Design
My greatest Design problem… a six foot nine ukulele honoring Hawaii’s Queen Kaahumanu
Aloha and welcome to the community fence post of my blog… Musical Musings. Today I will take on the wide ranging subject of Design, my favorite part of the entire process of Lutherie, the art of making stringed instruments. Design will rear it’s head over and over throughout a build, and without a plan, you can be dead in the water, waiting for inspiration. Each and every design decision will affect the next, and the entire instrument is the sum of it’s parts, so Design, in one way or the other, is the underlying theme that holds it all together.
Today I get to write from a new perspective, as I have (finally!) found a student/ apprentice to share my workbench with. God Bless the new student, and give them patience. How are they to manage the several faces of design, with no experience to guide them? From the big picture to the numerous tiny decisions to be made, the list of opportunities to stay with or deviate from a plan can be overwhelming. I hope to shed a little light on the subject.
I enjoy the freedom to create several versions of each size of the instruments I choose to make. I find it refreshing to start with a clean slate each time I root through the woodpile to begin another build. Within well established forms and sizes, there are so many available options that I am pretty sure I could never get bored, or complete each option… there are just too many to choose from. In my view, the most important consideration in Design is Scale length. Then there is Component size, woods used, Techniques, Finishes, Beauty and several other very important considerations to balance along the way to the ultimate goal of playability. We must keep that goal in the front of our minds; a non playable instrument is a light stand, at best, and using all that effort to make a wall hanging is simply not the goal. The most important goal to accomplish is a playable instrument, period.
Scale Length is defined as the active length of the strings from the nut to the saddle. A typical guitar would have a Scale Length of near 25 inches. A Baritone ukulele would be 19 inches, while a Tenor will only go 17, and a Concert is a mere 15, close to that of a Mandolin at 13 1/2 inches. A Bass guitar would be even bigger, but it is also much shorter than a stand up Bass. The longer Scale lengths generally take thicker strings to generate the right forces needed to make the music, while shorter scale lengths can get by with lighter, thinner strings ( that will get up to a certain pitch with less force than thicker strings). With scale length in mind, it is easy to imagine that a longer scale length will require a stronger body and neck, thicker and heavier, than a shorter scale. It also might influence how large the instrument’s body might be, or the dimensions of the neck, heel, and / or headstock. Also good to keep in mind, is that deviating from a popular scale length, even by as little as a half of an inch, is not quickly recommended. It can cause problems with intonation, and has contributed to string breakage issues. The worst offshoot of this is that a guitarist who is used to playing a 25 1/2 inch scale length may not enjoy trying a 26 inch scale… the muscle memory will object to the slight difference and the player may not be up for it… know your client’s purclivities! If he or she is a Fender player it is not likely that they will be excited about a Gibson setup; the two are different and you will find that most players are not interchangeable.
15th fret Body union versus 14th fret makes a difference in bridge placement of about 9/16ths inch Electronics placement cannot be ignored
It is extremely important to design around a known set of strings with a close approximation of the forces needed to bring those strings up to the pitch you intend to use them at. A set of bass guitar strings when fully loaded might need close to 200 lbs of combined tension to bring to pitch, while a Tenor ukulele will need only about 40 pounds. Strings are, therefore, a foundation stone of Design. It has been said…. “If you want to change the sound of your instrument, the quickest and easiest way to do so is to change the strings.” This not only implies that new strings can make better music, but also that a new selection of strings can make a dramatic difference in the music that you are making. Often a builder like myself, when discussing a custom instrument, will concentrate on the client’s background in music, their collection of instruments and the strings they prefer, to evaluate what the client currently enjoys about their guitar, and what they hope to find in the new creation. One thing is for certain… it will center around the strings.
From a builder’s perspective, although the strings are an obvious choice for ‘most important feature’ on an instrument, you might be surprised to find that I believe that title should go to the humble Bridge instead, especially on an archtop instrument. Surprised? Well, don’t be. First off, the mass of the bridge is a vital ingredient. A lightweight bridge will move much easier and quicker than a heavy one. So you have to find a good balance between weight and strength. It can be tempting to use your heaviest, strongest wood for the bridge, but that is not usually the best route. Next, the height of the saddle over the bridge (or, over the soundboard), is a huge consideration. On a flat top guitar, a high saddle will initiate tremendous extra force onto the soundboard, possibly distorting it over a relatively short time. Every millimeter that it rises above a certain threshold generates an additional load that combines with the natural torquing action of that system to test the strength of even the finest guitars. For this reason, many a fine guitar has failed as the neck/ body union becomes compromised, and the Action! rises, requiring a higher saddle… adding up to disaster.
