Wrong neck angle I suppose.

Construction and repair of Classical Guitar and related instruments
Costantino Proietti
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Wrong neck angle I suppose.

Post by Costantino Proietti » Fri Aug 24, 2018 10:28 pm

Few days ago after I glued the back to the sides, I could extract the guitar from the solera and finally checked the closed box and measured the relief between the neck and the body for gluing the fingerboard. Unfortunately, I noted the neck is sligthly higher, 15/100 mm, then the upper bout edge of the Sb, as I cut the slot on the heel a bit deep. But, as you can see from the pictures, I think I also have a problem with the angle or relief neck/soundboard. I'm absolutely confused about where the problem is :?: . When I built the solera its relief neck/bout was 2 mm. I thought this measure could not move. Mistake! Now the neck estension is ramped down just 8/10 mm. Maybe when I cut the slot on the heel, where to glue the Sb, I did not cut it plane. Anyway now I have a neck/body positive (?) relief till the soundhole upper edge (FB elevated) of 1 mm. The SB lower bout has a dome of 2 mm. The FB thickness is 6,5 mm. So it seems to me the only action is to lower the neck, by angled planing and sanding it to allow the Fb get in touch the Sb. I have no other idea. Any advice about this procedure, or any other, will be very appreciated.
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mqbernardo
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Re: Wrong neck angle I suppose.

Post by mqbernardo » Fri Aug 24, 2018 11:12 pm

Regarding neck angle (and not relief if I got you right), it also happened to me once: I got about half of what I should’ve after gluing the back. Still don’t understand why. Anyway, I use it a little above 1 mm (and a 3 mm dome under the bridge) so 0.8 mm doesn’t look too bad.
In any case you can have no neck angle and get proper geometry via FB tapering. Some folks hate the looks, some don’t mind it, most don’t notice it until someone points that out.
So, I’d say you’re cool.

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Steve Ganz
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Re: Wrong neck angle I suppose.

Post by Steve Ganz » Sat Aug 25, 2018 2:45 am

Before gluing the fingerboard, add a shim (made of the same wood as the neck) that goes from the location of the nut to the soundhole. Then plane it to the proper angle for the intercept of the bridge/saddle height you want. I'm sure you can do the math with your measurements.
Steve

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Re: Wrong neck angle I suppose.

Post by simonm » Sat Aug 25, 2018 7:30 am

I had quite a bit of difficulty trying to understand your post. I have never seen numbers formatted as you have and I have never seen the abbreviation Sb. After about 5 mins the penny dropped and I guess you mean the soundbnoard.

I have never seen mm fractions before and I am not exactly in the first flush of youth. :-)

15/100mm = 0.15mm
8/10mm = 0.8mm

To find out what to do with a next issue on a new build the first thing is to check the position of the top of the fretboard with respect to the bridge.

1) Put a block of wood 10mm high in the bridge position.
2) Put a long straightedge on the top of the fretboard and see where the end of it touches the front of the "bridge" - measure that height from the the top of the soundboard to the bottom of the straightedge. The target distance in some plans is about 3mm - 4mm (plan, and target action, dependent)
3) Once you have this number you can figure out what needs to be done.

There are three approaches.
I) As Steve says - shim on the neck.
II) Shim between the fretboard and the soundboard.
{ III) Planing as you mentioned. Disadvantage here is that you are removing wood from the top and would weaken the area between the sound hole and the neck quite a bit - 1mm is quite a bit to remove in that area. So let us eliminate this option.}

How to choose between I) and II) ?

Get the measurement above - and work out what the fretboard taper will look like with the two options and decide which will work best. Personally I would get uncomfortable is the soundhole end of the fretboard was to go below 4.5mm.

Let the guitar/fretboard dry for a good few days before you even think about planing it. Unless you use epoxy the glues (hot hide glue to titebond type) introduce a lot of water into the system and until this is dried out the geometry will be a bit unstable.



There is another (more radical) approach which I have never tried myself. Slip the neck. This involves opening the back joint again, repositioning the neck and glueing down the back again to hold the neck in the correct position. This method is, apparently, occasionally used to reset necks on classical guitars. Using this method you would have to be very sure that the solera geometry is correct.

I suspect that the original cause is that the ramp from the neck on your solera is not correct or you did not clamp the neck to the solera adequately when glueing the back. The neck part of the solera can warp quite easily especially if it is mdf or a thin plywood. I know one person who has a very big aluminum profile bar the full length of the solera to keep it flat.

Good luck.

Costantino Proietti
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Re: Wrong neck angle I suppose.

