Michael McBroom (Houston, TX, USA)
PAGE FIVE Journal of the construction of two 10-String Guitars

[Michael's journal is an edited conversation with other luthiers at Luthierforum.com. If you wish to comment or ask questions you may either post at Luthierforum (membership required) or email Michael directly.]

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Jun 15 2005, 01:50 PM

Yeah, I have Middleton's book, and I have reviewed his purfling installation techniques. In fact, I have tried out his method of installing the binding, then the purfling on my last two guitars, and this worked out quite well. But this purfling is a different matter altogether. The iron is not gonna do any good -- not if my heating blanked and a caul matched to my mold didn't. I'm still thinking the easiest way to go will be to remove material from the inside radii.
Best, Michael

Jun 15 2005, 02:31 PM

Yesterday, I began working on the bridge. I use my mill to cut the blank down to its rough outer dimensions, and to cut the slots. That's a 3/32" bit I'm using in the second picture to cut the saddle slot and the slot between the tie block and the saddle block.

Bridge dimensions for 10-string classicals are a matter of builder preference, it appears. I have seen a few 10-strings with bridges that are not really any bigger than 6-string bridges. The wings are just shorter and stubbier. I think the concern among the builders, such as Hippner, who prefer the shorter bridges, is that a long bridge may affect the ability of the soundboard to move freely.

Hey, makes sense to me. But reality doesn't seem to support this position. The Ramirez bridge, which is the one I used as a basic template, is 1.5" longer than a standard 6-string bridge, and that longer bridge sure doesn't seem to have an effect on the Ramirez 10-string guitars. The one I owned for many years was quite loud and reasonably well balanced.

Me, I prefer the longer bridge because it is acting as a cross brace and adds cross-grain stiffness to the top. But I want to avoid the extra weight, if at all possible.

So far, I have built three classicals using padauk as a bridge material. I like it because it is reasonably hard, but very light. A typical classical bridge made from EIR usually weighs between 26 and 30 grams. This padauk bridge that I just finished for guitar 8, even though it is 1.5" longer than a typical classical bridge, tips the scales at 16.8 grams.

Almost twice as light.

The EIR bridge in the photo weighs 28 grams. The padauk one below it, not even 17.
For the tie block inlay, I just went with ebony. I like the contrast between ebony and padauk, anyway.

Welp, the neck still needs a little more attention before I begin to apply finish for real. I should be able to complete that today. With a little luck, I can start on the finish tomorrow.
Best, Michael

Jun 15 2005, 10:01 PM

I'm enjoying watching this build (soon to be "these builds".) How well did your countour sanding work out? Was it just a few thousandths here and there?

I know so little about classical guitar construction (though I do have Sloan and Cumpiano/Natelson's books) that I was unaware that anyone used curved braces on classicals. I thought just about everyone making classicals used "classic" construction. (Other than the double-top stuff, and the radial brace guy, and...)

The Padauk looks sharp with the Ebony accents on the tie block. I'm quite surprised that there is that great a difference in density to EIR, I would not have guessed it.

Gonna need an MP3 when these babies are done, and settled in!

Jun 16 2005, 11:21 AM

Hey Dennis,
When you're referring to contour sanding, I take it you're referring to guitar 9's top?

As for the results of shimming my workboard to contour the top, I think it worked out pretty well. I have a dial-indicator setup that I used to check thicknesses after contouring the top, and they were coming out reasonably close to target thicknesses.
As far as I know, Contreras senior was pretty much the only classical builder of note who used curved fan braces. You know, Grant bends his braces for the pattern he uses with his steel-string builds.

I still wonder, though, just how much a classical's sound is dependent upon its bracing design. Of all the great classical builders, there are almost as many different bracing patterns, yet the sound quality differences between the guitars these guys make or have made are not as great, IMO, as the differences in the bracing patterns. Not nearly as great.
Best, Michael

Jun 16 2005, 08:49 PM

Yes, the contour sanding I was talking about was your innovative approach to sanding the top.
Your conclusions on variations in top bracing pattern snot having a remarkable result in sound/tone could be somewhat liberating. Now maybe you'll feel even more confident to experiment on other classicals.  

Jun 16 2005, 09:52 PM

Hehe, Dennis -- truer words haven't been spoken -- for quite a while, at least. If you investigate my earlier builds here, you'll note that I'm not a slave to tradition. I do, in fact, find this large "sweet spot" if you will, to be rather inviting, when it comes to developing bracing patterns.

I'm actually quite happy with the one that I've installed in guitar 8. This same pattern is in my 6th build. One of that guitar's most pleasing characteristics is the sustain that it produces. Its balance is great and its volume is comparable to that of more traditionally braced guitars. But the sustain is remarkable. I'm hopeful that build 8, which uses the same bracing pattern, will show these same properties. That would be fantastic.
Best, Michael

Jun 17 2005, 06:48 AM

Yes, I have read your earlier builds, (especially your Zen), and know that you do not fear innovation. I suppose there's just a chunk of the classical guitar buying public that will always want tradition, and for them, the more deviation from tradition they can see from the outside, the lower the chance they would buy it. But even for that group of buyers, innovations that are hidden from view, like the bracing, are probably not deterrents. Of course, whatever you build for yourself, well, the sky's the limit on innovation. I'm not expecting you to install a whammy bar or LED's in the fingerboard of a classical, but hope you keep on with the spirit of the Zen. For example, I could see you trying a radially braced classical, where the braces are scalloped and the distance to the peaks follow the Fibonacci sequence.

