I have gone down to .08 and up to .16 for a D melody string on a 25" vsl. Its mostly a matter of preference. The amount of tension on the strings affects tone, volume, and sustain. It also affects how comfortable the instrument is to fret. A lot of dulcimer players prefer pretty low tension, relative to an acoustic guitar of the same VSL, for example.

@gerardo1000, it's a good idea to start with the luthier's recommendations about string gauge, as you are doing, but don't feel locked into those gauges.  Follow your own preferences.  And in fact, a difference of 1 or 2 is inconsequential, so I wouldn't fret about the difference between .011 and .012 or .022 and .024.  

There are factors other than VSL to consider, and again, the most important is your own preferences.  One thing to remember is that you want some consistency of tension across the strings.  You might consult a string tension calculator such as this one to ensure that the three courses have similar tension.

FWIW, I prefer slightly heavier strings for a variety of reasons, including the fact that they are louder and also that they provide more resistance, allowing more precision when bending.  There is also a faster response to the flatpick (something enhanced with heavier picks).  On my dulcimers with VSLs in the 25"-26" range, I use .026 on the bass, .016 on the middle, and .013 on the melody.  YMMV, of course.

Strings are cheap. I would suggest buying single strings (not pre-packaged dulcimer sets) and experimenting to find your own personal preferences.

--
Dusty T., Northern California
Site Moderator

As a musician, you have to keep one foot back in the past and one foot forward into the future.
-- Dizzy Gillespie

So... McSpadden, for a dulcimer that has a 26in VSL, tuned to ddAD, recommends these strings gauges: 12 12 16 26. Quite heavy, considering that the McSpadden "short scale dulcimer" is two inches and a half shorter than their standard dulcimers that have a VSL of 28.5....  Folkcraft, for a dulcimer that has a 25in VSL (my custom Folkroots) also tuned to ddAD, recommend these strings gauges: 11 11 13 24. Very light. I know it because I asked them. How come ? These two dulcimers have almost the same scale length, I am surprised to see such a difference in the recommended strings gauge, a difference that ranges from very light (Folkcraft) to medium heavy (McSpadden)...these recommendations are also shown on the two makers web sites, when I look at "strings".  Any opinion? 

updated by @gerardo1000: 11/29/24 10:58:09AM