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Thread: Martin D-18 Bridge plate issue

  1. #1

    Default Martin D-18 Bridge plate issue

    I recently was asked to work on a Martin D-18 that had previously been repaired, but that had the bridge pull off. A closer inspection showed serious deformation of the top and evidence of a significant across the grain top break that emanated from the bridge area. After I removed the bridge with great care, I saw that the break extended underneath the bridge and had not been repaired.

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    Inside, there was clear evidence of an earlier repair that failed leaving several braces loose or badly glued with what appears to a titebond type glue. When I spoke with the owner, he confirmed that a previous repairman had tried unsuccessfully to remove the bridge plate and I am assuming from the damage, that he broke the top in the process. His attempts to repair the damage were the ones that failed.

    I tried removing the bridge plate myself but with the damage to the top, I decided not to continue and re-open old breaks.

    I'd love any thoughts on the best way to proceed from here. Here's a shot of the bridge plate.

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    This seems oversized to me, but I haven't dealt with too many Martins in the past so I can't say for sure. I am afraid that to remove the old plate, I will create more problems than solve them and I'm considering leaving it place and just repairing the brace damage. In addition to the loose braces by the bridge, the far end of the treble side X brace is also loose.

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    Any thoughts or suggestions from the forum on the best ways to deal with this would be greatly appreciated!

  2. #2
    Registered User j. condino's Avatar
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    Default Re: Martin D-18 Bridge plate issue

    'Looks just like half of the old Martins I have ever worked on....

    Make sure you charge a proper amount for all of the headaches it is going to give you!

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    Default Re: Martin D-18 Bridge plate issue

    Seems to me it's time to take a hard look at the true market value of the instrument to determine if the repair cost is justified. That top appears to be disintegrating (and note the curious rosewood cleat at the 'X'). Looks like widespread glue failure, too. Gomer Pyle sure didn't do anyone any favors by slinging glue all over the inside of the guitar.

  4. #4

    Default Re: Martin D-18 Bridge plate issue

    Agreed on all counts! Sadly though, this is the instrument of a friend and I don't think a pro repair shop would take this on for all the reasons you stated (and I can't image the bill if they did)!

    The side rosewood patch was a poor attempt to stabilize the top and deal with the traditional Martin pick guard split. I managed to get a bit of it off and will probably remove it all as I move forward.

    If I leave the bridge plate in place, and at this point I am concerned that removing it will cause even more damage, I can try to repair the bad glue work on the braces to stabilize it. Clearly, I'm going to have to inlay new wood under the bridge to repair the damage and make a proper flat surface to re-attach the bridge to. I've dealt with that before, though never to this extent!

    I assume since titebond was the glue used for the previous repair, I'll need to clean out as much as I can the use the same glue for the repair.

    A lot to consider....

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    Default Re: Martin D-18 Bridge plate issue

    Since this isn't a priceless heirloom, what about this idea: Clean up the topwood under the bridge as well as possible, tape the area off, and flow some watery epoxy in there to try to stabilize the area? Maybe even a ~1/4" bore on either side, down into the bridge plate, such that the epoxy ties the whole thing together so it can move as intended, i.e. bridge, plate, and top as a unit. Cutting the bad wood out and installing a patch seems like it would further harm the integrity of the top, such that there is any. Then finally you can epoxy the bridge to the patched area. (Nobody is ever going to do this again, so disassembly and reconstruction isn't a concern.)

    Just a thought. I may be wrong, but it certainly wouldn't be the first time.

  6. #6
    Mando-Accumulator Jim Garber's Avatar
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    Default Re: Martin D-18 Bridge plate issue

    Oh wait, maybe I misread the OP. This isn't a vintage D-18? Maybe at least tell us what year. In any case, it sounds like it was butchered by prior amateur luthiers.

    -----------------
    Having been looking at the market for vintage Martins lately which in my observation have skyrocketing in value lately, I would check very carefully. Retail prices for vintage mahogany Martins even from the 1960s are approaching 5 figures on the retail market. It still may be worth it for your friend to get an estimate and calculate whether it would be worth it.

