Dent Repair Help Needed

[Ted Uy]

I am a new poster and not a luthier. I am, however, an experienced woodworker of mostly small furniture pieces with some modest skills. Recently I purchased a used Martin D-16RGT guitar. It has a small 1 1/2 inch dent/crack on the bottom of the side. See photo. While the inside was patched by a luthier, the previous owner did not have the outside of the dent fixed.

It is not financially feasible to have a professional luthier do this repair. Plus, as a woodworker, I'd like to work on the guitar myself (cause these are the things I like to do as opposed to going outside and raking the Fall leaves that my wife is now asking me to do). I've read a number of articles on the frets.com site and looked at some stuff on YouTube, but I could not find anything that directly fit my situation. So I thought I would post this on the forum.

1. What sort of filler repair would you recommend? A hot melt repair? Some type of ready made wood putty? Would you try to color match with the filler material or after the dent is filled and sanded?

2. The body is finished with a satin finish. After the dent is filled and color matched, how do you blend in a satin finish? If it was a gloss finish, I would just spray, sand and buff. Would I do the same bur with a satin lacquer?

3. Finally, for purely aesthetic personal taste reasons, if I wanted to refinish the entire body with a gloss finish, would doing so adversely affect the guitar's tone quality?

Thanks very much for your help. Ted

[Ned Knepp]

Hi Ted, Welcome to the forum.

  First off, I'm not a  professional. I have dealt with this sort of thing a time or two. I never use putty and don't know anyone who would use it on a guitar though I've seen guitars with it on board. I don't even like using the glue/wood dust trick unless I absolutely have to. For a grainy fix like this, I would be more likely to try a small splint or even just a long grain "thread" cut with a small "V" carving chisel from some mahogany scrap.

Before anything you should look at the damage with the idea of getting it back into alignment. It appears to me that you are dealing with a crack more than a dent. Maybe I'm seeing it wrong but it looks like the typical impact crack with some offset in the side. Can you press the two sides back into alignment?   You said that it was patched on the inside, what form does the patch take? Is it a wooden patch, a cloth patch or some other sort of patch?

If the cracks can be aligned, there may not be much "fill" needed and it may be possible to hide most of the damage with dropped filled finish. 

 

 

[Greg Mirken]

Echoing what Ned said, it's hard to see how this could have been professionally repaired internally without even aligning the edges of the crack. If there's some sort of patch that prevents you from getting the edges aligned, your job is much harder; you would need to remove it. Once the outside surface is even, there shouldn't be need for fill, since it doesn't appear that any wood is actually missing.

Regarding your question of finish repair on a satin finish (actually this is below satin, somewhere near 'flat'), it's next to impossible to match. Keep the repair small and don't worry about matching. You can't do any sort of buffing or it will gloss up and look worse. This is a tough intro to guitar repair, sort of like starting in the middle of Book Two.

[Ted Uy]

Thanks to both Ned and Greg. I just got out my mirror-on-a-stick and light and took a close gander inside. I guess the seller was not totally accurate when he said the inside was patched since I did not see any glued on patch. (In my defense, I think I got a pretty good deal on the purchase as the price was reflective of the crack.). He could have meant that someone, as you suggested, pushed the indentation back out from the inside. He did say, as you surmised, that the crack was caused by dropping the guitar.

There is some slight outside surface un-evenness like maybe it was pushed a little too far back out.

The attached photo does accurately show that it looks like the injury splintered and there is a missing splinter and the better repair would be a sliver of donor wood.

Thanks again for your advice.

Any thoughts about the question of refinishing the entire body with a gloss finish?

Thanks. Ted

[Kerry Krishna]

Ted, this is a good thread for some of us here to learn what the 

'big folks' do. 

 This really does look like way more of a crack alignment problem to me than anything else.

 When you had initially said that you wanted to refinish the guitar, I GOOGLED your Martin and came up with nitro finish. I had thought that with Martin making just under 180 different models, that it was quite likely that they were using poly finish on some of them, which would have made everything quite difficult, whether you decided to just redo that small piece, or anything else.

  Many of us here have refinished entire guitars, and it is not an easy process, as the list of stuff lined up against the guitar looking good in the end is a long, long list. If you are not planing on taking the bridge off to do this, I would jump off this particular bandwagon right now. 

  I want to see what the folks here will come up with for the crack realignment. It seems to me that maybe the simplest repair would be the 'drill a tiny hole and get a  'B' string through the inside of it with the ball against the wood, and use loose  guitar tuner  mounted to a small piece of wood to pull it all back into shape. 

There is something on FRETS site on how to do this if I remember properly.

This is all my uninformed opinion though...