On an archtop instrument, the bridge is the most important factor to consider because this is where the downward force of the strings is centered. So far we have spoken of the force needed to get to pitch, let’s say 50 pounds on a Baritone uke. You wouldn’t want to see all of that being pressed downward! The actual downward force is a fraction of the total, and the decisive factor is the height of the bridge / saddle relative to the tailpiece and it’s base. If you care to build extremely lightweight, the key to success is a low saddle and tailpiece. The lower height and resultant lower break over angle will minimize the downward force and make using those lightweight components possible. In turn, you would use lighter strings with less tension (thinner diameters), and more subtle bracings, and probably less of everything. On your average archtop, as the saddle height and break over angle gets larger, the downward force grows quickly. Soon the sound board will be over powered and begin to fail. There is a fine line not to cross here. Robert Bennedetto, in his landmark book about making archtops, tells us that a breakover angle of about 14 degrees is optimal, both at the saddle, and also at the nut, for the peghead. Too much angle and the forces wear down the resiliance of the top, too little and there isn’t enough to give the maximums their best opportunity when you need them. In the mandolin world, the break over angle is even greater, as are the combined forces needed to get eight strings up to pitch.
So, between the string pull, and the the bridge / saddle height, it will tell you how strong and thick to make your body and braces. Body sizes are strongly dictated by scale length and desired projection. A larger body will have a deeper sound, a smaller one will generally not have huge projection. It’s very difficult to get everything, or even most of the good things, all in one instrument. Clients that want a guitar that hits the high notes cleanly and plays deep notes beautifully, and has endless sustain while playing an amazing lead with all of the mids being equal throughout… are asking too much. I am sure a few well known makers can pull that off, to some extent, but for most builders, it is just a dream to make such an instrument. The form will follow the function. If you want huge projection, build light. If you want precision and a great attack, use harder woods on the back and sides: but don’t be surprised if that weight has repercussions. If you want a smooth mellow sound, those back and sides could be less hard, heavy and dense. If your last build weighed in at 3.5 pounds, and that didn’t quite suit you, shoot for the next to be at 3. You might have to take that top down a bit thinner. Braces too, and the sides need not be so thick. It can be a delicate balance.
To make matters much more real and interesting, it is important also to design for a particular sound, or even a fundamental tone associated with a body. For instance, it is not a coincidence that most of those wonderful, deep sounding Dreadnaughts are tuned to G. Each body size has a home frequency built into it naturally, so you can be sure good luthiers try to find the correct volume inside to have a good backdrop for all of the chords and notes to be played overtop. An old Concert ukulele made in the 60’s will almost always have a cheery “C” resonant frequency, and if you were wondering why some models always look exactly the same size, now you know. We have some other controls in the archtop world when it comes to tone. If you push the F-holes out wide, you highlight the lower tones. Slide them closer together and the trebles are uplifted. In the same way, a high arch accentuates the highs and a heavy headstock combined with a stiff neck will help with sustain. It can be hard to catalog all of the design elements in a given build… the list goes on and on.
New style Rubner Mandolin Tuners need a carefully designed Headstock ( shown in progress)
Most folks, when talking about design, want to leap directly into how the instrument looks. The placement of the soundhole, the number of frets below the neck / body union, the placement and style of the bridge…the purfling and binding, the rosette or F-holes, the headstock and tuners. To be sure, I enjoy that also, but it is secondary. What is the hallmark of a great instrument? Playability and performance. The question really is… where should I put the bridge for best performance? At what size does the soundhole max out volume and still retain a sweet tone? What will make it feel as if it was made to sit on your leg, or on a strap because you always play standing. Where the neck / body union falls is more a matter of bridge placement on the soundboard than a request for a longer neck to practice scales on. The soundhole isn’t a venue for a rosette so much as it is the literal voice of the machine, and yes. size matters. Headstocks are a great place for both the tuning machines and also for a personal touch, but as a designer you have to design around your choices here. For instance, if your tuner posts are 1 1/2 inches long, you need to choose good dimensions to not only make your eye enjoy the flow but also to house those machines for playability. Slotted head tuners will be mounted a great deal differently than for solid head machines generating different breakover angles. The taper of the fretboard from the nut to the body union will decide string spacing (or, vice versa), which impacts tailpiece width, F-hole spacing, and bridge considerations including electronics below the saddle… no component stands totally alone.
