Thursday, November 17, 2011
Monday, November 14, 2011
The repair cost would come perilously close to the retail value of the instrument. Now. If the rod had been installed the other way - adjustable at the head, then there's a good chance I could have drilled it, hooked it with some pliers and pulled it out. At the very least I would have been able to release some of the tension hopefully making it playable.
Preserving strength around the headstock is a thoughtful design feature, but in this case it has made repair economically unfeasible.
Sunday, October 2, 2011
Friday, September 23, 2011
The back and front, ground in place and ready for body coats of reddish-brown varnish.
Tuesday, September 13, 2011
Monday, August 29, 2011
Friday, August 26, 2011
The inserts are set a little deeper than the surface of the neck to allow for some material removal if at some point it becomes necessary to change the angle. I don't see this as an eventuality, but I like to make repairs as easy as possible. Having done some tests with these inserts, I have every confidence in their ability to hold, even in end-grain. I did a test once where I suspended a cord through an eye-bolt (in mahogany) and stepped on it like a rope-ladder. I'm the biggest guy I know, and it held just fine.
Tuesday, August 23, 2011
Here's the assembled rim structure. For reference sake, it's about 12" (300mm) long, and almost as wide. I fashioned the end blocks from Douglas fir and you can see I've drilled them out to reduce weight. It may be difficult to see, but they are also curved slightly to reduce the possibility of standing waves in the finished box. (Caused when sound bounces repeatedly between two parallel surfaces.)
I rarely use my adjustable spherical workboard for guitars, but this seemed a good opportunity to put it to use. It's made from plywood and 1/4" hardboard tensioned with a machine screw. By cranking down the screw the radius is increased. I went ahead and pushed it to the limit - it's capable of a 10' radius, which would be extreme on a guitar. I'm thinking of this Morin Khuur as more of a flat-topped viola.
After scribing the contour of the form on the ribs, I went planed it down to an approximate fit.
Sunday, August 21, 2011
The idea took root. These instruments are associated with the Tuvan culture. Tuvan music is characterized by peculiar modal octave harmonies. You may be familiar with the Mongolian throat-singing tradition I decided on the Morin Khuur, which loosely translates to "Horse-head fiddle". It has two strings and is bowed something like a viol, being held between the knees . What's really interesting is that the strings aren't stopped on the surface of the board, but "pinched" against the side of the fingernail or fingertip. The sound produced is a shimmering raspy tone. It's evocative of wind and wide open spaces.
I've finished the rough work and will undertake assembly this week. As it happens, I managed to find all the materials necessary in my cast-off pile. There's a good stiff Sitka top, bigleaf maple for the sides and back, (rejected as guitar sides due to a knot), some rock maple for the neck and pegbox, and a slice of rosewood for the fingerboard. So far the only thing I've had to purchase was a piece of steel to reinforce the neck. It feels good "salvaging" these woods.
I'll document the assembly in coming days.
Monday, March 21, 2011
Space is always an issue. My shop is as small as some walk-in closets. Machinery has to be compact and portable. This limits me sometimes to "home handyman" items. That being said, I look for good value.
This little jointer is from Sears in the USA. It isn't available in Canadian retail locations, but ordering online was easy - Sears is using an online customs broker which means I don't get hit for duty fees at the time of delivery. That's a nice touch. It arrived within a week.
This model (351.217890) has a 4-1/8" capacity. Small? Yes. But that's wide enough for my purposes. The main feature that drew me to this machine was the lapped granite bed and fence. The major failing with all these little benchtop machines is warped castings. The customer feedback on this one was five stars. I felt safe taking the plunge.
Assembly was quick - just screwing some brackets in place and affixing the fence. The fence pivots to 45 degrees, a feature I'm not likely to use so I screwed things down firmly at right angles. What do you know! - It was both square and flat. The depth adjustment had me scratching me head until I discovered the locking knob on the back side of the machine.
In this price range, there's no hoping for a fence that slides across the bed. If I was edge-jointing 3/4" stock continuously I might devise a plywood arrangement to slip over the fence and move the cut forward to prevent all the wear happening in the same location on the blades.
I took it for a maiden voyage using some Douglas fir scrap. The universal motor whines in the usual fashion but at least the cutter head is belt driven.