 

[Ted Uy]

Kerry, thanks for the reply. Taking all of this into consideration, I think for the time being, I will just leave things as they are. Then, eventually, take it it a good professional luthier for repair. (I guess the easy part of woodworking furniture making is if I screw up, I have not irretrievably ruined a Martin.)

As for refinishing the entire guitar, the top spruce is already gloss, so it would just be the rosewood body. But, for that too, I think I will leave it for now. Eventually, when I run out of furniture projects, I would like to try my hand at one of the guitar kits and maybe after more experience, I can think about this repair and finishing job.

Thanks again. Ted

[Ned Knepp]

Ted, that last picture looks like the strip between the cracks protrudes above the main body of the sides. If that's the case your fix should be easier. BTW, I highly recommend that you get this repaired or do it yourself before too long. The cracks are completely capable of running plus the edged of the cracks, which look like they will line up pretty cleanly now, will easily snag on clothing or other things and rip more wood from the edge of the crack. If you don't take care of it soon, the repair may be much more involved down the road. 

[Donald A. Fortune]

Hi Ted-- If the inside was patched with a piece of material to keep the crack from opening up any worse than it is then all you need to do is mix some saw dust of the same kind of wood with some glue of your chose and then re finish the box with what ever you want to-- PS as a wood worker Im sure that you have used this repair trick before..

Just my two cents--

good luck with your adventure--

Peace, Donald

[Hesh Breakstone]

What I would do is hook up the Ohio Steel Lawn Sweeper to my Gravely ZT50 and in no time those pesky leaves would be all picked up in dumped in the vacant lot, up wind I will add from the neighbor that none of us like... and deposited there for nature and the wind to take it's course.  ;)

But you wanted to also know about how to fix this Martin 16.  Sorry, I try to be very comprehensive in my replies so I could not resist addressing the Honey-do stuff too.

This looks like the guitar hit a corner of something resulting in a crack and subsequent depression, depression of the side as well as perhaps the previous owner/steward.  These kinds of injuries and repairs are pretty common and we see them often.

Most of the time these kinds of repairs can be done without difficulty and also most of the time the repair can be invisible to most naked eyes.

If my hunch is correct, and it's very possible that it's not... and if this resulted from taking a blow, perhaps a corner of a table, etc. the approach is to carefully manipulate the crushed area back out into the curved plane of the sides while at the same time wicking glue (Titebond original is fine for this) into any and all cracks.  Dry runs, meaning practice runs.... are your friend and what you want are clamping cauls on the outside and inside that will bend to the curves of the sides but be very thin - more on why thin in a moment.

Ultimately you want the crushed area with all cracks having glue applied to be pushed back into the plane of the side curve with flexible cauls inside and out and then clamped back into the damaged area's original form, curve, and location.

We use rare earth magnets and not the girly-man ones that Stew-Mac sells but the 3/4" ones that you can purchase on line and that provide around 40+ pounds of clamping pressure per square inch.  Since we are using magnets this is why you want you clamping cauls to be thin and flexible in one direction, the direction of the curve of the sides.  Many sorts of plastics that are 1/8" thick of thinner could be used provided that once curved in the side curvature they are no longer flexible in any other direction.  It's also a good idea to cover the cauls with waxed paper, inside the box and out, because most cauls won't contribute well to the tonality of the repaired instrument if left glued to the sides.....

Hopefully you can reach the spot through the sound hole and press on it and see how well it closes.  My hunch is that since this is likely impact damage that this crack really is not at great risk of running and could be pressed back into place with only top and back clamping and perhaps no need to clamp the side top to bottom to encourage a crack to close.

If any areas of wood are missing use the same wood type to patch following grain appearance and direction.  Fillers never are invisible in my view and they all suck for this kind of crack.  So there is no substitute for using real wood if you want it to look like really wood.  

Once glued, clamped, and the magnets, cauls, waxed paper are removed sand with a block so as to not create a low spot and if the thing went back together nicely with no missing wood you are good to go to the finish repair stage.  Gluing, with the same flexible cauls, waxed paper, and rare earth magnets, a flexible backing would be prudent too depending on who you talk to or, conversely, if this is an impact crack and not the result of wood movement perhaps no cleating would do for some of that school of thought too.  

Be careful of the dreaded "scope creep" that will haunt you too while sanding.  First we sand this, then that, and in time re recognize that our quarter sized damaged area now requires refinishing most of the side.

Not sure if this is satin or flat and can't tell from the pics.  

Regarding refinishing the entire body.  Are you tooled-up and knowledgable in bridge removal?  If you intend to leave the neck on and in the way making refinishing even tougher do you have the tools, finishing tools required to get into the neck joint?

