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  #91  
Old 12-09-2018, 09:15 PM
printer2 printer2 is offline
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Originally Posted by Tim McKnight View Post
Observant eye there Neil. I made this jig out of similar material as a plastic cutting board. The material’s proper name is UHMW plastic and it is indeed impervious to glue adherence.
I found a few slabs of it at work when we were renovating an area. Naturally I grabbed a couple of them. Darn heavy.
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  #92  
Old 12-10-2018, 06:36 AM
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Originally Posted by David Wren View Post
I now officially have fingerboard-binding-jig envy!
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Originally Posted by j. Kinnaird View Post
I like that binding jig. I want one.


I think I saw a similar jig on your thread David or maybe it was yours John? It appears yours may not be adjustable? I had thought about making a wedge type jig but when I considered that I make various FB tapers then I would need several jigs. Therefore, I made mine so one side of the jig slides so its infinitely adjustable. Its actually worked our better than expected for a first attempt. If I changed anything I would add a couple of affixed thumbscrews, which would eliminate the need of the two Quick Grip clamps.



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Originally Posted by printer2 View Post
I found a few slabs of it at work when we were renovating an area. Naturally I grabbed a couple of them. Darn heavy.
That's quick thinking Fred. UHMW comes in handy for making a plethora of jigs. It works well too for vacuum jigs to since its so dense vacuum doesn't permeate it either. Rubber vacuum tape sticks really well to UHMW and you can make a variety of double sided vacuum chuck clamps to hold down work pieces to workbenches and other solid surfaces.
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  #93  
Old 12-11-2018, 05:55 AM
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And the "back goes on" ....










... and the "back goes on ... nah na, nah na, nahhhh"










Sorry for the out of tune singing but ... I've just got this weird song in my head this morning...
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  #94  
Old 12-11-2018, 07:29 AM
Neil K Walk Neil K Walk is offline
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Interesting...

As one who has come to appreciate what goes into making acoustic guitars and tinkering in general I'm noticing something: you're gluing the sides to the back, not vice versa - and the sides aren't even in a mold. I like that approach as it allows you to see how much contact there is with the kerfed lining, but I have to ask: do you have a radius dish or some other sort of jig underneath to act as a support to the radius that is sanded into the kerfed lining?

I only ask because I've struggled with the justification for having a radius dish for my limited need and have been looking for alternatives - such as spool clamps, which wouldn't be as effective since IME the sides that have built thus far are not rigid enough at this point to live outside the mold.
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  #95  
Old 12-11-2018, 12:56 PM
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Good questions Neil. I prefer to glue the back on first because this allows me to easily clean the glue squeeze out along the interior perimeter of the linings. If I were to glue the back on inverted glue clean up would be more difficult. This method also allows me to see the contact of the back to the sides. Yes, there is a 15í diamter circular radius dish beneath the white circular sheet of UHMW plastic. The .060Ē thick UHMW sheet prevents the back from sticking to the radius dish.

Since I've already dish sanded the correct angle into the sides and kerfed linings, while the rim was secured in the body mold, there is no longer a need to keep the rim within the body mold. The Go-bar sticks hold downward pressure on the rim forcing it into the back and radius dish below, which allows the rim to be perfectly aligned with the mating glue surfaces.

I hope that makes sense?
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  #96  
Old 12-12-2018, 06:22 AM
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After the back is glued on we trim rout the back's overhand so its flush to the sides.










Carbon fiber buttress braces are anchored at the stiffest area of the guitar's body, the apex of the waist, and terminate at the top of the neck block.
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  #97  
Old 12-12-2018, 12:15 PM
Knives&Guitars Knives&Guitars is offline
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Originally Posted by Tim McKnight View Post
After the back is glued on we trim rout the back's overhand so its flush to the sides.









