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1930s Gibson Advanced Jumbo Repair
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Author:  DanKirkland [ Tue Oct 23, 2018 6:53 pm ]
Post subject:  1930s Gibson Advanced Jumbo Repair
I got a call from one of the owner's friends. Says he had his grandfather's acoustic guitar that he bought new from a pawn shop back in the day.

This showed up a few hours later. A fairly rare bird.

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He had initially brought it in to get it dated and see what the heck he had inherited. I got pretty excited to say the least. But when I played it I realized that it had issues. Even with a new set of strings the tone was dead and flabby, had little to no sustain and very little of that typical pre-war Gibson sound, sounded very "compressed" if that makes sense. So I convinced him that it needed work and he agreed to it. It's had a rough life and he is wiling to have it made into a playable machine moreso than a perfect period correct collectors piece. Although it's a pretty desirable guitar even with the stupid "mods" that have been made to it.

Initial survey of problems. The projection is ridiculously low, neck needs a reset obviously. The bridge is a replacement martin style bridge and has been cut down to a sliver. The previous "tech" put these weird little "pins" on the wings of the bridge to keep it from coming up I guess? He did make sure to use the original screws from the factory. Add to all this the fact that someone also saw fit to slather finish on the bridge, top, and the fingerboard for..... reasons?

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And here is the reason I believe the tone is so dead.

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Another view
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Those are essentially added on braces to the factory braces. If this is factory original (which I *highly* doubt) then whoever assembled this thing was thinking through a bottle of meth or something. Add to that the fact that the bridge plate has been overlaid with a THICK piece of some weird hardwood.

So, here is my plan thus far and feel free to offer advice. I'm always willing to learn.
In no particular order.
1. Remove/replace bridge
2. Remove/replace bridge plate (I will try to save the original if possible, but I don't think it's going to be possible)
3. Remove extra "braces" from original braces
4. Patch cracks (there's only one small one from pickguard shrinkage)
5. Neck Reset/Refret if needed

What I'm curious about are the added braces. I'm going to crack into it tomorrow and see exactly what I'm up against with it. I sincerely hope that they're not glued to the original braces or something like that, it would suck to have to remove the originals and put them back. I can't tell with my mirrors exactly what is going on with them.

this'll be a great one I hope when it's done. I've only heard 1 other vintage AJ in my life and it was spectacular.

More to come, like I said feel free to offer thoughts/advice (constructive preferably)
Author:  Ruby50 [ Tue Oct 23, 2018 9:31 pm ]
Post subject:  Re: 1930s Gibson Advanced Jumbo Repair
Somebody added all that stuff to solve a problem - was the top doing the Pringles imitation? Did they scallop those braces pretty thin and think they had to add some back?

Ed
Author:  DanKirkland [ Wed Oct 24, 2018 8:37 am ]
Post subject:  Re: 1930s Gibson Advanced Jumbo Repair
Ruby50 wrote:
Somebody added all that stuff to solve a problem - was the top doing the Pringles imitation? Did they scallop those braces pretty thin and think they had to add some back?

Ed


Well I found a picture of another unmodified one from the same era, the scalloped braces are supposed to be like that. These were just braced very lightly, not a bad thing at all.

What's puzzling me Ed is that there is no apparent problem with the top. Even with string tension applied there is no potato chip happening. Just a graceful radiused top which is typical of Gibsons from this era in my experience.

That leaves me to a few different possibilities.
1.The guitar was being made "road ready" with the mods
2. The tech botched a repair job and had to cover his tracks
3. Someone didn't like the thin top reinforcement on the bridge plate and braces and thought it needed to be beefier.

Whatever the answer is they thankfully didn't do much damage except for the added "pins" in the bridge and the fact that they finished over the bridge and top in spots.
Author:  DanKirkland [ Thu Oct 25, 2018 6:58 pm ]
Post subject:  Re: 1930s Gibson Advanced Jumbo Repair
mistaken post
Author:  DanKirkland [ Thu Oct 25, 2018 7:39 pm ]
Post subject:  Re: 1930s Gibson Advanced Jumbo Repair
Mistaken post not-withstanding here's an update on this guy.