    In the meantime, you probably came across these two pages by Frank Ford on the topic.

    http://www.frets.com/FretsPages/Luth...lateover1.html
    http://www.frets.com/FretsPages/Luth...newbrplt1.html
    Jim

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  7. #7
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    Default Re: Martin D-18 Bridge plate issue

    Some technical information:

    Rosewood bridgeplates were factory original equipment from 1968 until 1988 on production line Martins, except for HD-28's and HD-35's.
    Most of the rosewood bridgeplates were indeed very large.
    Martin starts to experiment with glues in 1964 or 1965. White glue becomes the standard shortly after until it is replaced by Titebond in 1988.
    Instruments made in the mid-1960's may have incorporated a combination of glues. The neck on a '65 Martin that I reset had originally been glued in with a yellow glue.

    -----------------------------------------------------------------------------------------------------------------------------------

    The large rosewood bridgeplates have a nasty way of cracking across the grain between the pin holes, or simply losing a large chunk of wood in the same place.
    When this occurs, there are two options:

    1. Reinforce the damaged area with a hardwood cap [I have used maple or ebony]. If there is a lot of missing wood, you might consider using some filler before you cap it.

    2. Replace the bridge plate. I generally avoid pulling a bridgeplate unless there is no alternative. I have only pulled an oversize rosewood plate once. The risk of collateral damage is high.

    You will have to get a bright light in there and determine with absolute certainty whether the bridgeplate is damaged.

    Grafting new spruce into the top's glueing surface for the bridge is a technique we all must learn sooner or later. I've gotten pretty efficient at it. I regularize the damaged area, fit a graft that is a bit high, glue it in, then level it with a chisel and/or small sanding blocks. My current preference is for hot hide glue. Until a few years ago, I used Titebond.

    Cleaning glue out from under braces is a problem. I sometimes glue sandpaper to very thin palette knives, insert it into the joint, scrape as best as I can, and cross my fingers.

    ----------------------------------------------------------------------------------------------------------------------------------------

    The most reliable way to repair this guitar would be to open it, pull out everything that is loose or bad, clean the glueing surfaces completely, and reglue or replace the loose or bad parts. But guitars are not violins, and they are not made to be taken apart. The risk of collateral damage is high, and such repairs are difficult and require many hours of work. I only open a guitar when there is no alternative, and I've only opened 3 or 4 that I can remember. I've also opened 3 or 4 mandolins. They are easier, but still nerve-wracking.

    Another alternative would be to remove the fingerboard extension and re-top the instrument. Also a lot of work, and most owners don't want their guitars re-topped.

    So, since opening or re-topping the instrument are probably not viable alternatives, your current choice of doing the best you can through the sound hole is probably the best option. You will have to explain to the owner that the brace repairs might not hold forever. Clean everything up as well as you can, set your clamps carefully, and hope for the best.

    Good luck. Be patient, be thorough, and walk away for an hour or a day if you need to.
    Welcome to the wonderful world of re-doing someone else's work.

    Oh-- check the saddle location before you reglue the bridge. Most Martin saddles on later 20th century D models are too far forward. It's easier to fill and recut a saddle slot while the bridge is off the guitar. I get good results setting the first string saddle location at scale + 2.5 mm, and the sixth string at scale + 5 mm. I put a fence on my drill press, use a 1/8" downcut router bit, and fix the bridge to a sled that holds it at the necessary angle to make the cut.
    Last edited by rcc56; Jul-18-2022 at 6:08pm.

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  9. #8
    Registered User j. condino's Avatar
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    Default Re: Martin D-18 Bridge plate issue

    At this point, anything you do will likely be an improvement.

    If the rest of the guitar is in similar condition to what you've shown, it should be fairly simple to carefully remove the back binding and then remove the back. Even though I don't like to do that, it will make doing high quality repairs infinitely easier and you'll do a better job having access to the entire inside of the guitar. As with most repair work, 90% of your time will be spent cleaning up someone else's mess....

