8 String bocote falcate braced nylon string crossover guitar

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johnparchem
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8 String bocote falcate braced nylon string crossover guitar

Post by johnparchem » Sun Jun 03, 2018 6:05 am

I am ready to start cleanup and finish prep on this Bocote\Lutz spruce 8 string crossover commision. The 2 extra strings will be bass strings. I will have to play to see how low to go. The player would like to go down in fourths from the low E. I know I can make the 7th string a D and the 8 string an A and have it sound good with still useful strings. I started with the Gore medium size guitar and adjusted it for 8 nylon strings. The guitar has a 14 fret join, so I made the scale 660 mm to push the saddle down a bit. The neck has close to steel string spacing on a 55 mm nut and typical classical spacing on the bridge. The guitar will be played more like a lead guitar (thus the 14 fret join) than a classical. The player wanted the nylon string sound. It certainly is a somewhat unique instrument. I am interested to hear what it sounds like. I will install a K&K pure pickup, as it will be used in performances.



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Mark McLean
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Re: 8 String bocote falcate braced nylon string crossover guitar

Post by Mark McLean » Mon Jun 04, 2018 5:38 am

I love the design, love the bocote/lutz combination, but I especially love the really blonde colour of the neck timber. What is that? I matches so well with the spruce, contrasts nicely with the bocote.
It is great that you are getting commissions for interesting and unusual designs. But it must be a bit nerve-wracking to be in uncharted territory on a customer's job. I only build for myself - so if my experiments fail it is a private affair.

johnparchem
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Re: 8 String bocote falcate braced nylon string crossover guitar

Post by johnparchem » Fri Jul 06, 2018 6:35 am

Thanks Mark, The neck wood is mahogany, I think the light hit it funny in the picture. I build for a customer, but take no deposits. My thoughts are I will try and if I succeed and they still like it they can buy it. If not well it was just like a private build.

It has been awhile but she is all strung up. I still need a proper set up but she sounds good. Currently I am using .050" and .060" Nylon core silver wound strings for the sub base. They sound good tuned to a D and a B. I have ordered .054" and .064" strings to try and see if I could go down in 4ths from the E to B and F#.

The finish on the body is post cat Royal Lac on system 3 silvertip epoxy pore fill and seal lac. The neck has a gluboost fit and finish CA pore fill -> seal lac - wiped on Royal Lac.

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Dave M
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Re: 8 String bocote falcate braced nylon string crossover guitar

Post by Dave M » Fri Jul 06, 2018 6:51 am

As always nice looking work John.

As always I am interested in the falcate bracing. You presumably beefed it up a bit for the extra strings so I wonder what height you ended up with? I wonder if you have had time yet to look at resonant frequencies, and perhaps particularly with this one, the bridge rotation?
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Dave

johnparchem
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Re: 8 String bocote falcate braced nylon string crossover guitar

Post by johnparchem » Fri Jul 06, 2018 8:05 am

Dave M wrote:
Fri Jul 06, 2018 6:51 am
As always nice looking work John.

As always I am interested in the falcate bracing. You presumably beefed it up a bit for the extra strings so I wonder what height you ended up with? I wonder if you have had time yet to look at resonant frequencies, and perhaps particularly with this one, the bridge rotation?
Thanks, The main falcate braces are 10 mm at their thickest and the secondary braces are 8 mm. I used the classical top number in the equation to get the thickness. Right now I eye ball maybe more than 2 degrees but much less than 5. My saddle still needs to come down a couple of mm so I will measure the angle after I do the setup. The air and top are 80 and 170 Hz. I decided to try for a lower resonance because I had two additional bass strings. I was shooting for 180 hz but the big bridge dropped the tops resonance. The treble string sounds OK now but the guitar has K and K mini pure pickups, so if trebels ends a bit weak the player can bump up them up. The Bass notes are powerful.

I have the full blog of the build on my website http://harvestmoonguitars.com/bocote%208%20string1.htm

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Mark McLean
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Re: 8 String bocote falcate braced nylon string crossover guitar

Post by Mark McLean » Fri Jul 06, 2018 3:37 pm

Looks great. Elegant, but also looks very powerful. It is great that you have mastered the build techniques now, so that you can focus on the challenges of the unique new aspects of each build. Love your work!

Jim watts
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Re: 8 String bocote falcate braced nylon string crossover guitar

Post by Jim watts » Sun Jul 08, 2018 3:33 am

John,
That looks great!
How were you able to drop the main air that low? I'm primarily building with a Hauser plantilla and my air resonance is usually around 102 HZ and I would like to drop it some. Looking at Trevor's sensitivity analysis it looks like sound hole diameter and back stiffness are my knobs, was this you approach? I'd like to get to 95 Hz, maybe 90 Hz if possible.

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