Functional fix for a top plate crack

[supersoul]

I'm looking for advice or ideas about how to repair a crack in the top plate of an old archtop. I'm just interested in stabilizing it, it doesn't have to look pretty.
The guitar, when I got it, was in terrible shape, and I'm taking it apart to put back together into a playable form. It had been sitting in the front window of a record store for years. The poor thing was completely warped, unplayable, and it was covered with autographs done in black sharpie. I bought it for cheap when the store moved. The autographs mostly came off with lighter fluid, although some of the ink has gone through the finish checking cracks into the wood.
Which is why I don't care about how a repair will look!
From watching youtube videos and reading repair articles, I don't think humidifying the crack to close it would work in the long term. The split has been there for years; the wood likes it that way. So I'm thinking of a couple cleats to keep it stable.
My questions are: will cleats be enough, and I can just leave the crack open? Or if I have to fill the crack do I have to make a spline or can I fill it with some glue/sawdust combination?
As you can see from the pictures the back is off the guitar (as is the neck, for that matter). Which certainly makes any repair easier!

[Jimmy blue note]

Take it to a luthier. That crack has REALLY opened up. Lucky for you, the dry winter is the time to address that. A luthier (a good one) will open that crack into a V shaped channel and I would highly recommend a well matched splice be placed in there. That doesn't preclude the use of cleats, especially since the back is off. A splice will make the repair tight while the grain is dried out. Then, no matter what the humidity situation is or becomes, your chances of shrinkage (and further splitting) are greatly reduced.

That's what I'd do. It addresses all your issues and assures a sound repair from here on out. In my opinion.

[nevershouldhavesoldit]

My bet is that the crack is from severe dehydration. That guitar sat in a sun exposed window for years. I'm sure the record store didn't keep the HVAC running 24/7/365, so the temperature and humidity in the store probably varied widely - so the top shrunk. It looks wide enough that it couldn't even be clamped together & glued before cleating. The fact that the binding is still intact and the rest of the guitar is undamaged suggests to me that it's still solid overall and will be fine whether or not the crack is repaired. It's a shame you don't know how it sounds when it's together. If it plays well and sounds fine, there may not be any point to doing anything to it except humidification if the wood is really dry. This presumes tha the neck angle etc are fine and the top and back have not sunk from dryness.

You can get a decent digital humidity meter for about $20. I think it's well worth determining the moisture content of the wood before doing anything. If it's under 6%, it's seriously dry and needs to be rehumidified. Doing so will close the crack to some degree, possibly even making a traditional clamp & cleat repair posible. But even if it still needs a splice, it'll be more stable (assuming it's kept properly humidifed afterward). If it's really dry, rehumidifying will probably also help keep the binding in place and the rest of the instrument stable.

[RJVB]

German guitar?

Pity your pictures don't show if the split has been stopped by the brace or continues. If it has been stopped and the brace is still glued properly you could just add some cleats or, why not, a bit of carbon fibre mat to prevent the crack from growing wider/continuing. That might not be such a good idea if it has already continued past the brace.
If you decide to leave it open, do sand the 2 faces and put some finish on them before doing whatever else you do; untreated open cracks tend to make an instrument react more to humidity changes in ways that you'll probably notice when playing.

It looks wide enough that it couldn't even be clamped together & glued before cleating.

Plus it would have to be cleaned first to remove the oxydised wood so the glue would hold correctly.

[supersoul]

Thanks for everyones replies!

It's the repair of the guitar that is the project for me. I bought it two years ago and it's only been since this summer that I've had the time and a space to work on it. Everything about it was warped; the neck was bowed, the front and back plates are both warped away from eachother, part of the rim was cracked. I'll include a couple more pictures below.

I offered them a low amount and bought it, just as an experiment to see what I can do with it. A few years previous I had bought a similiar old East German hand carved archtop, in similiar condition, and after a years worth of thinking, researching, and actual work I was able to make it into what is now my favorite guitar.

This guitar has a Rellog pickup hidden under the fretboard. I've tested it and it works. Single coil, it looks like. When the guitar had strings on I could hear that the guitar has a nice acoustic tone.

The bowed neck: I removed the frets, sanded the fingerboard flat with sandpaper on a long straight level, re-radiused it to 10" with a radiused sanding block, put in new frets which I leveled, crowned, polished.

The top and back plates were warped, but I could push them back together and everything fit. I did some experimenting with applying boiling water with a brush to the warped areas, then clamping, which seemed to help. Then I just let them sit clamped in place for a few months, and now the warp is gone. Something about heat and moisture to reset the wood fibers. I dunno, I'm learning.

