Fiberskyn esraj head replacement

I do work on North Indian instruments quite often; sitar, sarod, tabla, etc. People have asked about replacing the traditional sheep or goat skin with a synthetic material, and now I have the opportunity to test it out.

This esraj had a large chip missing from the bottom rim of the bowl. I removed it, squared the edges, and prepared a piece of cedrela oderata which is an excellent match visually and for strength/weight ratio to patch it.

I shaped the new piece to match the rim, and scraped the excess sheep hide and glue from the gluing area of the rim. The patch ties in to a vertical support beam- one that is VERY sturdy- which will carry the string tension through to the neck. I am very confident this repair will hold, even with the very many strings putting tension on the assembly.

The next step is to test adhesives on the Fiberskyn head. Remo makes this excellent synthetic imitation skin. I chose the ambassador weight which is 10 mil thick. This matched a few samples I measured of the sheepskin from the instrument.

The material is mylar, and I opted to test three adhesives: cyanoacrylate (super glue), E 6000 (an industrial adhesive for exterior gluing on cars- recommended by 'the glue guy' at the hardware store) and long-cure epoxy.

I made a scrap assembly resembling the bowl. First I only glue the pieces to the top side of the rim (not wrapping around the edge for extra strength).

I applied some finger pressure, and both the epoxy and super glue broke wood away before giving up the bond. The E6000 bond broke quite easily; I would say I was only applying ca. 20 pound of finger pressue.

Next, I reglued the samples OVER the edge, to add strength. This mimcs the traditional attachment, and will really test the adhesives. Here is the result:

As you can see, I was able to clamp the mylar clear to the bottom of the channel; I would estimate forces in excess of 250 pounds and both the superglue and epoxy held fast. The mylar stretched to accomodate the pressure, and the glue bond held.

However, the E6000 let go after only a few turns of the clamp. Clearly, E6000 adhesive is not formulated to bond mylar.

I will feel very confident using superglue or epoxy. The epoxy was easier to bond the top of the rim with, so I will probably use it for that purpose. The superglue was much easier to use pulling the extra over the edge: the result also looked cleaner, and since that is the most visible part of the repair, I will probably use superglue for that.

Chromatic kalimba: possible tuning layouts

A customer recently asked me about potential note layouts on chromatic kalimbas.

I have crafted instruments with chromatic notes immediately adjacent, in linear ascending fashion, as well as Hugh Tracey style, where the chromatic notes are on the back surface of the instrument. I have also found a nice way to combine approaches, and essentially take the Hugh Tracey diatonic layout, and add chromatic notes adjacent to each pitch. This gives more pitch separation than the linear layout, but less than the Hugh Tracey arrangement.

I am not a physicist, so I have to go on observation of the work I have done.

I have found instruments with chromatic notes closer to each other to have more pitch separation. C and C# have very few overtones in common, so notes struck tend not to excite their neighbor notes by harmonic resonance. If there is a loss in sustain (from the fact that the note is not supported by sympathetic resonance of nearby notes) it is so minimal as to be not noticeable. And, a well-constructed kalimba could be built using dense woods to enhance sustain and clarity.

Hugh Tracey-style puts triad notes (chords) next to each other, giving a harmonic resonance- a very rich sound where the notes tend to blend into a wash of whatever the scale its tuned to. The harmonic similarity is only skin-deep though; if the instrument is tuned to equal temperament, even the I to V relationships are very slightly out of tune, and have little overtones in common. There will still be more overtones of a similar, if not exactly equal, resonant frequency.

Therefore, my idea is that if you want more of a modal, harmonically rich sound (sounds great, but only in the given mode or key) then go Hugh Tracey style and separate the notes as much as possible by grouping into triads. If you are musically more adventurous (most people using chromatics are!) then use whichever key arrangement gives you better access to the notes- the pitch separation will be there and I don't hear a major loss of resonance or damping by neighbor keys,

It is interesting to note that Zimbabwean mbiras are tuned with ascending scale tones immediately adjacent. The right hand notes are half and whole steps apart. There does not seem to be a problem in terms of richness of sound and resonance there!

Banjo 5th string tunnel (dual)

In creating a banjo for a lefty, I decided to tunnel the 5th string. I realize that this would prohibit the instrument from ever being set up right-handed, save carving a new neck. Anticipating that this banjo will be around long enough to potentially be in the hands of a righty, I decided to add dual 5th string tunnels.

The unused channel does not get in the way, negatively affect tone, etc; it only increases the instruments versatility. I also left the fingerboard a constant width to the nut in order to facilitate.

