Designing a Mandocello

One of my summer projects is to finalize the design for the Mandocello I plan to build this fall. I'm certainly not an instrument designer but I am trying to come up with a design that is both aesthetically pleasing and playable. I also have a certain skill level in building that I want to match.. So for now those requirements rule out a caved arch of the A or F style classic Gibson's.

Mandocellos are a bit of an enigma as far as instruments go, although some would say they are enjoying a comeback after years in obscurity they are still what I guess you fringe instrument. Most people have still never heard of one let alone thought of playing one. Designs of modern Mandocellos are all over the map. Ranging from those that closely resemble the classic Gibson'
s to guitar body shapes and beyond.

Historic Gibson K1

Also the tuning of what some people are calling Mandocellos varies some tuned more like an Irish Bouzouki and a Mandocello. I think of a Mandoceloo as still the Cello part of a Mandolin orchestra so still CGDA Exactly the same a bowed Cello.

So my plan is to build a Mandocello that is tuned to the standard tuning CGDA and use a guitar shape with an induced arch top and back. Now there are a lot of other parameters to consider, things like scale length, body size, depth and arch.

One of the big decisions with a Mandocello, at least for me is scale length, A bowed Cello is about a 27" scale length but for me anyway that is too long to play comfortably. The problem is the shorter you go with scale length the harder it is to the the low C string to have enough tension.. A good scale length for my hand size would be 24.25" but that is getting really short for a Mandocello. I will most likely use a 24.75" scale length which is the same as the old Gibson A style Mandocellos.

A modern Ovation Mandocello

You also need to consider the body size, and although I am using an Gibson A style scale length I think the A style body does not have quite enough internal volume for the lower register.. So I am going to use a Gibson L-0 bidy shape.

Next the stress on the body, since I am not using a carved body plates I need to account to the increased string tension of a Mandocello over what a 6 string guitar's String tension would be. The tension on a Mandocello is almost double a 6 string guitar.. I will be reworking the bracing pattern to mimic what would be a 12 string guitar X brace design.. perhaps with carbon fibre  Over the summer I'll be finalizing that design as well.

Gibson L-0 6 String Guitar

Also the neck has to withstand these forces as well so I am planning a Narra neck with a double acting truss rod and I am debating carbon fibre reinforcement.

Lastly aesthetics  Mostly because the last few instruments I've built have been darker tone I'll be going a bit lighter looking for this one.. I'm planning a Oregon Myrtle Back & Sides with a Sitka Spruce top (Sitka will help in withstanding the string tension) The trim on the instrument is planned for Indian Rosewood, I'm still deciding how I am going to do the rosette but it will be some form of segmented wood rosette I think.

So there is the process thus far.. Of course you can follow this Mandocello as I build it.

Celtic Tenor & Summer Plans

So As I said I did change strings on the little tenor I built and the new ones do work better. The guitar is settling in nicely and I quite happy with the sound.. It is an Octave Mandolin sound..

Summer is just around the corner - I hope so I doubt there will be much guitar building going on in the summer. I have lots of plans right now and not many of them involve Lutherie.. I do hope to get a few more jigs built over the summer and perhaps an new tool box made.

The other thing I really want to do is finalize the design for the Mandocello that will be the next instrument I build.. I've got the over all design in my head and just need to decide on all the details.. It is going to be a guitar shape based on the Gibson L-0 from the late 1920's.. It is going to be made of Sitka Spruce, Oregon Myrtle and Narra with most likely Indian Rosewood trim..

It is going to be a short scale instrument (as Mandocellos go) with a 24.75 or 24.4 inch scale length..

I may bet started on it over the summer but I doubt I'll really get into it until September.

And It's Playing Music

The Celtic Tenor Guitar is finished.. it has a coat of blonde shellac French Polish , Schaller gold tuners with ebony buttons and an Allen Tailpiece. Currently it is strung with 0.042, 0.030, 0.020 and 0.012 strings tuned to GDAE an Octave lower than Mandolin. So it's a Tenor Guitar tuned as an Octave Mandolin :-)

The strings are a bit floppy on it so I'm going to replace them with some Mandola strings which as 0.049, 0.034, 0.023 & 0.014 Which should give 21 to 23 pounds string tension across the board.

All in all I'm happy with the results, it has a Mandolin like sound and should be good for playing Celtic pieces.. One I sort ou the strings I'll try and post a sound clip.

Sanding and Pore Filling

Sorry no photos of the exciting task of sanding, but pretty standard, 80 grit with a orbital sander, 80 grit by hand then 150 grit by hand then 220 grit by hand..

After sanding it is on to pore filling, there are as many methods of pore filling as there are luthiers, I'll be using two methods for this guitar. For the back and sides I'll be using Zpoxy brand epoxy. I've used it before and it works well under a French polish. For the neck I'll just be wet sanding with shellac.

The Zpoxy needs to dry overnight then get sanded (more sanding) then probably a second coat and more sanding to insure all the little pores are filled.

Nice thing about Zpoxy is you start to get and idea of what the finished guitar will look like

Back & Sides  First pore filling

Looks good

High tech applicator....

The Neck

So at this point he neck is still a big block of wood. The fingerboard can now be glued on and the neck can be carved.. I've carved the neck both on and off the guitar and frankly kind of like doing it more when it is on the guitar, there is n more to hold on to when it is a complete guitar..

Once the fingerboard is glued on the carving can begin.. Preferred tools are a spoke-shave , chisels and rasps of various types.. it actually goes pretty quick.. This neck probably took me 4 hours total work time spread over 2 days..

Before, nice tapered fingerboard on a square neck

Partly done removing the "non-neck" bits

Done

Side view

Finishing the Fingerboard

So a few posts ago I cut the slots in the fingerboard. Now it needs to be tapered to the correct shape bound and the marker dots and frets installed.

It is rough tapered on the band saw and fine tuned with a apron plane or a block plane whichever is handy.

Then the fingerboard is bound, I am not a big fan of the look of unbound fingerboards, I don't like seeing the fret tangs, I know it is common in classical guitars but not something I like. Usually I use a contrasting wood for binding but this time since I am keeping the decoration simple I just used some 1mm strips of ebony I had ripped off the fingerboard before slotting.

The dots are installed and finally the frets.. With a bound fingerboard the tangs of the frets must be removed from the end of the fret where it overhangs the binding as there is no sot in the binding to receive the tang. There are special made nippers to do this or various contraptions to hold the fret while you file off the tang (nippers don't work on stainless frets) But I just took some cheaper common nippers and ground a slot in them so the fret sits flat

A half done fret and nippers,
you can just see the slot ground into the bad of the nippers

Close up of fret

Completed fingerboard with gold mother of pearl marker dots

Making a floating Bridge with My New Toy

The Celtic Tenor guitar I'm working on will have a floating bridge and tailpiece so tonight I thought I would make the floating bridge.. I just happen to have to have recently got a Bishop-Cochran preciscion base for my Dremel tool and this was a good opportunity ti try it out.. http://www.bishopcochran.com/

I used this to cut a 3/32" wide and 5/32" deep slot for the bone saddle that will be inseted into the bridge, which is ebony.

The precision base worked great and I thing the bridge turned out good. It is patterned after the period Regal bridge that would have been on this style of guitar in the 1920's.

The base (nice red colour) and a simple set up in a vise to cut the slot

The completed bridge