Dusty,  All I can say is in the few days I had the prototype before delivering it to Aaron, it didn't improve my playing noticeably.  It was a lot of fun to play, however, even at my meager ability level.  You notice how easy the slides are and the increased vibrato right away.

If I get a nylon string dulcimer will I be able to play like Aaron?

Bob, the instrument you built has an amazing balance of tone and surprising volume. It's nice to see Aaron employing some techniques that wouldn't work (at least not well) with steel strings.

Great job both of you! The video introduces a new (albeit old) tune and a new instrument to the dulcimer community.  I feel lucky to live in such inventive days.

Aaron O'Rourke just posted a new video demonstrating the nylon string dulcimer on a Scottish lute tune.  Gives a good sense of the unique tonal character of the instrument.

Since my body still seems to be on China time, I had way too much time to think last night and I thought of another major difference between my nylon string instrument and my steel strings.  Both instruments have soundboards that are free to vibrate for their entire length.  The method used to transmit the string energy to the soundboard is completely different, however.  On the steel strings the the string passes over the bridge and continues on to the tail block.  The force of the strings on the saddle is pure compression that passes down to the concealed soundboard as a downward force.  There is no torque applied to the soundboard- just a downforce of about 11 pounds.  You can think of it as a flat top mandolin from the standpoint of forces and the bracing required to resist them.  Simple transverse braces are all that is required.  I use a combination of wood and carbon fiber to keep the vibrating mass low.

Since the goal on the nylon string instrument was to pick up some sound characteristics of the guitar family, I chose a bridge system that applies a torque (twisting) to the soundboard.  This dictates a much more complicated system of bracing to resist the applied torque.  It also provides the opportunity to create varying size vibration zones to generate a uniform sound profile across the full frequency range of the instrument.  The bracing I use is an adaptation of an asymmetrical bracing scheme used by a ukulele maker.  It seems to be working out well in terms of both it's structural requirements and it's flexibility in providing the desired voice to the dulcimer.  I have a lot of options when I start to carve the braces and by testing along the way, can dial in the sound I desire.  I guess that's the part where science yields to art, but that's the challenge and reward of instrument making. Since I have done a lot of measuring, recording and adjusting of each soundboard's longitudinal and transverse stiffness along the way, I am pretty confident that the right sound is in there.  I just have to let it out.

Dusty Turtle, You make a good point about whether or not having a radiused fretboard as a standard feature is the way to go.  From the luthiers point of view, it is a tradeoff between extra setup and machine time (16 minutes in this case) vs. added inventory.  Sometimes there is no right answer.  Having tried the radiused fretboard, I don't see that it would be a problem for most players and I think many would grow to prefer it.  I do try to supply what the player wants, however, so if someone really wants a flat fretboard, I would try to oblige.  Since producing a flat fretboard would require additional programing (the fret slots would no longer be radiused) and an individual setup, there wouldn't be a cost advantage unless there were significant volume.  In the long run, I guess the market will decide what is standard and what is an option. 

Thanks for sharing your thoughts, Bob! 

I like the sound of fretless banjo and of Randy Adams's play of fretless mountain dulcimer.  So, was curious if you'd played around with a fretless design.

Robin, No I haven't tied anything fretless yet.  It does sound interesting however.  I don't think the sound would be appreciably different with or without the radius.  I was skeptical about the radiused fretboard since I play with the dulcimer flat in my lap.  Having now tried it, I didn't see any disadvantage to it and it felt quite natural from the start.  For those that play with the instrument tilted up, I can see a distinct advantage to the radius.

As to a fretless instrument, I fear I would not have the skill set to do it justice.  Note that I ordered my Ken Bloom bowed dulcimer with frets.  For the right musician, there may well be some interesting possibilities to go fretless.  I wouldn't be opposed to building one.  Since my fretboard/neck can be easily removed (and therefore exchanged) the risk wouldn't be too big if some adventurous sole wants to give it a try.  If Aaron has any interest in trying one, I could build a neck for the prototype for him to play with.  

I will add your suggestion to a growing list instruments to build in the future.  So many possibilities and so little time to pursue all of them.

