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Thread: Can I fix this without removing the top?

  1. #1
    Registered User Jritter3's Avatar
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    Default Can I fix this without removing the top?

    I realize that there are quite a few threads on here dealing with cracked tops, but I was having trouble finding one that matched what I am dealing with...my apologies if this is redundant.

    This is my main mandolin, and one that is near and dear to me since it was the first one I built. This crack showed up this past summer, and has slowly crept up to the bottom of the bridge. I have fixed cracks on it before around the bass side f-hole, but that was a pretty easy fix done with water thin super glue. I am afraid this one won't be that easy. As you can see in the attached pics, there is not only a hairline gap in the crack, but one side has bowed up, so it needs to be clamped somehow. My guess is (given the location) that the tension of the strings caused the top to bow up on the treble side of the crack. At any rate, you can see in the pictures how one side of the top is sticking out and revealing the inside edge of the crack.

    Id like to nip this in the but before it gets worse. I am plenty confident in my ability to do so, I am just trying to get a feel for how best to go about it. Can i glue in a cleat? Do I need a special clamp? It does not need to be pretty, just needs to work. If I have to remove the top, then so be it!

    Attachment 165712
    Attachment 165713

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    Default Re: Can I fix this without removing the top?

    Your attachments don't work, if you can post a picture that would help.
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    Adrian Minarovic
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    Default Re: Can I fix this without removing the top?

    Quote Originally Posted by pops1 View Post
    Your attachments don't work, if you can post a picture that would help.
    Just a blind guess... Is the crack going from under tailpiece towards bridge? Is it right on the center seam? If this is true, you may have the death crack there, meaning the top is too thin to bear the load (aften seen in first attempts- been there, or the arching is weak - too bulbous to start with) and it cracked and is slowly bulging out (in your case asymmetrically, perhaps one side is thinner...) or sinking in the recurve area... The only cure to this that works is fixing the problem (thin top) and not just gluing the crack (glued crack will never be stronger than original wood or original joint). Even cleats won't hold it (unless they are substantially strong across the area to keep it from bulging)
    I posted in the past pics of Schoffield F5 with such crack (someone attempted to glue it twice before me) where I removed the top sand-bagged (corrected) the arching and doubled it with new wood, but this mandolin required also neck reset... The mandolin is still going strong now, three or four years later. Normally I would remove back for access....
    You need to do thorough evaluation WHY this is happening and then decide how to fix.
    But the pics would really help. :-)
    Adrian

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    Default Re: Can I fix this without removing the top?

    Keep in mind that these days I’m just an “armchair luthier”, but I think Adrian has hit the nail on the head, as he usually does. It seems likely that your problems are caused by the top having insufficient structural strength to bear the string pressure. The only other things that can cause a crack are a physical blow or lack of humidity. If there was no blow and it was properly humidified that leaves the weak top as the only other possible cause. If you want to save the top you will have to remove it, restore the original shape, and fashion a reinforcing patch of new wood for the weak spot, not just cleats. Or you could just re-top it with a new top that has been more appropriately graduated. That’s probably the best way of preserving the mandolin as a whole. Stuff happens, and you could look at this as a learning experience. I had a similar situation with an Army-Navy style flat top I built. It kept getting cracks in the top which I fixed with glue and cleats through the sound hole but one day when I tried to play it the strings were laying on top of the frets. You guessed it, it had what Adrian calls the death crack, from one end to the other. The entire top had imploded. I thought about trying to re-top it but decided it just wasn’t worth it. Sometimes you just have to move on.
    Don

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    Registered User Jritter3's Avatar
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    Default Re: Can I fix this without removing the top?

    Quote Originally Posted by pops1 View Post
    Your attachments don't work, if you can post a picture that would help.
    Click image for larger version. 

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ID:	165718Click image for larger version. 

Name:	top2.jpg 
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ID:	165719

    Hopefully this works...the attachments on my first post worked on my computer, Im not sure what happened.

    In my mind there is no doubt that what ultimately caused the crack was due in large part to environmental changes...This past summer I traveled between Michigan and Colorado several times (Dry to humid and back to dry ) and sat around quite a few campfires in both states. At one point (in Colorado) I was playing around a campire when I noticed that the top of my mandolin was hot from the fire, and the back was so cold it there was some condensation on it. Obviously none of those things are good for any stringed instrument, and thats why I don't take my nicer ones out of the house. This one has always been my "beater" if you will, ever since I built my second one. (Maybe one day Ill get some gigs not around a campfire and my "beater" wont also be my main instrument ) It has gone under the knife more than once. When I originally built this one I knew nothing of graduating plates so the top is likely far beefier than it has to be, given my tendency to over-engineer everything I make.