    The runout in grain direction under the bridge is common. You should also prepare yourself for the idea that there will be some additional surprises hiding under that massive bridge patch.

    If you were local, I'd say bring it by if you get over your head.

    I would do everything with hot hide glue, that way everything is easily reversed and you can do a second take if necessary.

    If the back is removed, a go bar deck will help the clamping challenges & don't be surprised if you need to build a torture chamber to the alignment finessed back into position, similar to this:
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    Default Re: Martin D-18 Bridge plate issue

    I know of one repairman who took out old bridgeplates with a finger plane.
    I tried it once, and gave up after an hour. Fortunately, the scars on my forearm were not permanent.

    Standard procedure for pulling a plate is to soak it overnight with a wet cloth, heat it with a heat blanket or special iron made for the purpose, and pull it with a chisel bent into a reverse hook. It works, but there's considerable danger of heat damage to the finish. And the heat source can slip and get onto to the wrong surface. You don't want that.

    Pulling a plate is one of those jobs where a hundred things can go wrong. I don't like it, and avoid it whenever possible.
    I keep hoping someone will come up with a better method. If they have, I'm not aware of it.

    ---------------------------------------------------------------------------------------------------------------------------------------

    You could open her up. How brave are you? The quality of the repairs would indeed be much better, and you could pull out that famous Martin Tone Inhibitor that they called a bridge plate with no worries. The guitar would sound better. You could even scallop or taper the braces if you wanted to. But you would have to be prepared to repair any finish damage incurred from pulling the back, work very slowly and carefully with hot knives and a syringe full of water, and be extra careful working around the upper bout towards the waist and hope for no cracks. How brave are you??

    I pulled the back on a severely over-braced Goya 12 string a couple of years ago and re-braced it. It opened cleanly, and the project kept me out of trouble during lock-down. I didn't know how to voice it, though, and finished voicing it through the sound hole. The scars on my forearm were not permanent . . .

    The last one I opened was a 100 year old Martin. The X-brace was broken at the bridge plate, and the guitar was folding up. It was necessary to replace both the x-brace and the bridge plate. James mentioned surprises. When I pulled the plate, I discovered a large deep pocket of missing wood under the plate that had resulted from a botched previous plate replacement. A 1 1/2" x 6" graft had to be installed, and that was a fair amount of work that wasn't included in the price estimate.

    Unfortunately, opening that one up didn't go so well. Even though I took my time, I broke a chip off the lower bout. I now wish I had used a thin saw when I encountered resistance at that spot. There was also some finish damage. Fortunately, Martin had already oversprayed the finish during a previous repair, so overspraying it again didn't compromise an original finish. I got her back together and saved the guitar, and I was able to hide most of my sins, but I'm still disturbed that I didn't get the back off cleanly. Fortunately, the customer was happy, but I wasn't.

    If you read these forums, it's possible to get an impression that the more experienced repair people always get perfect results without anything going wrong. But sometimes things do go wrong, and you have to be prepared to deal with it.
    Last edited by rcc56; Jul-18-2022 at 7:08pm.

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  13. #10
    Registered User j. condino's Avatar
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    Default Re: Martin D-18 Bridge plate issue

    Quote Originally Posted by rcc56 View Post
    ....If you read these forums, it's possible to get an impression that the more experienced repair people always get perfect results without anything going wrong...

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    Mando-Accumulator Jim Garber's Avatar
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    Default Re: Martin D-18 Bridge plate issue

    I admire all the excellent builders and restorers on these forums. And those who do the quality repair work are truly faced with some incredible challenges. I know I have presented some to my luthiers over the half century or so I have been playing.

    It is true though, that yu never know what you are getting into. Many years ago I did a trade with a fellow musician for a 1935 Gibsons L-Century guitar. I never liked playing that one. It was cool looking but it always sounded choked to me as compared to my same era L-00. So I tried to sell it and shipped it to a buyer who promptly told me he would return it because there was a half inch block glued to the bridge plate.

