Michael McBroom (Houston, TX, USA)
PAGE EIGHT 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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Aug 9 2005, 08:35 PM

OK, it's been a while since I've updated this build, I know. I was hoping to post all the remaining photos, including the completion, but things have been delayed again.

I'm using a different french polishing technique on this build as opposed to my previous guitars. I'm used to being able to complete the french polish quickly with my old way of doing things. But when I try to do the same using this new method, I get patches of dull areas. After discussing this with a friend who's been building guitars and custom furniture longer than I've been alive, I've come to the conclusion that I haven't been allowing the finish to cure fully before attempting to polish it out. So, now the guitar is hanging on a hook in my shop, and will sit there for the next week to fully cure. Grrr. New experience for me. Fortunately Stephen, my client, is a patient soul.

So, anyway, rather than put things off even longer, I thought I'd show what I'd done since my last post. Here goes.

I finished up on the bridge, installing the tieblock inlay. I decided to use a strip of the top purfling to tie in the tieblock theme with the rest of the guitar.

The outer edges of the inlay are a synthetic mammoth ivory material I bought from Texas Knifemakers Supply. I decided to give this stuff a try because it was more uniform than the ivory that they had -- most of it had flaws bad enough across a 5" expanse, which is what I needed, to render it unusable. Plus this synthetic ivory is very hard and dense. It's harder than the mammoth ivory I've used in the past, and while I haven't run any density comparisons between the two materials yet, my bet is it is even denser than the mammoth ivory I've bought in the past.

The only thing kinda tricky about using it is I tried mitreing it the way I mitre wooden purfling -- with a chisel. This stuff chips when I cut it with a chisel. But that's what I used, because I figured a saw would be even worse. Next time, though, I'll give my dovetail saw a try.

Prepped the top for installing the bridge:

I take careful measurements (shown in a photo below) prior to laying down the tape. Obviously. For classicals, I use a 1.5mm (0.060") saddle setback for compensation, along with a nut set-forward of 0.8mm (1/32").

I lay a long ruler down on the fingerboard at the line that the high E string will follow, and make sure that the hole for the E string will coincide exactly with this line. This is an important step. The high E string needs to be set inboard slightly more than the low E (well, on a 6-string at least) because the playing technique of pulling off a note ( a slur downward in pitch), requires a bit more fingerboard, or else the string will slide off the fingerboard, making a nasty squelching noise. So. I want to make sure I have this dimension set up correctly.

Well, strictly speaking, the above comes under the category of "measure twice, cut once," since I'm laying down the ruler to double check things after laying down the blue tape. As does this next photo show. I've already taken the measurements, but the point here is to double check before I commit myself. Now, I know I could by a Stewmac Bridge-O-Matic, or whatever it's called. But why bother?

I butt a machinist square up against the 12th fret and then butt my rule against the square. I use the 1/100" readout on this rule. I know already that the width of my fret material is 0.083". So, the midpoint of the 12th fret is 0.0415" bridgeward from where the square sits. Which means I add 0.04" to the measurement from the 12th fret to the saddle centerline. I add another 0.06" to this dimension for the saddle setback.

This guitar's scale is 660mm, or almost exactly 26". So, the measurement from the 12th fret to the saddle is 330mm (12.99") + 0.04" + 0.06", for a total of 13.09".

Finally, the moment of truth.

And voila. More or less.

The little white specks you see in the finish are actually reflections. I tried filling the pores with less than great success. Maybe better luck next time. So anyway, now I wait for the shellac to fully cure so I can finish this thing at last.

Believe it or don't as a direct result of the 10-string Festival I attended last month, I now have two more 10-string builds ahead of me. I've already started on them. Hope I don't forget how to build 6-strings.


Aug 9 2005, 09:06 PM

Michael, this looks awesome! I am sure you'l get the minor dull patch problem worked out. Congrats on the 2 new 10-string commissions!

Aug 14 2005, 10:05 AM

Nice work Michael:
I am very curious how it will sound. Any chance of posting a wave file for us to hear when its complete?

Aug 14 2005, 11:07 AM

Hi, I'm Stephen Bright, the future owner of McBroom #9. I plan on picking the guitar up this week, and while down in Houston, Michael and I will be making a few movies of the sound of #9 compared to #8. Of course, #8 can be already be heard here (scroll down about 1/2 way):


We will be posting the new movies at cathedralguitar.com as well. We'll let you know.

Btw., it was my idea to use the cross motif in the purfling and the rosette, and when you see the Alessi tuners, the cross motif appears there as well. My main gig has been playing guitar at a 19th C. stone cathedral, and the 10-string fills up the space like no 6-string ever could.

