switching Bouzouki strings from octave to unison

I recently purchased a pretty nice zouk from a local shop.

http://alabama-music.com/?p=172

My problem is that the strings that came on it are octave pairs for the G and D strings, and I would like to have all unison pairs.

Given that this bouzouki has a longer scale, and no truss rod to be found, is it a good idea to change the tension in this way, from octave to unison?

If so, is there much of a job to widen the nut/bridge slots to accommodate the two new thicker gauge strings? Is it possible to do myself, or better off to be taken to a professional?

cheers

I'd say whether or not you add tension, the chances are good that the neck will bow eventually. I question the judgement of a builder who makes a very long necked instrument without a truss rod or at least some other reinforcement. If this change is important to you, I'd suggest stringing relatively lightly for the scale just to be on the safe side.

It is not hard to widen the nut and bridge slots. You will need files that are the correct size for the gauge strings that you are putting on. You also have to be very careful as you are filing not to let the slot "creep" over towards the string it's paired with. If the string spacing becomes too close, the strings will hit each other when played, creating a buzz you will probably not enjoy. If anything, let the slot expand AWAY from the paired string.

So it's not hard. But it is delicate work. VERY tiny increments of slot depth, width and placement make a big difference in playability and tone. Some experience with the materials and files makes the difference between whether it is done properly or not. If you have an experienced luthier (who already has the files on hand) in your area, it might be worth getting them to do it rather than purchasing files (that you will not likely use much afterwards) and risking messing up your nut or bridge. If you are keen to do it yourself, proceed carefully. If you can practice with the files on some similar material first (to get a feel for how it moves, cuts, etc.) it would be a good idea.

KE

Switching from octave to unison pairs on the bass courses does not necessarily increase tension. I suggest you figure out what gauges are already on the instrument, run them through this online string tension calculator:

http://www.bangzero.org/stringtension/

and then try replacing the octave string gauges with the same gauge lower string that is already on it.

For instance, if your current gauges are, say, .012/.012, .016/.016, .026/.012, .038/.018

and the scale length of your bouzouki is, say, 25 1/2"

then the tensions would look like this:

len 25.5"

D .012" PL == 18.53#
D .012" PL == 18.53#
A, .016" PL == 18.49#
A, .016" PL == 18.49#
D, .026" PB == 19.81#
D .012" PL == 18.53#
G,, .038" PB == 19.21#
G, .018" PL == 18.58#
total == 150.19#

and if you replace the octave strings with unisons then the tension would only increase by about 2 pounds, less than 2%.

D .012" PL == 18.53#
D .012" PL == 18.53#
A, .016" PL == 18.49#
A, .016" PL == 18.49#
D, .026" PB == 19.81#
D, .026" PB == 19.81#
G,, .038" PB == 19.21#
G,, .038" PB == 19.21#
total == 152.1#

So you would be safe to do that. Should be no problem as long as the strings that are on it are appropriate gauges.

As far as the nut and bridge slots go, I would suggest that you take it to a tech. Since you are going from smaller to larger slots on both then s/he will have the other, larger slots to go by and need only match that of the smaller string to that of the other, larger string in each of those two courses.

Good luck!

From the photo you have posted it looks like there is a truss-rod cover on the headstock - though the photo is very small and my eyes are not what they used to be!

John, they still seem to do the job!
There is indeed a truss rod cover, but underneath is just an empty cavity with no truss adjustment.
There isn't an adjustment at the heel either.

I appreciate everyone's help. I will most likely take her to my local doc to do the conversion, just to be safe.