Acoustic Guitar Construction in the small shop -- Kenneth Michael Guitars LLC

Information, ideas and help for those constructing scratch built acoustic guitars or acoustic guitar kits - © 2017
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PostPosted: Sat Feb 03, 2018 8:32 pm 
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Understood, thx.

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PostPosted: Wed Feb 07, 2018 2:22 am 
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Location: Seattle
Little by little I am making progress. I carved the tertiary braces all that remains is the upper transverse brace and capping the braces with CF. I decided to install the CF and the transverse brace in one glue up session.

You can see in the picture below that the falcate braces and two of the sound hole brace inlet into the upper transverse brace. I position the brace and use a scalpel to mark the brace from both sides.

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Lining up the brace

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I used my fancy new depth marker to transfer the height of each of the tops braces to the corresponding location on the transfer brace

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I control the depth of the cut with the jaws of the vice by setting the brace in the vice to the depth marks. Then I just saw and use a chisel to clear out the channel.

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It fit!
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I clamped the top on to the solera to push the lower bout into the 2 mm dish on the solera. Using a paint brush I applied epoxy to the top of the braces. I wetted the CF tow and applied it to each of the braces. I also used epoxy to glue down the upper transverse brace. Given that I was not using CF I could have used titebond on the upper transverse brace. But I had enough epoxy ...

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Spent some quality time with a chisel and plane to shape roughly shape the upper transverse brace.

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Cleaned the transverse brace up with sandpaper and trimed the ends to length.

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The next step was to install reversed kerfed linings for the top. You will notice that I prebend the linings by spraying them with water and clamping the to the rims. I do not break them as often with this technique.

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I decided to add side mass mounts to this guitar. They take me an extra 20 minutes to add and they provide the opportunity to tune the top resonance down a few Hz or more by add mass.

I use brass inserts. I like the one shown in the picture. They are self tapping and have a thread that can even hold in end grain. (I still apply so thin CA to the outside once installed

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I sand them to match the rims

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Not shown but I inlet them into the kerfed linings a few mms. and just used LMI instrument glue to glue them to the rims.

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The the mass mounts installed I added the fancy AST A4 kerfed linings. I like it as it bends in 4 directions. The 10' radius on the back is a doable pain with other kerfed linings. Also I like the look in the guitar.

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Enough for today.

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PostPosted: Wed Feb 07, 2018 10:27 am 
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This is a good construction log, thanks for going into this kind of detail.

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PostPosted: Wed Feb 07, 2018 11:47 am 
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Location: Creedmoor, NC
John, would you say this bracing pattern has some similarities to the new Taylor "V" bracing design?

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PostPosted: Wed Feb 07, 2018 12:26 pm 
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Location: Seattle
Tim Benware wrote:
John, would you say this bracing pattern has some similarities to the new Taylor "V" bracing design?


I think the one similarity is that it removes the cross of the X brace. Right at the cross of an X brace the contribution to stiffness to the pair of braces to the top halves; basically creating a discontinuity, not a bad thing but I think it can be heard in how the top responds. Having said that I think the falcate patten is more like an X brace pattern with the cross removed. Both the X braces and the pair of falcate braces terminate high in the upper bout and do not use a lower transverse brace to carry the string load. I make both X brace and falcate braced SS guitar. There are some who like the clean sound, a clarity in all of the notes played across the string, I get from the falcate and there are others who like the more complex response from the X brace. Also all of my falcate instruments sustain forever. Yet they are all loud guitars. One bit of feedback I got from my classical guitar instructor is my falcate SS sounds and responded like a powerful classical guitar. He had me build a falcate classical guitar after playing my falcate steel string; after more than a year it is still his primary guitar.

I wrote all of that about the classical because I see that the V brace, like most classical guitars, relies on a pretty stout lower transverse brace for structural reasons. So to me the V brace bracing pattern more closely resembles a classical fan brace design. So when the V brace market talks about more even intonation (does not make a lot of sense) they may really be hearing the clarity of removing the structural discontinuity at the cross of the major braces.

So those who like the X brace sound may not be happy with the Taylor. Probably not a Bluegrass guitar. Could be a good finger picker guitar.

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PostPosted: Sun Feb 11, 2018 12:37 pm 
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Location: Seattle
I have the guitar closed. I need to put it up for today and prepare the shop for a plate joining demonstration I am giving to the the Seattle Luthiers Group. Here is how I got there -

When I installed the tops reversed kerfed linings I left the space for the tops upper transverse bar. So with the rims complete I started to prepare for gluing on the top. I was careful when I install the linings but I did go around with a plane to make sure the linings matched the all ready profiled top. I had a minimal amount of work as I have been working on the solera the entire time. I cleaned up some of the CF tails off the braces so they would not fall under the linings. Also most importantly I made sure I knew where a straight neck lined up with the solera. When I work on a solaria the side to side angle is set when I glue on the top the tilt angle of the neck is set when I glue on the back. Setting the neck angle working on a solera with a spanish neck is much simpler than a bolt on or a dovetail neck. With the slots in the neck heel block you start with a perfect joint to the rims. Then you just need to position the neck when gluing on first the top and then the back. I will have more when I glue on the back.

Checking the neck alignment.

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Everything ready to glue the rims and the neck to the top. Unfortunately I did not take of the actual glue up but imagine the following picture and lots of cam clamps.

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After the glue up

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To clean up and installation of the kerfed linings and most important prepare to set the neck angle I put the body back on the solera with the neck clamped in the correct position. My solera has the neck angle planed in, so with the body in the solera and the neck clamped to the solera the front on the guitar top and neck are held in the correct position. With this position I cleaned up the linings and the spanish foot on the heel with my back radius disk (I use a 10' but 15' is more common.) When I have completed profiling the back the rims and the spanish heel will all be on the same sphere section ready for the back.

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With the body ready for the back I braced the back. The pattern I use is for a live back from the plans included in the Gore/Gilet Build volume. I start by laying out the back braces using the previously profiled back stock. They are profiled to the gabled house shape.

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As mentioned above I use a 10' radius. The 10' radius when making an active back allow one to gain back some stiffness after thinning the plate to reduce mass. It does help and of course there are limits. The 10' radius is quite a curve especially when gluing down the linings. You will see in the picture how much of the longer brace needs to be removed to apply the radius.

I start out by first drawing on the radius to the bottom of the brace. I plane the brace to the line and clean it up by sanding in my radius stick.

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I usually use my vacuum box to glue to glue on the back braces but I have had problem with the severe radius. This time I used my gobar deck stealing an idea I think I saw on The Luthier Community forum. I made a bunch of gluing culls using scrap from my profiled back braces. Basically gluing two together at their base provides a perfect shape for the profiled braces.

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The bracing pattern includes radial braces as well. I used two glue ups as there are only some many gobars that I can deal with before I start popping them out.

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I profile all of the braces to 2 mm on the ends. To make this really easy I have a 2 mm template that I use to both protect the back and to know when to stop. With the template in place it takes well less than a minute to profile each brace.

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With the back positioned I used a scalpel to tightly mark where the braces come through. A straight edge to connect the scalpel marks. I use a pencil mill grinder to route out rebates for the brace ends in the linings.

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With the back fitted, I rechecked the backs alignment. Not shown but I pulled the body out of the mold to make sure the back joint reinforcement strip would not end up under the heel slipper. With everything good I glued on the back.

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