Official Luthiers Forum!
http://mowrystrings.luthiersforum.com/forum/

How to correct an neck angle that is too high
http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10101&t=50002		 Page 1 of 2
Author:  Bryan Bear [ Wed Nov 29, 2017 5:07 pm ]
Post subject:  How to correct an neck angle that is too high
Okay ladies and gentleman, I have discovered a new (to me) way to mess up. I'm sure I'll do them all before all is said and done :)

I have two bodies I just finished up and am in the process of making necks for them. They were made a long time ago before some other issues kept me from guitar making for a good long while. As such, I can't really remember what I would have done differently to cause this. Both bodies have the same issue. Bolt on butt joint. I have roughed out the angle on the heel such that the plane of the FB is in line with the plane of the top from heel to soundhole. At this stage I would normally be able to set the fretted board on the neck and a straight edge on top of the frets would hit right around the top of the bridge. That seems to work out well for me so that adding the height of the saddle gets my string action in a good zone. However, I just checked both bodies with UNfretted FBs and the straight edge projects several millimeters above the bridge. Adding fret height will make this worse.

So what now? I can understand how needing to add neck angle during a reset can be done even if it means increasing fall-away beyond the neck joint. I don't know how to go about decreasing the neck angle without causing the FB extension to rise at the body joint.

I have some ideas but I don't like any of them very much. I think I'll wait for some answers before I offer my thoughts.
Author:  WudWerkr [ Wed Nov 29, 2017 5:44 pm ]
Post subject:  Re: How to correct an neck angle that is too high
how much are we actually talking here ? actual Amount above
Author:  Bryan Bear [ Wed Nov 29, 2017 5:56 pm ]
Post subject:  Re: How to correct an neck angle that is too high
I didn't measure at the time (I just walked away to think. . .) They are both slightly different but I would guess around 5mm not including fret height.

A I sit here, I think I may have realized what went wrong but I'm not 100% sure this explains it. Both of these are my first two 12 fretters but using the regular shape (not having a longer upper bout). As such, the bride position is slightly further back than it would normally be. I would not be surprised to find that if I laid a bridge blank in the normal position it would like up properly. :(

At any rate, the boxes are done now so I have to figure out a workaround. . .
Author:  Ken Lewis [ Wed Nov 29, 2017 6:14 pm ]
Post subject:  Re: How to correct an neck angle that is too high
Remove material from underside of fretboard over body area to keep things straight, as well as adjusting your
neck angle of course.
Ken
Author:  SnowManSnow [ Wed Nov 29, 2017 6:46 pm ]
Post subject:  Re: How to correct an neck angle that is too high
If it’s only a few mm high flossing under the front cheeks should ease you into where you want to be shouldn’t it?
Disclaimer : I’m too new to be taken seriously haha


Sent from my iPhone using Tapatalk Pro
Author:  Bryan Bear [ Wed Nov 29, 2017 6:53 pm ]
Post subject:  Re: How to correct an neck angle that is too high
To clarify my question, I know HOW to change the neck angle but moving it forward will make a slight angle between the neck plane and the plane of the top. This means the fretboard plane will rise slightly at the body join which is the opposite of what you want.

On one of them, I can remove some material of the fretboard extension but the other fretboard has side purflings which would get (at least partially) removed.
Author:  jfmckenna [ Wed Nov 29, 2017 6:58 pm ]
Post subject:  Re: How to correct an neck angle that is too high
It's possible that you could run into intonation issues if it's really off by that much, assuming the bridge is already glued down. If that is the case your best option would be to rout a thicker bridge saddle slot or just make a new bridge. Otherwise just plane the end of the fretboard down and feather it off into the whole of the fretboard, it's a typical classical guitar approach. You will just have to do the purflings over again. Sucks but what are ya gonna do?
Author:  George L [ Wed Nov 29, 2017 7:11 pm ]
Post subject:  Re: How to correct an neck angle that is too high
You might be able to create a little more space beneath the fretboard extension by slightly thinning that area of the top. Depends on how thick it is now, of course, and how it's braced.
Author:  Bryan Bear [ Wed Nov 29, 2017 7:12 pm ]
Post subject:  Re: How to correct an neck angle that is too high
Bridges are not on yet. So, I have the option of using thicker bridges but that could possibly change the stresses involved.
Author:  J De Rocher [ Wed Nov 29, 2017 7:58 pm ]
Post subject:  Re: How to correct an neck angle that is too high
If I understand correctly, when you place the neck in position with the fretboard in place, the fretboard still contacts the fretboard extension area evenly. No gaps, correct?