Post by Costantino Proietti » Sat Aug 25, 2018 4:22 pm

Thank you all for your kindly and exhaustive advices. I apolologize for the abbreviations, I read them somewhere, and for fraction formula; I will use the decimal point for the future. Unfortunately my poor English doesn't allow me to be completely clear.
So, I would like to abuse your patience. Summarizing it seems I have five options:
1) tapering the fretboard;
2) shim from the nut to the soundhole;
3) shim between the fretboard and the soundboard;
4) flip the neck;
5) plane the neck ( not the soundboard!)
Simonm as you explained I measured the high from the top and the lower ruler edge positioned over the fretboard. I have 3.5 mm relief. So it seems good.
I have to clarify that my main problem is the correct gluing of the fretboard, as the gap between it and the soundboard doesn't allow sticking the part over the SB unless bending it or making a rung.
Now to the suggested solutions:
1) Simonm, sorry but my limited technical skills don't allow to understand why to unglue the back. I don't see the link with my problem. It seems to me much simpler, I have a little elevation 1.0 mm of the neck over the upper bout of the soundboard.
2) gluing a shim under the fretboard should be the correct solution, but won't the shim be visible, specially the part over the soundboard?
3) tapering the fretboard could be the simpler solution. But how to clean the gap over the SB?
simonm wrote:
Sat Aug 25, 2018 7:30 am

{ III) Planing as you mentioned. Disadvantage here is that you are removing wood from the top and would weaken the area between the sound hole and the neck quite a bit - 1mm is quite a bit to remove in that area. So let us eliminate this option.}

Simonm again, surely I didn't explain well my tought but I did not say to reduce 1.0 mm of the soundboard thickness! I was referring just to the neck, to get the soundboard level.
To me it seems the logical and the easiest solution though it should lower a bit the above measure. Luckily the soundboard
is sufficiently domed.
As for the cause I agree with you: my solera has sprung back so the 0.8 mm ramp is absolutely inadequate. Just for curiosity: my solera is 30 mm plywood and when glued the soundboard and back I completely blocked them. It should had happen.
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Les Backshall
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Re: Wrong neck angle I suppose.

Post by Les Backshall » Sat Aug 25, 2018 6:22 pm

Steve Ganz wrote:
Sat Aug 25, 2018 2:45 am
Before gluing the fingerboard, add a shim (made of the same wood as the neck) that goes from the location of the nut to the soundhole. Then plane it to the proper angle for the intercept of the bridge/saddle height you want. I'm sure you can do the math with your measurements.
This would seem to be the most elegant solution; and it should allow you to keep the fingerboard at constant thickness if that's important to you.
A while ago, a professional friend of mine asked me to sort out a buzzing string on his guitar. This is superb instrument by a top English maker, and somewhat to my surprise the neck was shimmed exactly as Steve describes. It was beautifully done and you had to look hard to see it, but it does show even the best makers can run into these issues.

Les
Lester Backshall, Guitar Maker - Aylesbury UK

Costantino Proietti
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Re: Wrong neck angle I suppose.

Post by Costantino Proietti » Sat Aug 25, 2018 6:56 pm

Les Backshall wrote:
Sat Aug 25, 2018 6:22 pm
It was beautifully done and you had to look hard to see it, but it does show even the best makers can run into these issues.

Les
If I should adopt this solution I'm pretty sure you will see the repair :D.Working with a plane on the soundboard....mmmm :shock: :shock:
I don't feel able to risk. I'm afraid about Murphy's law..But it is very intriguing as well as elegant. Thanks Les for the anecdote and Steve for the solution.
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Steve Ganz
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Re: Wrong neck angle I suppose.

Post by Steve Ganz » Sat Aug 25, 2018 7:38 pm

Constantino.
The fingerboard shim idea is to avoid touching the top with the plane.
Many of the world's finest guitars are designed to have such a shim from the beginning. For instance Dammann guitars.
If you use the same wood as the neck, and make a good joint, the shim can be no more evident than any other joint on the guitar.
HOWEVER... I haven't seen your guitar, or much of your work, and I do not know if you can bring off this solution... I think you need to go with whatever solution you can understand and execute the best.

If you put a straight edge on the fingerboard and measure how far above the top (at the location of the bridge), what is the measurement... in mm?
Steve

Costantino Proietti
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Re: Wrong neck angle I suppose.

Post by Costantino Proietti » Sun Aug 26, 2018 12:55 pm

Steve, I took two measures. The first one you suggest with a straight ruler on the fretboard I have 5.2 mm at saddle position. Then I tilt down the fretboard to close the gap with the soundboard and it measures 4.0 mm. My alternative idea is to fix a little shim, 1.2 m thick, at nut position and with a stick sand the neck to get the correct lowering. Could be 3.5 mm the target? Another solution suggested by Mqbernardo is tapering the fretboard.
As for my skills I learned the practice notions during a once a week course. Here I build my first guitar. All my moulds and jigs, solera, radius dish, many sanding sticks, radius sticks, routing jig etc. are built by myself.
So I post few pictures shows my first guitar and the second one we talk about. I hope not to bore you too much.
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Re: Wrong neck angle I suppose.

Post by Steve Ganz » Sun Aug 26, 2018 4:40 pm

Right. You need to get the first measurement down - the rough rule is 3.5mm. Have fun!
Steve

Costantino Proietti
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Re: Wrong neck angle I suppose.

