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-   -   MARK BLANCHARD Bristlecone [Italian Spruce | Brazilian Rosewood] (https://www.acousticguitarforum.com/forums/showthread.php?t=596397)

iim7V7IM7 12-13-2020 06:53 PM

Rough Bracing
 
Mark was delayed in being able to move ahead with bracing the top due to low humidity conditions in his shop. Now the the % RH is in an acceptable range again, his rough bracing pattern now installed using Red Spruce braces and Brazilian Rosewood bridge plate. The rough braces have a 30’ radius dish.
.
https://hosting.photobucket.com/imag...71961B4BB.jpeg

Alan Carruth 12-13-2020 08:20 PM

Chladni patterns are simply a 'tech' version of 'tap tone' tuning, with the advantage that you get to see the patterns of the resonances. The shapes of the vibration modes gives information about the way mass and stiffness are distributed in the plate, while the pitch is related to the overall ratio of stiffness to weight. Looking at the pitch of a given mode, then, can enable you to get the top to the 'right' thickness; stiff enough to hold up under string tension, and light enough to work well with the limited horsepower.

Looking at the mode shapes can tell you where to remove wood from the plate or the braces to get everything into balance, so to speak, so that the whole top is working well. You can get much of this information from tap tones, but it takes a lot of practice, and it's hard to communicate with other makers. There are also cases where you might not hear something in the tap tone that you'd see in Chladni patterns: the patterns give you more information to work with.

OTOH, tap tone tuning goes very quickly when you know how to do it. I spend hours sometimes tuning the top for a guitar using Chladni patterns, while Dana Bourgeois can tap tune one in a few minutes. There's no one 'right' way to do it; there's just the way that works best for you. ;)

mhw48 12-14-2020 06:52 AM

Quote:

Originally Posted by iim7V7IM7 (Post 6575051)
Mark was delayed in being able to move ahead with bracing the top due to low humidity conditions in his shop. Now the the % RH is in an acceptable range again, his rough bracing pattern now installed using Red Spruce braces and Brazilian Rosewood bridge plate. The rough braces have a 30’ radius dish.
.
https://hosting.photobucket.com/imag...71961B4BB.jpeg

The top bracing looks like an interesting hybrid of "X" and ladder bracing. What's Mark's thinking behind that choice, any idea?

mhw48 12-14-2020 06:58 AM

Quote:

Originally Posted by Alan Carruth (Post 6575127)
Chladni patterns are simply a 'tech' version of 'tap tone' tuning, with the advantage that you get to see the patterns of the resonances. The shapes of the vibration modes gives information about the way mass and stiffness are distributed in the plate, while the pitch is related to the overall ratio of stiffness to weight. Looking at the pitch of a given mode, then, can enable you to get the top to the 'right' thickness; stiff enough to hold up under string tension, and light enough to work well with the limited horsepower.

Looking at the mode shapes can tell you where to remove wood from the plate or the braces to get everything into balance, so to speak, so that the whole top is working well. You can get much of this information from tap tones, but it takes a lot of practice, and it's hard to communicate with other makers. There are also cases where you might not hear something in the tap tone that you'd see in Chladni patterns: the patterns give you more information to work with.

OTOH, tap tone tuning goes very quickly when you know how to do it. I spend hours sometimes tuning the top for a guitar using Chladni patterns, while Dana Bourgeois can tap tune one in a few minutes. There's no one 'right' way to do it; there's just the way that works best for you. ;)

Thanks for a very readable and concise explanation.

iim7V7IM7 12-14-2020 07:23 AM

Quote:

Originally Posted by mhw48 (Post 6575351)
The top bracing looks like an interesting hybrid of "X" and ladder bracing. What's Mark's thinking behind that choice, any idea?

