Om neck dimensions

[mpeg2]

I"m about to embark on building a solid body electric Octave Mandolin (after completing mostly successfully #an electric mandolin). I need a little help figuring out the dimensions for the neck - there's no place nearby that has any OMs to check against.

Since I'm building the neck from scratch, there's a lot of flexibility - just need some starting suggestions. I'll be using the inner 4 saddles from a 12 string guitar bridge at one end - which sets one of the dimensions. The scale length that I've chosen is 22.875". What's missing (I think) is the width at the nut (the rest becomes simple geometry).

So - what are typical neck widths at the nut for OMs???

# Thanks,
# # Rich

[Celtic Saguaro]

My eight-string is a generous 1 5/16". #If you are thinking about a four-string electric a tenor banjo is more like 1 1/8".

I might add that 22.875" might be a little long for an eight-string OM, even an electric. #My tenor banjo is fine at 22.75, but a number of people complain about the combination of the extra width and a 22.50 scale on an eight-string. If you are going to use it like a short bouzouki, it will be no problem. #Using it like a giant mandolin, like many of us do, could be a problem.

[mpeg2]

Thanks - gives me a starting point. I chose the scale length based on what I could find in pre-slotted fretboards. Lets see how it works. Since I'm primarily a guitar player, I have no preconceived expectations on how the fingering is going to work...

# #Rich

[steve V. johnson]

Hi Rich,

There have been a lot of discussions here about scale lengths, and I don't really know how those will translate to a solid-body electric design. I believe that the majority of OMs these days come in at 22 - 23". More and more that seems to be an ideal
length.

I came to OMs/zouks from guitar, so I asked Phil Crump to make my instrument the same scale as my main guitar, so my scale length is 25.4", more often called a bouzouki than an octave mandolin, and yet shorter than a mandocello.

One of the things I like best about my Crump is that it feels wide enough, and the string spacing is comfortable enough as well,
that I can do hammer-ons and pull-offs in first position. I also like that it doesn't get much wider toward the heel, so it feels the same and doesn't require more grip to play it up the neck.

The neck width is 1 7/16" wide at the nut and 1 3/4" at the 12th fret. I'd probably keep these proportions, or as close to them as I could, for an instrument of a shorter scale, too, were I to order another one.

Good luck with your project, and keep us informed of your progress?

Thanks,

stv

[mpeg2]

Steve: Thanks. I'll keep the group posted on progress - this'll take a while - the rest of the instrument has become pretty easy, but I'm still learning on necks - I'm doing a guitar & OM at the same time (when I have the time to put in)...

#Rich

[Graham McDonald]

34mm at the nut suits most people, with a 12th fret width of 44mm, which should then be about the outside string spacing at the bridge. If the bridge string spacing is constrained by the saddles you are using, then things can change. The nut width is dependant on personal preference, and I have made them from 32mm up to 38mm, but 34mm is a good place to start.

A simple way to get an OM fingerboard is to buy a pre-slotted guitar board and chop off the first two or three frets. A standard Martin scale board less three frets is close to 22", (but check that before taking a saw to it) You can work out the scale length of a shortened board by meauring up 12 frets from the new nut and doubling that measurement.

good luck with the project

cheers

graham

[mpeg2]

Again, thanks.

Your suggestion of chopping a guitar fretboard makes a lot of sense and is very clever - I never would have thought of it by myself...

Rich

[mpeg2]

Looks like its back to the drawing board. The original plan was to use the 4 inner pairs of a 12 string guitar bridge. This worked fine for a Mandolin - but the strings are too close together for an OM (the outer string width is about 35mm).

Now, I've got to come up with a new approach to a bridge. One option is to get some sheet brass - drill & bend it and use the saddles from a 12 string guitar bridge...

I'll post when I get this one solved...

# #Rich

[Graham McDonald]

Here is a fairly simple solution. The base of the bridge is a bit of brass angle, more or less like a Strat bridge base. The saddle is a piece of 1/4" x1/4" square brass rod with compensation ramps filed in as per an acoustic saddle. Back and forwards adjustment is done with two Strat saddle adjusting screws tapped into the brass and height adjustment is done by two small grub screws (like Strat saddles use) but these were slightly larger ones from an old bass bridge.

If the compensation is cut correctly into the saddle in the first place, that will give you pretty accurate relative intonation between the courses and you still have overall adjustment back and forwards and up and down.

cheers

graham

[mpeg2]

Graham: Looks interesting - may hold that as plan B. What I'm currently thinking of is getting a piece of Brass sheet about 1/8" thick & bending it to form a lip at the end - then drilling so I can use the saddles from a 12 string guitar bridge. I like those saddles - correct string spacing & totally adjustable.

Of course, this plan depends on being able to find the bits I need (and being able to bend the brass successfully).

Rich

[Graham McDonald]

I suppose it is good to have everything at the bridge fully adjustable, but after the initial setup, how often are those adjustments going to be used? If parts are adjustable they will tend to move a little over time and will need to be brought back to their original positions, but other than that if you keep with the same string gauge/tuning/action there should never be any reason for the bridge to be adjusted and you could safely replace it with a solid block of brass or carve one out of ebony. And I suggest this from having spent 8 years in a guitar shop doing a lot of setup work on electric guitars.

Trying to bend 1/8" brass is not easy. Find some 1/8" angle. It should come in various sizes. That bridge in the pic above was made from that. Solid body OMs/bouzoukis are quite fun and not all that hard to do.

cheers

graham