Matt, the other thing to consider is the string tension. If the dulcimer strings are under too much tension it will be hard to get them into the sweet spot. I have an excel spreadsheet that calculates the tension of any string at any pitch for a specified scale length. If you have that info send the sizes and pitches of each string and and I'll run that through my String Tension Calculator.

BTW, that excel spreadsheet is freely available to any who wish it.

I purchased a fretting slot saw blade from Stewmac.  I went from dreading the fretsaw to gliding through cutting frets.

@ken-longfield Yea, cutting a dowel down sounds like a good plan.

Thanks, Matt. That sounds like a lot less work. If you want a round top you could cut a dowel in half or sand it down. Using an overarm router and an extremely small straight cut bit you could rout out the slots for the frets. Just trying to imagine some possibilities.

Ken

"The dulcimer sings a sweet song."

Well, the person I referenced did not have a problem with the scalloping with jumbo frets bending the notes.  I'm sure the extra space would make bending easier.

I play several dulcimers with different vsl.  When I move from a shorter to a longer vsl, my fingers tend to do down nearer the previous fret.  If I don't press hard enough, I get fret buzz.  //adjusting to play nearer the proper fret eliminates the buzz.  I believe this is what is meant by the sweet spot.  There is a larger space between two frets where you can press down and be sure there is no unwanted buzzing.

Like most of my builds, I like to experiment with different setups.  I have heard of scalloping, but never tried.  I will in some future build and wanted to hear thoughts on the best way to do it.

From my limited experience playing the tagelharpa/jouhikko (where you press the strings with the backs of your fingers to fret notes, but there is no fretboard to press the string to), I'd guess that pressing down the strings to a fretboard that was deepened down could very easily bend the notes. Most of us are used to feeling the fretboard there with the soft pads of our fingers without necessarily 'mashing' the strings. Of course, one could also use this to purposely create bending and vibrato effects. 

I'm still not sure why scalloped frets would 'create a bigger sweet spot' between the frets (assuming one does not aggressively 'mash down' while fretting anyway). The fact that the note is created off the metal fret does not change. I always thought that scalloped frets on guitars were there to better facilitate bending the notes, as in blues or jazz playing.  ?

@dwain-wilder,  Yep, his dulcimer had both scallops and jumbo frets.  To oversimplify, it think high end dulcimer players can be separated into two types, the mashers and the dancers.  The mashers slam down the strings into the fret board, the dancers press the strings down so they touch the frets, but try not to push the string into the fret board.  I can't say which is better as either type has a much better playing skill set than I do.  Good idea about the fret slots.  Scallop will weaken the top.

@ken-longfield  Ken, I was considering cutting a string of wood with chamfers on both sides and gluing them to the fret board and then cutting the fret slots.  Should accomplish the same thing.

@skip  Skip, agreed,  Any fret higher than the eight fret will need files.  

Thanks all for your thoughts.  I doubt I will get anything done for a couple months, but will post what I do, if I choose to work at it.

Are you considering making the scallops after fretting? or before? I would recommend scalloping afterward, as any error in marking and carving to the mark would be very obvious.

I would also advise taking a step taught me by the owner of Buck's County Music Shop: chamfer the edges of the fret slot outs to the width of the fret tang's barbs, so the barbs do not pull out surface wood during fret removal —no need to heat the fret, which always risks marring the fretboard. Future repairers and re-fretters will bless you, and the scallops will be preserved intact.

As for scalloping the fretboard, do you know why higher frets weren't chosen? That would effect the sweet spot as well, without the unusual effort.

For me it would depend upon how deep the scallops are. One method might be to use a variety of thickness of drum sanders. Another method would be to cut kerfs across the fretboard and then use a chisel to remove the wood left after sawing. You might need a file to smooth out the surface a little. Just a couple of quick things that come to mind.

Ken

"The dulcimer sings a sweet song."

Sanding drum[s], round files, roundnose end mills [combined with flat cutting for the longer spaces]. Use sacrifice scrap wood on each side to prevent tear outs. 

I had an opportunity to talk with a well known dulcimer couple.  The gentleman showed me a fretboard he had made with scallops between the frets.  He said this created a much larger sweet spot for fretting.  The scallops worked well, but I could see they were a bit uneven.  I am considering making a fretboard with scallops and am looking for ideas on how to smooth out the scallops.  So, any thoughts on how to make smooth scallops between frets?