To be honest, I do not know the full method behind the madness. I can ask him. Mark has not always used this bracing pattern. Below I am showing a guitar by Mark closer to 20 years ago (left) and a guitar that he made for me about 5 years ago.

https://hosting.photobucket.com/albu...psluerjpw4.jpg

With Mark's top bracing pattern at a high level, I see some similarities to one of Jean Larivee's top bracing patterns. I also see influence from classical guitar building in his sound hole reinforcement approach and stiffening of his rim linings. I also see with many builders who utilize Chladni patterns to interpret their tops a trend to use of symmetrical bracing patterns.

What I can say is lay people we see a "pattern" and think that is "it", when in fact many subtle factors in the choice of bracing material, the shaping of the braces, the variable top thickness, the dish and rim radius all contribute to how the top as a "system" sounds.

mhw48 12-14-2020 02:04 PM

Quote:

Originally Posted by iim7V7IM7 (Post 6575371)
To be honest, I do not know the full method behind the madness. I can ask him. Mark has not always used this bracing pattern. Below I am showing a guitar by Mark closer to 20 years ago (left) and a guitar that he made for me about 5 years ago.

https://hosting.photobucket.com/albu...psluerjpw4.jpg

With Mark's top bracing pattern at a high level, I see some similarities to one of Jean Larivee's top bracing patterns. I also see influence from classical guitar building in his sound hole reinforcement approach and stiffening of his rim linings. I also see with many builders who utilize Chladni patterns to interpret their tops a trend to use of symmetrical bracing patterns.



What I can say is lay people we see a "pattern" and think that is "it", when in fact many subtle factors in the choice of bracing material, the shaping of the braces, the variable top thickness, the dish and rim radius all contribute to how the top as a "system" sounds.



I wondered if there was some way in which the bracing pattern was influenced by the Chladni patterns. It's interesting to see the evolution of Mark's placement of the braces: One of the things about these build threads that I really enjoy is to get glimpses of how luthiers (at least the best) are willing to rethinking the process, to challenge themselves and are open to discovery.

iim7V7IM7 12-15-2020 03:40 PM

Quote:

Originally Posted by mhw48 (Post 6575755)
I wondered if there was some way in which the bracing pattern was influenced by the Chladni patterns. It's interesting to see the evolution of Mark's placement of the braces: One of the things about these build threads that I really enjoy is to get glimpses of how luthiers (at least the best) are willing to rethinking the process, to challenge themselves and are open to discovery.

In a sense it did to the extent that tops braced with traditional asymmetric “Martinesque” bracing patterns (there, I created a word!) are more difficult to interpret using these techniques. As I mentioned in my earlier post that some builders who use Chladni methods gravitate towards symmetry for easier interpretation of the patterns.

Forgetting Chladni, I think that you will find it is common that across a luthier’s years at their bench they modify their approach. Sometimes they start using traditional approaches and break out later in their careers and other times it is just the opposite (a return to traditional approaches)!

mhw48 12-15-2020 04:42 PM

I like "Martinesque", it’s a good creation!:up:

iim7V7IM7 12-15-2020 07:35 PM

Carving the Top Braces
 
Mark spent a couple of hours removing wood from the braces today. It’s not finished, but he tells me that the Chladni modes are indicating that the top plate/bracing balance is “good ”.

https://hosting.photobucket.com/imag...BD231D8C6.jpeg

The ring and a half mode is well shaped with crisp node lines that form up with fairly low power input from his signal generator/frequency counter. He feels that the frequencies are still a little higher than he wants to see, so he will be removing a little more wood in key places to bring them down while hopefully, retaining the overall balance.

https://hosting.photobucket.com/imag...75EE743A4.jpeg

iim7V7IM7 12-19-2020 07:56 PM

Back Braces
 
Mark has taken a pause in the refinement of the top braces and has moved on to ladder brace the Brazilian Rosewood back while the humidity in his shop supports these operations. He first installs his mahogany back reinforcement strip on his go-bar deck.

https://hosting.photobucket.com/imag...868B4134E.jpeg

He just made 30 new 46” hickory bars for his go-bar deck. Here is a shot of the raw four Red Spruce ladder braces being glued in place on his back dish.

