Bridge Replacement on Puerto Rican Cuatro

[morgan]

Asking for advice in replacing the bridge on this instrument. (It’s not a mandolin but it has double courses…)

I purchased for $25 a hurtin’ Puerto-Rican style cuatro this week (ten strings; all fourths, BEADG; low B and E in octaves, high pairs in unison). It was playable, but the bridge was pulling up and was held in place by screws. The bridge pulled up more as I brought it up to proper tune and my expectation was that the bridge would blow out if got all the strings on it and kept it at proper pitch. I’m trying to repair this as cheaply as possible. I suspect this was probably a $175 Chinese instrument in the first place.

I took the screws out, heated up the bridge with a hair dryer, and managed to get the bridge off without any damage to the top.

The instrument top under the bridge was finished, which probably accounts for the failure of the glue to hold.

I had my daughter stick her hand in the soundhole (mine won’t fit) and under the bridge area and she found two small blocks under the screw holes. Two of the three holes on each side led to these blocks, the third hole on each side “missed.” (only two of the three screws had any “bite” on removal, consistent with this observation.)

The bridge is a somewhat crude classical guitar bridge that is fairly warped, in various directions (i.e., there’s not one consistent bend or one arch; the rear center is arched, the front center is flat, the ends pull up a bit from the screwholes .

Looking at various internet photos of cuatros, there does not seem to be a “standard” bridge type but classical-style guitar bridges are not unusual.

I sanded off the excess glue and finish from the bridge footprint on the cuatro top and am ready to replace the bridge.

Questions:

Is it worth trying to straighten out the bridge, and if so, how? I can get a new bridge for about $20, I think (if a new bridge is in line, any recommendations would be appreciated). I’d need to drill some more holes in the bridge to accommodate the ten strings but I don’t see that being a big issue.

Is the Tite-Bond ready-to-use hide glue a good choice for glue?

What’s a good technique for getting the existing saddle out of the bridge?

Should a properly glued bridge be sufficient to hold the tension without the screws?

I don’t have any deep-throat C clamps and will have to purchase them to install the bridge. To keep my costs down I am contemplating buying one clamp for the center of the bridge, and using the screws to hold down the ends of the bridge. Is that likely to suffice?


Thanks for answers to these questions or any other advice!

[Paul Hostetter]

Is it worth trying to straighten out the bridge, and...

No. Make a new one, and put a slanted/compensated saddle in while you're at it. Instruments that play in tune are more fun to play. Adapting an inappropriate nylon string guitar bridge is a waste of time.

Is the Tite-Bond ready-to-use hide glue a good choice for glue?

No, it's very weak and prone to loosening with humidity. Use Original Titebond, not Titebond II or III. It's the yellow stuff.

What’s a good technique for getting the existing saddle out of the bridge?

Don't worry about it, throw the bridge away, saddle and all. Start from scratch.

Should a properly glued bridge be sufficient to hold the tension without the screws?

Screws are a major liability. Just glue.

I don’t have any deep-throat C clamps and will have to purchase them to install the bridge. To keep my costs down I am contemplating buying one clamp for the center of the bridge, and using the screws to hold down the ends of the bridge. Is that likely to suffice?

That is an invitation to big trouble. I have worked on many cuatros (they all need better bridges, or at least rebuilt ones) and the bridges are hard to clamp because the soundhole and the body are small. There is a one-clamp possibility, and it looks like this:



Stew-Mac sells this but it's not really quite right for the bridge like you'll need, so you'll have to make one. And it should have a substantial caul inside that's the size of the actual bridge. It's the only way to get the bridge down flat and evenly glued.

Sure you're up for this?

[DavidKOS]

I have worked on many cuatros (they all need better bridges, or at least rebuilt ones)

I wonder why so many cutros and similar instruments have inaccurate bridge placements? Almost all of the cuatros, lauds, etc. I've tried play a bit sharp at the 12th fret without further work.

[Paul Hostetter]

I wonder why so many cuatros and similar instruments have inaccurate bridge placements? Almost all of the cuatros, lauds, etc. I've tried play a bit sharp at the 12th fret without further work.

It's the usual unconscious thing of doubling the distance to the 12th, oblivious to compensation. The model for the benighted makers is nylon strings. Most aren't made in PR, but rather Paracho, Taiwan, Korea, etc.

[DavidKOS]

It's the usual unconscious thing of doubling the distance to the 12th, oblivious to compensation. The model for the benighted makers is nylon strings. Most aren't made in PR, but rather Paracho, Taiwan, Korea, etc.

Thanks, I was wondering if they were using nylon string guitar scaling for the frets and bridge placement. The few PR made ones I've played are pretty good.

[Dobe]

[QUOTE=Paul Hostetter;1429820]
Don't worry about it, throw the bridge away, saddle and all. Start from scratch.


