Official Luthiers Forum!

Hey all, I am finishing up a solera modeled mostly after Waddy's (pictures are around here somewhere). Its for classical guitars. Anyway I have been trying to think how much I need to slope the neck extension in order to get the correct angle.

I have the lower bout scooped out by 2mm. I also have a raised lower bout, and its raised 3mm. Anyway, I have been drawing out the dimensions and have a drawing here to show.



So what I have here is that since the lower bout of the finished guitar will be lowered basically by the raised portion of the solera, the spot where the bridge is will end up 1 mm below the plane of the guitar. With an 8.5mm bridge height, the top of the bridge is 7.5mm above the plane of the guitar. From what I understand the strings should be at about 11mm above the guitar at the bridge location, so I may need to make a bridge that is a bit taller by 1.5mm or so. If I made it 9.5mm, with a 2mm saddle height, then the strings will be straight with the plane of the guitar from the nut to the saddle. This would mean that at the 12th fret they would be way too low, so I would need them to be about 3mm higher. I guess this means put a 3mm slope on the neck of the solera???

Does this sound right?

I would appreciate you guys correcting any errors I have probably made.

If you have a 2mm scoop that will raise the bridge by 2mm
If you have a slope of 3mm from waist to tail, the bridge is in the centre of this so the drop at the bridge would be 1.5mm
This gives you the base of bridge 0.5mm above the body plane

7mm is a bit thick for a fretboard alone, I generally use fretboard plus frets at 7mm and assume the nut slots are no more than 0.25mm above this.
You need to add another line to your diagram representing the underside of the strings.
I go from 12mm above the base of the bridge to 3.5mm above the frets at 12th, project this through to the nut and then take off 0.25mm clearance plus the fretted board, and that is where the face of the neck needs to be.

3mm fall off in the solera is generally fine, you can shim up from there to dial in the neck angle to exactly what you need.

Thanks for the reply Jeff, I did forget to factor in that the slope on the lower bout wasn't 3mm at the bridge location, that's for picking that up. However there is clearly some inexactness going on, since if I was .5mm above the plane of the guitar, I would be sanding into the MDF that the solera is made of, and im not, so I am still below the plane of the guitar at the bridge location.

I dunno, maybe my scoop isn't exactly where it should be or something.

Anyway, if I go by your measurements and assume that the strings will be 7.25mm above the plane of the guitar at the nut end, and that's .25mm above the frets, then to make the strings level all the way across to the bridge, and assuming that I am correct in my estimate that the bridge is about 1mm below the plane, then the bridge + saddle would need to be 8.25mm high. 2 mm saddle, and the bridge is only 6.5mm high.

Of course, I don't want the strings to be level all the way across. If I make the bridge 11mm + a saddle of 2mm, and if the bridge sits 1mm low, then the strings will be at 12mm above the body of the guitar at the bridge. Hmmmmm.... would it be a problem to make a bridge this tall? Should I scoop out more material? And how to I figure out how high the strings are at the 12th fret?

Matt, I have a suggeston for you;
Get a long piece of paper, about guitar size and do the following.
1) Draw a straight line along the paper representing your string (scale length).
2) Draw the nut and the 12th fret (about 1mm tall or so) in proper relationship to the string for your desired action.
3) Draw in your fingerboard.
4) Move down to the saddle location and draw the saddle off of the string.
5) Draw the bridge.
6) Draw the top with your 2mm scoop.

The action is defined now showing the bottom plane of the finger board and the top , you should be able to to clearly see what your solera should look like now.

Your Drawing needs to as accurate as you can make it.
Hope this helps,
jim

_________________
Jim Watts
http://jameswattsguitars.com

Matt,
The string height at the bridge is fixed to the desired height, I aim for 12mm
The string height at the 12th is fixed to the fretted board height plus desired action height.
Project this through to the nut and work from there to determine neck angle

Draw it up like Jim says, but put all your known information in and your neck angle will be the result.

Thanks guys, great suggestions. Ill tape up some printer paper I guess.

You can get a roll of freezer paper at the grocery store, it works much better than taping pieces of paper together.

_________________
Jim Watts
http://jameswattsguitars.com

My fingerboards are 7mm at the nut, tapered to 5 ish treble side and 4 ish bass side.

Good advice above. The key to your bridge height is the height of the top under your bridge. That will depend on the rise of the lower bout in the solera at the latitude of the bridge location and the doming at that point. Is it at the apex of your dome? etc. Optimally, it probably should be at the apex, or close to it. Other things, such as tapering the finger board also have to be taken into account.

_________________
Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

There are many approaches to fretboard preparation.

I do mine the same as I do on a steel string-uniform 6mm thickness, slotted and fretted before gluing to the neck.
The only tapering I do is just before gluing, to the underside of the board to match the upper bout of the body.