Here is a view of the brass tubes used for tunneling:

The termination of the rods at the nut end looks like this:

A hole is drilled in the nut to allow the string to escape; if the instrument is ever retrofitted for a R.H. player, a new nut would simply be made with the hole drilled on the other side.

Here is a view of the brass tubing exiting the fingerboard just before the 5th fret:

As you can see, I have inserted .020 wound strings in to the hole. These prevent the tubes from crushing during bending, and as you pull them out, clear out any debris or adhesive that may have got in. This fingerboard is ebony, bound in cherry and ebony.

Antique Stanley Pullshave

At the Picadilly Flea Market today (Eugene, OR) I scored this Stanley tool- the seller called it a pull scraper, but I believe it is probably better known as a pullshave. Veritas and Stanley both make modern versions of this tool, but I couldn't seem to find any pictures or references to this old Stanley model, presumably antique.


I know furniture builders use this type of tool to hollow out the inner curve of a chair seat, and wooden boatbuilders would also find it useful for all of the inner curves they work with. I am thinking it could come in handy for luthiery, either in carving necks where I use a spokeshave quite a bit, or in hollowing out the inside of an archtop soundboard.


The modern versions offer an improvement in the addition of a handle above the blade- this would give more control of the cut. At any rate, I think once I tune it up it should be a joy to use! The handle is very comfortable and feels massive- like it has the right mass to balance a steady pull.

I also think its cool that at least two tools in daily use- the vegetable peeler and the shaving razor- operate on the exact same principle. It somehow makes using these tools that much more comfortable.

MYRTLE

Myrtle is a wonderful wood to work with. I used to bend it wet, but I have found that bending with no water actually works better- you get little to no cupping effect, whereas when I've used is wet it has often cupped quite a bit (not unlike maple).

Tonally, it seems to be bright and reverberant. I think it supports a crispness in the sound, and seems overall brighter than mahogany or walnut. I don't think that the bass suffers though- the high frequencies enhance the definition of the bass tones, and possibly the sustain as well.

Take this all with a grain of salt of course- I believe that most of the voice of the guitar comes from the bracing design and execution above wood choice, by a large amount. The wood just seems to accent or reinforce certain tonal aspects more than others depending on the species.

INSTRUMENT VOICING

The most useful technique I have found is what I would describe as a sort of creative process of imagining the sound transformed by guitar strings/tension. If you tap every piece of wood regularly as you shape and construct the guitar, and also tap parts of completed instruments and various instruments you own, you begin to develop a sense of what the wood sounds like, and how that sound interacts with the vibration of strings under tension. As you refine this perceptive ability, you can begin to creatively imagine how each part will sound in the completed instrument by tapping as you work on it.

More specifically, by tapping I mean holding the piece of wood approx. 1/9 of the length in from the edge, lightly pinched between two fingers. This is derived from Young's modulus, or the vibration of free bars (which most pieces of wood resemble before being glued into a box shape). Each piece of wood will sound different, and some are more musical than others.

For example, dense wood such as rosewood and ebony tend to have a loud and clear pitch, like a marimba bar. Softer or less dry woods will have a muted, unclear note, and most other woods are somewhere else in between. I believe that all pieces of wood in an instrument contribute (even if an imperceptibly small amount) to the overall musical vibration/resonance, so in a handcrafted instrument it is essential to select the most musical sounding wood, or to shape the piece sin such a way as to accent that characteristic, regardless of the species.

Good compilation of tonewood sources

http://www.coneguitar.com/tonewood.html

Thanks Cone Guitars for this thorough list.

Oregon locals should add:

Urban Lumber
2440 Main Street
Springfield, OR 97477

(541) 988-9663

Apple wood as tone wood for bouzouki

Lately I've been experimenting with apple wood as tonewood. It compares in density with cherry, a bit softer than maple, beautiful color, and is stiff and musical when tapped.

Apple tonewood is all but impossible to come by. About 6 years ago I had a huge (almost 4' diameter) apple felled in my back yard. I had it milled and dehumidifier kilned, and then it air dried for about 5 years. Just now, it is coming into it's own sound-wise- I resawed a piece of it and the nice tap tone made me want to try building with it.

Here is an Irish bouzouki I recently built with the apple from my yard.:

The sides bent easily and the wood has a smooth surface feel that takes finish beautifully. I am also encouraged by the tone- I would say it is more in the warm type of tonewoods like mahogany or walnut, but it also seems to have clarity and sustain in the high register. It's actually right in the pocket of what I seem to go for- granted design, bracing and top wood play a much more substantial role in the equation, but the apple seems well suited for stringed instruments.