The tilt of the guitar neck

Construction and repair of Classical Guitar and related instruments
Joe Medina
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The tilt of the guitar neck

Post by Joe Medina » Tue Sep 19, 2017 6:44 pm

Hello Everyone,

I have a question about neck tilt. If a guitar neck is tilted forward on average between 1mm to 2mm, how can the neck maintain that tilt forward if the heelblock slot if cut straight up and down? Wouldn't the stiff vertical sides once inserted into the heelblock slot cause the neck to spring back to horizontal? Shouldn't the heelblock be slotted the same millimeters in the opposite direction that the neck is tilted to counterbalance the pressure from the guitar sides?

Joe

chiral3
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Re: The tilt of the guitar neck

Post by chiral3 » Tue Sep 19, 2017 6:57 pm

In the Spanish method the slots are cut to compensate for the angle. The angle is set when the back is glued on (in the Spanish solera method).
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simonm
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Re: The tilt of the guitar neck

Post by simonm » Tue Sep 19, 2017 7:01 pm

If you are using a solera then when you glue the back on you lock in the angle, in essence bending everything into place. I believe there are some makers who do exactly as you suggest and cut the slot at an angle - it certainly makes sense.

mitch lees
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Re: The tilt of the guitar neck

Post by mitch lees » Tue Sep 19, 2017 7:44 pm

I asked exactly the same question a few months ago and there were a number of posts from experienced professionals: the consensus was that for 1 or 2mm the angle was so small that it could be ignored. I also exchanged emails with Bogdanovich, whose book I find most useful. His view was exactly the same a Simonm - cut the slots at 90 degrees and let the gluing of the back hold the small angle required as long as the solera is built that way. I have done this and there was no 'spring-back'. However, when we go to so much trouble not to build in any stress - even though it is small, by using the gluing process to hold the angle seems to go against the 'no stress' building method.

Practically however there are difficulties in cutting the slots with a compound angle both sloping back to take account of the guitar shape as well as having a different depth cut at the top and bottom of the slot, and now sloping in another direction to incorporate the small angle. As I use the table saw to cut the rib slots this would have required a rather complicated sledge arrangement - so I gave up and ignore it!

My current instrument has no neck angle at all, and I now rely on a slightly larger lower bout dome to achieve the correct saddle height. This is the method advocated by Rik Middleton and to me it seems a more elegant solution - others may not agree.

Let us know what conclusion you come to.

Mitch

Joe Medina
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Re: The tilt of the guitar neck

Post by Joe Medina » Tue Sep 19, 2017 8:28 pm

Hi Mitch. I agree. The sides put upward pressure on the neck angle in one direction, and then once glued on, the back then puts downward pressure on the neck angle. Talk about putting stress on glue joints. Couldn't the heel block slots be cut to the required tilt in the opposite direction using a handsaw. Pablo Requena has a video on YouTube where he cuts the slots nicely using a jig, but he too does not cut the slots with a tilt. I don't think anyone does that I know of. It seems everyone just relies on the force of the back glued on to the planed forward heel block.

chiral3
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Re: The tilt of the guitar neck

Post by chiral3 » Tue Sep 19, 2017 9:01 pm

Joe Medina wrote:
Tue Sep 19, 2017 8:28 pm
Hi Mitch. I agree. The sides put upward pressure on the neck angle in one direction, and then once glued on, the back then puts downward pressure on the neck angle. Talk about putting stress on glue joints. Couldn't the heel block slots be cut to the required tilt in the opposite direction using a handsaw. Pablo Requena has a video on YouTube where he cuts the slots nicely using a jig, but he too does not cut the slots with a tilt. I don't think anyone does that I know of. It seems everyone just relies on the force of the back glued on to the planed forward heel block.
I worked on the benches of two established luthiers, probably 800-900 guitars between the two of them over a combined 80 years. They both taught me to take a small angle at the cut and then set the angle on the solera. So people do it. It's so small it probably doesn't matter. There's so much gluing surface it's arguably inconsequential. I've done the cuts by hand and with a table saw. It doesn't really change anything.
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mqbernardo
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Re: The tilt of the guitar neck

Post by mqbernardo » Tue Sep 19, 2017 9:13 pm

I've done it like that (tilting the slots) on my first couple of guitars but stopped doing it since. not that it was hard but it was a nuisance with a marginal gain.
lots of guitars have been built with square to the top heel slots - i like simmon´s expression : "bending everything into place" - and it surely won´t ruin a good guitar.
you can, like mitch says, build with no neck angle.

edited, to delete an humiliating interpretation error.