    I asked my friend about it and he did not know it either. It is rare that we take the time to look inside our instruments. So I took it to my luthier who did a masterful neck reset on that guitar—as I understand made more difficult due to the mother of toilet seat fretboard—as well as removing the impediment block on the bridge plate. While she was inside she found a loose brace and probably someone’s lunch left over from the 1950s (kidding!). Suffice it to say the guitar breathed and sang again.
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  15. #12

    Default Re: Martin D-18 Bridge plate issue

    Thanks very much for the excellent comments and advice. Yes indeed, things DO go wrong! I've made plenty of mistakes over the years.

    Here's a few more details:

    I did soak the bridge plate overnight and heated it with a hair dryer and a bridge plate removing block. It didn't budge and clearly was stressing the top in ways that were not good. It was quite apparent that a previous attempt to do this was the cause of the damage to the top.

    I do agree that the best and proper way to restore this is to remove the back. However, since this is a job for a friend rather than a paid restoration, I don't see a major re-build in the picture, though I do have the skills and nerve to do it under the right circumstances (and may yet have that conversation with him). I expect I'll try to repair the brace damage and stabilize things as best I can through the sound hole unless that proves untenable.

    I've pondered the best way to deal with bridge tear out for years and have settled on Frank Fords method of removing damaged wood and grafting in new wood. I would glue and stabilize it first, then chisel out and glue in an appropriate spruce piece and shave it down to size. That being said, I'd appreciate the thoughts of the forum on this.

    While I appreciate the ease of using epoxy as a filler, I myself wouldn't use it on a Martin. I've had epoxy based fillers fail to hold glue in the past and I wouldn't want to take the chance. No matter how badly damaged this is, it has the potential to be a good instrument if properly repaired. I agree, hot hide glue (because I may need to re-do it!).

    I could see glueing in a thin re-enforcing plate of Rosewood to the top of the existing bridge plate (assuming it is level) with the grain running in the opposite direction of the original bridge plate, but I'd want to avoid adding in too much mass and killing the tone.

    Re age: I don't know, but I don't think it's particularly vintage, perhaps the 70s, though it does have the tiniest side tone bars I've ever seen. I'll ask the owner and let you know.

    Wow, much to ponder here. Again, I appreciate your insights and will continue to keep you in the loop as I move forward. Wish me luck!

  16. #13
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    Default Re: Martin D-18 Bridge plate issue

    Using a hair dryer to loosen a bridge plate will not work. The heat has to be applied directly to the bridge plate from the inside. Touchy business. Stew-mac used to sell an iron made for this purpose. It is clumsy to use. LMI sells a couple of specially shaped heat blankets that are probably a bit easier to deal with. If you get one, instead of using their overpriced temperature controller to control the heat, you can use a Harbor Freight router speed control to regulate it.

    I use heat blankets from McMaster-Carr or MSC for loosening bridges and fingerboards-- 5 watts per square inch. You could find a rectangular or round one that would probably work for a bridge plate if you don't want to pay 92 bucks for the special trapezoidal shaped ones that LMI sells.

    For most top grafts, I simply carve a regularized recess into the top wood without going all the way through the top, and graft new wood into the recess. It's somewhat similar to a violin soundpost patch, except that it's ground completely flush. It's plenty strong, because you're creating a sandwich with the graft, top, and the bridge plate. In most cases, the worst that can happen is that on occasion, the graft will have to be re-done if the bridge comes loose again in 5 or 10 years.

    If the Frank Ford article you're referencing is the one where he cuts completely through the top, I would reserve that technique only for situations where there is a long cross grain fracture that goes all the way through, or where the wood is so chewed up that there's nothing solid to graft onto. Now that I look at your first picture again, that might be necessary, but I would avoid it if possible. It's easy to run out of surrounding surface to scab onto without getting into the finished surface of the guitar.

