ukulelebadass
Well-known member
Have you ever had a string go out of tune sharp? How is this even possible? Can someone explain the physics behind this?
How can a string go sharp? Any physics people?
- Thread starter ukulelebadass
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I think the strings can go sharp if the temperature get colder. That's my experience anyway (not a physics expert... but my brother is). I could ask him if you would like me to.
–Lori
–Lori
snowcooley
Well-known member
Do you mean out of tune just as a general thing that happens ("oh look, I've got to tune up again!") or when strings start to go weird and it's time to change them?
ichadwick
Well-known member
Changes in humidity can cause the neck to move, and depending on the wood and structure, it can move backwards or forwards. If it moves back, the strings will stretch, making them sharp. If it moves forward, they will loosen and flatten.
If only one string is affected, it could be a twist in the neck.
It's also possible that changes in humidity affect the top board and bridge, which could possibly shift a bit, too.
Finally there's the gremlin factor: unconsciously bumping a tuner peg, say when you're putting the uke to rest in a case or on a hook, and not noticing it until you sat down to play again. I often find that I've done this when putting a uke into or removing it from a case.
If only one string is affected, it could be a twist in the neck.
It's also possible that changes in humidity affect the top board and bridge, which could possibly shift a bit, too.
Finally there's the gremlin factor: unconsciously bumping a tuner peg, say when you're putting the uke to rest in a case or on a hook, and not noticing it until you sat down to play again. I often find that I've done this when putting a uke into or removing it from a case.
OP
OP
ukulelebadass
Well-known member
It was a general thing- relatively new strings that when I went to play and pulled out the tuner the E string was sharp instead of flat.
ichadwick said:
Of course that is probable what happened- good point. My brain is mush today.
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No Talent
Active member
All the explanations provided cover the topic well, but if you like big words… Coefficient of Expansion (COE). All materials have a COE that describes how they will expand or contract when exposed to temperature changes. As your Uke and strings are made of different materials they will expand/contract differently to the same delta temperature conditions. It's conceivable that a string could contract more than the wood structure holding it, but I prefer the bumped peg explanation.
Choboy
Well-known member
ive been thinking about this also.
every time i tune my uke some of my strings are sharp rather than flat.
im glad this question got answered.
curiosity solved.
every time i tune my uke some of my strings are sharp rather than flat.
im glad this question got answered.
curiosity solved.
OP
OP
ukulelebadass
Well-known member
Yes, that would explain why it doesn't seem to happen to the wound strings (the times I didn't bum the pegs)
Now, do you know anything about tensile strength or torsional rigidity?
ukulele2544
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Just tune the string half-step up
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ukulelebadass
Well-known member
Ummmm.... If it's already sharp? Then I won't be able to play cause my ukulele will be out of tune, unless I tune the rest of the strings 1/2 step up also, and even I know enough about tensile strength and torsional ridgidity to know that that's not a good idea.
Dude, not for nothing, but don't give people wrong advice it doesn't help any and it takes away from your credibility. If I didn't know what I was doing you could have gotten me to break a string or worse. Stick to making the funny posts.
ichadwick
Well-known member
It's been a while since I studied it, but I suggest that the COE of a plastic material used in uke strings is rather low, and - combined with the small volume/small diameter of the string - would be negligible in affecting the pitch of a string. The string would have to shrink to go up in pitch, but that would mean a significant temperature drop to shrink it enough to make it noticeably sharp. And that temperature change would affect the wood a lot more than it would the strings; so long before the string's COE came into play, the wood would have changed. I don't think he's playing outdoors in the Antarctic...
OP
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ukulelebadass
Well-known member
Yeah, but no talent is right, it works both hot and cold. It's totally conceivable that on a hot day the wood could expand enough to make the strings go sharp. The point about the different COE's of the different materials in the uke leading to irrational expansion/ contraction between the different parts makes total sense.
No Talent
Active member
As a matter of fact yes. I know a little bit about a lot of things but not a whole lot about anything.
salukulady
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My brain is full of useless knowledge.....