After observing for a while I noticed that there also have been side reinforcements added in multiple places. They're fairly thin but they're not hurting anything so I'm going to leave them be. This makes me think that my theory on someone wanting to "toughen up" the guitar may be why all this extra wood was added. The other possibility is that they got tired of doing bridge resets and were trying to keep the bridge glued down by making the top immovable. I had posted a while back about a 1930s or so L-0 that had had a big chunk of plywood added in almost the exact same manner. The top had no issues except that the bridge likely was just coming unglued.

The bridge was removed without much trouble. Peeled off easily. There was slathered finish over the entire thing including the area around the top. To get it off I had to cut it free from the finish before I could work it off with a little heat.
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Also in an effort to get an exact date on it here is a photo of the neck block. The typical black stamped numbers are illegible (anyone got a photoshop trick that can bring them out?) But the pencil marks are "-B" or "-13" and "16" below where the ink stamps would be.

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Once I had the bridge plate off I was able to put my phone camera up to the pin holes and get a nicer view of the braces and the "add ons". This made me aware that those add on braces are glued directly to the original factory braces. There is no gap whatsoever between them. I'm going to think on it for a while and see if I can come up with a way to remove them without having to remove the original braces and put them back in. That is not impossible but I'd like to avoid the task if I can.

With the bridge off I also got a closer look at the bridge plate and it's exceptionally thick marriage partner. This again makes no sense to me other than someone just trying to keep the bridge from coming up or just trying to toughen the guitar.

I tried to seperate the two but they were glued tight as frig. There is no gap between them. So the only option was to remove them as one piece. The problem that was presented is that the overlay was so thick that the heat would not penetrate very well. So to soften the glue on the original bridge plate I heated up my caul and clamped it to the top as per normal procedure. I also wet the overlay a bit before I did this. While it was clamped and hot I took a dropper and dripped some water through the bridge pin holes onto the caul. The caul was slightly over 250'F which created steam. The steam loosened the glue on the original plate below the overlay and it popped out without much trouble or wood loss.

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With the overlay it is a THICK piece of wood. Perhaps a large contributor to the dead tone. One thing I noticed too was that the overlay was forcing the top into an odd shape, when it popped off the top I saw the top physically go "oof" as if it suddenly was released of a huge amount of tension and returned to it's normal shape.
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All for today. Going to see if I can get the braces separated from the add ons tomorrow. Any ideas on this?
Author:  mountain whimsy [ Fri Oct 26, 2018 11:10 am ]
Post subject:  Re: 1930s Gibson Advanced Jumbo Repair
Really enjoying this! Keep the updates coming.

What's your method for getting the bridge plate off? And I'm really interested in how you get those sister braces off!
Author:  DanKirkland [ Fri Oct 26, 2018 7:39 pm ]
Post subject:  Re: 1930s Gibson Advanced Jumbo Repair
mountain whimsy wrote:
Really enjoying this! Keep the updates coming.

What's your method for getting the bridge plate off? And I'm really interested in how you get those sister braces off!


Glad you're enjoying it.

Bridge plates I have a myriad of small chisels that I heated up and bent. But I'll be honest I bought one of the Stew Mac bent thingys and it works really well.

My method is pretty much the one that Frank Ford shows on Frets.com, well worth printing out that entire bit and reading it over and over. Lots of wisdom there from him.

So updates for today. I thought really long and hard on how to get the add on braces off of the original braces. However considering that they're glued to the braces and not the top the risk of working on them blind while they're in the guitar is really high. Plus these are the old school long braces that reach way down into the bout of this beast, impossible to reach with a separation tool or knife in a delicate manner.

So I decided that I'm just going to have to remove the braces entirely, cut off the add ons, and then re-install them. Fun....

My method was simple, take a bent feeler gauge that's fairly thick and carefully work it under the brace to break the glue line. Then take my bent SM chisel and use the differential pressure (not the scooping motion) of the thick blade and pop the brace out. I watched a luthier remove a double bass top using a similar method and that's where I got the idea. The idea is to "break" the glue and not the wood. These braces sit so far back in the guitar that this method made the most sense.

I made certain to work from behind the braces so that the add ons are what would get scuffed and chinked and not the factory braces. That was a nice benefit of them being in there.

Success

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These are glued to the original braces really well, had I tried to force these apart I feel as though more damage would've been done than with this method.
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The removal method worked well, I only lost the tiny spruce fibers of the top, literally nothing I could do about it.
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I also took the time today to carefully remove the frets and scrape off all that nasty finish that had been on there. There was one section where a human hair was caught in the finish and had cured into it. Fun...
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More updates later. Have to separate these braces and get them reinstalled along with a new bridge plate.