Bob, I've wondered what a fretless with Nylagut-type strings on a flat fretboard would sound like.  In your experimentation, have you ever tried such a set-up? 

Got it!  I'm glad you plan on making this dulcimer as a regular offering.  I have no doubt there will be serious interest.

I have mixed feelings about the radiused fretboard. Unless you barre with a single finger I am not sure how useful it is.  And the only people I've seen do this on a regular basis are Aaron and Stephen Seifert (and they use different fingers). It is possible that more people would play that way if they had a radiused fretboard, but since we have five fingers and only three strings, I find using three fingers to barre still allows two other fingers for playing, and I'm pretty satisfied with that option.

If the radiused fretboard adds a lot of labor (and therefore expense) to the production process, you might make that an option rather than a standard feature of the dulcimer.

The jumbo frets that Aaron likes, however, should be used by everyone.  They make fretting the strings so easy and smooth.

I look forward to seeing how you refine this dulcimer and perhaps one day purchasing one of your nylon-string dulcimers for myself.

DustyTurtle, I am afraid I didn't make myself clear when I referred to "high volume" (I edited my post below).  I meant volume in terms of the number of instruments produced.  As to the the loudness of the instrument, the nylon string version holds its own pretty well with the steel string.  When I first strung the prototype up, I was pleasantly surprised at how loud it was.

The nylon string version is definitely headed into production early in 2019.  As soon as I can get Aaron's performance instrument done and he has a chance to provide feedback, it will be released for production.  A number of people have expressed serious interest in the nylon string  version already, so there may be a bit of a backlog initially, but instruments will be getting into player's hands by the spring.

Thanks for such a detailed response, Bob.  I have to admit that since I'm not a luthier, some of that is over my head; I'll have to reread portions before it will sink in.

I do find it curious that you state that your "goal is not to produce high volume." When I mentioned to some dulcimer friends that you had developed a nylon-string instrument, their first comment was that it would never be loud enough. I assured them that I had heard Aaron play and that it was, so whether it was your intention or not, I think you did achieve more volume even than most steel-stringed instruments.

In the "live hangout" Aaron hosted perhaps a week ago, someone asked if nylon-string dulcimers were only appropriate for expert players.  Aaron assured them that the tonal qualities of nylon strings might be interesting to anyone regardless of skill level.  I think the point is that there would be a market for you if you decide to make a nylon-string dulcimer as a regular option for your customers.

I thought of a few additional differences between the nylon string and steel string instruments. While the use of the CNC router is valuable tool on the steel strings, I can't imagine trying to produce the nylon string version without it.  The accuracy and repeatability of the CNC makes holding the very tight tolerances required possible.  Aaron is very sensitive to even minute variations in the ergonomics of the instrument and a few thousandths of an inch can be critical.   The CNC router can achieve the accuracy required, but it comes at a price.  For example, the fretboard requires four separate setups and tools to produce.  One setup to add registration holes, another to add the 10.00 radius, another to put in the position dots and a final one (with a 0.020 diameter bit) to do the fret slots.  The mating neck requires individual setups for the carbon fiber slots, putting on the taper angle (with the part rotated 90 degrees) and adding the mounting hole counterbores relative to the taper.  The two components are then glued together and put back on the router to cut the outer contour of the assembly.  So in all, thats eight individual setups to produce the neck/fretboard assembly and that doesn't include several more for the headstock.  Still, the accuracy achieved makes it all worthwhile.  

Another process difference between the two types of dulcimers is that on the nylon string instrument, I use a fixture that clamps the top in place so I can hear the instrument prior to gluing it in place (see attached photo).  This allows me to carve the bracing away in a slow and measured manner.  Carve a little, listen to the result and either stop or carve some more.  The removable neck/fretboard makes this possible.  It's a slow, but worthwhile process that pretty much assures that the final result will be satisfactory.

As you can see, my goal is not to produce a high volume of instruments.  There are many excellent dulcimer makers that can fill that need.  My interest is in making a small contribution to the development of this unique instrument and to satisfy the requirements of a dedicated few players who want to push the limits of what can be done with it.

