Official Luthiers Forum!

I just read Nicks’ thread on maple/sycamore topped guitars and thought some of you might be interested in how I approached a recent job requiring a hardwood top.

The commission was for an all koa guitar, to live in DGDGBD tuning, strung 13-56, ultra low action, hyper loud, with sound port and wedge body. Other options included rope binding, slot headstock and custom inlays.

The hyper loud, low action and koa top all seemed rather mutually exclusive, so this was going to force an out-of-the-ordinary approach.

As a guitar’s loudness is closely related to the effective mass of the top, I worked out the mass of a spruce top for the same guitar and took the koa down to that mass, noting its stiffness. It ended up somewhere under 2.00mm thick. Then to support the very wavy short grain figure in the top, I used a classical style (Smallman type) dense lattice in King William Pine and carbon fibre, sized for the steel string loading. So that was the structural design for the top sorted out. There’s a pic below of the almost finished bracing prior to it being topped off with CF. (…and before anyone tells me it’s over-braced, you need to figure out the size and Young’s modulus of the bracing in there… . I can tell you, though, that the bridge mass is 15 gms)



I reckoned this was going to be a pretty lively sounding guitar, so opted for a non-live back to maximise loudness rather than a live back looking for more tonal colour.

The client had an idea for a rosette he liked inspired by one of Michael Dunn’s and you can see how this turned out. The red is bloodwood (Brosimum Rubescens) and the green is English lime that I dyed. The brown is natural EIR.

The fretboard inlays are original scrimshaw of sea life (running with the Hawaiian theme) engraved into fossilized walrus tusk set into the fretboard.

Its new owner has an up-market Gibson J200 and a Takamine Anniversary dread in his stable and in terms of loudness, it was more than capable of running with those two. I had no real idea what to expect tone-wise from an instrument like this, and was very pleasantly surprised. Its acoustic sound I can best describe as a sort of blues crunch tone (slightly over-driven tubes) with lots of headroom and long sustaining high harmonics. The K&Ks captured the acoustic sound very well.

Anyway, the customer was really happy, which is what counts at the end of the day. Here’s how it turned out:

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

I like it

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久保
美智え

Good lord. More guitar porn.
I have GOT to find some of that buttery koa to work with.

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"Act your age, not your shoe size" - Prince

Trevor that's a very interesting thread and the guitar itself is stunning.
Interesting approach, and shows what can be done with hardwood tops.
Beautiful workmanship, on the bracing especially. (to me it's as as beautiful as the top and back woods)
But a sound clip would have been better than a description of the sound! (Hint)
Thanks for taking the trouble to post.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Beautiful guitar but what's the bridge? I assume it's not Ebony or Blackwood to be only 15g.

Kevin Looker

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I'm not a luthier.
I'm just a guy who builds guitars in his basement.
It's better than playing golf.

Well, I think the whole concept is awesome and so are the results. It's interesting how one thread discussion can lead to another. Since you understand the concepts of guitar building that most of us (at least me and a few others) are still trying to pull out of the "white and black" books, you leave us asking for more. If you ran frequency spectrums on this guitar, I would love to see them. And following on a recent thread regarding bridge weight and the fact that you got yours down to 15 grams, I would like to see a close up of the bridge and as Kevin asked, what wood did you use. I've been wondering about using a hardwood top myself, since I seem to have accumulated more back and side sets than tops. I was assuming that you would have to make the top pretty thin, but 2.00 mm doesn't seem too drastic considering. Anyway, outstanding work.

Trevor, another question. Did you do the scrimshaw? I know that ivory can be a controversial topic, but I have some old piano key ivory (1880's) that I purchased a while back and was thinking about scrimshaw as inlay pieces, also have a piece of fossil mastodon ivory pulled out of a Florida river by a local fossil collector. Just wondering.

vy cool,an unique from ,Trev/s gtr shed.

Wow! Excellent work. I am personally not a fan of paddle shaped headstocks, slot head or otherwise, but I have to say that one is beautiful. The adornment and the way you handled the rope binding and the slot ramps is really nice. Love the casual quality of the fret markers too. T

Outstanding!


Ken Jones
Mountain Song Guitars

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Mountain Song Guitars www.mountainsongguitars.com

Very nice Trevore ... excellent all round.

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Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

Trevor, I think it's as fascinating as it is beautiful. The lattice bracing shot left me scratching my forehead in wonderment.
I will say (not as a criticism) that the rope binding seems visually "busy" to me, but that's just my personal taste. If I could execute ANY binding scheme as well as this, I'd be very happy. It's a knock out. Thanks for posting it.

Patrick

WOW!!

That is Beautiful... I love the snappy sound of koa. What about koa as a top wood with back and sides of something else other than koa? Would that work?

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Steve Sollod (pronounced sorta like "Solid")
www.swiftcreekguitars.com

also... No bridge patch?

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Steve Sollod (pronounced sorta like "Solid")
www.swiftcreekguitars.com

Oh man, my eyeballs jumped right out of their sockets!
Love tHe rope binding in particular.

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wah
Wah-wah-wah-wah
Wah

Thanks for all the kind comments. It was a fun guitar to build!

Now to all the questions...
Sorry, no sound clip. My mate who used to help me with recording sadly passed and I haven't found another handy room that gives a decent sound. Plus I only know a couple of slide tunes in DGDGBD tuning so I would need to find a player, too. I'll see if I can persuade the owner...
Ebonised black walnut, with my usual CF sandwich. You can see the CF better in this pic on my website.
Tap response of the finished guitar:
No, not part of my skill-set.
Why not? Many of the constraints in guitar work stem from tradition rather than function.
Yes, but not in that picture (or any other picture for that matter, as I found I hadn't taken a pic of the finished top !) If you look carefully, you'll see two of the pre-drilled bridge pin holes on the second diamond down. That diamond and the two above on either side had rosewood bridge plates dropped in.

Edit: Fixed a broken link

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

Didn't notice that! Did you use CF under the bridge plate sections as usual?

No. The CF in the bridge plate of the falcate design is to raise the cross grain stiffness, because there's no continuous bracing across the centreline other than the bridge. There's plenty of cross grain stiffness in a CF/lattice, so it doesn't really need any more.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

Beautiful guitar Trevor! I like your approach to the top.

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Jim Watts
http://jameswattsguitars.com

Fascinating, as always. Beautiful guitar!

Max

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Max Bishop
Brighton, Michigan

Very beautiful, Trevor!

Ken

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http://www.casperguitar.com

Pretty slick Trevor. I noticed a fairly high saddle. What's your cutoff for saddle height on a brand new build?

How did you handle the mass of the sides to increase loudness?

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It's not what you don't know that hurts you, it's what you do know that's wrong.

Trevor, is it cheating to ask the approximate final dimensions of the braces*? The sycamore's weight and stiffness figures seem quite similar to the koa. I'm guessing 4.6mm wide? 13mm high? Seems barely enough room for bridge pin holes! Pinless bridge is tempting. And I don't know where I'd put a k & k. Seems the middle transducer is difficult to place under the saddle!

I'm also guessing you didn't scallop the centre of the lattice(?)

*I know it's all down to stiffness of the bracing, and the Douglas would be stiffer than the King William, but I can't see myself going much lighter than your bracing here. Thinking abut it, White Willow may be a better choice for bracing than Douglas. Closer in stats to King William anyway. King William 5.8Gpa/350Kg/m^2, White Willow 7.7/400Kh/m^2... Sorry, just thinking aloud now.



Thanks in advance for any clues

I love the rosette. Great design work all around!