I'm asking because I am not recommending a complete refinish unless you know how to pull a bridge (and not damage the instrument) and how to get it back on safe and sound and in the correct location.  It's way easier to finish a new build before the other parts are in place than a refinish.  Just thought that you should know that before proceeding.

Lastly tone you say.  Tone is so very subjective that it's always a crap shoot to answer any questions about tone.  I will admit to being the sort that believes that I can hear certain finishes, very thick, plastic finishes that tend to sound like a $150 Kentucky mandolin with that "clicky" plastic tone.  I'm bringing this up because guitar finishing and doing it well is an art.  It's not easy and it's been said more than once in my world that whom ever decided that guitars should be shiny should be dug up and shot....  Kidding of course... ;)

Just know what you are getting into before going the full refinish route.  Stew-Mac used to have a free PDF available for download of Dan Earlywine's finishing schedule that you could download from the Stew-Mac dread*ught kit web page.  His schedule is excellent and works well but you are in for a month of work, most of it waiting for paint to dry, six cans of rattle can nitro or nitro for your spray equipment, lots of papers, and what about a buffing rig - do you have one of those to buff out a nitro finish.  You could leave it satin with less work but still expect the refinishing to be a big deal, take a long time, not something that first timers often do well..., and when done you still have to get the bridge back on.

Lastly since this is a 16 check the neck joint in terms of where the heel rests on the sides of the body.  These models often need the neck reset because of the glued mortice and tenon design that does not hold well.  There is a bolt in there, under the name plate on the neck block, that comes off and covers the bolt.  If you can tighten this bolt and the neck moves as a result the glue joint is gone and needs attention.  Again this is very common on these models and can be needed on a guitar only a few years old.

Back to tone.  A nicely done, thin finish with a final thickness of .003 - .004 will have less impact on tone than a thick finish.  Thin finishes are not easy to do well unless one has done them some number of times.  It's possible that you could pull it off but it's also just as possible that your refinish will add more finish to the instrument than it originally had.  Something to consider before taking the refinishing long walk on that short pier....

Hope this helps.

[John McDonald]

Hesh, would you use a 1/2" or a 1" diameter magnet for a repair like this one?

[LARRY KLOSE]

I haven't done one of these so I'm speculating here, but how about: 1) aligning with correctly shaped cauls and rare earth magnets, 2)use hot hide glue for the bond.  Frank has a whole section of www.frets.com on using these magnets and making fixtures to facilitate their use.  He demos on a Taylor with a back crack that has lots of the characteristics of the crack here--pushed out, displaced edges, etc.  After stabilizing and leveling the crack, a sliver could be used to fill any missing wood, if necessary.  A molded exterior caul could be made from the undamaged portion of the same side that has the crack.  Frank also has pages on how to make molded cauls.  The downside is that making some of the fixtures per Frank's articles might take more time and cost a lot more than taking it to him for repair--He's got all the stuff already.  But maybe for one small area like this, smaller magnets could be successfully used.

Re satin restoration, I have a mandolin built by the late, great Taku Sakashta.  When I had a minor finish issue to deal with he told me how he did his satin varnish finish.  Basically, he used French polish technique using very fine 2500 sandpaper in place of a pad on the final surface.  I never did the repair because I sent it back to Taku for some other work and he handled it at the same time.  This would take some practice on scraps (which Taku recommended!) and I don't know if a match to the original could be achieved but if you're experimenting, it may be worth a try.  What I can't recall is whether FP can be used to restore a damaged area of nitro lacquer.  Getting an exact match might be the real issue in any case.

Re getting gloss finish on the whole guitar if that's what you want, why not just gently buff it out after doing the repair and touching up?  That usually happens anyway with handling of flat finish nitro.

Lots of questions here but thinking about the job is often 3/4 of the work.

Larry

[Thomas James]

Ted, Another easy to make method are these "Side Patch Repair Gadgets", as illustrated/demonstrated in Don Teeter's guitar repair book one. Missing pieces in my photo are the guitar string and the actual patch material. These align the crack and allow a for an easy dry clamping run before applying glue. I also echo Ned's comment about doing this repair sooner rather than later. Tom

[Ted Uy]

Thanks to all for the recent posts. I will take the advice and go for a fix sooner rather than later. What I may do is first undertake the inside fix using the drilled hole guitar string method myself -- rookie mistakes easier to hide on the inside -- and then after that, get the cosmetic fix done professionally.

Thanks again for all the helpful advice. Ted

Ps. The bad news is that while my uncertainty on how to fix my guitar festers, I've had no similar excuse to raking the Fall leaves.