Carbon fiber buttress braces are anchored at the stiffest area of the guitar's body, the apex of the waist, and terminate at the top of the neck block.
Would love to hear more about these carbon fiber rods and how they aid the guitars sound:
* Is this something that You came Up with?
** I would assume that part of the function is to further strengthen the sides so that the back can work more freely?
*** Or are there other reasons?
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Old 12-12-2018, 06:31 PM
Neil K Walk Neil K Walk is offline
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IIRC the rods are meant to structurally stabilize the neck block and/or the upper bout in general. Their effect on tone is that it allows him to brace the sound board more lightly.
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  #99  
Old 12-12-2018, 07:04 PM
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Originally Posted by Knives&Guitars View Post
Would love to hear more about these carbon fiber rods and how they aid the guitars sound:
* Is this something that You came Up with?
** I would assume that part of the function is to further strengthen the sides so that the back can work more freely?
*** Or are there other reasons?
Several years ago, we received an order for our first 12 string and it was keeping me up at nights trying to engineer a solution to counteract the added string force on the guitar, while still maintaining our super light build philosophy. The top is under compression forces, from the strings, trying to fold itself into the sound hole and these compression forces are much higher on a 12 string. These stresses also apply a rotational torque or moment around the neck block, which the neck is mounted to. This moment, originating from the strings compression and tension forces, loads the neck joint which eventually distorts the top, rim, back and ultimately leads to a need for a neck reset.

It was in the middle of the night it dawned on me that if I could redirect that moment into the stiffest point on the guitar (the apex of the waist) it would stop the rotational torque on the neck block. It would in turn stop the deformation of the body which would negate the need for a neck reset. The idea of my buttress braces was born, at least in my mind.

I thought I had developed something new but later I learned a few other builders had come up with very similar designs and my bubble was broken. Oh well, just goes to prove there is rarely anything new under the sun...

My first design was quite unique and brings a smile to my face when I think back. It’s been said that necessity is the mother of invention. Since I needed some light tubular buttress braces the only thing I had at hand was an old 2 and 3 iron. I cut the two [steel] golf club shafts to the correct length and they were subsequently used for my first 12 string buttress braces and that 12 string guitar is still going strong today with no hint of neck movement, action change or body deformation. Since then we have used carbon fiber hollow tubes exclusively, as a weight savings over the previous steel golf club shafts.

My original design was intended to be purely structural but I have a hunch that there are some tonal benefits too but I don’t have any data to back it up so the following is strictly my opinion and YMMV. Since the top, above the soundhole, is under a lot less string compression my gut says it has to vibrate differently. I have put a ToneRite on two similar guitars, one with and one without buttress braces, and then I ran my fingertips all over the top. Above the soundhole one can clearly feel that the top vibrates more aggressively on the buttress braced guitar. There are scientific ways to measure the difference between guitars but I’ve never had the time nor the tools to do so. For now, I’ll rely on tactile feedback and let players relate their positive experiences to us.

The buttress braces don’t strengthen the sides IMO. I do think they help to relieve some of the tension stresses in the back because the back’s radius is trying to flatten due to the tension stress induced by the rotating neck block. Since the buttress braces have stopped the rotation of the neck block it has to relieve tension stress on the back. Therefore, it stands to reason that the back could vibrate with less tension or restriction.

Before the top is joined to the rim and back I can easily deflect the neck block area. It’s very flexible as is the tail block. You can grab a hold of each block and flex them towards each other quite easily. However, after adding the buttress braces I can literally stand on the neck block and it does NOT move. It’s amazing how these two little carbon fiber tubes stiffen the neck block. But then again, the simple triangle is the stiffest geometric shape found in nature.