Weird hobby, I guess: buy an old busted up carved archtop for peanuts and set about making it playable. But the process is meditative for me. I don't do anything until I'm absolutely sure. Sometimes I just think about it for months before I can see a way forward.

Very few people seem to care about these old German archtops. If it was a Gibson, of course I would take it to a luthier. For me it's a way to learn about hand carved solid wood archtops without the expense and mystique of something collectible.

to RJVB, the split stops at the brace and does not continue beyond. It cannot be pressed together.

So this split in the wood… it doesn't have to be a pretty repair, it just has to have structural integrity. I’m actually cool with leaving the split open, with cleats bridging between both sides. I'm thinking vibration transmission, basically.

[RJVB]

Very few people seem to care about these old German archtops

On here Hammertone does (if I'm not mixing up user names). And since you're in Germany: the people at german-vintage-guitar.com do too. They might even accept to give you occasional advice by email.

to RJVB, the split stops at the brace and does not continue beyond. It cannot be pressed together.

So this split in the wood… it doesn't have to be a pretty repair, it just has to have structural integrity. I’m actually cool with leaving the split open, with cleats bridging between both sides. I'm thinking vibration transmission, basically.

When you tap around the intersection of the crack and the brace, are there noticeable differences with the sound you get at the corresponding location on the other side, and that suggest the left brace is not properly glued anymore? That would be a source of rattle when playing (remember there will be downward pressure on the top that would make any gap between brace and top grow bigger), and it will also give the crack an opportunity to continue. I'm assuming the shop keepers were clever enough not to tune the strings up to normal tension while the guitar was sitting in the window and if so you don't really now how stable the crack really is.

The crack is a long way back from the saddle; I'm not convinced that there are many vibrations to transmit at that point. But instead of multiple cleats you could consider a single "longitudinal" one if you manage to make one with the proper curvature. If you really don't care about looks and "proper repair" you could then even run some wood glue into the crack that dies up transparently and can take finish.

[nevershouldhavesoldit]

remember there will be downward pressure on the top that would make any gap between brace and top grow bigger

Maybe I’m missing something here. But if the brace is directly under the top and positioned & shaped to abut it, why would downward pressure on the top increase any space between brace and top? It seems like any space would be closed by such pressure. If the brace is loose now (which is easy enough to determine with the back off), it would be reglued before reassembly.

Great pics of a really cool project, supersoul! But to be honest, I’d have left the graffiti alone. I don’t understand why anyone would mark up a decent guitar like that. But it was already done, and yours had a look that was both artsy and ironic. I’m anxious to see future pics of the project - it looks like great fun!

[supersoul]

the brace itself isn't loose at all.

nevershouldhavesoldit: I did think about keeping the graffitti, but theres no way I could play it in public with all that! Ugh, to me it was horrendous, and I was so happy when the lighter fluid cleaned it up.

[RJVB]

Maybe I’m missing something here. But if the brace is directly under the top and positioned & shaped to abut it, why would downward pressure on the top increase any space between brace and top? It seems like any space would be closed by such pressure.

Indeed, it would depend on where the gap is and what curvature there is at that point. Your reasoning is correct if there's a support under the brace (hah ) or enough properly glued brace length on both sides of the gap. In this case we're very close to the end of the brace. I've had an old German archtop where the end of the brace had come loose and you could clearly see the gap close when I removed string pressure. This was a tranverse brace so there was a bit more curvature (and the gap easy to see through the soundhole) but the principle should be the same in this archtop.

Another way to think of it is that pressure on the top will make it want to become flatter. The brace is shaped, so the deformation of the top can turn into some kind of lever. And an additional analogy (not sure if it's a good one but it may help you see what I'm seeing in my mind): workers once screwed a dark veneer of some kind of maybe 5mm thick plastic to the weathered wooden binding-like rim around the top of my parents' garage. They didn't use a lot of screws nor any glue. In summer that smooth plastic rim turned into a wave because the plastic expanded but couldn't go anywhere because of the screws.

[sgosnell]

I think a crack like that needs to be filled, and since you're doing this for fun and learning, it's a skill that you need to learn anyway.

[wintermoon]

If you can't get it closed don't fill it, splice it w a piece of spruce and clamp it.