Post by Costantino Proietti » Fri Jan 11, 2019 11:07 pm

I resume the topic for a clarification about the relationship between action and the total height of the bridge with the saddle. As this seems has affinity with the previous posts. When I measure the neck angle I place, as suggested, a straight ruler over the fretboard, already glued but without the frets, and measure the gap between its edge and the soundboard. Now it measures 4 mm. A little high because the correct measurement should be 3.5. When I measure the action, I place the ruler above the first fret and the saddle and control the space at the 12th fret (I use two pieces of fret wire without barbs) . I measured 3.7 mm at 6th string. That should be fine because acting on the saddle I can adjust the action 3/4 mm respectively to 1th and 6th string. However, in this way the total height of the bridge from the soundboard will raise from 12 to about 13 mm, a little high. It seems that I have to taper the fretboard towards the sound hole a bit. I assume ~ 0 .6 mm at saddle (0.4 at 19th fret). So I can maintain the total height of the bridge to the planned 12 mm, (8,5 bridge+ 3,5 saddle) otherwise it will raise to 13 mm. So it seems to me I can simplify that:
the neck geometry affects the right height of the bridge but not the playability as the action can be set to the standard measures regardless the neck geometry, just acting on the saddle. What about this?
A final question: could be a problem in intonation or for break angle or for anything a bridge higher then 12 mm??
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Steve Ganz
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Re: Wrong neck angle I suppose.

Post by Steve Ganz » Sat Jan 12, 2019 3:52 am

Costantino Proietti wrote:
Fri Jan 11, 2019 11:07 pm
I resume the topic for a clarification about the relationship between action and the total height of the bridge with the saddle. As this seems has affinity with the previous posts. When I measure the neck angle I place, as suggested, a straight ruler over the fretboard, already glued but without the frets, and measure the gap between its edge and the soundboard. Now it measures 4 mm. A little high because the correct measurement should be 3.5. When I measure the action, I place the ruler above the first fret and the saddle and control the space at the 12th fret (I use two pieces of fret wire without barbs) . I measured 3.7 mm at 6th string. That should be fine because acting on the saddle I can adjust the action 3/4 mm respectively to 1th and 6th string. However, in this way the total height of the bridge from the soundboard will raise from 12 to about 13 mm, a little high. It seems that I have to taper the fretboard towards the sound hole a bit. I assume ~ 0 .6 mm at saddle (0.4 at 19th fret). So I can maintain the total height of the bridge to the planned 12 mm, (8,5 bridge+ 3,5 saddle) otherwise it will raise to 13 mm. So it seems to me I can simplify that:
the neck geometry affects the right height of the bridge but not the playability as the action can be set to the standard measures regardless the neck geometry, just acting on the saddle. What about this?
A final question: could be a problem in intonation or for break angle or for anything a bridge higher then 12 mm??
I think we have communicated well. You now understand the interaction of
  • neck angle
    fingerboard thickness
    slope intercept of the fingerboard top on at the saddle location,
    and saddle height
    fret height
    and
    desired action
With an intercept of 3.5 mm (instead of 4), I think your saddle height would have been about 12, not 13. If everything else in the construction is good, 13 will probably be OK. Or you could try lowering the intercept by sanding or planing the fingerboard.
On some guitars the neck pulls up a bit, so the saddle may need to be lowered. On others, the top might collapse a bit, requiring more saddle. On others everything is perfectly stable.
Aiming for the middle is (perfectly stable) is probably the best option.
Congratulations on the work so far.
Steve

Costantino Proietti
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Re: Wrong neck angle I suppose.

Post by Costantino Proietti » Sat Jan 12, 2019 6:19 pm

Thank you Steve. Now I have a bit clearer notions to make better job. I hope to finish my guitar this month and to give the shellac for February. Maybe it will deserve to post few pictures on this forum.
A fact is the most obstinate thing in the world. Bulgakov
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Re: Wrong neck angle I suppose.

Post by Dave M » Mon Jan 14, 2019 12:16 am

I won't try to answer the original question as others have done so very well. But I would express my sympathy.

This is an aspect of building that is really dificult. Whether using a solera and the traditional neck to body joint, or a separate neck and body arrangement getting the geometry right is always hard.

It is only on builds 6 and 7 that I feel confident that I have got it right. (Could be i’m a slow learner)
Dave

Costantino Proietti
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Re: Wrong neck angle I suppose.

Post by Costantino Proietti » Mon Jan 14, 2019 10:45 am

Hello Dave.
I completely understand you thought. With the help of the forum I just cleared few aspects of the neck angle geometry. But I have to work on the field, making trial and error to achieve the way to obtain reproducible results with my tools and my sensibility and... my luck. For now I'm working on a new guitar, walnut back and sides, so I can try some modifications to obtain the rigth things. A big problem is that I am lacking so much in patience...and skills.
A fact is the most obstinate thing in the world. Bulgakov
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