John Kinnaird recently starting using similar buttress braces in his guitars. Perhaps he will drop by and voice his opinion and experience since he’s started using them?
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Last edited by Tim McKnight; 12-13-2018 at 07:26 AM.
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  #100  
Old 12-13-2018, 07:29 AM
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Originally Posted by Neil K Walk View Post
IIRC the rods are meant to structurally stabilize the neck block and/or the upper bout in general. Their effect on tone is that it allows him to brace the sound board more lightly.
Your reply is spot on Neil. Thanks for mentioning that I do brace the soundboard much lighter now since using the buttress braces.
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  #101  
Old 12-13-2018, 07:48 AM
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Yes indeed, I have been following Tim’s example and bracing the neck block with the carbon fiber rods pretty much the way Tim does it. As has already been said, this relieves the top from structural responsibilities and allows the builder to brace it lighter for more resonance. It seems to me that my recent guitars using this design have been louder and more sensitive.

I am gravitating toward a cantilevered fingerboard extension so that the fingerboard does not glue to the top and this helps free things up even more.
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  #102  
Old 12-13-2018, 10:01 AM
Knives&Guitars Knives&Guitars is offline
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Originally Posted by Tim McKnight View Post
Your reply is spot on Neil. Thanks for mentioning that I do brace the soundboard much lighter now since using the buttress braces.
Truly we live in an age of discovery for the Acoustic guitar. All of this is so exciting to myself. Coming from years past where most guitars were made with just slight differences from one another. Now we have a new generation of exotic woods, different bracing patterns and techniques, new body sizes and shapes, and new techniques for enhancing resonance.
Who doesn't want more resonance? Certainly not me. I thrive on as much as I can get.
We also live in an age where the classical guitarist and the steel string guitarist have crossed over into each others territories. I myself like to combine heavy finger style with heavy strumming intermixed. From what I know, most of today's modern finger-stylist use light gauge strings.
*Are the braces the only part of the top that is lightened? Or is the top itself also thinner?
** Will a lighter braced top still be able to take medium gauge strings? Even a custom set with some heavy gauge strings thrown in? I would assume the answer might be that lighter gauge strings might give the sound of medium gauge on a lighter braced top? But some of us play with medium gauge due to how the strings react for heavy strumming.
*** With more resonance does headroom remain the same. Or is it even more?
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  #103  
Old 12-14-2018, 08:37 AM
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Originally Posted by Knives&Guitars View Post
Truly we live in an age of discovery for the Acoustic guitar. All of this is so exciting to myself. Coming from years past where most guitars were made with just slight differences from one another. Now we have a new generation of exotic woods, different bracing patterns and techniques, new body sizes and shapes, and new techniques for enhancing resonance.
Who doesn't want more resonance? Certainly not me. I thrive on as much as I can get.
We also live in an age where the classical guitarist and the steel string guitarist have crossed over into each others territories. I myself like to combine heavy finger style with heavy strumming intermixed. From what I know, most of today's modern finger-stylist use light gauge strings.
*Are the braces the only part of the top that is lightened? Or is the top itself also thinner?
** Will a lighter braced top still be able to take medium gauge strings? Even a custom set with some heavy gauge strings thrown in? I would assume the answer might be that lighter gauge strings might give the sound of medium gauge on a lighter braced top? But some of us play with medium gauge due to how the strings react for heavy strumming.
*** With more resonance does headroom remain the same. Or is it even more?

Good morning K&G.
Youíve asked some good questions that bear some in depth response so grab a cup of coffee because I sense I may get a bit long windedÖ

Early guitars were built much lighter and more fragile than the instruments being mass produced today. They were built to be strung with gut strings and history has taught us they held up well until the advent of steel strings. Players gravitated towards steel strings to gain more volume from their guitars. What they soon realized was those guitars structurally failed because they were so lightly built they distorted under the higher (steel) string tensions. History can be a good teacher if we pay attention.

Today's mass produced guitar tops, backs and sides start out being thickness sanded to a companies predetermined standard set of dimensions. Those numbers are likely based on their structural designs and perhaps archived historical data. They've found their dimensions held up under a wide range of string tensions. They are so robust they prevent expensive warranty claims and structural failures under a wide range of players, climate and travel conditions.