[Hammertone]

A few East Germans built some fine fully-carved archtops in the 1950s, hidden among the garbage generally made the Worker's Paradise. These good ones are often stupidly cheap. This slightly inelegant Lang copy is definitely one of the good ones. My three cents:

1.
Use a splice to fill/repair the crack.

2.
While the back is off, install a cleat below the point of the bottom soundhole on each side. Preventative in nature.

3.
If there's not already a wide cleat installed below the two points of the upper sound hole on either side, install one on either side there as well. Preventative in nature.

[supersoul]

well, the overwhelming consensus seems to be to put a splice into the split, so that is what I'll do! And it's a good idea to do preventative cleats where the holes end in points.

Aside from not matching the existing wood, is there any harm in using wood that isn't spruce? I was thinking pine, as it's lightweight and easily available. I don't have any spruce lying around either.

Does it matter for the cleats as well? I think I understand about how the grain of a cleat should run perpendicular to the grain of the top plate.

I've been using hide glue for everything, so it'll be reversible in the future.

Edit: nevermind about the pine, i'm just being lazy. I'm sure I can find some small pieces of spruce at a lumber, hardware or art supply store.

[supersoul]

I finally finished it!
All in all it took about 3 years from start to finish. A year and a half break, work for a month, a year break, another month, six months, 2 months... something like that.
I figured I'd just write it all out, in case it is interesting to anyone.


For that split in the top plate that I initially asked about in this thread, I made a long sliver of spruce and glued in it with hide glue. Then I put cleats to keep it from moving in the future, as well as cleats on all the discontinuities at the sound holes. I haven't tried to match the color of the splint to the rest, but I might in the future.


The entire body was warped from years of being in the sun. The two plates had bent away from eachother, and that had torn the rim apart. I removed the back plate and set about flattening the plates. My solution was to "paint" on boiling water on the plates and them clamp them flat. I did that every day for about a week, then left them clamped flat for a summer. Afterwards the plates were flat once again.
The rim had also swollen out; basically its length was too great to fit back properly. I removed the heel block, removed a couple millimeters of the rim, reglued it, and it fit the back plate again. The massive split in the rim fit back togther perfectly and so I glued the crack togther with hide glue.


The neck was bowed and there is no truss rod. I first removed the old frets and then flattened the fingerboard with a long straight balance (spirit level, for you Brits), which I taped sand paper to the side. I also used a radius block to give it a 10" radius.
I had to take off a fair amount of material at the ends, enough so that I nearly sanded thru the inlay up by the nut as well as the intricate carved wood which hid the pickup at the other end.
In order to strengthen the ornamentation that at part I hand carved a thin piece of hardwood to sit behind in the cavity. It was shaped so the Rellog pickup would sit in there snugly. Glued it in, and then filled in the empty spaces with superglue and dust from the finger board. It gave a nice darker color that I think looks good. It was all sanded flat with the rest of the fingerboard.
The old fret slots were too wide for my new frets. They wouldn't stay in at all, so I used hide glue to hold them in. That worked and it should be easy to remove them in the future by applying heat. I leveled, shaped and polished the new frets and set the neck aside.


At this point the back plate needed to be reattached to the body. I realized that the operation it would be a big undertaking. Hide glue sets quickly, within a couple minutes. In that time I would have to apply the glue, set the back plate into position, and then clamp it all.
So first I made a mold to go around the entire rim. It was in two pieces, one for each side. That was relatively easy with a jigsaw. Then I made 26 clamps out of small pieces of wood, long threaded bolts, washers and wingnuts.
The back plate fit, but there as a place where the rim was too low to meet the plate. I made little shim risers, which I made by soaking the wood in water and then bending them in a mold. Worked pretty well. I attached them with hide glue, then shaved them down to the correct height with a sharp chisel.
I began to look upon the regluing as a performance that had to go quickly. I practiced it over and over, each time working out kinks. The clamps needed a fair amount of adjustment so they'd go on quickly. It probably took two weeks to where I could do it consistently quickly. In the end it was over in 5 minutes, and I had a hollow body when I took the clamps off the next day.


The neck attachs with a Stauffer bolt. As it was, it was tilted too far forward and so the action was a couple centimeters high. To remedy this I made a shim out of hardwood, cutting it down with a handsaw and sanding it all to the correct shape. That took a couple days to get the angle right. (I had gaffer tape on my finger tips so as to not sand them down anymore!).
Reattached the neck, put on the tuners and then trapeze and strung it all up with €1,50 strings from Harley Benton. It actually fucking worked! I took it home to play for a few days and work out the kinks. I had to lower the nut, align the tailpiece better, and fit the bridge to the top. But it played and sounded pretty good.

