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  #1  
Old 04-04-2020, 07:46 AM
Arumako Arumako is offline
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Default 5-string Guitar Tuned Like a Cello

Hello AGF! Just finished an interesting and super educational conversion, and thought it'd be worth sharing here. Last summer an acquaintence's son whose an accomplished cellist asked if I could convert a steel string acoustic into a 5-string instrument tuned like a cello. The chap already has a converted Alvarez, but he was looking for something to play while he was working in Japan.

Pictures of the Alvarez were not available, but the conversion required a tail-piece, bridge and nut. The first thing to do was to look for an appropriate instrument that would serve as a good starting point.

This is a 1976 MIJ vintage Three S, W-200 dreadnought built by the Suzuki Violin Co. It required some brace repair, a few new frets, and overall maintenance; but once the preliminary repairs were done, the instrument sounded amazing. It's all laminate, but it looks nice and resonates very well.



The obvious solution was to use a tail-piece like the Alvarez; so, I examined an old one I had in stock, and bought a CFR cello tail-piece that was way too big; a CFR violin tail-piece that was a tad too small; and a black arch-top tail-piece that looked promising.



It seemed that a tail-piece construction would hinder the flat-tops acoustic resonance. The tail-piece is most often utilized on archtop instruments. By design, the arched top requires less bracing and can be made to resonate quite well. The arch pushes up against the strings suspended between the nut and the tail-piece which pushes down at the saddle. The tension between the two forces concentrated at the saddle transfers string vibration to the arched top which in-turn creates the resonance and voice of the instrument.

The flat-top acoustic has no arch and no upward force to counter the downward push of the strings. The top cannot move freely because it is constantly being pushed down by the strings at the saddle. In addition, the break angle of the strings are too shallow when a tail-piece is used on a flat-top which can potentially deaden the sound.

After making string tension and break angle calculations, it was pretty apparent that a standard arch-top tail-piece would hinder this W-200's voice. Somehow, the bridge would need to be re-worked to accommodate 5-strings, and a matching nut would also be needed. The bridge re-work started by carving the existing bridge to make room for an extension. I just really love these Japanese chisels!



Once space for the extension was made, the surface needed to be sanded and flattened.



The bridge extension is made out of Canadian Birch. I love working with this stuff. It's actually re-purposed hockey sticks. Some time ago, an avid hockey fanatic gave me a bunch of old hockey sticks, and they were perfectly suited for this kind of application. The basic shape is routed using my Dremmel.



A small section of the hockey stick is covered with just enough masking tape and the basic shape of the bridge extension is drawn on the masking tape to ensure that I don't over-shoot with the Dremmel.



At this point, the basic rough cut is done. The rest of the bridge extension will need to be shaped with hand tools.



More masking tape to draw center lines for correct positioning.



After much chiseling, filing and sanding, the extension's shape is nearly perfect. After the shape is finalized, the string holes will be drilled.



Once fit is verified, the bridge extension is ready for gluing. Canadian Birch is very hard and smooth which can be a problem for adhesives like epoxy that rely on mechanical adhesion. The bottom of the extension is roughed up with files and chisels to ensure the glue has something to grab on too.



Multiple "dry runs" are performed before actual gluing to ensure my clamping strategy is sound. For this application, a space age epoxy called Hysol 9462 will be used. Once cured, it will not soften until it is heated to 350 degrees C. Nothing is ever going to separate this bridge extension from the existing bridge or the top.



After waiting 48 hours, the bridge extension is irreversibly attached to the top. It also covers the bridge pin holes nicely. This bridge extension is designed like a classical top loading bridge. To ensure ease of adjustment after completion, a few saddle shims were made out of high grade 1mm thick holly. Hardwood shims are much much better than plastic ones.



Stay tuned! Proceeding to a good finish!

Last edited by Arumako; 04-04-2020 at 08:30 AM.
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  #2  
Old 04-04-2020, 08:23 AM
Arumako Arumako is offline
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Took some final measurements before stringing and testing. Everything fits perfectly. A light coat of lacquer to protect the wood from discoloration. This should work out pretty well (fingers-crossed)



Preliminary tests were performed before the nut was made using medium gauge Adamas 1919E strings. String gauges were 1st - .013; 2nd - .016; 3rd - .035; 4th - .047; and 5th - .056. The desired final gauges are 1st - .012; 2nd - .019; 3rd - .032; 4th - .045; 5th - .060. Since I always buy strings in sets, I was really surprised to see how some gauges matched the top's resonance while others didn't. Some strings were too loose or tight and hindered resonance.



All of the custom gauge strings were ordered from my supplier with the acoustic ball-end; but several days later, I got a call saying that there was a system error and the .060 was not in stock after all! They quoted me a lead time of 2-weeks to 3-months and the price was over 20 bucks for one .060 string! I opted for a .060 bass string with a much larger ball-end requiring an additional shim to be added to the bridge extension as a temporary measure. Really looks funky. However, I was quite pleased with the final instrument.



Here's a short demonstration clip...



Nice deep basses, punchy mids and sparkling highs. This guitar is tuned like a cello in fifths with the 5th string tuned to C, but I think I was able to maintain the resonant qualities of a flat top dreadnought. Really interesting instrument. Can't wait to hear my customer playing this instrument. He was pleased and will be sending a video of him playing this 5-string guitar soon.

Thanks for letting me share AGF! Stay safe everybody!

