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Thread: Top deflection under saddle?

  1. #1

    Default Top deflection under saddle?

    I am new to mandolin, purchased an Eastman MD304 about 3-4 weeks ago at a shop
    several hours away that has a good rep. As I learned basic chords I noticed buzzing
    at the G string and that the strings were way high at the nut and took it to another shop
    that is very reputable and much closer, they adjusted the action by lowering the strings in
    the nut and raising the saddle. Buzzing gone and much easier to fret. However there
    is very visible deflection in the top under the bridge, is this normal and how much is too
    much? Also it seems like the G strings are buzzing again a little like the action has gotten lower again and I'm wondering if its because the top is continuing to deflect.
    The shop making the adjustments thought the neck had the correct amount of relief.
    I have several acoustic guitars in a little music room where the humidity is kept between
    45-50 % year round and thats where the mandolin lives.
    I hate to drive 4 hours to have the shop it came from tell me " thats normal"
    suggestions?

  2. #2

    Default Re: Top deflection under saddle?

    “That’s normal” is especially egregious when it comes from a medical person.
    Anyhow, perhaps you might keep tabs on possible sinkage by measuring the action height, over the next weeks, maybe at the end of the fretboard, and/or post a photo of the suspect area with a straightedge across the dimple. Buzzing can also be anywhere beyond the string, from as trivial issues as loose tuner buttons.
    Hopefully you will get more specific guesses here.

  3. #3
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    Default Re: Top deflection under saddle?

    Agree, post a photo. There are some very talented luthiers on the Cafe who are likely to chime in. IMO, there shouldnít be top sinkage on a new mandolin, if, in fact, thatís whatís happening. Should be covered by warranty if the mandolinís a new instrument.

  4. #4

    Default Re: Top deflection under saddle?

    Not sure Im attaching the pictures correctly, I tried attaching two.
    One at the 12th fret showing a Dava delrin pic thats 1.10 mm thick,
    this just raises the G string at this position a little bit, my guess is
    the action is a little low, I don't think it was this low right after they
    raised it. The second picture is an attempt to show the deflection and it does
    not really do it justice , it is visible because the shop I took it to for adjustment could see it. The owner has seen many, many hundreds of mandolins if not more in his life time go thru his shop, he inspected the interior to look for loose bracing and found none.
    I purchased it new from an Eastman Dealer, looks like I'm just going to have to drive down there in a couple weeks when time allows. I bought where I did because they were the only shop I could find that hand one and I wanted to play it first.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  5. #5
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    Default Re: Top deflection under saddle?

    By “deflection of the top” are you looking at the gap under the bass side of the bridge?

    As for ”correct amount of relief”, on a mandolin, that should be “none”, or as near as.

  6. #6

    Default Re: Top deflection under saddle?

    I am looking at a slight depression in the top of the mandolin that just does not show well in the picture.
    The depression is directly under the point that the bridge contacts the surface of the top and extends roughly
    3/4 '' front and back of bridge and 1/2" either side of bridge. If more relief isn't the solution , and the neck
    is straight, and subsequently to raising he action via the saddle height adjustment and then couple days later the
    action has again lowered, then either the top continues to deflect down or the screws holding the saddle up are some how
    turning on their own allowing the action to lower, given the tension on the saddle I'm not sure how that could be the case.
    I have owned several arch top guitars with similar bridge / saddle set ups and not seen any thing similar, also
    had no problem adjusting those to get the action I desired.

  7. #7
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    Default Re: Top deflection under saddle?

    The necks on all my mandolins have zero relief and I’m sure most people would have theirs set up the same way. I’ve never heard of an adjustable bridge winding itself down - it’s hard enough to lower the bridge with the strings loosened let alone up to tension. Unless you’re experiencing some wide swings in humidity, it can logically, only be an issue with the top.

    If it were mine, I’d start by carefully/accurately monitoring the gap between the strings and, say, the 12th fret to see if the action is reducing and by how much. I suppose that the mandolin could be going through some sort of settling in period if it’s new but it’s something I would want to monitor closely.