    If the crack is indeed the "death crack" then I am happy to say that over the course of almost 10 years this one instrument has taught me everything I know about building and repairing mandolins. It was originally built from an IV kit, but today the only original parts on it are the top, neck, and sides. I did a neck re-set once and put a new back on it, and later went and replaced the fretboard. All of this was thanks to countless hours sifting through this forum for information I might add.
    Last edited by Jritter3; Mar-08-2018 at 10:47am.

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    Registered User fscotte's Avatar
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    Default Re: Can I fix this without removing the top?

    How thin is the top just in front of the tailblock?

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    Registered User Jritter3's Avatar
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    Default Re: Can I fix this without removing the top?

    Quote Originally Posted by fscotte View Post
    How thin is the top just in front of the tailblock?
    It is very likely thicker than it needs to be, since I built this without knowledge of graduating top plates. MY best guess is at least 1/8'' thick at the tailblock

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    Default Re: Can I fix this without removing the top?

    1. Get the strings off the mandolin right now.
    2. See if the crack can be gently pushed into alignment with your fingers.
    3. Order some f-hole clamps from International Violin Co. or Metropolitan Music.
    4. Glue with grade 215 hot hide glue, using a flexible caul and the f-hole clamps. If you can't pull it into line that way, you will have to use what is called a cross patching device. Stew-mac sells one, or you can make your own using scrap wood and a tuning machine. See Don Teeter's "The Acoustic Guitar" for details of repairing cracks with a cross patching device. If the crack won't close side to side, you will need to install a splint.
    5. Install cleats, using the f-hole clamps. Considering the location of the crack, I recommend a cleat ever 3 cm, including at the north edge of the crack. The cleats should be .060" to .080" in thickness. Taper the edges of the cleats down to nothing to avoid a new crack developing along the edge of the cleat.
    6. Monitor your humidity and use a humidifier. Are you at high altitude? You may need to humidify all year round.

    If the above does not work, it is usually better to remove the back rather than the top unless you intend to replace the top, unless loosening the top for just an inch or two will give you enough flexibility to repair the top.

    Just took another look at your pictures. Check with a light and a mirror to make sure the tailblock is not loose! It looks to me like there may have been some movement there.
    Last edited by rcc56; Mar-08-2018 at 11:46am.

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    Registered User Greg Mirken's Avatar
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    Default Re: Can I fix this without removing the top?

    Good eye on catching the tailblock issue. In the last pic there does seem to be a small offset in the binding. If the tailblock is moving, that would explain why the top is displaced up relative to the outboard side of the crack.
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    Registered User sunburst's Avatar
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    Default Re: Can I fix this without removing the top?

    Previous questions about top thickness are on target, but if the top is thick enough, that crack can be fixed without opening the box.
    I would first remove the strings (as has been suggested), try to close the crack with humidity, and if that works well, I'd probably (meaning I never really know what I would do without examining the instrument in hand) use an internal prop or props (sticks set between the top and back much like a violin sound post) to align the crack, then glue it by forcing hot hide glue into the crack with the instrument warmed to "body temperature". To force hide glue into a crack I simply brush the glue onto the top surface over the crack then rub/pat/massage the glue into the crack until it can be seen along the crack inside the mandolin. If it needs to be clamped from the sides to close the crack completely, perhaps padded bar clamps, but likely some sort of jig for clamping the non-parallel side surfaces.
    As for cleats, if the top is plenty thick and good alignment can be had, they probably aren't necessary. If they are needed to help with alignment, I would probably use Don Teeter style "gizmos", if they are just for a little help maintaining the glue joint (not for alignment) I'd install and clamp them with magnets after the crack is glued.

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    Registered User sunburst's Avatar
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    Default Re: Can I fix this without removing the top?

    If the tail block is loose, putting it back in place might require a jack going from head block to tail block. I procedure much more difficult working through f-holes than working through a central round hole. Not sure what I would do with that without examining the instrument.

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    Adrian Minarovic
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    Default Re: Can I fix this without removing the top?

    Quote Originally Posted by sunburst View Post
    If the tail block is loose, putting it back in place might require a jack going from head block to tail block. I procedure much more difficult working through f-holes than working through a central round hole. Not sure what I would do with that without examining the instrument.
    Perhaps steel rod inserted in endpin hole and some gentle leverage could align the block again.
    Adrian

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    Default Re: Can I fix this without removing the top?

    It appears to me its originating from the tailblock area. So if you think that the top is thick enough, then perhaps it has started to separate somewhere. The way it warped there looks like it has more to do with the pull of the tailpiece rather than the down pressure at the bridge.

