bridge movement:

**300win** · Oct-09-2009, 10:54am

Wonder if anyone else has ever had a bridge move due only to changes in humidity ? My mandolin became in the past week or so kinda hard to tune correctly. I checked it a couple of days ago with a very good tuner. The G side of the bridge had moved forward 1/16 ", thus puuting the intonation out considerably. I know that my mandolin has not been knocked around any what-so-ever, the only way that could have happened in my opinion was the drastic changes in humidity and temp. here in the past couple of weeks caused this. Has any of ya'll ever noticed or had the same thing happen ? Also I promise to everyone here and the owner of this site that I WILL NOT EVER GET mean spirited in my post. My apolgies to all I might have offended in the past month. I've been instructed by the owner that I have two strikes against me and a third will put me out. Everything I say from now on will either make sense with no offense or I'll just keep my mouth shut. But I would like some input if any of ya'll have ever noticed such a thing as I described. The mandolin I have is very, very, good, in fact the best I've ever played, so I don't think it would be fair to say that it was because of inferior quality. Thanks for any info.

**Mandobart** · Oct-09-2009, 11:02am

I was just noticing the same thing on my insts. I believe it to be weather related, we've just recently had a few nights below freezing and daytime temps have lowered. It would make sense that as humidity level changes and the wood expands/contracts as moisture is absorbed/evaporated, the bridge and/or neck and fingerboard could move sligthly. I use damp-it humidifiers on all my insts, too.

**talbotpat** · Oct-09-2009, 11:29am

Could very well be humidity changes...when you run central heat in a home as winter approaches, the humidity can dive to ridiculously low levels. It is common for humidity in my home to dip into the low 20 percent range during the winter months. I keep all my instruments, even the Fender electrics, in cases and a humidifier running in the room to keep as close to 45% as possible. I also use dampits on all my Taylor acoustics as well as my LM-600-VS mandolin (running out to get one for the LM-600 today). In addition, I place a damp sponge in a plastic soap holder with holes drilled in it in the headstock area of my cases to provide additional humidity in the case. All of these measures have worked well to prevent any top or back cracking, top sinking (lowering action and causing buzz), and fretboard shrinkage, which can affect the electrics just as much. I'm not as 'up' on the mando characteristics as far as bridge movement is concerned, but as the thing is made of wood and not carbon fiber, movement is inevitable. Get a digital hygrometer from RadioShack or find one online and keep it where you keep your instruments in order to keep an eye on your humidity levels. I keep them in my cases as well just to make sure it stays in the 'safe' zone.

Pat

**AlanN** · Oct-09-2009, 11:38am

The only effect I've ever seen with humidity changes is going sharp or flat. Bridge 'moving'? Never.

**OldSausage** · Oct-09-2009, 1:22pm

You said you checked with a tuner, and the bridge had moved forward 1/16". The only way to be sure your bridge actually moved would be with a ruler or if there were marks. As Alan says, humidity is not going to make your bridge move, but it could make your mandolin change shape slightly. But also, if you are working out the distance only from checking the intonation of your strings, I have found that intonation changes as strings age, so it could simply be time for a string change.

**Big Joe** · Oct-09-2009, 1:48pm

Your bridge will not move without some kind of force. On a mandolin it can take quite a bit of force. What can move is the fingerboard. Check the truss rod. If it has moved you may think the bridge is off to get it to play in tune again. You could also be having some top sinkage. The amount of movement you indicate would be pretty radical for the top sinkage, but not always for the neck. Look down the fingerboard from the headstock (ignore the headstock itself) and see if the neck looks like it has a bow in the middle.

**fishtownmike** · Oct-09-2009, 2:47pm

If anything it would be the top shrinking and expanding due to humidty and not actually the bridge moving itself..

**allenhopkins** · Oct-09-2009, 3:43pm

Originally Posted by fishtownmike

If anything it would be the top shrinking and expanding due to humidty and not actually the bridge moving itself..

Second the suggestion. Basically what you're saying, 300win, is that your mandolin went sharp the equivalent of a one-sixteenth movement of the bridge. What normally makes a mandolin go sharp is expansion of its wood; the instrument is "bigger," which tightens up the strings. I keep my collection in a fairly humid environment, my basement, and I find that an instrument tuned to pitch and played "upstairs," then left in the basement a few days, will be sharp when I bring it out again.

There are people who have "winter bridge saddles" and "summer bridge saddles" for their acoustic guitars, because the generally dryer (at least in the Land of Central Heating) winter environment changes the guitar's wood enough to affect the action. Presumably would affect the intonation as well.

I have often recommended the Taylor Guitars Tech Sheets for their discussions of humidity's effects on stringed instruments. Although they're aimed at guitarists, there's info there that can be helpful to mandolin owners.

Secondly, I applaud your decision to be less combative in your postings. We're all trying just to get along, here, and exchange information and opinions with other mandolin-playing friends.

**EdHanrahan** · Oct-09-2009, 3:54pm

Originally Posted by fishtownmike

If anything it would be the top shrinking and expanding due to humidty and not actually the bridge moving itself..

... although YOU may have moved the bridge by 1/16" to compensate for the difference.

But you probably also had a change in string height (with either increased or decreased pitch before re-tuning) and you should have moved the bridge either up or down to compensate for the top's movement and/or neck position/angle, that would have negated the difference in pitch, and that would also have negated the "apparent" 1/16" movement of the bridge.

This amateur interpretation of all the above plausible & probably correct comments is worth maybe $0.02!

(Whoops! Just read Allen's post, but I don't think we disagree.)

**300win** · Oct-09-2009, 5:00pm

Neck is straight. The reason I know it moved 1/16 inch forward is because it was a slight mark on the top where it was sitting after I adjusted it. Intonation is perfect now, Strings are only 2 weeks old, in great shape. Here where I live due to the changing of the season it has been fairly drastic changes in the hunidity even in one day, and from one day to the next, a common thing here in northwest N. C., so therefore I still think the top swelling and contracting caused movement in the bridge. Like I said I know it has not been bumped out. I play it everyday, no top sinking I'm sure. It's a great mandolin, not a cheap one. It is the most sensetive instrument I've ever owned as far as the weather effecting it. Possibly because it is brand new,?, only assembled in May of this year. Not disagreeing with any other comments that have been made, just got my on ideas on it, but thanks for the input.