  8. #8
    Registered User J Mangio's Avatar
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    Default Re: Top deflection under saddle?

    Call the dealer, explain the situation, forward pictures, and mail it off.

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    Default Re: Top deflection under saddle?

    Quote Originally Posted by Ray(T) View Post
    . I’ve never heard of an adjustable bridge winding itself down - it’s hard enough to lower the bridge with the strings loosened let alone up to tension.
    I beg to differ, if you bridge is set up very well you should be able to lower it under full tension with your fingers. I can even raise one of mine with my fingers under full tension.. Your bridge saddle is binding on the posts.
    THE WORLD IS A BETTER PLACE JUST FOR YOUR SMILE!

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    Default Re: Top deflection under saddle?

    Quote Originally Posted by pops1 View Post
    I beg to differ, if you bridge is set up very well you should be able to lower it under full tension with your fingers. I can even raise one of mine with my fingers under full tension.. Your bridge saddle is binding on the posts.
    Tell that to the luthiers who built them!

  11. #11
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    Default Re: Top deflection under saddle?

    A little deflection from the bridge pressure is normal. In fact, if there isn't any deflection, to me that's a sign the top is overbuilt. An oval hole may act a bit differently. I've built about half a dozen, all x braced, and they hold up fine.
    Another factor is that it's the time of year when the furnace is on and humidity changes. As things get drier, the action will lower because the whole top is changing.

  12. #12

    Default Re: Top deflection under saddle?

    Well I removed the mandolin from the wall , room humidity 47%, temp 69 , and put it in its case with for a couple days with
    some small case humidifiers, the action on the G string at the 12th fret has raised ever so slightly such that the same pic that raised the
    G string slightly now has a gap and does not touch the strings. The very slight top deflection is still visible but the the G string now plays
    cleanly in first position which is where it did not before. I have two hygrometers in the room one says 44% and one says 49%.
    I got to 47% above by averaging the two. While the room humidity works fine for my guitars looks like its too low for the mandolin.
    I am going to buy a case hygrometer , a Caliber lV, and let the mandolin live in its case. I may try to raise the room humidity
    after I find out what the case is averaging, how ever here in upstate NY on 20 degree or colder days I'll have condensation on
    my thermal paned windows all the time at anything approaching 50 % humidity.

  13. #13
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    Default Re: Top deflection under saddle?

    Wow, glad thatís all the issue was, but sorry you have to go to the extra trouble, Iím able to keep my house at 50% +/- with a whole house humidifier in winter and a couple of floor dehumidifiers in summer. All of mine seem to sound best at 40-50% without the issue youíre describing.

  14. #14
    Registered User MandoMack's Avatar
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    Default Re: Top deflection under saddle?

    How did 1920's Gibsons survive wood and coal burning stoves with no humidity control?

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    Fingertips of leather Bill McCall's Avatar
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    Default Re: Top deflection under saddle?

    Careful owners, given the number that survived. They weren’t particularly inexpensive for the time. $177 for a new 1919 F4, $88.65 for an A4. Average wage was $0.56 per hour.
    Not all the clams are at the beach

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    Registered User Louise NM's Avatar
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    Default Re: Top deflection under saddle?

    Quote Originally Posted by MandoMack View Post
    How did 1920's Gibsons survive wood and coal burning stoves with no humidity control?
    My grandparents' house, built in the early 1890s, had a coal furnace and radiators. My grandmother always kept a roasting pan of water on top of one of the radiators, I suppose to protect the furniture from the winter's dryness. Any 1920s Gibsons in that house would have been OK. (Too bad there weren't any.)

  17. #17
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    Default Re: Top deflection under saddle?

    Most of those houses were also drafty and not insulated much, if at all. They didn't dry out like a tight insulated house made later.
    THE WORLD IS A BETTER PLACE JUST FOR YOUR SMILE!

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