I have not decided if I want to pursue an overlay with this one or not. The benefits are big but this top hasn't displayed the need for one.... yet. We shall see. More to come soon.
Author:  Barry Daniels [ Sat Oct 27, 2018 7:47 pm ]
Post subject:  Re: 1930s Gibson Advanced Jumbo Repair
Instead of trying to separate the braces I would just cut them in half on a bandsaw with the saw kerf in the non-original brace. Then plane away the remainder.
Author:  DanKirkland [ Sat Oct 27, 2018 8:13 pm ]
Post subject:  Re: 1930s Gibson Advanced Jumbo Repair
Barry Daniels wrote:
Instead of trying to separate the braces I would just cut them in half on a bandsaw with the saw kerf in the non-original brace. Then plane away the remainder.


That is an excellent idea Barry. I have a friend that owns a really good bandsaw so I'll have to see if I can hope over there and use it.

If not, I might be able to use some careful applications of light steam to remove them.
Author:  profchris [ Sun Oct 28, 2018 5:34 am ]
Post subject:  Re: 1930s Gibson Advanced Jumbo Repair
DanKirkland wrote:
Barry Daniels wrote:
Instead of trying to separate the braces I would just cut them in half on a bandsaw with the saw kerf in the non-original brace. Then plane away the remainder.


That is an excellent idea Barry. I have a friend that owns a really good bandsaw so I'll have to see if I can hope over there and use it.

If not, I might be able to use some careful applications of light steam to remove them.


Or just plane, plane, plane. I have a wooden smoother where I've given a deep camber to the blade, and that would remove 90% of the add-on brace in under a minute. Then go slow with a more precise plane. A jack which can take a thick shaving should do the job in just a few minutes, again moving to a finer plane for the last fraction.
Author:  DanKirkland [ Mon Oct 29, 2018 5:35 pm ]
Post subject:  Re: 1930s Gibson Advanced Jumbo Repair
I like the idea of planing profchris, I have multiple planes that would do the job. However I've already sorted it out today, but thank you for the advice.

So the bandsaw was NOT a safe bet it turns out. I don't think my friend's saw is up to snuff for this job. A few test runs showed that his blade is rather dull so the ripping action was happening and I did not feel safe putting those fragile original braces through that.

So, second plan is a bit more direct. I decided to use the steam method and just be extremely patient. I didn't dunk the braces in the boiling water but rather let them sit one corner at a time just over my kettle. I then applied my pallet knife slowly as I worked my way down. The glue broke up nicely. The original braces have been saved.

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Tomorrow is an actual work day so I'm going to take some time and cut some templates to replicate these braces, you know, posterity and all.

Thank you both Barry and chris for the suggestions. The nice part of this is now I have these two uncut braces that are OLD and aged quite well. Might be an interesting experiment to use them to brace a guitar in the future should I ever decide to build one. Might be appropriate to make a pre-war Gibson style Jumbo using these braces pulled from a pre-war Gibson jumbo. Ironic, but appropriately ironic.

Before I left I also started "mapping" the top for reinstalling the braces. I'm going to use OBG for this instead of hot hide glue. I don't want to have to rush this part of the job as I want the braces put back in exactly where they came from. I love acrylic cauls for jobs like this.

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Author:  Haans [ Mon Oct 29, 2018 7:24 pm ]
Post subject:  Re: 1930s Gibson Advanced Jumbo Repair
Hard for me not to believe those "original braces'' haven't been tampered with a bit. The scallop looks kinda hacked...
Author:  DanKirkland [ Mon Oct 29, 2018 8:24 pm ]
Post subject:  Re: 1930s Gibson Advanced Jumbo Repair
Haans wrote:
Hard for me not to believe those "original braces'' haven't been tampered with a bit. The scallop looks kinda hacked...


I had considered that. It's not something the owner wants me to replace at this time (not sure I'd even want to do that, even if they have been modified). The only photo I'm going from is the one from guitarhq and it shows a much more squared off shape on the tips, the scallop is pretty much the same however.

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Author:  DanKirkland [ Wed Oct 31, 2018 8:56 pm ]
Post subject:  Re: 1930s Gibson Advanced Jumbo Repair
No pics today, both braces are back where they came from. To remove the old glue I just held them over the kettle again until the glue softened up and then just rubbed it off gently. Didn't have alot of time to work on it in between the regular jobs.