https://hosting.photobucket.com/imag...0C7CFA39F.jpeg

Alan Carruth 12-20-2020 11:24 AM

It's not so much that the patterns are hard to 'interpret' with asymmetric bracing; it's just harder to get symmetric patterns. I started thinking about the double-X pattern I now use during a post-tuning evaluation session with a student. I'd found the more symmetric patterns seemed to work better in producing the sound I was after, and he questioned why we were trying to put a square peg in a round hole, as it were. Since he was also one of my acoustics gurus the opinion carried a lot of weight. As it turns out the 'Martinesque' asymmetric pattern does give a more 'traditional' sound, so it's an option to keep open.

iim7V7IM7 12-20-2020 11:32 AM

Quote:

Originally Posted by Alan Carruth (Post 6581121)
It's not so much that the patterns are hard to 'interpret' with asymmetric bracing; it's just harder to get symmetric patterns. I started thinking about the double-X pattern I now use during a post-tuning evaluation session with a student. I'd found the more symmetric patterns seemed to work better in producing the sound I was after, and he questioned why we were trying to put a square peg in a round hole, as it were. Since he was also one of my acoustics gurus the opinion carried a lot of weight. As it turns out the 'Martinesque' asymmetric pattern does give a more 'traditional' sound, so it's an option to keep open.

Thanks Alan...:up:

mhw48 12-20-2020 12:26 PM

Quote:

Originally Posted by Alan Carruth (Post 6581121)
It's not so much that the patterns are hard to 'interpret' with asymmetric bracing; it's just harder to get symmetric patterns. I started thinking about the double-X pattern I now use during a post-tuning evaluation session with a student. I'd found the more symmetric patterns seemed to work better in producing the sound I was after, and he questioned why we were trying to put a square peg in a round hole, as it were. Since he was also one of my acoustics gurus the opinion carried a lot of weight. As it turns out the 'Martinesque' asymmetric pattern does give a more 'traditional' sound, so it's an option to keep open.

Quote:

Originally Posted by iim7V7IM7 (Post 6581133)
Thanks Alan...:up:

Yes, thanks for your input, and the wise reminder that the aim is the sound. The Chladni patterns -- and bracing patterns -- are valuable means, but not the end in themselves.

iim7V7IM7 12-22-2020 07:39 PM

Back Braces
 
Mark sent me a photo of the Red Spruce ladder braced Brazilian Rosewood back (below). Mark uses a 12’ radius dish.

https://hosting.photobucket.com/imag...267B62E18.jpeg

Mark also told me that he thinks that the top bracing refinement is now complete. After trimming some material from all the braces a little bit and brought what he calls the “ring+ mode” (shown in a prior post) down by about 15 Hz to where he wanted it. He will evaluate the top again tomorrow with a “rested ear” in the morning and run a full set of Chladni modes. If he thinks it is as good as it can be, he will prep it for being glued to the rims.

iim7V7IM7 12-23-2020 12:44 PM

Top is completed
 
After listening to the top with some fresh morning ears and running some confirmatory Chladni modes, Mark has declared the refinement of the Italian Spruce top and its Red Spruce bracing complete. He was kind enough to forward me the pages from his notebook.
  • The braced top ended up being 228 grams (8.0 oz.)
  • The top is thickest between the sound hole and the bridge plate at 0.133” (3.4 mm) and is thinnest near the end block at 0.095” (2.4 mm). Interestingly, the finished top differs about 0.012” (0.3” mm) in thickness across the lower bout from 0.098” to 0.110” (2.5 to 2.8 mm). Mark made the top a little thinner on the low E string side of the lower bout. The idea is to allow a little more mobility on the bass end of the bridge. The height of the lower X-brace arm on the bass side is also slightly less than it is on the treble side. He tries to follow the general rule that the brace heights and top thickness should correlate. The brace heights should be the highest where the top is the thickest, and the lowest where the top is the thinnest.
  • The braces appear to be stiffest near the bridge and taper thinner toward the perimeter/linings. The top is also thickest near the bridge and thinner near the perimeter/linings.

