Solera functional dimensions

Construction and repair of Classical Guitar and related instruments
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memit
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Solera functional dimensions

Post by memit » Fri Jul 28, 2017 1:07 pm

Sorry for asking such a stupid (!?) question. I need to understand how this works.

In Bogdanvich's book (Classical Guitar Making pag. 56) I found this:
2,5 mm under the solera level at the nut position and aprox. 2 mm OVER the solera level at the brige position.


Image

In Courtnall's book (Making Master Guitars pag. 165) I found:
3mm under the solera level at the nut position and aprox. 2 mm UNDER the solera level at the brige position.

Image

It looks to me that for the same dimensions of the bridge+saddle, will result in a very big difference in action beetween the two approaches/models.

Thank You for any kind of opinion/answer.
mihai,

John higgon
Amateur luthier
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Re: Solera functional dimensions

Post by John higgon » Sat Jul 29, 2017 10:32 am

Not a stupid question at all! Unfortunately, I am not sure of the answer, but I think I recall reading that the Courtnall neck ramp measurement is a mistake, and it should be closer to 1.5mm - IIRC. Also, the dimensions of the fretboard may make a difference, i.e. the fretboard may be an even thickness along its length, or thicker at one or the other end. I'm sure others will be able to explain it better, though.

John higgon
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Re: Solera functional dimensions

Post by John higgon » Sun Aug 06, 2017 12:39 pm

Another way to think about this is to start with the desired action - for example, 1mm above the first fret, 4mm above the 12th fret. Doming of the lower bout is typically around 3mm and you are aiming for the top of the saddle to be around 11mm or 12mm higher than the soundboard. All of these are ballpark figures, and some makers will work to their own figures. Anyway, the point is that you can use these figures to calculate the neck angle and / or the tapering of the fretboard. Final setting up will probably involve some minor planing of the fretboard or adjusting of the saddle height. when doing the maths, do remember to include the height of the fret along with the thickness of the fretboard. 😉

Dave M
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Location: Somerset UK

Re: Solera functional dimensions

Post by Dave M » Mon Aug 07, 2017 5:08 pm

First you are quite right to be concerned on this. Getting the geometry right is not particularly easy but is very important. Trying to fix it later can lead to bridges which are either much too low or too tall. I have been there!

There has been quite a lot of discussion on this forum with a strong suggestion that the 3 degrees in the Courtnall book is too much.

This is one of the topics:

viewtopic.php?f=11&t=93356&hilit=courtnall+ramp

If you search for Courtnall ramp you will find several discusssions which should help.

Good Luck
Dave

Dave M
Posts: 191
Joined: Tue Aug 05, 2014 1:39 pm
Location: Somerset UK

Re: Solera functional dimensions

Post by Dave M » Tue Aug 08, 2017 8:34 pm

I have been looking at John's book and watching his videos on this. I think that he is saying that he is dishing the lower bout to the point where the saddle position is actually pretty much at the level of the solera. His additional material below the saddle position is going to slope the top down below the saddle towards the bottom of the guitar. ie reducing the depth of the guitar at the butt compared to the waist. This will not affect the geometry of the strings, fretboard, saddle.

So this starts looking more like Roy's jig but with somewhat less backward tilt of the neck.

I may have this wrong and I am sure there are people on the forum better qualified to talk about this.

I personally, as an amateur builder, now use a bolt on neck design as in Trevor Gore's work, but getting that neck/body geometry is still tricky and needs to be right.
Dave

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memit
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Re: Solera functional dimensions

Post by memit » Mon Aug 14, 2017 11:39 am

Thank you, I appreciate all your answers !
mihai,

Jim Kirby
Amateur luthier
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Re: Solera functional dimensions

Post by Jim Kirby » Mon Aug 14, 2017 12:03 pm

The ramp on Bogdanovich's lower bout is very similar to how Jose Romanillos shapes this area. Jose's process, with the top cut to fit inside the unprofiled sides (which have a flat edge and sit on the flat solera outside of the ramp) is a lot easier than the profiling needed in John's process.
In any event, as hinted at above, you need to draw a reference line and then establish what the nut and saddle positions are, what the layout of the fretboard is to get the right action, and how high you want the saddle above the soundboard. Once you get these relative positions established, the entire assembly can be moved/rotated/et w/r the referenc plane to suit your building tastes, and this in turn establishes how you would shape the solera. There are going to be differences in everyone's soleras.

There is a simple formula that does the math for all of this, but coffee hasn't kicked in yet and I can't remember it. I'll look later.
Jim Kirby
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