Questions about finish touch ups after structural repairs

DaveR

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I have several different questions here....hopefully someone has the patience to read this and advise...

I've likely bitten off more than I can chew with these guitars, but the good news is they all belong to me, they're mostly worthless and I'm only repairing them to gain experience! I've just completed some structural repairs that now need finish work. All three have similar but different problems and I honestly don't really know where to start because I know almost nothing about finishing. I have done a few repairs and some buffing, but never shot any finish. I recently built a proper buffer and purchased an HTE gun. My intent this spring is to get my compressor tuned up and start practicing shooting nitro. I was originally leaning towards 2k, but there is such a wealth of information here about nitro and it seems like the ability for coats to melt into previous coats could be a bit more forgiving for a beginner. That being said, I think all these guitars have poly, so I should probably be prepared for that...

First up is my first attempt at a typical Gibson style headstock break and repair. I made a cool little jig to pull the two halves together under clamping pressure. The front side is a busted up mess, but I intend to sand down the face and apply a new headplate as I have some beautiful veneer scraps laying around. This is a cheaper Epi acoustic and I'm assuming a poly finish.
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Everything closed up good on the sides, but on the back, I have some missing chunks and need to fill this gap.
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What is the best way to fill this? I'll likely sand and refinish the entire neck, but am curious how one could go about blending in the finish/color without going that far. Is it possible with poly or are you just guaranteed to get nasty witness lines? I know I've seen people mix up a more opaque similar color to hide a repair like this. Never done anything like that before, so I'm not sure what steps are involved to properly fill, prep and then promote adhesion to the existing finish.

The second repair is a cheap Chinese made Ovation with a nasty headstock break. I don't need a fancy jig for this one because it clamps together nicely. The tip of the headstock had some busted chunks, so I snipped it off straight with a chisel and patched in a piece of wood that matches reasonably and reshaped it.
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Rough 80 grit scratches right now, but I'll make it smoother.
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The neck break does have a few missing chunks, and there are also missing chunks where the nut will sit.
Same question as the first guitar, what's the best way to fill these in?
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This Ovation has some sort of satin, presumably poly finish with a glossy front face to the headstock. On this one, I'd love to be able to just touch up the problem areas, but am unsure how to proceed. Can you get a color match, and reapply a clear coat while still getting it to blend in with the rest? Is that even possible without having wizard level finishing skills?


Last is a 40 year old Ibanez acoustic that had a crack on the back side. I asked about this a few months ago, and @Freddy G as well as a few others suggested filling this crack with thin CA, followed by wet sanding and buffing. The crack mostly disappeared, but I must have gotten into the color layer, because the color started getting blotchy as I worked through buffing. A luthier buddy of mine suggested I could touch up the color with an air brush and shoot new poly clear over the top, but I'm not confident in my ability to pull that off. I'm considering just stripping and refinishing the entire instrument because the whole thing is fairly rough and I feel like that would be good practice. Is this a bad idea? If I were to strip it to bare wood, and refinish in nitro, what should I use to seal the wood before switching to nitro? Any recommendations on good chemical strippers that won't melt binding or otherwise wreck the guitar?

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And lastly....Does anyone have any recommendations for removing super thick Squier polyester finish? I've heard a heat gun and a putty knife....is it that simple? I have a junk Squier Strat that could be fun to refinish. Is it necessary to even remove the thick polyester or could you just sand to 220 and shoot primer and color right over the top?
 

cmjohnson

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For that first guitar's neck repair you're going to be well advised to fit spline repairs into it. I'd use a round file and file two clean round notches into the repaired area until you're past the damage, and then shape dowels of matching wood, cut them, lay them in and fit them precisely, glue them in, and then shape the outer surface to blend into the neck.

Grain direction of the dowel fills is a bit less important than just adding wood to that area. But of course you can try to shape the dowels with the grain orientation set to match the neck repairs. It won't make it much harder.

I have no advice for repairing a polyester finish. I've never attempted it.
 

Roxy13

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I only know one thing, sorry. But after stripping poly I've been advised to shoot it with BIN shellac, and the nitro will adhere to that.

I'd also like to see the answers to the rest for my own further learning so I'll be watching this thread.
 