    I don't use rosewood to cap bridge plates. It is too soft and the grain can tear out too easily, which is often what caused the problems in the first place. I have found that hard maple or ebony work well. Keep it small and thin. It only has to be large enough to give perhaps 1/8" - 3/16" of coverage around the perimeter of the pin holes, and perhaps 1 mm. thick.

    I almost never use epoxies for instrument repair. The only thing that I generally use epoxy for is for glue and filler for fingerboard inlays. Other than that, I've only used it maybe 2 or 3 times for other things [I can't remember what] over the course of 25 years. I did use it once many years ago to replace a badly broken neck heel.
    Last edited by rcc56; Jul-19-2022 at 1:25am.

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    Default Re: Martin D-18 Bridge plate issue

    Seems like fitting a new AAAA torrefied spruce top would likely produce a superior instrument to the original.

  18. #15

    Default Re: Martin D-18 Bridge plate issue

    A new top would almost certainly improve things, but that IS well beyond my pay grade! I did speak with the owner and we agreed that removing the back is more work than this guitar warrants. I'll try to re-work the damaged braces through the sound hole and re-build the bridge damage. He mentioned this is a '72 Martin.

    To clarify a couple things, the hair dryer was to warm the top and the inside of the guitar so any heat I applied didn't dissipate as fast. I did use a bridge plate shaped heating iron but as mentioned, it was clumsy to use and even though it did heat the bridge plate, that thing wouldn't budge.

    I do plan on grafting in new wood, but as you suggested, I will not cut all the way through unless there is simply no other way to deal with the damage. The article I was referring to talked about removing damaged wood from below and keeping the original top wood intact. I'm planning on a reverse variation on that idea.

    By the way, the damage you see under the bridge isn't tear out, it is an across the grain fracture which occurred when the previous repairman tried to pull the bridge with brute force. When I try to clean out the glue from under the loose side tone bar, the pallet knife comes out through that break. There is a corresponding across the grain break on the bass side as well.

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    I appreciate the info on not using rosewood for a cap and keeping it small. I have some thin ebony I can use for that. I've just glued up the under the bridge break with HHG and will start to work on removing and replacing damaged wood

  19. #16
    Registered User Tom Haywood's Avatar
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    Default Re: Martin D-18 Bridge plate issue

    I think you have figured out the best course of action. I had to do a somewhat similar repair on a mid 70's D-28 a while back. I'm trying to remember the details. The bridge and bridge plate were coming off and resulting in an excessive belly bulge. I got a feeler gauge between the plate and the top and determined that there were gaps in the glue. I made a reverse chisel, a couple of other knife tools to heat up and insert, and a small pry bar tool to hold whatever progress was made. The plate was a sort of thick rosewood. I could not get the parts hot enough to release the glue without causing damage, and the pry bar and knife blades were trying to do some damage. Doing it all through the sound hole made it slow and tedious. After flattening the top a bit for a few weeks, I finally made a not too thin maple plate to glue over the rosewood, and glued the rosewood plate to the top thoroughly by inserting Titebond into the gaps. After some spruce tear out repair on the top, I put the bridge back where it was . Everything worked and the guitar played and sounded good. The owner told me about a year later that it sounded better than ever. I've learned from building that more mass on the braces sometimes improves the sound. That seemed true for this guitar with the bridge plate cap.

    BTW, there should be a 6 digit number on the end of the neck inside the body. A quick google of Martin serial numbers will tell the year it was made.
    Tom

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    Default Re: Martin D-18 Bridge plate issue

    I agree with the OP, in that I would not(in most any circumstance) use epoxy to reglue a Martin bridge. The best repairs to this D-18 can only be achieved, IMO, and as others have suggested, by removing the back, but that's not in the budget(understandably). Given the existing damage, perhaps epoxy would be the best fix: it would be quick, and it may well hold everything together, and yield a playable instrument. If it doesn't, what have you lost? Fixes through the soundhole(given the failed area under the bridge, and the failed brace reglues)may well not last. It's a dilemma for sure: best of luck!