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geoff-bristol
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Re: The tilt of the guitar neck

Post by geoff-bristol » Tue Sep 19, 2017 10:11 pm

Think about it. 1 deg at 325 nut to 12th = arc of 1/360 circumference at 325 rad (2042mm) Which gives you 5.87mm arc on 1 deg. So even with a 2mm neck rise that equates to an angle of about 1/3rd of a degree over 100mm at the heel cut. Just about markable with a sharp pencil !
I'm not sure i would be able to measure if the sides at the heel were out of square by 1/3rd of a deg ?

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Steve Toscano
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Re: The tilt of the guitar neck

Post by Steve Toscano » Wed Sep 20, 2017 12:42 pm

If cutting the slots by hand: i would say they will end up out by more then the required angle anyway, no one is that perfect with a handsaw, as geoff pointed out - we are talking about a third of a degree here, or something like 0.25 of a mm at 90mm (bush calcs). My pencil doesnt get sharp enough to measure that. :lol:

If you want to limit the stress then why not build with perfectly flat tops and backs - theres way more stress in doming a top or back then the twist at the side slots.
(I dont condone building with non domed plates, just mentioned for an example)


By the way, im one of those makers who builds with a zero degree neck angle so my slots are at 90degrees without stress.

robinfw
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Re: The tilt of the guitar neck

Post by robinfw » Wed Sep 20, 2017 2:01 pm

But I thought the angle was accomplished via the fretboard.
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mitch lees
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Re: The tilt of the guitar neck

Post by mitch lees » Wed Sep 20, 2017 6:19 pm

That is an alternative way to tackle it. I have always used parallel finger boards myself (perhaps with a little relief on the bass side) so I am not sure what advantages/disadvantages, if any, this might have - I think some of the famous builders have used a taper fret board. I recently did a repair on what was quite a good luthier-built instrument that had a marked taper to the fret board, so much in fact that in order to get the action to a reasonable height I had to change the finger board to a parallel one. At the risk of becoming a bore, if anyone is interested in playing around with all the variables that go into establishing the desired action at 12th fret, a couple of weeks ago I posted a draft Excel file (string action calculator). I had hoped to get some help in improving the calculator from the Community, but sadly the response was rather underwhelming !

Mitch

Joe Medina
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Re: The tilt of the guitar neck

Post by Joe Medina » Thu Sep 21, 2017 12:06 am

Not the fret board. The question is in regard to the tilt of the neck established by a solera where the neck is tilted and clamped down about 2mm on the solera.

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Manuel Najera
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Re: The tilt of the guitar neck

Post by Manuel Najera » Tue Oct 24, 2017 3:43 pm

I have never used a neck angle. I have my solera built flat and my fretboard parallel to the neck, no tapper. However, I just had my first customer complain about a buzz from the 11th fret and forward on the bass strings. I have tried everything, the action is at its highest (4mm on the bass side at the 12th) and I lowered those frets just a little bit, and still have the buzz. :x
In this case, my only conclusion is that I should have had an angle on the neck.
I am going with the fretboard tapering option, as it will be easier to achieve. And I do not like the idea of tapering on the lower side of the fretboard to compensate the angle between he neck and the lower bout of the soundboard. Too much trouble. If that doesn´t work, I will modify my solera and give it a try.
Have anyone has any experience with this method of flat neck and tapered fretboard? It will be appreciated.

Joe Medina
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Re: The tilt of the guitar neck

Post by Joe Medina » Tue Oct 24, 2017 7:23 pm

Have you attempted to recrown your frets, and have you checked to see if all the tops of the frets were level with each other? I haven't tried the tapered fretboard simply because I don't like the appearance from the side.

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Trevor Gore
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Re: The tilt of the guitar neck

Post by Trevor Gore » Tue Oct 24, 2017 11:20 pm

Manuel Najera wrote:
Tue Oct 24, 2017 3:43 pm
I have tried everything, the action is at its highest (4mm on the bass side at the 12th) and I lowered those frets just a little bit, and still have the buzz. :x
That sounds rather like too much relief, giving the effect of a rising fretboard extension, rather than a wrong neck angle. But the two do interrelate, of course.
Trevor Gore: Classical Guitar Design and Build

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