Since I didn't want to be rushed at all from the set time of hot hide glue, I decided to use OBG for the job. Good stuff.

Tomorrow the new bridge plate will be made. The top is in great shape so I doubt I'll have to use an overlay for this guy. Still going to bump up the bridge plate size a bit considering the footprint of the bridge that was installed by the previous..... guy. I really wish that the rectangular bridge had just been left alone, oh well.
Author:  DanKirkland [ Mon Nov 05, 2018 10:59 am ]
Post subject:  Re: 1930s Gibson Advanced Jumbo Repair
It is becoming more apparent that this top has the exact same type of extreme bubble that the L-00 did. If you look on the right side you can see exactly where the bubble exists.

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What this leads me to believe is that Ed (ruby50) was right about the "add ons" being to fix a problem. The problem likely being that this guitar was constantly having to have the bridge reset. This is the exact same problem that happened with the 34' Martin and the L-00 I just finished up.

What I'm finding interesting is that in each of the previous cases I've posted about like this one the repair men took different routes to fix the problem. This seems to be a common theme amongst old guitars like these. I could be mistaken, but it really seems like they should've have larger bridge plates that extend past the edge of the bridge.

For this one what I'd like to try is the same overlay technique that I've been employing for this kind of situation. However instead of enlarging the bridge plate along with the overlay, I'm going to only slightly enlarge the bridge plate but let the overlay do the flattening work. This plate is extremely wide and to extend it past the edge of the bridge would require it to be butted up against the braces nearly. Plus that'd be a HUGE piece of maple to slap onto the top, this seems like it would deaden the sound (ala late 60s Gibson). So I'm going try the overlay with this one as well. Honestly if the original rectangular bridge had survived I doubt the top would've bubbled so much. No way to know now.

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That's the general idea of the overlay, it'll be a bit shorter to fit the top better. Extend it to where the bridge plate should be and put the replacement bridge plate in place. The spruce with the grain oriented the way it is will keep the shape of the top but add direct reinforcement to the area of the bubble. We will see how this turns out. Nothing but OBG for this guy so if anything needs to come out again it's doable.

The overlay was intalled over the weekend, I give it a few days to full dry and cure before I go in to install the bridge plate.

For this overlay I had no single piece of wood that was wide enough to cover the span. So I did a little edge joinery to make the single piece. Before it was installed I thinned it down significantly. I also tapered the edges a bit. For thickness I just thinned it down until I could start to see light coming through the spruce.

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By the way, that Lie Nielsen Violin Makers plane is a seriously great tool for a small shop. The wife gifted it to me in September and I've used it on nearly every job like this since then.
Author:  DanKirkland [ Wed Nov 07, 2018 8:12 pm ]
Post subject:  Re: 1930s Gibson Advanced Jumbo Repair
Update time

For this guitar I decided to bug a luthier friend of mine and see if he had any BRW he'd be willing to part with. I got a nice piece but it had a few worm holes in it. Thankfully I was able to cut around the worm holes and get a decent bridge out of it. The replacement bridge I decided to just copy the Martin footprint of the previous one and just add some Gibson-esque design to it. For a while the Souther Jumbos had martin style bridges with dots added to them. I have not decided if I want to add dots to my replacement or not

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One thing I noticed too, the bridge that I took off of it was also glued to the guitar crooked. There's a section where the oversprayed finish had left a line and the top hadn't darkened much over the years. I'm just going to leave it as is and not try to color it to match the top. Most folks won't see it anyway.

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yesterday I glued and clamped the bridge (OBG again) but while it was setting I decided to try to figure out a way to safely get this neck off.

The problem with this guitar is that it's one of those lovely wide and thin heel designs. So the slightest overtorque on my edge and I'm looking at a cracked heel. I don't want to do that. Plus the heel is cut at an angle so it's not flat, which makes things more fun.

So I decided not to use the SM neck removal jig and I came up with a simple solution. A 2x4 with a leather pad super glued on top is clamped in my vise. My vise lets me angle the little block to match the angle of the heel. Having it setup like this prevents the heel from being pushed in an akward way and with the angle being a match to the bottom it'll work to keep it from being dented/smushed. So hand pressure and careful wiggling it is with steam.