I took it back to the studio where I did those things, then I went about putting the pickup in. The electronics are in the pickguard. The neck had a useful place to attach a jack, but it was a design I had never seen before. I thought about gluing a jack to the bottom of the pickguard, but I ended up buying a Switchcraft endpin jack and drilling a clean hole thru to the inside. I used a 12mm bit and it fits so well it actully screws into the wood. I sacrificed a guitar cable, soldered it, and fished it out thru a sound hole.

The pickup required that I remove the neck. It stuck a little too far out the bottom so I made little wood spacers (and glued them with wood glue). Remounted the pickup, bolted on the neck, then tried to figure out what the hell was going on with the electronics. There is a tone and volume but it was connected differently than I am familiar. I changed it to 50s wiring and soldered in the pickup and output cable. It worked!


I strung it up this time with Pyramid flatwounds. That was about a week ago and I'm loving it. It plays well (I don't mind baseball bat necks) and it sounds great both acoustically and with the pickup.
One thing that is interesting to me is how different it sounds to my previous German archtop resurrection. That one is dark sounding, this one is much brighter. The old one is 8cm deep, while this new one is 7cm, which I guess makes a pretty big difference. It's cool to have two different voices.
I've attached some pictures (sorry about the wrong rotation of some of them. They were all saved orientation).
The old one is burgandy, the new one is blonde.

[nevershouldhavesoldit]

That is truly fantastic! Thanks so much for sharing it with us in such detail. But we’re never satisfied - now we want sound clips.

[supersoul]

But we’re never satisfied - now we want sound clips.

Righty-o, I will! It might take a couple days for me to get around to it but I'll play them side by side.

[bluenote61]

Saubere Arbeit!
Did you get some more information about provenance of the guitar in the meanwhile?

[ArchieHollow]

Supersoul:
That's a really worthwhile restoration! Looking great. Hope you're enjoying playing it.

[supersoul]

Saubere Arbeit!
Did you get some more information about provenance of the guitar in the meanwhile?

If you look close you can tell I'm not a professional luthier, lol. It just blows my mind that there are hand carved archtops out there for peanuts. Half the fun is just seeing how fine the craftsmanship is from whoever built it.
Which, I have no idea other than looking on websites. Perhaps a Herrnsdorf? The last guitar on this page has the same Rellog pickup.
HERRNSDORF

The neck heel has some writing that is basically illegible. That's it for markings.

[ArchieHollow]

That old adage applies here: "One man's junk is another man's treasure." She's turned out to be a beaut by means of caring hands and a tender heart. The recurve in the carve must add delivery to the crisp tones you describe.

[garybaldy]

Thanks for everyones replies!

It's the repair of the guitar that is the project for me. I bought it two years ago and it's only been since this summer that I've had the time and a space to work on it. Everything about it was warped; the neck was bowed, the front and back plates are both warped away from eachother, part of the rim was cracked. I'll include a couple more pictures below.

I offered them a low amount and bought it, just as an experiment to see what I can do with it. A few years previous I had bought a similiar old East German hand carved archtop, in similiar condition, and after a years worth of thinking, researching, and actual work I was able to make it into what is now my favorite guitar.

This guitar has a Rellog pickup hidden under the fretboard. I've tested it and it works. Single coil, it looks like. When the guitar had strings on I could hear that the guitar has a nice acoustic tone.

The bowed neck: I removed the frets, sanded the fingerboard flat with sandpaper on a long straight level, re-radiused it to 10" with a radiused sanding block, put in new frets which I leveled, crowned, polished.

The top and back plates were warped, but I could push them back together and everything fit. I did some experimenting with applying boiling water with a brush to the warped areas, then clamping, which seemed to help. Then I just let them sit clamped in place for a few months, and now the warp is gone. Something about heat and moisture to reset the wood fibers. I dunno, I'm learning.

Weird hobby, I guess: buy an old busted up carved archtop for peanuts and set about making it playable. But the process is meditative for me. I don't do anything until I'm absolutely sure. Sometimes I just think about it for months before I can see a way forward.

Very few people seem to care about these old German archtops. If it was a Gibson, of course I would take it to a luthier. For me it's a way to learn about hand carved solid wood archtops without the expense and mystique of something collectible.

to RJVB, the split stops at the brace and does not continue beyond. It cannot be pressed together.

So this split in the wood… it doesn't have to be a pretty repair, it just has to have structural integrity. I’m actually cool with leaving the split open, with cleats bridging between both sides. I'm thinking vibration transmission, basically.

