We are sticklers about intonation. There’s no reason that a ukulele shouldn’t have perfect intonation all the way up the fretboard. Yet, many if not most ukuleles fall short in this regard.
Achieving perfect intonation is more difficult as the scale length (distance from nut-to-saddle) gets shorter, so ukes are tough in this regard with the soprano being the most difficult. Furthermore, with larger diameter nylon (or nylgut, or fluorocarbon) strings it is more difficult for the intonation to be perfect.
But, these are not excuses. Merely, they put more demands on the luthier and the precision to which the ukulele is built. Fret slots must be cut in exactly the right place, the action must be correct, and the saddle compensation must be perfect (the saddle compensation is the distance beyond the theoretical scale length that the saddle is placed to compensate for string stretch).
In short, we take great pride in building our instruments very precisely and setting them up for perfect intonation.
But, and here is my real point, sometimes an instrument that is built & set up correctly doesn’t have perfect intonation on one or more strings. Why? The answer is that the string is most likely at fault. Either the strings are old, and when you fret they are stretching unevenly, or you’ve just restrung and one of the strings is bad.
We’ve just experienced this on two different ukuleles. One of which we just built and strung, and the a-string was flat by about 15 cents. It turned out to be a bad string (all the other strings were dead-on, and all the measurements checked out). In another case, a customer had restrung their uke, and the intonation was off on one string. Again, all the measurements checked out. We replaced the string and all was well.
Happy Holidays,
Gordon & Char