morning practice all the strings would be a half tone sharp. I'd adjust the tuning and when I'd come home after work everything would be a half tone flat. I know it was the RH because that was the only time I have seen swings like that (in both the RH and the tuning). It was very consistent for a week or two.

I'm not sure the difference between a quarter and half tone. Maybe it was quarter tone. But, for example, the G string would be half way between G and Ab. Not sure if you call it a full tone between G and Ab or a half tone. But anyway, you get the picture. I thought that was really interesting. I also thought I should keep my mandolin in the case when that's happening.

[sblock]

I'm an engineer, so I decided to check the numbers. According to this site, music wire meeting ASTM 228 specifications has an ultimate tensile strength of between 230 KSI and 399 KSI. It's incredibly strong, considering that normal mild steel that you see every day for structural steel members like I-beams are typically in the 58-80 KSI range (again, we're talking ultimate tensile strength, not yield strength).

Keep in mind that there are only a couple of wire manufacturers that supply wire to the string companies. When you say "reputable manufacturer", it's important to note that companies like D'Addario and GHS and the others aren't actually manufacturing the wire. They buy spools of it and just cut it to length, then form the loops, do the winding, coating, etc., to make it their own special style. It's the wire manufacturers who are responsible for the quality and strength of the wire.

So, with that said, let's look at an 0.011" E string from your example. At that diameter, it has a cross-sectional area of 0.000095 in^2. So at the low end of the tensile strength range (230 KSI), it will break at 21.86 lbs. At the high end (399 KSI), it will break at 37.91 lbs. One would typically expect wire that meets this specification to fall right in the middle of the range, or around 315 KSI, giving it a break strength of 29.93 lbs.

Now that we know that, we can go back and look at tuning pitches from the D'Addario link you provided. You can see that wire which falls in the low end of the acceptable ASTM 228 range would break somewhere between Eb (20.71 lbs.) and E (23.25 lbs.)! On the strong side of the curve, an E string should be able to go all the way up to G# (36.90 lbs.), almost to a high A (41.42 lbs.) before it breaks. But the "average" music wire that's in the middle of the acceptable range will break somewhere around F# (29.29 lbs.).

Another way to look at it is this: A typical 0.011" E string that is of average quality (i.e. having strength in the middle of the acceptable range) is tuned up to 23.25 lbs., with a break strength of 29.93 lbs., so it's expected to perform at around 78% of its ultimate strength. Or, we could say that it has a safety factor of about 1.29. That's not a huge safety factor, especially considering that this average-quality string will break when tuned up a whole step.

Yes, your analysis seems reasonable me. It confirms that an "average" E string (of diameter 0.011") from D'Addario should be able to handle being tuned from E up to F, and may make it to F# as well. So mere changes in humidity are not likely to break an E string that's tuned to standard pitch (based on A = 440Hz). One should look to other reasons why the string keeps snapping. But I also agree that there's not much of a margin for error, when it comes to E-strings!!

[Bill Cameron]

Last sentence is key--frequency of string breaks is E,A,eventually D if theyre not changed. Also, the strings snappng -at rest- is an isolated occurrence. I'm sure that we all have the same experience that strings break more when they are played hard for a long period of time. Obviously that is because there is more load on the strings as they are played than the various numbers cited, which I can only presume are stationary tension measurements. In that light, I agree strongly with Tobin that a safety factor of 1.29 -especially applied to the stationary string--is not a whole lot. It wouldnt be nearly adequare on a ski lift cable ;/=. But the stakes are different. I agree that it is informative that the strings always break on the saddle--but it stands to reason that there is always going to be a point of highest stress, doesnt necessarily follow that this is a defect as such. (Yes, I'll get my favourite repair guy to look at it. I'm on my way now in fact --cheerio!)

[sblock]

I have a hygrometer in my house (two actually) and always pay attention to the relative humidity. Things are usually pretty consistent here in Colorado (i.e. dry), but last spring there were a few weeks where the temperature would drop over night and the RH would go WAY up ~75% or so in the house. Then as it warmed up over the day the RH would drop down to around 25% or so. I can't imagine this is good for the mandolin, but I was keeping it out on the stand anyway.

When I'd wake up in the morning and get some morning practice all the strings would be a half tone sharp. I'd adjust the tuning and when I'd come home after work everything would be a half tone flat. I know it was the RH because that was the only time I have seen swings like that (in both the RH and the tuning). It was very consistent for a week or two.