Now that I think of it, that classical with a whammy bar sounds like a great idea!  

p.s. Sorry to veer off the 10 string road. These builds are plenty interesting!

Jun 17 2005, 08:12 AM

Hah, My brother has been playing for 40 years and the inside of a guitar to him amounts to nothing more than a hard place to get a pick out of.  
I kinda like the idea of a classical with strings lit from within by a complicated fiberoptic network, computer driven to respond to the sound frequencies, each note having a different color. 

Jun 17 2005, 10:42 AM

That's what I did with the steel string I built. Dunno if it had much of an effect. I've got some other Fibonacci-based patterns in mind for classicals, however.
Best, Michael

Jun 18 2005, 11:00 PM

Welp, today I finally bit the bullet, sucked it up, and cut the tuners. The Hauser style tuners by Schaller are the ones I selected for guitar 8. As it turns out, for the cleanest installation, there was only one possible way to cut the tuners. My measurements told me that everything should fit up correctly after being cut. But the real world has a way of intruding. The way things wound up, I was left with about a 1/32" gap between the two pieces. I don't consider this excessive, and I still consider the way I cut them to be the most secure method of installing them.

Here's a shot of the tuners still mostly dismantled, after I cut them on my milling machine. 

And after I've assembled them. Notice the two "leftover" tuners. Dunno what I'll do with them. They only have one screw hole each.

Mounted onto the guitar:

Here's a close-up of the joint, showing the gap I'm talking about. Now, I could close the gap next time I build a 10-string by closing the distances between strings 2 and 3 and 8 and 9 by 1/32". But then, only cut Hauser-style Schaller tuners would fit the guitar. I'd rather have the slight gap, just in case one might wish to change out the tuners to a nicer quality set at some later date.

Jun 18 2005, 11:21 PM

Got a little bit of work done on guitar 9 also. I used my bandsaw to cut the neck heel's toe and tongue to approximate shape, then got out the mallet and chisel to hog off some big chunks.

Next, I could have used rasps to bring the heel into the desired contour, but I didn't feel like messing with them this time, so I dug out the Big Blue Bit. Chucked it up in my Dremel Advantage, and got busy.

These bits -- the ones that have the thousands of sharp teeth -- are super aggressive on wood, and make a ton of dust. Because of this, whenever I'm working on wood with one of these bits, I'm doing it outside. Speaking of which, it was 98F outside today. Hot and sweaty and dusty. Fortunately, it was less than 10 minutes that I had to spend out in the heat because of the super aggressive nature of that bit. But still . . .

Back inside my air-conditioned shop, I used a 4-in-hand to rough the heel into an approximate final contour. Glad I have about 0.2" of extra heel length to deal with. You can see at the bottom surface of the heel where the bit wiped across it, leaving a nice divot in the process.

I've roughed out the neck heel enough now where I can turn my attention to other matters. Next is to glue down the headstock veneers and headplate, then cut out the headstock, tuner holes and slots.
Best, Michael
Jun 19 2005, 09:53 AM

M-I can see where the sides are going to go into the block, when you get to this point could you post how you get them to butt the outside of the block(heel) so they look nice and tight?

PS Nice job on those tuners by the way
Jun 19 2005, 12:54 PM

That was a problem I ran into with Guitar 8 -- getting the sides to butt up flush with the neck heel. Problem has to do with the angle of the upper bout where a 10-string neck meets the sides. It's a few degrees greater than where a 6-string neck and sides meet. I failed to account for this, but in the ensuing residual neck heel contouring, this gap has all but disappeared.

For number 9, however, I increased the side slot angle by a few degrees to account for this. I am hopefull this will take care of the "problem."
Now, as to how I actually clamp things down, here's a photo of guitar 8 with the clamps in place:

Note the black grip-style clamp situated behind the big Jorgensen clamp. I have the grip-style clamp applying pressure at the top of the wedges (in this orientation) and the Jorgensen applying pressure at the bottom. When the sides are inserted in place, the wedges stand slightly proud, since the sides are thicker than the kerf from cutting the wedges. So, I just clamp down on the outside flats of the wedges and apply pressure. This forces the sides and heel block to butt up tight with each other -- providing the cut angle is correct, of course 
Best, Michael

Jun 20 2005, 11:49 AM

Too hot to be outside! This should be fun - not punishment. 
The other benefit of the Middleton wedges at the neck is the clearance for rasp work on the heal. I had not seen that before.
Yesterday our RH finally had been hovering around 50 percent long enough that I felt good about bracing the tops and backs of the two I am working on. So far, I do not own a dehumidifier. 

I think you got along very well with those tuners. As long as there are no little burrs to catch a cleaning rag, nobody will ever look at those joints. Nice job.

Jun 22 2005, 04:18 PM

Good point, Steve, and one I failed to point out. With the extra width of the 10-string neck, the extra clearance is nice.
Best, Michael

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