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Extra neck angle compensation?
http://www-.luthiersforum.com/forum/viewtopic.php?f=10101&t=45032		 Page 1 of 1
Author:  Cablepuller [ Sun Feb 01, 2015 4:49 am ]
Post subject:  Extra neck angle compensation?
Hi

Have dry fitted neck and all looks good, i have checked the height at bridge position and have 9mm with unfretted fretboard and 2.5mm with just neck. Fretted this will land ontop of bridge

Should i set the neck back a bit to allow for a bit of movement under string tension?

Thanks
Author:  Hesh [ Sun Feb 01, 2015 7:23 am ]
Post subject:  Re: Extra neck angle compensation?
Hopefully this will be helpful to you: http://www.luthiersforum.com/forum/viewtopic.php?f=10102&t=15022%22

Regarding over compensating for string pull, not necessary and instead neck angle has to be a very precise fitting with little room for error.
Author:  Tom West [ Sun Feb 01, 2015 10:13 am ]
Post subject:  Re: Extra neck angle compensation?
Cable: I would go with what you have. Quite easy to go a bit extra later if needed but if you over set its harder to retreat. You can even leave the fingerboard extension unglued for a while to see how it settles. Then if you need extra, popping the neck off is easy. You can get a bit extra without ungluing but think it's easier with neck off.

Tom
Author:  Clay S. [ Sun Feb 01, 2015 10:17 am ]
Post subject:  Re: Extra neck angle compensation?
"Should i set the neck back a bit to allow for a bit of movement under string tension?"

If you have a lightly built top you may get some "pull up" and want to compensate for it with the neck setup. It is hard to know how much compensation to add (if any). I generally set up the guitar's neck angle toward the high side and if the top pulls up it is usually still within the acceptable range of saddle/action height. Over time guitar bodies usually distort and "pull up" making neck resets necessary. Better to have the neck angle start out at the high end of acceptable (strings 1/2 inch above soundboard@ bridge).
Author:  meddlingfool [ Sun Feb 01, 2015 1:12 pm ]
Post subject:  Re: Extra neck angle compensation?
I would not.
Author:  Colin North [ Sun Feb 01, 2015 1:29 pm ]
Post subject:  Re: Extra neck angle compensation?
+1
As per Cumpiano and Natelson book I find all of my (6) guitars tops have lifted after stringing up and settling in, about 0.5 - 1 mm IIRC.
In the book they give a typical range, depends on the stiffness of the top/bracing system.
After 4 builds where I found this (slow learner), falling short in the string height above soundboard than where I was aiming, I took my courage in both hands and went for an extra mm (as the top was thin and bracing light)
Ended up just where I wanted it. idunno

Go with what you've got, and you'll get a feel for it as you go along.
Just my $0.02
Author:  Toonces [ Sun Feb 01, 2015 2:14 pm ]
Post subject:  Re: Extra neck angle compensation?
One of these days, I will post my SOP (Standard Operating Procedures) for my builds. I will need to remove specific information to my instruments (which is why I haven't done this yet), but it would give some of you a step by step of how I build my guitars -- which might be useful.

I mentioned this before -- but I sand the upper bout so that when the fretboard is perfectly aligned with the upper bout region -- the perfect neck angle is achieved. However, in order to sand the upper bout, you need to know how much neck angle you need. I call this the "airspace" (at the saddle) under a straightedge when laid atop the upper bout.

Here is what you need to know

1) Fretboard + Frets + Minimum Airspace = Bridge Height

2) Minimum Airspace + Additional Compensation = Ideal Airspace

On my guitars, my minimum airspace is 0.040". The soundboard rises about 0.020" under string tension and I like to have the neck angle proud of the bridge by about 0.040". That means an additional compensation of 0.060". That makes my ideal airspace 0.100". It looks like some individuals above don't like to have any additional compensation -- that wouldn't be my advice but either way, you will still end up with a good neck angle. I use that information to sand my upper bout using a shim at the saddle and a flat sanding board. The board rests on the shim and I sand the upper bout lightly so that the upper bout takes on the proposed geometry. Please note, you don't want to be sanding a lot off your top so you need to pick a radius for your top that "almost" gets you where you need to be. I end up sanding maybe 0.010" off my tops right at the upper bout binding when using a 25' radius top.
Author:  Cablepuller [ Sun Feb 01, 2015 4:11 pm ]
Post subject:  Re: Extra neck angle compensation?
Thanks toonces ..sorry you say when the fretboard is perfectly aligned with the upper bout you have perfect neck angle, does that include frets.. so when you have a straight edge on frets its level with top bout? And is that unstrung cheers
Author:  Hesh [ Sun Feb 01, 2015 4:31 pm ]
Post subject:  Re: Extra neck angle compensation?
Perhaps it would be prudent to consider that this is Cablepuller's first, it may be a kit, we don't know, but as a betting man it's likely over built/braced just as many of us have when we started, me included. As such allowing for some yet to be determined amount of top pull-up is in my view an exercise in reading tea leaves and not likely to get a new builder where they wish to go.