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    Default Re: Martin D-18 Bridge plate issue

    The most labor-intensive and time-consuming repairs I have done have all been for friends who had instruments with sentimental value. All challenging, none where I could (or would) charge remotely near what the job was worth. It is what it is.

  22. #19

    Default Re: Martin D-18 Bridge plate issue

    72, eh? I’m no expert but that bridge plate looks HUGE—is that one of the infamous oversize tone-killer plates that appeared in the 70s? I thought they were later in the decade. This is the old bridge plate from my 73 O-18 which was replaced last winter to great effect. No wonder the pins were always loose…

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    Default Re: Martin D-18 Bridge plate issue

    You may want to try and fit unslotted bridge pins, they need a larger hole, and a slot, and push the string balls forward so the sit on the plate. They also don't bend causing the damage to the plate. Stu Mac has a tool to remove rounded pieces of the plate and replace with a matching piece from another tool. I have done this to repair holes, but these days I simply place tape across the plate, put in some epoxy and wood dust, thickly mixed, and let dry. Just to the thickness of the plate, you don't need to fill the hole. Remove the tape and redrill the holes. What you add will be much less this way for weight than another piece on top of the plate and seems to work well. I usually follow this with solid pins instead of the slotted ones.
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  24. #21

    Default Re: Martin D-18 Bridge plate issue

    Thanks very much for all the comments and advice! Very much appreciated. Here's where I am at now:

    As discussed, I'm working through the sound hole (there are several cracks around the sound hole from previous "in the hole repairs" which I've glued up). Last night, after cleaning any glue remnants out, I used HHG to glue the treble side top break which was under the bridge. I was able to open it up and make sure that the glue got all the way in through the split. I clamped this up and let it set overnight.

    So far, things seem to be going well. Glueing the big cross grain split immediately made a big difference in the top stability, leveling out the area and stiffening the top. Today, I re-glued the loose X brace end (treble side lower bout end) and that is currently clamped up. I used titebond on the X brace due to it's location and the fact that I would need the longer set up time to get the glue in properly and set the clamps (the lose brace extended from the very edge of the guitar in about 3").

    RE the bridge plate, without knowing better, I would have assumed that this was a replacement bridge plate from its size. That being said, it isn't in bad condition... no chewing out of the pin holes or other serious damage. I tried to pull it because of the serious bulge in the top and the fact the owner told me that had it been attempted before. I'm not sure I need to worry about it. I do have a piece of ebony that is about .07 thick that I can use for a plate cap, but I'll see how things work out first. I am concerned that the guitar already has enough tone killing properties in place! I'll continue with the brace glueing and see how this are then.

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  26. #22

    Default Re: Martin D-18 Bridge plate issue

    Here's an update:

    I completed glueing up all the loose braces and gluing the damage to the top beneath the bridge. It was apparent that even with a careful glue job, there was enough damage and tear out to the top, that I'd need to graft in quite a bit of new wood to create a solid, level surface for glueing the bridge.

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    Once I began that process, it quickly became clear that was still significant internal damage to the top wood beyond the actual break. These were small, internal fractures that the glue had not reached and it meant that I would be grafting in more wood that I had hoped to. I tried to shave down through the damage to solid wood, but there simply wasn't any.

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    In fact, the damage at the far treble end went all the way through the top. This is the area that presented itself as a loose finger brace when actually that was part of the top fracture. In this shot you can see the edge of the fingerboard, the X brace, then a hole!

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    I'll graft in new top wood, but also re-enforce this area with spruce from below.

    Lots more work to do on this, but I am getting hopeful for a good turn out.

  27. #23
    Teacher, repair person
    Join Date
    Oct 2017
    Location
    Southeast Tennessee
    Posts
    3,310

    Default Re: Martin D-18 Bridge plate issue

    Yeah, that'll be a patch it up, cross your fingers, and hope that it'll hold job.
    With luck, it might hold for a very long time. Clean up the underside of the top really well where the reinforcement will go.