Nice project.
Please could you tell me what the black square is that holds the pg bracket on the rear of the pg. Is it just a sticky foam pad?
I'm prepping for an overhaul of my German Fasan. I have some white pearloid pg material on order to make a Hofner Congress style pg. I've seen some with the bracket made from the same pg material but I'm not sure whether I'll do that.
I've no cracks to repair but I'm going to be attempting heat clamping of the neck to rectify a large relief. It has a non adjustable steel rod in the neck. Not sure if it'll be a success!
Also some of the binding needs glueing and the bridge base needs shaping.

[RJVB]

So this split in the wood… it doesn't have to be a pretty repair, it just has to have structural integrity. I’m actually cool with leaving the split open, with cleats bridging between both sides. I'm thinking vibration transmission, basically.

As a friend taking both cello and luthiery classes once told me, sometimes you have to listen to what (old) wood wants. This was after at least one of the repaired cracks on his teacher's instrument reopened and she was happy to recognise its sound again.

[supersoul]

Nice project.
Please could you tell me what the black square is that holds the pg bracket on the rear of the pg. Is it just a sticky foam pad?
I'm prepping for an overhaul of my German Fasan. I have some white pearloid pg material on order to make a Hofner Congress style pg. I've seen some with the bracket made from the same pg material but I'm not sure whether I'll do that.
I've no cracks to repair but I'm going to be attempting heat clamping of the neck to rectify a large relief. It has a non adjustable steel rod in the neck. Not sure if it'll be a success!
Also some of the binding needs glueing and the bridge base needs shaping.

The black square is hard plastic. It's actually a sandwich of two layers, with a channel for the bracket to slide thru. Hopefully you can see it in the picture.

You're project sounds fun! I'm especially interested to hear how it goes with the heat clamping. Do you just heat it up to a certain temperature, clamp it straight and then leave it for a while? I just did the brute force sand everything flat method, but I also wanted to have a different radius.

[garybaldy]

The black square is hard plastic. It's actually a sandwich of two layers, with a channel for the bracket to slide thru. Hopefully you can see it in the picture.

You're project sounds fun! I'm especially interested to hear how it goes with the heat clamping. Do you just heat it up to a certain temperature, clamp it straight and then leave it for a while? I just did the brute force sand everything flat method, but I also wanted to have a different radius.

Thanks so much for that photo. As I mentioned I'm toying with the idea of making a bracket out of the same pearloid pg material that I should get in a couple of days. I've seen that sandwich idea which I should be able to put together. I will have to experiment on the bend in the plastic bracket. It's taken a while to source solid pearl rather than the very much more common laminated white black white.
I've not done anything like this before.
With regard to the heat clamping, I have watched several youtube vids by the likes of Dave's World of Fun Stuff, Twoodfrd and Peter Naglitsch Luthier. They have made their own heat bars out of aluminium section with electric heating elements inside. They seem to heat to around 60 to 70 deg C which is just enough to soft the glue between neck and fretboard. Heat for about an hour and then clamp and allow to cool while clamped for about a day. May need a few goes at it.
My novice plan is to make a bar filled with masonry cement like a mini storage heater and heat it with a domestic iron, top up the heat as necessary, possibly make a rice filled sock and an insulation blanket to help maintain the temperature. I have a meat thermometer to monitor the temp. This probably sounds nuts and it probably is but it'll be a fun thing to try.
I have some steel box section that I'm planning on using. I just need to get one more clamp and will need to make some curved timber formers for the back of the neck where the clamps go. Judging the over bow that I need to create is the most open ended. It's bound to spring back a certain amount and then be pulled further when the strings go back on. I may just start by getting the neck as straight as possible first time or maybe say a 10 thou back bow. I don't think I'm up to the precision of sanding flat and forming a fretboard radius. I've only ever sanded a bridge saddle radius and the feet of a double bass bridge.

[supersoul]

I don't think I'm up to the precision of sanding flat and forming a fretboard radius. I've only ever sanded a bridge saddle radius and the feet of a double bass bridge.

Sanding the fingerboard flat really isn't hard. I just used a cheap level with a one edge that had a flat surface. I cut sandpaper into long strips that fit and used double sided tape. You can get a radius block on Amazon for cheap. The process of getting flat really wasn't difficult or tricky.

You get it all level when you put new frets on and do a setup. But of course you do have to remove the frets (the original frets on mine weren't worth saving).

But the heat press method sounds cool. I'm interested to hear how it turns out!