George L wrote:
You might be able to create a little more space beneath the fretboard extension by slightly thinning that area of the top. Depends on how thick it is now, of course, and how it's braced.


I was going to suggest the same as George with the same caveats. If you tape a spacer on the top at the saddle position the thickness of which matches your target height, you can sand the desired angle into the fretboard extension area with a flat, straight board resting on the spacer at one end and with adhesive-backed sandpaper on the other end over the fretboard extension area. I use this approach to flatten the extension area with the correct angle on my guitars. I'm assuming if you tried this on your two guitars, it should start removing wood first at the sound hole end of the extension area which would end up creating more vertical space for the end of the fretboard after adjusting the neck angle. The question would be if you could adjust the angle of the extension area enough without removing more wood than you would want. A little math could give you an idea if it would be feasible.
Author:  Bryan Bear [ Wed Nov 29, 2017 8:03 pm ]
Post subject:  Re: How to correct an neck angle that is too high
Thanks all! I’d like to keep the discussion going for a while before I do anything. I’m getting lots of good ideas. Each of them have drawbacks; I promise, I’m Not trying to shoot them down. I think in the end, I will do a little bit of all of them to reduce the drawbacks and hopefully get where I need to be.
Author:  Clay S. [ Wed Nov 29, 2017 9:24 pm ]
Post subject:  Re: How to correct an neck angle that is too high
You could do a "millennial" guitar.... which is to say a - little - bit like the millennium guitar design Thomas Humphries created, with the neck raised above the top of the guitar. You wouldn't have to make it as radical, but bring it up enough to make it look intentional. [:Y:]
Author:  Trevor Gore [ Wed Nov 29, 2017 9:59 pm ]
Post subject:  Re: How to correct an neck angle that is too high
Double post. Don't you hate slow connections!
Author:  Trevor Gore [ Wed Nov 29, 2017 10:03 pm ]
Post subject:  Re: How to correct an neck angle that is too high
Bryan, the approach you are taking means that it's the slope of the upper bout that sets the neck angle. Nothing wrong with that, it's an approach that works well, but the slope of the upper bout has to be right. When you place a straight edge on the upper bout (no neck or fretboard) the clearance over the saddle position for a twelve fret neck joint should be around 2.5mm (or a little less, depending on your preference). If you thin the top just above the sound hole by, say, 0.5mm you will get just over 3 times that in drop over the saddle (~1.7mm). Depending how thick your top is you may be able to find ~ 2.5mm of your several there. If you want to attempt that, think about how thick your rosette is. You will need a matching heel angle adjustment, too. After that, if you still have to find more, it's thinning or tapering the fretboard or a bit of both. If you can get the string height off the soundboard at the saddle into the 12-14mm zone with the action you want, all will be good. Then just thin the bridge to give the saddle protrusion you want, maintaining the 12-14mm string height.

If the error is too large to allow those numbers to work, Clay's approach above is a good one. If the truss rod adjusts from the body end, make sure that you can still do that with the "Humphrey wedge" in. This is what it might look like with a modest wedge (this one's a tilt-neck, which obviates the problem ;) ).
Author:  Hesh [ Wed Nov 29, 2017 10:37 pm ]
Post subject:  Re: How to correct an neck angle that is too high
Not sure that understand what's different here than setting the neck angle and fitting the neck. I just had a forum request today for this toot: http://www.luthiersforum.com/forum/viewtopic.php?f=10102&t=15022&p=214039&view=show#p214039

These days when resetting necks I only use a chisel and it's faster and only floss after I get close. But I also suspect that you are not asking about setting the neck angle and I'm not understanding the issue. What am I missing if this is not setting the neck angle?

Image

BTW what Trevor and others are discussing is a technique often done on instruments during a reset and it's called a "tongue shim."

So I'm not understanding why this is not an setting the neck angle issue but you also have the option of shaping the fret plane including the extension after the neck is on and before fretting.

In our classes we teach people to mill fall-away into the board on the guitar prior to fretting. If it comes to pass that it's not a neck angle issue to get to a static and predetermined bridge height, which is pretty important in terms of rotational forces on the bridge then it's an issue with how flat and what angle the upper bout is. Trevor said that and I agree completely. That's one of the reasons why we flatten the upper bout or build less radius into it or both. This subject is addressed in a tutorial called "Flattening the upper bout."