Last edited by Arumako; 04-04-2020 at 08:37 AM.
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  #3  
Old 07-21-2023, 05:45 PM
s11141827 s11141827 is offline
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Default New idea

I have a 6 string Version tuned C, G, D, A, E, B w/ these Magma GCT-Cello 5ths Tuned Nylon Strings & that gives me a much larger range also the High B is super strong. I had to make sure to add enough Guitar nut lubricant. The other thing I did rather cleverly here is to Tie Guitar String Ball Ends so that they work w/ both a Pin Bridge & a Tie Block bridge plus I have more clearance. I even changed the original bridge pins to Brass Power Pins that come w/ a JLD Bridge Doctor.

Last edited by s11141827; 07-21-2023 at 07:26 PM. Reason: Fine tuning needed
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  #4  
Old 11-13-2023, 04:53 PM
s11141827 s11141827 is offline
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Default Update

I do have a 6 String Version tuned C, G, D, A, E, B using Magma GCT-Cello 5ths tuned nylon strings which have a lower tension.
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  #5  
Old 11-14-2023, 07:03 AM
Mandobart Mandobart is offline
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There have been lots of guitar to mandocello conversions done. Typically an old archtop guitar is used. It greatly simplifies the process - just a new floating bridge and nut, unless you want traditional paired strings. That will require two additional tuning machines, and it can be be reversed if desired.

I once simply restrung my old Applause 6 string appropriately to tune F-C-G-D-A-E. The low F was too floppy (i used a .077). It would have to be much bigger, like a bass guitar G string to really work. I think C-G-D-A-E-B would work better, or go 5 string as you did.

I've had two mandocellos. The first is an Eastman MDC 805. Good quality and tone like all things Eastman I've ever played. I liked it so much I commissioned a custom 10 string mandocello (C-G-D-A-E) based on an F4 body. This was my primary gigging instrument backed when I regularly gigged.

Chording is a different experience on a 26" scale fifths tuned instrument for sure!

For now I've converted the Eastman to a 6 string guitar simply by swapping out the bridge and nut. It could easily go back to being a mandocello or octave mandolin by swapping back to the original nut and bridge.

I've found the Curt Mangan light mandocello strings to give excellent tone. Of course they are loop end, but the thing to note are the cages - .070 for the C ranging up to 20 for the A's. My friend Martin at emando can make up custom string sets in ball or loop ends.
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  #6  
Old 01-07-2024, 05:56 PM
s11141827 s11141827 is offline
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Actually a Tailpiece never hindered the resonance of my W-200 because I've shaved one of the braces off to compensate for it.
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  #7  
Old 01-07-2024, 05:58 PM
s11141827 s11141827 is offline
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Quote:
Originally Posted by Mandobart View Post
There have been lots of guitar to mandocello conversions done. Typically an old archtop guitar is used. It greatly simplifies the process - just a new floating bridge and nut, unless you want traditional paired strings. That will require two additional tuning machines, and it can be be reversed if desired.

I once simply restrung my old Applause 6 string appropriately to tune F-C-G-D-A-E. The low F was too floppy (i used a .077). It would have to be much bigger, like a bass guitar G string to really work. I think C-G-D-A-E-B would work better, or go 5 string as you did.

I've had two mandocellos. The first is an Eastman MDC 805. Good quality and tone like all things Eastman I've ever played. I liked it so much I commissioned a custom 10 string mandocello (C-G-D-A-E) based on an F4 body. This was my primary gigging instrument backed when I regularly gigged.

Chording is a different experience on a 26" scale fifths tuned instrument for sure!

For now I've converted the Eastman to a 6 string guitar simply by swapping out the bridge and nut. It could easily go back to being a mandocello or octave mandolin by swapping back to the original nut and bridge.

I've found the Curt Mangan light mandocello strings to give excellent tone. Of course they are loop end, but the thing to note are the cages - .070 for the C ranging up to 20 for the A's. My friend Martin at emando can make up custom string sets in ball or loop ends.
For CGDAEB get Magma GCT-Cello Strings
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  #8  
Old 03-09-2024, 10:18 AM
s11141827 s11141827 is offline
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Because the GCT-Cello Strings don't have ball ends, you need to tie guitar string ball ends onto the ends of the strings to help keep them in place.
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  #9  
Old 03-09-2024, 10:19 AM
s11141827 s11141827 is offline
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Rather than rework the bridge, you could've maybe done some interior body modifications to make a tailpiece work.
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  #10  
Old 03-09-2024, 10:20 AM
s11141827 s11141827 is offline
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Quote:
Originally Posted by Mandobart View Post
There have been lots of guitar to mandocello conversions done. Typically an old archtop guitar is used. It greatly simplifies the process - just a new floating bridge and nut, unless you want traditional paired strings. That will require two additional tuning machines, and it can be be reversed if desired.

I once simply restrung my old Applause 6 string appropriately to tune F-C-G-D-A-E. The low F was too floppy (i used a .077). It would have to be much bigger, like a bass guitar G string to really work. I think C-G-D-A-E-B would work better, or go 5 string as you did.

I've had two mandocellos. The first is an Eastman MDC 805. Good quality and tone like all things Eastman I've ever played. I liked it so much I commissioned a custom 10 string mandocello (C-G-D-A-E) based on an F4 body. This was my primary gigging instrument backed when I regularly gigged.

Chording is a different experience on a 26" scale fifths tuned instrument for sure!

For now I've converted the Eastman to a 6 string guitar simply by swapping out the bridge and nut. It could easily go back to being a mandocello or octave mandolin by swapping back to the original nut and bridge.

I've found the Curt Mangan light mandocello strings to give excellent tone. Of course they are loop end, but the thing to note are the cages - .070 for the C ranging up to 20 for the A's. My friend Martin at emando can make up custom string sets in ball or loop ends.

Magma GCT-Cello 5ths tuned Strings w/ Guitar String Ball Ends tied onto them might help for CGDAEB Tuning.
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