I'm not sure the difference between a quarter and half tone. Maybe it was quarter tone. But, for example, the G string would be half way between G and Ab. Not sure if you call it a full tone between G and Ab or a half tone. But anyway, you get the picture. I thought that was really interesting. I also thought I should keep my mandolin in the case when that's happening.

The G and Ab notes are a SEMITONE apart on the scale. That means a half tone. What you are describing is something around a quarter tone. And yes, that is typical for a humidity change with a mandolin.

[Stevo75]

The G and Ab notes are a SEMITONE apart on the scale. That means a half tone. What you are describing is something around a quarter tone. And yes, that is typical for a humidity change with a mandolin.

Thanks for the info. I was surprised to see that much change over the course of the day but maybe that's par for the course. It's unusual for us to see humidity changes like that. But I'm guessing it probably happens a lot in late spring when the high/low temps have a wide daily variability and there's still a good amount of moisture in the air. Once we get into the summer it's pretty much dry no matter what the temperature is.

[s1m0n]

Wood expands a bit as it absorbs moisture. That could push the arch of the top a bit higher, make the neck just a bit longer, etc.

Wood gets wider and thicker as it absorbs moisture, but it doesn't get longer. Ie, movement is across the grain, not along it. I suspect that in this case the top and back are changing in width as the humidity varies. This alters the tension transmitted by the sides between the neck and heel blocks, pulling the blocks closer together or farther apart. That'll be enough to change the scale length.
The grain runs the length of the neck. I doubt that the distance from the neck block to the tuners is changing at all.

[Ivan Kelsall]

Mark - You may have misunderstood me slightly,or,i didn't explain my point too well. The mandolin 'wood' contracts less than the steel strings,so,the string contraction is the main cause (possibly) of the strings going sharp. It's not the mandolin getting longer - it's the strings getting shorter.

These are the figures for longitudinal & lateral wood expansion from the chart i posted :-

It shows that wood ''across the grain'' expands (contracts) 10 x the expansion ''along the grain'' ie - 30 against 3. Steel expands (contracts) between 16 & 17.3 along it's length. It's the contraction along the length that's important. The steel in the strings will contract at between 5.3 & 5.8 times as much as the wood. I don't think that it's any more complex than that (IMHO),
Ivan

[Tobin]

I agree that steel contraction is the main source of strings going sharp when stored in a case. But it's important to note that the strings don't actually get shorter as they cool; they just get tighter. The fact that they can't get shorter is why the pitch gets raised.

But there's merit to the idea that expansion of wood across the grain with high humidity will cause sharpness too. The arched top is responsible for this, because as the wood tries to expand laterally, it is generally restrained by the sides, so it will take the path of least resistance. The arch will rise and fall as the wood expands and contracts, respectively. It will be virtually imperceptible, and we may be only talking fractions of a millimeter, but it's enough to affect string tension. With greater humidity change, the player will even notice a change in the action, including buzzing of strings when the instrument is extremely dry. This is a telltale sign of the arch lowering due to contraction across the grain, and the tuning is the first indication.

There are lots and lots of variables that will cause tuning instability with temperature and humidity fluctuations. I wonder, too, if steel truss rods which will expand and contract more than the parent wood of the neck will throw the instrument out of tune.

[MANNDOLINS]

Buy a handful of these and keep one in every case..check them often..accuracy is not absolute but close enough ..within 2-3%.
http://www.ebay.com/itm/Mini-Digital...8AAOSwhOVXc-07

[Mark Gunter]

Ivan and Tobin -

Ivan, I understand completely what you've written and it's easy to think that way (as I once did) but the answer is more complex and involves humidity affecting the wood in the box end. It causes a similar final effect as raising the bridge would cause: Increased tension on the strings, thus a sharper pitch.

Tobin, I think you've got the right of it, there are many variables. Much of this will be qualified by location. In my location (from East Louisiana to West Texas) humidity varies quite a bit, and based on my own experiences I've come to believe that humidity has a greater impact than temperature alone.