https://hosting.photobucket.com/imag...946916FD5.jpeg

None of measurements likely mean ANYTHING without years of: 1) building guitars, 2) taking measurements during the build process, 3) recording them in a notebook and 4) evaluation of the finished instrument’s sound. Mark told me it wasn’t until he had about 50 guitars using these methods before any correlations to what made one of his guitars “great” guitar and another just “average” guitar began to stand out to him.
  • Mark told me that he knows when it is time to stop carving the top braces because the patterns and frequencies presented match up, more or less, with good examples of his previous work recorded in his notebook.
  • The Chladni patterns can be seen as a surrogate “fingerprint” of the overall structure of a top. It is a reflection of the top’s intrinsic properties, thickness and the impact of the bracing structure.

https://hosting.photobucket.com/imag...3918F1CD1.jpeg

Alan Carruth 12-23-2020 07:17 PM

Yup; looks good!

Mark and I use the same general methods, and get together when we can to bounce ideas off each other. Not nearly as often as I'd like, though.

iim7V7IM7 12-25-2020 08:12 PM

Top to Rims
 
Mark glued the braced Italian Spruce top to the reverse kerfed lined Brazilian Rosewood rims. The rims have a 47’ radius while the braced top has a 30’ radius to the bracing. The rims are still oversized and will be cut down to incorporate a 1” Manzer wedge before being lined and having the back glued on.

https://hosting.photobucket.com/imag...8FCDDF80C.jpeg

https://hosting.photobucket.com/imag...4945E48B1.jpeg

iim7V7IM7 12-27-2020 03:09 PM

Trimming the Rims and Establishing a Wedge
 
This is Mark’s rim trimming set up. Note the X and Y axis arched guides used to establish a dish with his router. Like on his top/side junction where he uses a 47’ radius on the rims with a 30’ dish radius on the top; he uses larger 18’ radius on his rims than what he dishes his back to (12’ radius). My Bristlecone is getting a 1” Manzer wedge for enhanced playing comfort; so the low E string side of the lower bout is only 3-1/2” deep and the high E string side is 4-1/2” deep. He marks target depths on the rims for the wedge and elevates the guitar from beneath on his work-board to establish the angle relative to the router to create the wedge.

https://hosting.photobucket.com/imag...5E33EE5F2.jpeg

iim7V7IM7 12-28-2020 06:55 PM

Back Linings
 
Now that the Brazilian Rosewood rims have been cut to size and radiused, Mark is now is installing some Spanish Cedar reverse kerfed linings. You can see how this is done in two steps. First the kerfed portion of the linings are glued to the rims followed by separate step of gluing on a thin cap.

https://hosting.photobucket.com/imag...C9624B43C.jpeg

iim7V7IM7 12-29-2020 09:00 PM

Linings on and ready to close...
 
Today Mark trimmed off the Spanish Cedar reverse kerfed linings and drilled the holes for the neck bolt and a truss rod access port through the upper transverse brace.

https://hosting.photobucket.com/imag...01701BC7B.jpeg

He also made some clamping molds for both the bridge and fingerboard extension.

https://hosting.photobucket.com/imag...00912D387.jpeg

iim7V7IM7 12-30-2020 11:36 AM

Clamping
 
Mark’s clamping molds conform to the irregular shape on the inside of the guitar and result in him being able to apply much more even clamping pressure when he glues on the bridge and fretboard extension. Both the bridge and the fretboard extension have large surface areas. With these molded cauls on the underside he can apply a lot of clamping pressure without damaging anything. Here’s a photo of the two molds. You can see the impressions of the bridge plate, popsicle brace, X braces, and upper transverse brace. The molding compound is a thick layer of a pasty consistency plaster (Fix-it-all) and backing blocks are 1” plywood.

https://hosting.photobucket.com/imag...8F37F4596.jpeg

iim7V7IM7 01-01-2021 03:13 PM

Neck Blank
 
Mark typically roughs out neck blanks in batches of 8 or 10 at a time. Currently, he is all out of 14-fret length neck blanks, so he started making some more.