Maybe measure your string spacing 1st, if the original looked good. Then pitch it, or just keep it to show what you had to replace !

[Paul Hostetter]

The most helpful measurement would have involved the intonation, but now that the bridge is off, it's too late. None of that stuff is very difficult to figure out.

Keeping the old bridge as example of how wrong a bridge can be might be worth it.

[morgan]

Paul - First, thank you very much for your reply.

In response to your final question ("Sure you're up for this?), I'm not sure! My concept in buying this thing was that it was a flyer to see if I could learn to /enjoy playing cuatro on the cheap, and if so I would consider upgrading to something better. Cuatros are not commonly seen here in central Massachusetts, so it was an impulse buy when the opportunity presented. It was a cheap instrument in its best days, so I don’t want to put too much into it. I suspect that your concept as a luthier is that there is a certain level of care that every instrument demands, in which case we are coming at this from different directions. Nonetheless, I am trying to use your comments to inspire me to do a little better.

So-

I will use yellow Tite-Bond.

You recommend that I build a bridge. I did a google image search of Cuatro’s and it seemed like the cheaper versions (e.g. the Parachos and the $100 ones on ebay) had a heavy, shorter bridge, but some of the better ones had what looked to be classical bridges, or very close (photos of each type below. There were also a few that have floating bridges/tailpieces but that doesn’t apply in this case and I assume they are not “real” cuatros anyway). What is a “correct” cuatro bridge?

Regarding comments about saving the bridge & saddle for string spacing – I did save them for that purpose. The string spacing seemed right.

I borrowed an endoscope –a camera with a light on a flexible tube –to look inside the body. There is a brace perpendicular to the long axis of the body about 2 inches from the soundhole, and a smaller brace parallel to the long axis behind that. There are also two relatively large blocks glued in next to that small brace. These extend to below the bridge, and are what the bridge was screwed into. I assume that these weren’t original and were installed by the same prior owner who decided to screw the bridge on. A sketch of this layout is attached. The ends of the blocks “hide behind” the first brace, so it seems like they’d be pretty difficult to remove.

[morgan]

Trying again on the sketch of the innards.

[k0k0peli]

My Chinese-made Harmonia PR cuatro (model No.T-10 EW-2) was cheap a couple months ago, cash in hand US$70 from the importer. (Here. Price is now up a few bucks and you pay tax and shipping if you aren't local.) The intonation is fine. The bridge looks very much like that on my Ovation 12-string guitar so I'll guess the designer took a scaled-down approach that worked.

Retrofitting a bridge on your cuatro may require more skilled work than it deserves, like removing the top so you can do a good clamping job. Then you've got to replace it, ay yi yi! It may be more feasible to go with a tailpiece and floating bridge. Don't worry, that won't make it any *less* a cuatro, but it might be slightly quieter. That's how my other cuatro, a 4-course 12-string Paracho cuatro-menor, is set up.

Mass-produced Paracho instruments aren't so great.

[Paul Hostetter]

You recommend that I build a bridge. I did a google image search of Cuatros and it seemed like the cheaper versions (e.g. the Parachos and the $100 ones on ebay) had a heavy, shorter bridge, but some of the better ones had what looked to be classical bridges, or very close (photos of each type below.

Sorry, I couldn't see much in those images, because of how you wrapped them in pdfs. Jpegs work way better than pdfs.

You need to spend some real time looking through this site, starting here: http://www.cuatro-pr.org/node/70

This is a classic 10-string (if it was strung up!) with a typical bridge:



Many makers laminate pretty bridge blanks, for the visual effect. Structurally not necessary, probably not even a good idea. Notice the parallel saddle. These do not play in tune. Notice also the length of the bridge. The typical classical guitar bridge will be much longer, and that length is unnecessary, but fundamentally, it's about the same thing as the shorter, stouter and more traditional bridge.

There were also a few that have floating bridges/tailpieces but that doesn’t apply in this case and I assume they are not “real” cuatros anyway.

Ah, but they are. Look through Cumpiano's page, above.

What is a “correct” cuatro bridge?

One that holds the strings in the right spacing and has a saddle that allows good intonation. Here's a modern, real cuatro puertorriqueño:



The bridge, typically, is a mess. The bridge itself is cockeyed and off-center, the saddle is way too long and uncompensated, etc. Comparing to the original (L), on the right is an idea of doing it better:



I rebuild cuatro bridges like this, using a typical Gibson slant, drop-in bone saddle, after filling in the useless one. You compensate for the main strings in the octave pairs, never mind the high octave strings (unless you're really anal and have a lot of time).

Do NOT use screws! Glue it right. Alas, now that you have that big bare area on your cuatro, you'll have to make a bridge that covers it.