Official Luthiers Forum!

Do's
Design your guitar from the start with near exact dimensions for:
a) bridge height with saddle
b) fingerboard thickness with frets and string height
c) rim shape on top side either flat or radiused with your top sitting in place and the exact dome height
d) draw this full scale

Don't
a) mix methods
b) assume a radius is an angle
c) build your body and attempt to fit the neck so as to achieve the correct string height
d) substitute proper design for jiggery

The photo shows the angle gauge sitting in place. If you design and hope the fingerboard will be glued right on the top with good action on low, mid and high frets, then this angle has to be designed. It is not something that can be altered or compensated for.

How this is achieved is what is up to the individual. There are many methods.







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Ken

Here is one method that I used.

After deciding on the method parts described above, I measured the exact amount my top will dome when the braces were glued. I chose to use a selara. This is a way to achieve the plan is followed.


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Ken

I put in the rosette and placed the top on the solera. The bridge area has a dished out section but the rims sit flat. The upper bout area of the solera has my exact angle. This is from mid upper bout to the neck.


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Ken

I glue in the braces.


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Ken

Bend the ribs and remove the top plate for the next critical operation.


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Ken

I hope I can describe this well. I place the bent side and use the slope that I built into my solera to scribe a pencil line where I can cut the side to its proper eventual slope.


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Ken

That line is cut and the top goes back into the solera


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Ken

I use a rim mold to help with trimming the braces. Then I glue the sides to the top by pressing in these whatchamacallits.


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Ken

The blocks which are pre shaped also get glued


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Ken

Like this. Ready to shape the back contour which is another story. Once the back gets glued, there will be no question that my angle is as I designed it.


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Ken

That is an example of one way to leave nothing to chance.


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Ken

What a beautiful guitar!

That's pretty much the same way I do it too. Several years back I sat down and gave this whole thing a lot of thought and came up with something that works for me. I too like to build on an open work board. What I do for any given model of guitar is make a workboard shim out of Balsa and then harden it in place with epoxy. I arch the UTB and cant the top from the sound hole forward just like you do, to create the ski ramp up to the bridge saddle.

Pics to explain:

The work board with shim:





The arched UTB:



The ramp:

Some good advice. One of these days, I want to build something using the workboard/solara style. It makes good sense in a lot of ways. For whatever reasons, it seemed cumbersome to me when I was starting out so I went another direction. But, I bet I could get some valuable experience trying it out now.

I’m confused by what you are saying with C under your don’ts above. You say not to make the body and attempt to fit the neck to the body to achieve correct string height. That seems to contradict what you are domonstrating. String height is built into the upper bout geometry. When you make the neck, you mate it to that built-in gometry. You are fitting it to the body; it will fit only one way and that fit will set the string height.

At least that is how I have always looked at it. My current thread about my neck angle problems is an example of what I mean. I made the bodies using a process that builds the string height into the upper bout. Errant execution of that process (not accounting for a 12 fret neck and unintentionally altering the rim geometry when re-topping) built in geometry flaws.


Your process is showing the geometry built into the body such that the neck will be fitted to that geometry resulting in the desired string height. If I am misunderstanding, then I have an opportunity to learn something huge and exciting.

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

Right on Jfmckenma. I like your method.


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Ken

Hesh wrote a great thread about adding fall away. I did not describe it in mine but know it is important as a feature to both help in long term stability as well as compensate for a pull up of the neck when strung to tension. It is important so give it the importance that he emphasizes.


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Ken

Ok Bryan. I am thinking


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Ken

I see in your thread that you say you have a method to slope your soundboard so that the fretboard sits flat on it and projects to the correct height. That is what is important here. We all make mistakes. I certainly do.

What I mean by c) don't do. Is don't expect solely a method to attach the neck to the body to achieve more than the correct string height at the bridge. That is essential but must be in conjunction with the fingerboard being parallel to the strings (with a little fall away).
So I did say it confusingly. I should have written, don't solely use a neck angle jig. Because the fretboard might not sit on the top correctly which is flat (except small fall away).


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Ken

You don't need a solera to achieve the proper upper bout slope.

