my neighbor wants me to build him a cbg with 5 strings no bottom e string. He wants to tune it like a regular guitar eadgb. Does anyone know how well regular tuning works on a cbg? thanks!
If you maintain a 24-to-26 inch string length (VSL), then you shouldn't have a problem with using guitar tuning assuming you also are using guitar strings.
However, if you increase or decrease the string length significantly (by several inches or more), then you'll find you can't tune it without having very loose strings, or popping (breaking) the strings when you try to tune it up to your desired tuning.
As you may know, the shorter the string length, the higher the pitch the instrument will be. So, if you compare a ukulele to a guitar, with it's very short string length, there's no hope in tuning it to the same notes of a guitar, although it may be possible to tune it an octave (or two?) above the standard guitar tuning.
I make short necked stick-dulcimers in the range of 16-to-20 inches and the resulting instruments are higher pitched than guitars. The only way I have found to make them lower in tone is by switching to nylon strings, choosing strings 2,3 and 4 (for instance) and the resulting instrument will have a lower pitch, but will have the "plunkish" sound of a ukulele, especially with wooden sound boxes. With a cookie/cake tin resonator and nylon strings you can get better results with nylon strings on a short neck instrument, but I have to play around finding the right bridge to get the sound I'm looking for.
However, a 24-26" VSL 5 string cigar box using standard guitar strings should be able to handle "eadgb" tuning any of the problems I mentioned above.
Good luck with your build...
I mostly make short scale instruments, and I (so far) have just increased the pitch and used string thicknesses corresponding to a standard guitar. For example, if the instrument has roughly the scale length of a standard guitar capoed at the 5th fret, I use a tuning consistent with the pitches that implies. But, if you're dealing with fewer than 6 strings, that does give you some options.
To stay with the above example, let's say I'm making a 3-string instrument with a scale length about equal to a standard guitar capoed at the 5th fret. That means, without changing the string tension at all from the way they'd be tuned on a standard guitar, I could tune: A-D-G, D-G-C, G-C-E, C-E-A, just by choosing the string thicknesses corresponding to neighboring strings on a standard guitar, in this case, the E-A-D, A-D-G, D-G-B, or G-B-E.
Then factor in the fact that standard guitars sound just fine with a number of alternate tunings using the same set of strings, as long as you don't deviate too much from standard, and that gives you a bunch more options, And finally, if you're talking about an instrument that uses less than 5 strings, you don't even have to pick string thicknesses that would be neighbors on a standard guitar.
So - I wouldn't worry too much about this. If you want a shorter-scale instrument that preserves A-D-G-B-E, you can get there - up to a point - using slightly thicker versions of standard strings, or you can "jump" down a string, i.e. use the E-A-D-G-B strings in a standard set, and tune them up a 4th (assuming your scale length is short enough).
Of course, at a 24" scale length, all of this is academic - you'll be fine with standard strings, tuned normally.