There seems to be an onboard impeller that sends the shavings flying . I'll need to buy an adapter to perfect the fit between my shop vac and the dust port.
The lines on the face of the board are from rough planing. The joined edge came out dead straight over 15". I was pleased.
Time for something more challenging. Here's a neck blank about 3-1/2" (88mm) wide. It's Honduran mahogany with some ribbon figure and a twist in the grain.
And voila! Shimmering clean. There are a couple of little burnish marks from where I'd neglected to wipe the shipping oil off the edge of the machine. The 29" board came out nice and flat.
Tuesday, March 8, 2011
(him) "I'll never use maple again, it sounds awful! There's hardly any sound."
(me) "Are you sure it's the maple?"
(him) "It has to be. The first one I made I used rosewood. It's twice as loud."
(me -resisting the urge to point out that a jackhammer is loud too...) "Let me have a look at it. "
Upon inspection I could see where things had gone off the rails. The finish work was good, as was the action. The bridge however, was very low - only about 1/4" (6mm) high. This, coupled with the beginners propensity to leave things a bit thick (just in case!) had produced an instrument with the resonant properties of a solid-body electric guitar sans amplifier.
We talked about it for a while. He had the makings of a half-decent flamenco instrument, if he wanted to strip the top and scrape the periphery down to make it more responsive. Or, if he was set on a classical sound, the other option involved loosening the bindings around neck end of the back and trying to pry it free from the heel block. With some clamping pressure and a little luck, he might be able to deform the box enough to tip the heel back a degree or two. He said he'd give it some thought.
I think the most vexing thing about the situation was that he'd done nothing wrong. He'd been very conscious about following all the instructions in the manual. Unfortunately, most of the literature available to beginners just doesn't address this issue. "Standard" dimensions are given, and things just sort of come together. Unless they don't. Most of them expect the maker to go ahead and fashion the standard bridge without measuring the geometry of their instrument as it exists. I wonder how many bridges have been discarded when it was found that they produced unplayable guitars?
What are the two factors that should most interest a guitar player? Sound and playability. (In reality cosmetics play a key role, probably more than any of us might like to imagine).
Think about this: the difference between a "flamenco" instrument and a "classical" one is a matter of two millimeters. That's the difference in height of the strings above the soundboard. Classical guitars usually have a height of between ten and 12 millimeters, flamenco guitars - more like 7-9mm. These measurements include the height of the protruding bridge bone.
Interestingly, 2mm is also the difference between "good" action, and unplayable. These measurements are directly tied to one another. Two little millimeters between success and failure.
I have a large collection of reference books. I think it's safe to say that if there's an English-language guitar construction manual I have owned it or have read it. What's amazing is that most describe the design process for the beginner in terms of the face-view of the guitar. They give average measurements for string spacing, scale length, fingerboard and body lengths. None describe a method for predicting the action of an instrument.
If I were teaching a class in construction, I think I would have students begin by drawing a simple plan view of the geometry of the bridge, action, and string lengths. Will there be a dome or arch in the top? How high? Will the fingerboard remain a constant thickness from nut to sound hole? Will the neck be pitched forward or in plane with the soundboard? What are the requirements in terms of action and string height? And what will happen if I change the thickness of my fretboard from 6mm to 5? This is the dynamic geometry that underlies the instrument. In many ways it's more important than bracing schemes or top material.
Here's a sample drawing detailing the differences between my classical and flamenco set-ups:
The tolerances are pretty close. If things are glued up and something did go wrong, it's important to realize that there's only about a millimeter of adjustment in action available to us in the saddle bone. If we're savvy, we can gain an extra half-millimeter by planing the fretboard in one direction or another. Reducing it in thickness by one millimeter at the nut end, for instance, will raise the convergence point with the saddle by a millimeter - the twelfth fret becomes the theoretical pivot point.
What's nice about the Spanish method of construction, using a workboard and having the guitar neck in place, is that this tricky geometry can be locked in and clamped down. Assuming things are kept square and measurements are accurate, there shouldn't be more than .5mm deviation in any direction, well within the adjustment tolerances of the standard set-up.
Monday, January 31, 2011
But, that said, I look forward to writing more frequently. And thanks to all who've been so supportive. :)