  28. #24

    Default Re: Martin D-18 Bridge plate issue

    That is the original Indian rosewood bridgeplate, which is 3 1/4" wide. Those began in 1969 on dreadnoughts. Indian rosewood turns out to be a poor choice for bridgeplates. Chips and cracks between and around the pin holes are almost universal.
    Oversize bridgeplates in the normal cross-grain orientation are not a great idea, because the bridgeplate can curl across the grain as the top bellies.
    That top has obvious runout, which should dictate the direction that is taken when removing bridgeplates. The same applies to removing bridges, braces, and under-finish pickguards.
    I have done this very repair too many times to count.
    In few cases, I have deemed it necessary to remove a back. All the others have been done working through the soundhole.
    The first one where I removed the back was a 1939 D-45. That was around 1988 or 1989. In 2020, I removed the large rosewood plate from a 1941 D-45, working through the soundhole. Many older Martins have had the large rosewood plate retrofitted at the factory. This follows Martin's policy of repairing using current designs and materials.

    In several cases, I have planed the bridgeplate thinner with a finger plane. This reduces the stiffness of the plate, which will minimize the chance of top damage during removal.
    My heating iron is a soldering iron with a 1" X 3" aluminum block attached to the tip. I wet the bridgeplate beforehand. These plates take a lot of heat to remove. I judge the amount of heat by laying my hand on the top. If the heat is uncomfortable to my hand, it can damage the lacquer. I keep wetting the bridgeplate while I heat it, which does two things: it helps soften the glue, and it prevents shrinkage of the top, which can cause the center seam to separate.
    A quartered red spruce patch (triangular in shape, fitted to the X-braces) is applied inside the top. A flat board is clamped across the lower bout of the top while gluing in the patch to flatten the top. Grain in the patch is parallel with the top grain. It typically extends up to 1" below the bridge, and adds as much as 0.08" to the total top thickness. I have found that this added thickness is not a detriment to the sound, because it has the desired properties of spruce (low mass, stiff along the grain to resist top distortion, but relatively flexible across the grain for sound). In any case, it is superior both sonically and structurally to the oversize rosewood plate. After gluing it in place with HHG, the spruce patch can be tapered on the lower side to feather it to the surface of the top, using the finger plane.
    Damage to the top can be patched with spruce, either as a partial thickness patch, or one all the way through the top, sandwiching it to the triangular patch underneath. Repair of a hole can also be executed by carving the triangular patch in one piece from thicker spruce such that it plugs the hole(s). I have done this repair on guitars that have no original top under the bridge. The first of this extreme version of the spruce patch was my own 1930 OM-28 with a pyramid bridge. That repair was done in 1994, and the guitar is still solid today.
    With the added spruce, a thin hard maple bridgeplate that is no more than 1 3/8" wide is all that should be needed.
    Last edited by John Arnold; Jul-26-2022 at 6:17am.
    John

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  30. #25

    Default Re: Martin D-18 Bridge plate issue

    This is my most recent spruce patch repair, on a 1945 D-28 with a long history in Folk/Bluegrass. The hole through the top was 1/4" bigger than the bridge, all the way around. Previous repair from the 1970's included a drop-in Sitka spruce patch, a giant, extra thick rosewood bridgeplate, replaced oversize X-braces, finger braces and upper tone bar, and a sloppy back removal with binding that didn't match. Since it was best to redo the back (in addition to all previous repair attempts), I removed it to facilitate the work.

    When the guitar arrived, the top was severely bellied. The bridge had been cut down half thickness to lower the action, and it sounded like it was stuffed full of socks. The elderly owner (who said she acquired the guitar in 1958) had been informed that the guitar was not worth repairing. She was also afraid to tighten the strings, since the belly was so severe. Another testament to the fact that oversize bridgeplates are not the way to go.

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    [ATTACH=CONFIG]202290[/ATTACH

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    Last edited by John Arnold; Jul-26-2022 at 2:05pm.
    John

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