Ivan, I discussed this with a fellow from the UK in the past, where I was holding the same view you're expounding. He made the point that when he takes his instrument on a very cold evening to play in a pub after having played it in tune in the warmth of his home, he finds that the notes have gone flat on the cold instrument. That's the opposite of what you'd expect if temperature were to blame. Since I've noticed that often (not always) in cool and cold conditions the strings on my instruments and those in guitar shops will go flat - the opposite of what I'd expect if temperature were the cause. I've also known them to go sharp in hot environs with high humidity. In the climates where I live and play, humidity seems to make more trouble with tunings going out than temperature does. I have no way to gauge whether that is the case in your own environment.

[Mark Gunter]

Ivan, another thing - I know that you didn't intend to say a mandolin gets longer, your point is that expansion of the wood along the grain is negligible compared to the expansion of stainless steel and I was a little snarky with your words because you seem unable to concede that expansion across the grain, for example in the top plate, can have an effect on tuning. That is my point. No woodworker or engineer would ever mistake the tenfold difference between wood expansion with the grain vs. across the grain.

[Tobin]

Tobin, I think you've got the right of it, there are many variables. Much of this will be qualified by location. In my location (from East Louisiana to West Texas) humidity varies quite a bit, and based on my own experiences I've come to believe that humidity has a greater impact than temperature alone.

Well, I believe that humidity can have a greater impact than temperature alone. But not always. It really just depends on the circumstances. Both temperature and humidity are in constant flux. Sometimes they will work together to make your instrument sharp or flat, sometimes they work against each other. As for which one "wins", it just depends on which fluctuates more in relation to the various coefficients at play.

I will say this, though: I've never experienced a mandolin going flat when it gets cold. It always goes sharp in my personal experience. I remember one particular cold day when my wife and I were playing indoors and we really didn't want to stop playing but we wanted to go out on the porch for a smoke. We both stepped outside, and you could tell immediately that both instruments went sharp. I mean, literally, you could pluck a string and hear it rise in pitch just like when you twist the tuner button. We quickly ducked back inside, fearing damage to our instruments (finish crazing, wood cracking, etc.).

Such a drastic and immediate change in temperature will, of course, have an immediate effect. The very small mass of a mandolin string will not hold any heat, and will adjust very quickly. So the tuning goes sharp when walking out the door. Humidity changes, though, will take longer. Even if you go from a dry indoor cooled environment to a humid foggy day, it can take minutes, hours, or longer for the wood to react.

So I guess my point is that temperature change may immediately pull the tuning one direction while humidity is pulling it the other direction, and temperature may win the battle of the moment while humidity wins the war. One thing is for certain, though: mandolin tuning is never really "stable" unless it never leaves the room.

Some folks tend to think that mandolins going out of tune is a sign of a poorly designed or built instrument. That's not true. I find that my higher-end mandolins like my Ellis are much more sensitive to changes than, say, my old Michael Kelly.

[Ivan Kelsall]

Hi Mark / Tobin - I take all your points on board - but !. I'd agree that the 'whole answer' is maybe more complex than we assume,but,as a simplistic answer, i think that the 'contraction of materials' one is pretty close.

From Tobin - "I've never experienced a mandolin going flat when it gets cold". Me neither, & neither have several Cafe members with whom i've discussed this same point for the exact same reasons.
You folks over in the US have the additional problem of humidity changes far in excess of what we get in the UK,unless it's unusually humid during our summer months,so there is a strong possibility of humidity having an additional effect.

I remember reading about Dave Grisman playing a concert somewhere where it was pretty cold & he simply couldn't keep his mandolin in tune from one song to another. I think i'd be a tad concerned about the functionality of my fingers - i simply can NOT play with cold hands.

I agree with Tobin,that mandolins with a higher 'pedigree' (more responsive), might be affected more than more lowly ones, although all my 3 are effected. Yesterday it was the turn of my Ellis to be re-tuned,
Ivan

[Bill Cameron]

Wow, this has been a really interesting discussion. I enjoy the combination of engineer talk, luthierspeak and experiential observations from the rest of us. Thanks, everyone.

It's occurred to me that if we agree that cross-top swelling in is -one of the factors- likely to alter the pitch by pushing the saddle up, it will simultaneously alter the string angle at the bridge, and at the tailpiece if any. I just noticed that the cast tailpiece of the Eastman actually pushes down on the strings--which of course adds to the angle at the bridge. Not all Eastman's fault since I squeezed a small piece of cloth under the front edge of the tailpiece because I felt it was contacting the strings and making the tone kinda brassy, which of course presses the strings down that much more. (Guess I'll take it out). Just now I took it off the wall and whaddaya know, it broke another e-string overnight--but right at the tailpiece this time. (Instrument was not even tuned up since I was tinkering with it yesterday--thats another thread). That will teach me to make categorical statements.