    This would be a good time to learn how to take a back off.

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    Default Re: Can I fix this without removing the top?

    Inspect it with a mirror and a light before you think about taking it apart.
    Find out what is really going on, only then will you know how to proceed.

    If the instrument can possibly be repaired through the f-holes using any of the methods described by John or myself, that is the way you should go. We generally avoid back or top removal unless there is no practical alternative.

    And it is not possible for any of us to correctly appraise the situation without the instrument in hand.

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    Default Re: Can I fix this without removing the top?

    Jritter3,
    That's why they have those pointy things on the sides of mandolins - to dissipate the heat from the campfire torrefaction process. Just kidding.
    Looks to me since you have already changed out back, reset the neck and changed the fingerboard it might be time to pull the top to see and evaluate what you have.

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    Default Re: Can I fix this without removing the top?

    If the block has come loose there is still no reason to remove back or top. Depending where it has come loose you may have to open part of the seam. I designed a tool decades ago to glue the block in violins from the outside, easy in and out and clamped the block to the sides. If it is the top coming loose from the block loosening the side to top seam to insert glue and clamping would be sufficient without removing the entire top or back.
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    Default Re: Can I fix this without removing the top?

    Highly recommended to all who are interested in repair work:
    "Complete Guitar Repair" by Hideo Kamimoto. Currently in print.
    "The Acoustic Guitar" by Don Teeter.

    Also recommended: any of the time accepted books on violin making and repair. Also, Frank Ford's frets.com website.

    An awful lot of forum questions are covered in detail in these resources.

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    Default Re: Can I fix this without removing the top?

    The more I look at this, the more confident I am that this crack can be repaired through the f-holes with intelligent consideration and the right tools. The trick will be to determine the best method of aligning and clamping it. It's possible that it might be helpful to work through the opposite f-hole.

    One of the biggest challenges in lutherie is coming up with creative ways to clamp something. Another way to align the crack might be to build a "temporary bridge" that will span across the mandolin top. One way to do this would be to make a couple of spool clamps with shafts that are long enough to create a space that will allow a bar to fit between the top of the spool and under the adjusting nut. Install one spool clamp on either side of the mandolin with the bar running across the mandolin over the top-- this will create the "bridge." Then you can use a padded wedge between the "bridge" and the mandolin top to push the high side of the crack down. I wish I was computer literate enough to draw you a diagram of what I mean.

    If you use John's method of propping it up, a soundpost setter would facilitate the job. If you use the Teeter alignment method but don't want a permanent cleat, you can wrap a temporary cleat with wax paper or [possibly] Scotch Magic tape so it won't stick. Whatever you do, go through a couple of dry runs [without glue] on the alignment and clamping process before you do the actual gluing.

    If the block is indeed loose, Pop's method should work well, unless the sides are coming loose from the block [which would be highly unusual on an instrument of this age]. Pushing with your fingers and looking and feeling for movement will help you to diagnose the location of any loose joints.

    I will mention that I recently re-glued the loose tone bars on an A-50 through the f-holes with success. I used the T-94 2" and 4" f-hole clamps available from International Violin Co.
    Last edited by rcc56; Mar-09-2018 at 10:51pm.

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    Default Re: Can I fix this without removing the top?

    As Rcc56 says the biggest challenge is figuring out how to do something, as each repair is a little different. I don't know about other folks, but I like puzzles, and I feel figuring how to clamp or repair is like a puzzle. I also doubt the sides are loose from the block, but should they be let me know, there is a simple tool you can build to make clamping easy. The hardest part sometimes is getting the glue in and the clamps on. Again as Rcc56 says, dry run. Do it several times so it is quick and easy. It is like playing an instrument, practice practice practice.
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    Registered User Jritter3's Avatar
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    Default Re: Can I fix this without removing the top?

    Thanks everyone! Honestly I cant say enough about how helpful this forum has been. It's worth pointing out that this mandolin was built only after spending countless hours reading various threads on here regarding what to do or what not to do.

    Anyways, I took the strings off to keep it from destroying itself. Upon doing so the crack closed up a little bit, but not completely, and without the strings it's easy to push it back together. I totally understand its impossible to fully diagnose the problem based on pictures, but you all have given me plenty to chew on as I move forward.

    Im going to start out by taking John's advice and seeing how humidity affects the crack. Im at just shy of 5,000 feet altitude in CO, so it is no doubt dryer than it should be. I'll keep posting updates on the repair here. But first, a little spring break vacation is in order.....maybe it will help relax my nerves as I move forward.

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