Our tops starts out in a similar manner because we too skim sand them to an overly robust thickness. Itís after that I begin a deflection process which is one area where we begin to diverge from the mass produced guitars. I measure the stiffness of each top in my deflection jig. I continue to reduce the topís thickness while carefully measuring the change in deflection or stiffness. I not only gradually reduce the overall thickness but I also taper and graduate the thickness of each top on different areas of the sound board plate. Therefore, my tops do not end up being one constant thickness like the factory tops but rather they are thick where they need to be thick and thinner where they need to be thinner. My deflection measurement process gives me a metric to chart how each top will hold up structurally but also allows it to be responsive for each individual playerís unique string attack that we are building that guitar for.

We never build two tops the same way because each player has unique needs. Player A might need her top to respond to a very delicate string input while Player B may need his guitar to respond to a heavy hand and flat pick. Therefore, player Bís top would not respond as efficiently to Player Aís string attack and vice versa. Player A may want her guitar to respond for her with medium gauge strings (strange I know) and Player B may want his guitar to respond to his style of playing with light strings. We try to intently interview and listen to a players needs which helps us determine how to brace and voice each top to respond to them and for their unique preference in strings, playing style, set up, etc...

Braces play a vital role in the culmination of the finished product. They are primarily a structural element but they also act as a conduit to spread vibrations over the top. Not only do brace patterns affect the sound but also the width, height, wood material, placement and profile of each brace all play a role in the tops final voice. If a top is thicknessed and graduated in a particular way it will hold up structurally and it can also vibrate more freely in areas where it may not have done so efficiently being the same overall thickness.

A lighter braced top can hold up to medium gauge strings {IF} it is braced and voiced properly. If one scallops some braces to make them lighter how much is too much? Which braces do you scallop and how much wood do you remove? Those are the $10,000 questions. The answers usually come through experience, documentation, trial and error or proper training by someone with prior experience. We usually build our guitars for only one gauge of strings per the clientís needs. If we build the guitar for 12-54 strings then we donít recommend any lighter or heavier strings be used on it. Lighter gauge strings will not have enough tension to pull enough relief into the neck, will likely have string buzz and it could actually sound thin or tinny. Heavier strings could cause too much relief, raise the action to make it uncomfortable to play or worse yet cause deformation in the top.

A thick top with light braces can hold up surprisingly well to a lot of string tension. A thin top with heavy or taller braces can hold up well to but could stand a greater risk of top or brace deformation which may or may not affect structure and playability. A combination of thick in the right places and thin in all the other places is what some strive for as a compromise of the two building philosophies. That is what is so great about our craft because there are a lot of different paths to arrive at the final destination.

Many players are accustomed to playing with medium or heavy gauge strings. But I would ask why? Itís likely because the mass produced guitar youíre playing sounds significantly better with heavier gauge strings so youíve grown accustomed to using them for the sound and not necessarily for the tactile feedback. One should ask why IMO. Itís well known that most all mass produced guitars are over built and over braced. Therefore, they usually sound better with heavier strings to drive the heavy top. I can assure you that they are not overbuilt to make them sound better but rather itís to significantly reduce returns and failures. Thatís not to say that there are not great sounding factory built guitars because there are. Keep in mind that they are mostly built to an engineered standard and one has to search for the best ones that stand out significantly from the others.

Iíve found headroom is more often a function of the top material itself though bracing does play a role as well. Cedar tops are generally found to have lower headroom than Sitka or Red Spruce. However, Cedar can have a lot more headroom if left thicker in the right places while Sitka and Red Spruce [can] have lower head room if one thins them too much. Itís a compromise of understanding the characteristics of the wood one is working with and how to manipulate it by adjusting the thickness or stiffness in all the right places.

I hope I've addressed your questions thoroughly.
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  #104  
Old 12-14-2018, 03:41 PM
Knives&Guitars Knives&Guitars is offline
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I will gratefully take, enjoy and even relish your long winded answers anytime! Great explanations!
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  #105  
Old 12-14-2018, 04:45 PM
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Thanks for the detailed response Tim, this is something I that would revisit with you for sure closer to time nearing my build
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