Hesh describe how to di it without one here. Flattening Upper Bout (Pics..)

https://r.tapatalk.com/shareLink?url=ht ... are_type=t


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Ken

This photo shows how I achieved the flatening which gets the same results as Hesh only a totally different way.
Guide to proper Neck To Body Angle


Guide to proper Neck To Body Angle


I hope I can describe this well. I place the bent side and use the slope that I built into my solera to scribe a pencil line where I can cut the side to its proper eventual shape

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Ken

Ah, I see what you meant now. At first read, it felt like there was some other approach (perhaps associated with the work board style) that I was missing out on or didn’t understand. Never hurts to ask. . .

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

first is it classical or steel string.
They have differing neck angle requirements.
too much of a neck angle is not a good thing so you have to understand what your shooting for. Neck angle starts with the sides , and how all the geometry mates .
There is no one perfect formula but understanding the end result will help you get there.
If you have too much of a neck angle the string height off the top can actually over stress a top. I shoot for about 1/2 in. so I need about a 3/32 point above the top at the location of the saddle , for a steel string. Once you have your target you know where you have to go.

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John Hall
blues creek guitars
Authorized CF Martin Repair
Member Board of Directors ASIA
You Don't know what you don't know until you know it

I imagine Ken is talking about steel strings here. On my classical guitars the neck comes in dead straight and then the fretboard is planned thinner as it approaches the bridge so in essence there is a forward angle. 1/2in string height at the saddle with a 3/8th bridge is what I shoot for and now I'm able to do it 100% of the time.

I still don't understand fall away though. I just go for dead straight from nut to the last fret. I used to have to either shim or press fit the fretboard extension and press fitting always caused a hump and it drove me crazy.

GREAT thread Ken!!!

We should ask Lance to put it in the toots section so that it can help others for years to come.

JF fall-away is generally not associated or in my view benefitted from in the classical world. It's a steel string thing. I'll add that yesterday our students saw the value of fall-away after they milled it into an L-7 from the 40's, a custom made shredder that did Zepplin fantastic and a BEAUTIFUL Om made from a $3,500 set of "The Tree."

Point being all three steel strings are made for different types of music, jazz, heavy metal vomit, and finger style and all three will benefit from fall-away.

Good thread! This is what I’ve been doing.

After the back is glued and you are dealing with a relatively stable “boat” clamp a cross piece across the rim so the front is where the front of the bridge will be. Thickness is basically anticipated bridge thickness. Sanding board has a 1/4” piece of plexiglass attached to mimic the fretboard covered with 80 grit.

Rims are marked with white chalk and sanded to about the level of the sound hole to get the angle.



After the top is on the angle is fine tuned with the Fox paddle. Pivot point thickness is generally about bridge thickness. This is only for minor fine tuning as you can thin the top too much otherwise.



I know Charlie Hoffman and Jim Olson use a router jig that attaches to their mold to get the angle and others use a flat radius dish and a shim taped to the tail block. I think Sylvan Wells has a thing on that on his website.

Many good ways to arrive at the same goal.

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

This is fascinating! Who knew there were so many approaches! I was familiar with Mr. Cumpiano's building board technique, and has read about the tapering and wedging of the upper bout, but the photo essays were quite illuminating. Thanks so much to all that took the time to so beautifully illustrate your techniques and equipment!

The approach used in the build/repair shop where I spend my spare moments differs a bit, but works well for scale lengths and bridge placements from 3/4 size guitar (~20.5" scale and 12 fret neck) to 12 fret-to-body dreadnaughts (and ABG's where the string height is 9/16"). In summary: the upper bout bracing radius and glue-up is directly modified to ensure an natural fit for the fretboard extension at 1/2" string height over the top at the saddle location. Other than a method to accurately radius top bracing at both 28' and 60', no other jigs or fixtures are used beyond the basic outside mold for the body shape and the 15' and 28' radius dishes common to the radius dish/go-bar approach to construction.

Preparation: The rim is radiused at 28' for the top and 15' for the back. X-brace, tone bars, bridge plate, and fingers are radiused at 28', with the upper transverse brace radiused at 60'. Any sound hole braces and any upper transverse graft are left flat.

Execution: X-brace, cap, tone bars, fingers, and plate are glued up in the 28' dish. When dry, the remaining bracing (UTB, UTG, sound hole braces) are glued up on a flat caul, resulting in a preload that resists further flattening of the upper bout.

We fret after the instrument is finished and assembled, but I'm not sure that is really necessary to success. No wedges or tapering of the fretboard is necessary - the extension lies naturally on the top, and the fretboard gluing area is nearly dead flat (no further flattening of the area is done to fit the extension).

Again, thanks for the discussion!

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