Back to the present, recently my student picked up my personal uke, an archtop baritone, and said “Ahhh, this is the right size for me.” and we chose some side material and got started. We had the body molds already made, and had used them many times. But shortly after bending the sides, I ran into the wall. I had not yet gathered enough information to proceed. I needed a design. Not the general dimensions; but the nitty gritty. It’s not enough to say that we will make the sides out of Mahogany and the soundboard will be Sitka Spruce. I need to know her playing style, the size of her hands, the types of music she wants to excel at. And I need to know exactly what bridge and saddle we will use. I have to either make it, or know that I can make it to certain dimensions. I pulled out a large piece of paper and traced out the mold’s ‘original’ template. I added a basic neck and bridge, marking out where things would lie if she chooses the 14th fret for the body union, or the 15th, or any other reasonable possibility. I made a good size soundhole out of black cardboard to place where we feel best about it, and also a set of F-holes for her to consider. I lightly sketched in probable bracing patterns and tone bars… fan shapes mostly. I looked up the numbers to locate the important frets to aid in decision making… It is her first instrument, and I clearly remember my first as if it were last week, seventeen years and 85 instruments ago. I wanted it to be pure gold plated perfect. It was not. More like pure fun and a good laugh! Very few students know what they are in for… how each early decision leads you to the next, and before you know it, the guitar is building you. I remember asking my mentor Craig for some exact numbers to go by, many times. ‘How thick should the tops be?’ Up to you. ‘Where should my bridge go for best sound?’ I am not sure, he would say… where do you imagine it will be best? ‘How about my string spread?’ Well, you might look at an instrument you admire, and go with that, or do your own thing’. Helpful he was, my good old pal “Yoda”… the keeper of mysteries. But to be fair, it was, and is, up to me.
No one can tell you how to make a great guitar. It’s entirely up to you to find the right combo for your tastes. Design it the best you can. Many folks know that a lighter weight instrument will normally be better at resonance, volume, variety of tones, playability and first impressions, but on the contrary I have personally tested very heavy guitars ( think well over 20 pounds) that sounded wonderful. I did not pretend to think it was possible! But the designer did an excellent job of resolution; he chose his own parameters and made it work. You might have to warn your client that he may want to brace himself as you hand it over, but what a first impression as he strikes the strings! I say that because I test drove that guitar in an empty room, and was amazed. Then I stuck around for twenty minutes and watched as several others got the surprise of their lives as they each took a turn… then they hefted it. Unbelievable that something that heavy sounded about as good as a guitar can.
In the guitar family, the design process of building can be a monumental challenge, especially when you have a new instrument size in mind. But don’t be put off. Much of it will ‘come out in the wash’, like wood thicknesses. If your sides won’t bend around the cutaway because the sides are .100 in. thick, then scrape them down to .080 in the worst of it. If your back is too stiff, keep making it thinner until you like it. If your tuning machines dictate that the headstock has to be 18mm, then choose a slotted head design and thin it side to side. If your ‘axe ‘ is heavy, consider a thinner fretboard, or a thinner neck and heel, or a different style truss rod, or graphite stringers instead… But stick to the basics and don’t deviate. Scale Length, breakover angle, bridge height, soundhole size and placement, weight. And then bring it all together with beauty. Make it pleasing to look at, balanced in substance and also with color and significant features. Compliment the gold tuners with some gold elsewhere; balance that Ebony fretboard with your idea of a headstock veneer, and a pick guard. Choose high quality components, especially tuning machines. The investment is well worth the expense because Playability is still the cornerstone, and likely will always be.
A student, who is a lifetime player and a friend who managed a fine art gallery, Michael Gilbert, shows off his first hand made ukulele.
I find myself running out of words and we haven’t even spoken of electric guitars and how to get some heavy sustain yet… ( hard bodies and long scale length). There are so many possible combos, as said before, that I can’t count that high. I will leave it up to you to decide what is “in” this time, what is not, and what you hope to achieve. As for me, I hope to give my new student all the info she can absorb on the way to making all of those decisions for herself, and I hope to be more helpful when it is my turn to be asked “Hey Rave, how thick should we make this soundboard?” I will confidently blurt out a definitive answer with absolute authority, and then laugh like a crazy person. Then I will explain it all as best I can, assuring her I don’t know a darned thing. I just experiment and take notes.
Best Wishes to all, and thanks for stopping by, Raven J. Ravary, from Fayetteville WV