The first photo shows 20-year old 3” X 4” X 30” Honduran Mahogany neck blanks and a 12-fret version of the final result.

https://hosting.photobucket.com/imag...5F88BD1B6.jpeg

After cleaning them up and milling the blanks square, neck profile patterns is drawn on to them. Next step is off to the band saw....:)

https://hosting.photobucket.com/imag...BF4D39B6C.jpeg

Eight 14-fret Honduran Mahogany neck blanks are now completed. The two outbound slots to either side of the truss rod slot are to accommodate 1/8” x 3/8” x 18” carbon fiber reinforcement rods.

https://hosting.photobucket.com/imag...F710B26A4.jpeg

iim7V7IM7 01-02-2021 07:42 PM

Neck Support
 
Mark installed one of his patented (US7507887B1) double action truss rods into the Honduran Mahogany neck blank today.

https://patents.google.com/patent/US7507887B1/en

Mark’s truss rods are unique in they have two axial threaded sections with differing pitches. When you turn the adjustment nut, it causes the threaded sections to advance at differing rates changing the length of the rod creating a controlled bend. The mechanism provides extremely fine, controlled adjustment. Mark manufactures and sells them to many luthiers. My guitar from Michael Bashkin has one for example.

The truss rod was capped by an Honduran Mahogany insert. He also epoxied in two supportive 3/8” x 1/8” x 18” carbon fiber bars as well.

https://hosting.photobucket.com/imag...660606838.jpeg

https://hosting.photobucket.com/imag...1870E3A55.jpeg

iim7V7IM7 01-03-2021 02:49 PM

Headstock Veneer
 
Mark has inlayed a Paua Abalone “B” into a book a matched Brazilian Rosewood headstock veneer. He uses alignment pins outside the profile to locate it on the Honduran Mahogany neck blank when gluing it.

https://hosting.photobucket.com/imag...5A31A011C.jpeg

iim7V7IM7 01-04-2021 07:13 PM

Headstock Bindings
 
Mark is fitting some Macassar Ebony binding with curly Koa purfling to the headstock.

https://hosting.photobucket.com/imag...57F1CAA0B.jpeg

iim7V7IM7 01-05-2021 07:34 PM

Headstock veneer done.

https://hosting.photobucket.com/imag...097F35761.jpeg


Fretboard glued on.

https://hosting.photobucket.com/imag...4ADC032FA.jpeg

iim7V7IM7 01-08-2021 07:14 PM

Box is Closed
 
Mark has closed the “box”. You can begin to see just how nice the Brazilian Rosewood set is...:up:

https://hosting.photobucket.com/imag...13C1E547F.jpeg

Rwpierce 01-08-2021 07:59 PM

Absolutely gorgeous back Robert, pretty certain this guitar will sound fabulous!

iim7V7IM7 01-08-2021 09:06 PM

Quote:

Originally Posted by Rwpierce (Post 6599295)
Absolutely gorgeous back Robert, pretty certain this guitar will sound fabulous!

Thanks Rob...:)

iim7V7IM7 01-10-2021 01:36 PM

Truing up the Sides
 
Here’s Mark’s sanding setup for truing up his rims. The horizontal drum sander that you see in the image is actually an attachment for his wood lathe. He is using an aluminum drum has no compliant cushioning, so it does a good job of eliminating irregularities in the sides and it is incapable of reaching into low spots. Care must be taken when using this method to avoid creating “washboard” on the sides.

https://hosting.photobucket.com/imag...766AF280D.jpeg

After the horizontal drum sanding to true up the sides is completed, Mark “hard blocks” the sides by hand with 80 and 120 grit sand paper to eliminate any minor washboard.

https://hosting.photobucket.com/imag...B7A48DDDD.jpeg


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