Sure - it's a consideration granted but for now with all of the variables that we have AND more importantly cablepuller has to deal with top pull-up is something that we all tend to consider, well many do..., after we have some data and experience as to how our style of bracing/building, top thicknesses, etc. pans out when she has strings on.

Cablepuller what are you building, style, kit, etc? Thanks.
Author:  Cablepuller [ Sun Feb 01, 2015 5:02 pm ]
Post subject:  Re: Extra neck angle compensation?
Hello hesh
Your bang on the money
Its a martin dreadnought kit and i was cautious with bracing (its pretty thick still)
Thanks for all the input
Author:  Hesh [ Mon Feb 02, 2015 6:52 am ]
Post subject:  Re: Extra neck angle compensation?
Cablepuller wrote:
Hello hesh
Your bang on the money
Its a martin dreadnought kit and i was cautious with bracing (its pretty thick still)
Thanks for all the input


Thanks CP (I don't have to fight my spell checker if I call you "CP"....;)).

For a Martin kit simply setting the neck angle correctly with no allowance for string pull should serve you well IMO.

There is lots of related stuff that as mentioned can be part of how you refine your settings in the future. Top pull-up, fall-away (not everyone likes fall-away but I do...), etc. and some of this stuff will be things that you learn to compensate for as you gain experience and as you dial-in your own bracing style, top thicknesses, etc.

For now though completing the first, getting strings on her, and letting you experience the great feelings of accomplishment associated with building a guitar is a worthy enough goal also IMO.
Author:  Toonces [ Mon Feb 02, 2015 12:03 pm ]
Post subject:  Re: Extra neck angle compensation?
Hi Cablepuller,
I think Hesh made a salient point -- just getting in the ballpark is good enough for your first attempt. Regarding my post, what you want to visualize is the neck without a fretboard forming a perfectly straight line when fused to the body. The fretboard then rests on a perfectly flat surface across its entire length. You can still change the neck angle at this point but consider what it does to the fretboard -- you basically end up with some sort of hump or curve at the body joint -- this is what is often called the 14th fret hump. Some builders avoid this by leveling the fretboard after they have attached the neck and then fretting.

IF you fret the fingerboard before you glue it to the neck -- then your neck angle must absolutely align with the soundboard at the upper bout. This is why I ensure that my upper bout has the necessary geometry -- then I match the neck angle to the soundboard -- then I can glue my already fretted fretboard while ensuring a perfectly level fret plane.

You will find with guitar building that methodology and sequence of events is extremely important -- doing a step out of order can possibly improve the end result or cause disastrous results.

Best of Luck on your build
Author:  Cablepuller [ Mon Feb 02, 2015 2:58 pm ]
Post subject:  Re: Extra neck angle compensation?
Thanks toonces
Author:  kencierp [ Mon Feb 02, 2015 6:46 pm ]
Post subject:  Re: Extra neck angle compensation?
OK -- so your concern is real, wood is wood and it expands and contract etc. Every top of the line Martin neck is machined with a 88.7 +/- degree angle machined on the heel. The main sound board bracing is contoured to 52' radius. The rim and area under the finger-board extension is sloped with a complimentary angle 1.3 +/- degree angle. But even with all their precision machining and assembly capabilities Martin still uses several different bridge thicknesses (I know at least three likely more) to tweak the bridge/saddle height to match the finger-board plane. Thousands of samples have given them a clue of where everything will end up when string tension is applied.
Author:  Terence Kennedy [ Mon Feb 02, 2015 7:47 pm ]
Post subject:  Re: Extra neck angle compensation?
What kind of neck joint are you using Toonces. Glued extension?
Author:  kencierp [ Mon Feb 02, 2015 8:05 pm ]
Post subject:  Re: Extra neck angle compensation?
I certainly agree with Toonces I cover the straight line principle in detail in this article:

http://www.kennethmichaelguitars.com/neckangle.html
Author:  Cablepuller [ Tue Feb 03, 2015 1:41 am ]
Post subject:  Re: Extra neck angle compensation?
Thanks kencierp .. good info on the link
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