Because I do it this way, rather than tapering and fretting after as most classical makers do, I have to get the geometry right to start with.
Remember, the neck angle is not set in stone untill you glue the back on.
David Schramm offers some useful techniques for setting neck angle in his two online apprentice courses.
The geometry involved here is really worth understanding, rather than just working to a cookbook of -so much dome, so much neck angle.

Here is an update, having taken Jim's suggestion and drawn the whole thing out.
I took some pictures of the drawing so here they are first.









In order these are the right end, the middle, and the left end of the drawing. At the bottom is kinda the best picture I could get of the whole thing.

So, I started off by drawing a straight line representing the string, then making my string to body distance at the bridge 12mm. I then made a mark about .7ish mm below the string at the nut end, and 4mm at the 12th fret. Underneath these marks, which I made about 1mm in thickness, I drew a line representing the top of the fretboard. I made the fretboard 7mm thick at the nut and 4mm thick at the 19th fret position. This made it so that the distance from the string to the guitar body right at the end of the fretboard was 11mm, which is what it should be based on my somewhat of a guess that the bridge is 1mm lower than the plane of the guitar.

When I make a mark 11mm below the string at the nut, it is right around 2.5mm below the bottom of the fretboard, which would mean I need a slope of 2.5mm in the neck extension of my solera.

Everything look good now?

That's very close to what I have, Matt. Mine is about 2 mm. I changed it to 2 from 4 when I added the raised section in the lower bout. My raised section is about 4 mm, I believe, and scooped to give me a final 25' radius. At 2.5 mm you are going to be in the ballpark, I believe. I do taper my fingerboard, which you may choose not to do, and that will have some impact on what will work best. The main thing you want to do is make sure you are within a comfortable range to be able to adjust to exactly what you want and still maintain the height of the strings at the saddle.

_________________
Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

From what I have drawn it looks like I will have little choice but to taper the fingerboard. I suppose if I didn't want to do that I could add another 3mm to the neck taper at the end to get the 4mm clearance at the 12th fret.... but I am not sure if that would be too much strain at the neck joint. Plus, if its similar to what you are doing, then I know it works.

Matt, did you account for the doming in the top? Looking at your bridge area drawing the top appears to be a straight line.
BTW - You can play with the angles of the fingerboard extension by pivoting the top about the saddle.
Jim

_________________
Jim Watts
http://jameswattsguitars.com

Matt, it is good that you have drawn up the diagram, it will certainly help you understand.
A few comments
-I would use 3.5mm action at the 12th as an average between bass and treble.
-If you are not wanting to taper, I would not use a 7mm thick board.
-what i do between 12th and soundhole is taper the underside of the fretboard to match up with the soundboard before iI glue it on.
-The 0.7ish figure you are using t the nut is too much clearance 0.25 is plenty.

Measuring from the drawing gives you an idea of what you need but for accuracy a few simple calcs are worthwhile
Everything is measured from a baseline (underside of freboard at body joint)
Here is how I would do it based on a 6mm fretboard
at 12th
6mm fretboard, 1mm frets, 3.5mm clearance----------10.5mm
At bridge
12mm bridge plus saddle, 0mm doming-ramp 12mm

Now notice that between bridge and 12th the height above baseline reduces by 1.5mm
So take another 1.5mm off to the nut position 9mm
From this 9mm
0.25mm clearance above fretline
1.0mm fret
6mm fretboard---------total 7.25mm

Take this from the 9mm you have available and you end up with 1.75mm forward set on the neck.

My preferred way to achieve this would be to construct the solera with 3mm falloff then shim to 1.75 gives you the flexibility to use the soleral for different arrangements.

Well the top is domed, but the height at the bridge in relation to the baseline is actually 1mm below the baseline, then it slopes down another 2mm towards the sides from there. This is actually a point of confusion for me since it seems like all the pictures I see, the bridge is a bit higher than the baseline. However with the type of solera I have built, I'm not sure how it can be any other way.



I guess I was thinking to build it for 4, then plane down the treble side about 1mm...



This makes sense to me in that a straight fretboard won't be able to follow the change in angle between the neck and the body, although maybe its slight enough that some don't think its that important.



I like this idea as well. What do you use for a shim?

Thanks for all the advice everyone!

I guess I was thinking to build it for 4, then plane down the treble side about 1mm...



This makes sense to me in that a straight fretboard won't be able to follow the change in angle between the neck and the body, although maybe its slight enough that some don't think its that important.



I like this idea as well. What do you use for a shim?

Thanks for all the advice everyone![/quote]

If you build for 4mm action you cant plane down on the treble to reduce it,
Think of your diagram as being along the centreline of the fretboard
I just use a stack of cards as a shim, it only need to be 10mm wide right at the nut end not supporting the neck all the way
You will need to put an angle on the underside of the board through to the soundhole or it the top of the board will rise.

Oh yeah lol thanks for pointing that out. I had it backwards.