It was also my contention that from a design point of view, today's classical luthiers are mostly conservative and modernistic when it comes to the exterior design of the guitar. So I asked Michael to do this 'purfling run amok' idea to see if it crosses the line into 'too much.' From the pictures, I think it looks great, and I can't wait to see it in person.

Aug 14 2005, 12:57 PM

Nice job Michael!
I think you have found a market. Stay there.

Aug 14 2005, 03:10 PM

Thanks, Steve.

Only problem with the 10-string market is it is a tiny one. Building four 10-strings in a row is very unusual. I figure that your average master classical builder probably builds maybe on the order of one 10-string for every hundred 6-strings that he builds. Maybe that is, at long last, beginning to change, though.

Best, Michael

Aug 14 2005, 03:13 PM


Aug 22 2005, 10:20 PM

Okay, here's the latest, and hopefully concluding post in this thread -- at least as it pertains to the construction of these two guitars.

At long last I have strung up number 9.

This event was delayed almost a month because of a different french polish technique I've been trying to master. I decided to forsake the relatively quick and easy method Brian Burns taught me and instead switch over to the more traditional approach as outlined by Orville and Robert Milburn.

The Milburns' approach did not work out all that well for me. What I came to find out, after weeks of pulling my hair out over a few dull spots in the finish was that these dull spots were due to there not being enough finish in these places. So, purely out of frustration, I reverted back to the technique I've adapted from Brian Burns, and whammo, all of a sudden I'm buffing out the guitar to a nice shine. Grrr. It wasn't a complete waste of time, however. I did pick up several useful pointers from the Milburns that I've since incorporated into my old regimen, and it seems that this combination works best of all.

Okay, so back to the guitar --

Today, I cut the nut and saddle. First, I tried using the synthetic ivory I used to inlay the tieblock. Simply put, it was awful. The guitar sounded like a dud -- dull with no volume. I knew it couldn't be that bad -- not with a Euro spruce top and Brazilian rw back/sides -- so I yanked those two pieces out, and turned to this large plank of Corian I have, courtesy of Manitou, one of the members here. I cut the saddle and nut out of Corian instead, and wow! What a huge difference it made!

BTW, here are a couple of shots of the finished instrument:


Immediately after stringing it up, it sounded rather tight. Number 8, my first 10 string, is louder -- but then it's been strung up for a couple months now, and has gotten played quite a bit. But this guitar has deeper sides, and is more resonant in the basses -- a good thing with a 10-string.
After it had been strung up for a few hours, it began to settle in. It sounds louder and the balance has improved. It has a clear and warm tone -- quite different from number 8.

The top's resonant frequency has dropped from being slightly sharp of G# down to G. So it's a bit boomy when I hit a G, especially 3rd fret, 6th string. I may try shaving one of the braces and see if I can drop the pitch just a tad.

Oh, and just as a reminder, this guitar has a pickup. Man-o-man, it kicks butt through an amp! The basses are positively massive sounding! I hope Stephen likes it. Cuz it's time to move on.

Got two more 10-strings in the works. I'm thinking about doing separate threads for each here, if anyone has an interest, mostly because they're so different. Number 10 is a highly customized instrument, whereas number 11 will be an entry-level no-frills model.

Best, Michael

Aug 22 2005, 11:25 PM

Michael and Stephen:
Nice Work! Great Ideas! Thanks for sharing with us.

Aug 22 2005, 11:34 PM

The guitar looks wonderful. What a far cry from ZEN 1 - which wasn't bad - it's just that this latest 10 string looks great and we know that inside it looks great too because you showed us the whole process.

I for one vote for you showing us every build you care to. I have enjoyed and learned from every one.

So, why is synthetic ivory inferior to corian? Any thoughts?

Aug 23 2005, 08:55 AM

I'm not sure. Even though the synth stuff feels very hard -- it chips easily in fact -- and is pretty dense stuff, I guess it's sound transmission properties are poor. Texas Knife Supply has some other stuff I'm interested in trying. They've got knife handle sets made from camel bone which might be pretty interesting. About $15/set, and I reckon I can get maybe a half dozen saddles and three or four nuts (10-string size, that is) out of each set. Dunno how camel bone compares to cow, but the bone they use is leg bone, and seems to me that, given a camel's rather spindly legs and rather large body size, the leg bones might actually be quite strong.

I don't mind using Corian -- in fact that's all I've used except for a bone saddle on one of my earlier builds -- but I keep hearing from others that bone sounds better, so I really want to give it a try. Problem with cow bone nuts and saddles is I can't find them in the size I need for 10-strings. And I really don't feel like getting a big bone and doing all that cutting myself. One thing I have seen other 10-string builders do is use two-piece nuts and saddles. Seems to me this might work pretty well.
Best, Michael

Aug 23 2005, 09:00 AM

Congrats on another beautiful guitar finished, and I look foreward to the next two.


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