[sblock]

Wow, this has been a really interesting discussion. I enjoy the combination of engineer talk, luthierspeak and experiential observations from the rest of us. Thanks, everyone.

It's occurred to me that if we agree that cross-top swelling in is -one of the factors- likely to alter the pitch by pushing the saddle up, it will simultaneously alter the string angle at the bridge, and at the tailpiece if any. I just noticed that the cast tailpiece of the Eastman actually pushes down on the strings--which of course adds to the angle at the bridge. Not all Eastman's fault since I squeezed a small piece of cloth under the front edge of the tailpiece because I felt it was contacting the strings and making the tone kinda brassy, which of course presses the strings down that much more. (Guess I'll take it out). Just now I took it off the wall and whaddaya know, it broke another e-string overnight--but right at the tailpiece this time. (Instrument was not even tuned up since I was tinkering with it yesterday--thats another thread). That will teach me to make categorical statements.

Bill, at the risk of repeating myself, something is wrong with your mandolin (or strings). E strings are not supposed to snap spontaneously, and certainly not with the high frequency you're experiencing. You should make sure you're using strings from a manufacturer with a decent reputation (D'Addario, GHS, DR, Nanoweb, others). There have been cases of cheap, counterfeit strings from Asia bearing a forged "D'Addario" label, and these reports have surfaced from time to time here on the MC. Beware of counterfeit strings. Who knows? Maybe you have some bad sets?

Then, check that your E strings are not binding in the slots at the bridge and nut. And lubricate these slots with graphite, or with a commercial product. The tilt of your Eastman bridge should be at exactly the same angle as the break angle over the bridge; that is, the strings should aligned straight with the bridge angle, and should NOT bend at the point where they first enter
the bridge. In other words, the bridge is not supposed to produce additional "down-bearing" pressure on the strings. Finally, check the tuning and verify that you are tuned to the right E note -- and that your tuner is set to A=440Hz and not some other value, by mistake.

Normal humidity changes should never break strings. What you are experiencing is not normal.

[pops1]

If I remember you said you were working on it, if you tune the strings up and down they are much more prone to breaking. I would as sblock says look for sharp spots or pinching as that will break a string quickly.

[Willie Poole]

Has anyone ever noticed a difference like the ones being mentioned when using a mandolin made of carbon fiber? I don`t know a lot about CF but have heard that it is more stable than wood so it would be nice to hear what effects if any that humidity and temps have on Cf mandolins...ANYONE?

Willie

[pops1]

Way to go Willie, wish I had thought of that. I would also be interested in your question.

[Mark Gunter]

About strings going flat in cold, this is just something I've noticed from time to time and found confusing, because I just assumed the tuning changes were due to strings expanding or contracting, and these experiences didn't fit that model. While discussing this with a cafe member from the UK, Bertram Henze, he made this comment:

The interesting thing is that a temperature drop will contract the string and make it go sharp. That is not what I get when carrying my instrument through cold winter weather to a session: I open the case and the cold instrument comes out slightly flat. I wait half an hour (a pint) and it's about right again. There is much more moving than just thermal expansion/contraction.

After Bertram's comment I thought of all the times I'd experienced this type of anomaly myself, and it was then that I began thinking about how the pitch might change more due to humidity. Since the neck can't get longer, the only explanation I could come up with is the one I've been ruminating about here: expansion/contraction across the grain of the top plate.

We don't all have the same experiences, and maybe most people have not experienced strings going flat in cold weather. But I have, and I've noted the same on other stringed instruments besides my own.

[minuteman]

I tend to think it's more to do with humidity than temperature, especially for household instruments. I used to battle tuning often until I got a whole house humidifier. Set at 55% year round, no more tuning issues. Strings tend to last three times as long as they did before the humidifier also. Come to think of it, I haven't broken a string since then either.

That said, my current travel mandolin (which used to be my household mandolin) goes all squirrelly when on a trip. I've got in the habit of tuning it down in transit to keep things from getting too tight for the old bowlback. It gets tuned up, played, and tuned back down a bit when done.

My 2cents.