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I found that the block provided decent pressure and to keep from cracking the heel I worked in a left and right pattern and not the usual rotation. The left and right helped encourage the dovetail out while the hand pressure pushing the neck out made it gently "pop" out as they normally do.

Success

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And the nice part? Even though this neck was REALLY stubborn There is no evidence of blush or steam damage to the finish whatsoever! I got lucky this time, that almost never happens with these. I use one of those little handheld yellow steamers with the button so instead of a constant blast I use little spurts of steam to break up the glue.

And the weird part, a shim only on one side? maybe I'm not the first one in here. Oh well, life continues.

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And since the little block method worked so well I had to cover all the bases.

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All for now, the neck I'll leave to dry for a while before I start to cut.
Author:  DanKirkland [ Sun Nov 11, 2018 3:10 pm ]
Post subject:  Re: 1930s Gibson Advanced Jumbo Repair
Update time

Neck has been recut and is glued back into it's home. OBG again was used, I am REALLY liking this stuff, the open time lends itself to more accurate work. All I've been doing with it is just putting some into a jar and heating it up like hot hide glue in a kettle. Brush it on like normal and it's no different than the mixed hot variety, good stuff.

The bridge has been completed and has been installed. When I set intonation on these I have a piece of 1/8" rod that I can move over the top of the bridge. String it up to pitch like normal and you can get a very accurate intonation. The tone isn't the same because of the metal but it does let you play the guitar sans having the saddle installed. Plus the length makes it easy to adjust until you can get an accurate measurement. You can put a pencil right up under the curve of the rod and get a really close measurement. I usually cut these for 1/8 saddles to give some space for intonation adjustments.

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Through saddle to keep with what little I have left of the guitar originally. I aged this saddle with tea but it's hard to see the color difference versus a regular unbleached saddle.
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I did a prelim stringing up to pitch, strummed a few chords and the tone on this thing is just BEASTLY. Super fat and powerful, I can see why these command the prices that they do apart from the collectability and rarity. Will sound and play alot better once the saddle is cut to proper height and the frets are done. All for now.
Author:  DanKirkland [ Tue Nov 13, 2018 7:48 pm ]
Post subject:  Re: 1930s Gibson Advanced Jumbo Repair
Alright update time. All is completed

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New frets are in and the new nut is cut and fitted as well. This guitar is seriously one of the fattest and most thunderous instruments I've ever heard in person. The top also has lost it's excessive belly and it now has a nice graceful radius.

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And two soundclips, Before the repairs and after

Before: https://flic.kr/p/2aYbzUM

After: https://flic.kr/p/2a7ycrS

My little camera phone really can't capture the difference very well (cheap). But After the repairs the volume definitely has increased three-fold over what it was. The tone is bombastic to say the least. Just big fat and round. Very scooped mids to my ears? The treble strings are almost double the volume and tone of what they were before.

I decided to leave the dots off the new bridge, I did save them however and if someone feels inclined they can easily add them on.

Anyways, client should be picking it up soon. Hopefully he'll be happy that it's no longer a little kitten. I'm beginning to see a pattern here of vintage Gibsons having bridge issues and people just doing all sorts of random crap to try to the solve the problem. Ciest la vie

Anyway, this one was a really fun repair, I don't know if I'll ever get the chance to work on another one anytime soon considering how rare these are. But hopefully I did it some justice and gave it a longer life.
Author:  SteveSmith [ Mon Nov 19, 2018 7:38 am ]
Post subject:  Re: 1930s Gibson Advanced Jumbo Repair
Nicely done Dan. I've been rebuilding a '49 ish J45 that was in such bad shape they had added a tailpiece for the bridge. That one ended up having to get a new top. It feels good to bring them back to life.
Author:  Johny [ Tue Nov 20, 2018 10:02 pm ]
Post subject:  Re: 1930s Gibson Advanced Jumbo Repair
Great job!
Author:  Smylight [ Sun Nov 25, 2018 10:00 am ]
Post subject:  Re: 1930s Gibson Advanced Jumbo Repair
Very nicely documented and helpful. Thanks Dan for taking the time to share.


Pierre Castonguay
Author:  DanKirkland [ Wed Nov 28, 2018 10:03 pm ]
Post subject:  Re: 1930s Gibson Advanced Jumbo Repair
thanks gentlemen
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