DaveR

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I only know one thing, sorry. But after stripping poly I've been advised to shoot it with BIN shellac, and the nitro will adhere to that.

I'd also like to see the answers to the rest for my own further learning so I'll be watching this thread.
Actually I saw you mention that in another thread which is what got me thinking about that. Real glad you mentioned it because I hadn’t considered that even after sanding poly back to bare wood, there will likely be remnants of the prior finish present. Makes perfect sense though.
 

Roxy13

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Actually I saw you mention that in another thread which is what got me thinking about that. Real glad you mentioned it because I hadn’t considered that even after sanding poly back to bare wood, there will likely be remnants of the prior finish present. Makes perfect sense though.
Yes, my understanding is that you'll never get it all off!

Some people actually put down the shellac and then respray right over the poly with nitro, but often these poly guitars have a thick finish already so then you might end up with a super thick one.
 

DaveR

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Bumping and going for less words this time, I’m pretty sure I lose a lot of people with too many words.


How do I fill this?
IMG_6023.jpg
 

cmjohnson

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I repeat my previous advice:


For that first guitar's neck repair you're going to be well advised to fit spline repairs into it. I'd use a round file and file two clean round notches into the repaired area until you're past the damage, and then shape dowels of matching wood, cut them, lay them in and fit them precisely, glue them in, and then shape the outer surface to blend into the neck.

Grain direction of the dowel fills is a bit less important than just adding wood to that area. But of course you can try to shape the dowels with the grain orientation set to match the neck repairs. It won't make it much harder.
 

DaveR

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Thanks! I may not be picturing it right. I was thinking of splines as two thin parallel strips on either side of the truss rod and wondering how to fill in the rest of the missing bits in between.

For what it’s worth, I accidentally got to test the integrity of my glued repair when I dropped the stinkin guitar on its headstock this past week. It knocked a small chunk off of one of the corners but the joint held up great and there are no new cracks or any other signs of damage.

I doubt my skills in actually pulling off a tight fit with a patch or splines by hand, but that’s why I picked up this broken guitar, to get some practice.
 

P.H.Fawcett

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I'm sure if you're able to make the jig for gluing up the broken headstock you'd be able to make a jig to allow you to rout the channels for splines.
 

DaveR

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I'm sure if you're able to make the jig for gluing up the broken headstock you'd be able to make a jig to allow you to rout the channels for splines.
That is something I’ve been considering. I’ve seen a lot of those jigs that route an arced path and I’m sure I could build one. Still not sure how people get such a tight fit, especially at the rounded ends of the splines. I know wood glue isn’t a great gap filler. I’ve heard Titebond and wood dust can be used for filling small gaps like this, but wanted to seek a lot of opinions before just diving in.

My biggest gap on this one is right in the middle. I couldn’t route very deep there, but I suppose I could just cut it off straight, patch in a little cosmetic piece and shape to fit.

The Ovation guitar with the jagged break is honestly the one I was leaning more towards splines. But both guitars are now glued back together and feel totally rock solid. Structurally I don’t think they need it, but if splines is a good way to cosmetically repair the missing bits, I’m all for it.
 

P.H.Fawcett

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Here's a link to Ted Woodford's channel on Youtube. He shows a typical headstock repair that most repairers would do but adds splines as a "belt and braces" approach to really creating a strong repair.

At about the 6 minute point he shows the very simple jig he uses and explains how it's used. You don't have create an arc for the bottom of the splines as you will see. You're the right man to replicate his jig.

As for how a nice fit for the rounded ends you'll find that even done by hand they'll look pretty good when finished. Any gap can be hidden with something like Timbermate or epoxy coloured with stain.

 
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DaveR

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Thanks @P.H.Fawcett ! I think I have a new favorite YouTube channel! I’ve already got a ton of ideas from his videos now. Very interesting that he touched up the clear on that black Yamaha with lacquer over the original poly finish. I didn’t know you could even do that. Also interesting that he’s using rattle cans for things, which makes a heck of a lot of sense to me for a touch up.

One of his other vids showed how to add a rosette to an existing acoustic. I have an upcoming refinishing project and I’m pretty sure the existing rosette is a decal that will disappear when I sand the finish off, so that’s relevant and timely info for me as well.
 


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