Dusty-Turtle, Just got back from three weeks in China and I am trying to catch up with the interest Aaron is creating in the nylon string dulcimer.  I will be back to work building Aaron's performance instrument now that I have returned.  It will be very similar to the prototype he has been testing, but it will have some slight improvements.  It will also have a bevel on the top to accommodate his style of play.  

 I will try to describe some of the major design elements that differentiate the nylon string dulcimer from my steel strings.  These features were all derived from Aaron's description of the ergonomics and sound character he was looking for.  I decided early on that the sound should be a blend of a dulcimer and a baritone ukulele with a bit of guitar thrown in.  To achieve that, I wanted the top of the instrument to be the soundboard (unlike my steel strings where the soundboard is concealed inside).  In order to obtain the volume and tone I was looking for I decided to raise the fretboard completely above the soundboard so that the entire soundboard could resonate.  I could do this because I use a structural i-beam that runs the length of the dulcimer (photos at stephenslutherie.com ) and the fretboard can be supported on four posts rising up from the i-beam.  Like my steel strings, the fretboard is bolted on and can be removed at any time.

In chasing the sound of guitar family instruments, it seemed appropriate to taper the sound chest as is typical on those instruments.  There is a slight taper so that the height of the rib is less at the head than the foot.  The profile of the nylon string instrument is the same as my other dulcimers and it is built in the same mold.  

The bridge is totally different from my normal bridge- designed for minimum mass and it has a unique string retention system that goes with it to provide for fast easy string changes and very direct application of the torque that excites the top.  This feature is under review and will probably be enhanced to provide an easy means of string height adjustment as well as compensation.  

The sound hole is located immediately below the point where the strings are picked to give maximum clearance to the soundboard with a relatively low fretboard height.  The fretboard itself is tapered (lower at the bridge end) to provide the optimum combination of fretboard height without getting the string height at the saddle too high (which would require heavy bracing of the soundboard).  

The bracing is loosely based on the asymmetrical bracing being used on some contemporary ukuleles.  This has to be controlled with top thickness to achieve adequate volume without too much sustain. With Aaron's fast fingerstyle technique, we wanted to limit the sustain so that each note could be heard clearly.

The fretboard has Aaron's preferred 10.00" radius and the fretwire is also specified by him.  

The tuners are ultra light GOTOH UPT with a 4:1 gear ratio that suites the nylon strings.

I am sure there are other differences, but at the end of the day there is not one part of the nylon string instrument that is common to my steel strings.  It's been a great experience working with Aaron to bring his vision to life.  Something tells me, this won't be the last dulcimer we collaborate on.

Bob, I've had the opportunity to hear more of Aaron playing this instrument and also to talk with him about it. Yes, it's true that he could make any instrument sound good. But I know he's very happy with the possibilities this fine instrument offers.  And I'm sure there would be a market for this instrument if you decide to build more.  You've done good work here and I dare say a solid nylon-string dulcimer could be a major game changer in the evolution of the instrument we all love so much.

Robin, you have to realize that this was the first time I heard the instrument other than a few seconds when I dropped it off.  Of course, Aaron could make anything sound good, but I am pleased with how the project is turning out.  Still a few tweaks to go on his actual performance instrument, but we are very close.

Bob, I also just heard Aaron's demo of this instrument. It sounds wonderful!  You've done really impressive work.

When you get a chance, could you explain what it means to build a dulcimer "from the ground up" for nylon strings?  Aaron made a similar comment, explaining that he had put nylon strings on regular dulcimers and was never fully satisfied with the result.  In terms of construction, how is this instrument different than one intended for steel strings?

I heard Aaron playing this beauty-- wow!  The sound was so fine, Bob. 

Aaron will be doing an audio file shortly.  Once his final instrument is delivered (this one is only a prototype) he will do a video to demonstrate it's capability.  He has only had the instrument for a little over a week, but he is a fast learner and I expect some pretty amazing results based on what I heard when I delivered it to him.  As soon as I have some sound files I will post them on my website, stephenslutherie.com

Beautiful instrument!  Hope to hear it soon!

I look forward to hearing this instrument!