Here is "Flattening the Upper Bout". http://www.luthiersforum.com/forum/viewtopic.php?f=10117&t=25931&hilit=flattening
Author:  Bryan Bear [ Wed Nov 29, 2017 11:01 pm ]
Post subject:  Re: How to correct an neck angle that is too high
Hesh, I am sure I am falling short in describing my issue. As Trevor pointed out my method for setting the neck angle has been to build the neck geometry into the body. I flatten the upper part of the rim, not unlike the way you show in one of your tutes. The resulting upper bout plane dictates the angle of the neck set. That has always worked well for me. For some reason, the two boxes ended up with an upper out plane that sets the string height too high at the bridge location. I suspect that it is because I am using 12 fret neck attachments and I didn’t account for the bridges being a bit further away than normal.

Now, setting the neck angle that would give me the proper string/bridge height would not be in line with the plane of the upper bout. Essentially giving me the ski jump instead of fall-away. Or, setting the neck angle to match the plane of the top would make the string height too high.

One of the boxes has a WRC top so I don’t want to just raise the saddle height. I don’t want to increase the stress on the bridge/top glue line.

Edit:
Trevor actually linked to your tute I mentioned above. . .
Author:  Hesh [ Wed Nov 29, 2017 11:13 pm ]
Post subject:  Re: How to correct an neck angle that is too high
Cool, thanks for that now I understand. OK my approach now would be a combination of a tongue shim and inducing fall away to eliminate excess fret board extension kick-up. You will have to do this with the neck installed on the instrument and it can be done after finishing and during final assembly.

Some fret slots at the end of the extension may have to be deepened.

Or, in other words the shim under the extension, wedge shaped butted next to the heel raises the board angle in that location and thinning the board extension progressive from the neck joint to the last fret lowers the extension angle. That should do it.

This is also one of the reasons why fretting on a finished instrument has advantages since we can shape the neck and fret plane at will in respect to the top and bridge. Ultimately how the strings see the fret board is what matters, what's under it simply how we get there.
Author:  Trevor Gore [ Thu Nov 30, 2017 3:13 am ]
Post subject:  Re: How to correct an neck angle that is too high
Bryan Bear wrote:
Edit:
Trevor actually linked to your tute I mentioned above. . .

I know there's some weird stuff happening on the forum. I thought it was my computer getting hung up with a slow connection that makes it look like a total drop-out and then, hey, all of a sudden I have two posts. But I didn't link to a tute. Not anywhere I can see anyway! But I can see how you can see the link and my name in the same window!

Anyway, regarding the neck angles, a bit of measuring and you should soon be able to figure out what will and won't work for you. You may well choose a different option for the different guitars. There's no reason why they shouldn't both play good and look good.
Author:  truckjohn [ Thu Nov 30, 2017 10:37 am ]
Post subject:  Re: How to correct an neck angle that is too high
I have done the wedge under the fretboard a couple times... It works well.

The biggest thing I see is doing it so it looks like you planned to do this on purpose - not as a way to cover up a mistake... ;) ;) ;)
Author:  Bryan Bear [ Thu Nov 30, 2017 11:01 am ]
Post subject:  Re: How to correct an neck angle that is too high
That is so very strange. I could have sworn that post was under your name. Maybe my little phone screen was playing tricks on me last night. Sorry for the confusion everyone!
Author:  Quine [ Thu Nov 30, 2017 1:06 pm ]
Post subject:  Re: How to correct an neck angle that is too high
How about changing it to a floating bridge and tailpiece. Claim that was the original design
Author:  rlrhett [ Thu Nov 30, 2017 2:03 pm ]
Post subject:  Re: How to correct an neck angle that is too high
Don't scold it. Time for that later. Give it a blanket, turn down the lights, put on soothing music...





Oh, sorry, I guess I misunderstood. ;-)
Author:  Bryan Bear [ Sat Dec 02, 2017 3:30 pm ]
Post subject:  Re: How to correct an neck angle that is too high
After letting my frustration subside a bit, I finally got a chance to get back down and take some measurements. One of the guitars will be okay. The wood I was planning to use for its bridge was on the thin side; a slightly thicker bridge should get me there. If need be, I could also remove some material from the underside of the FB past the 12th fret. This is the second one I looked at after discovering the problem on the first. Looks like I panicked when giving it a quick check and it was not as bad as I thought. I’m placing the blame on this one squarely on forgetting to account for he bridge placement being a bit further back for a 12 fret.

The other one is in worse shape, so I must have made some other error when assembling the box. I’ll probably never figure out what it was which is a shame. This is the second top because the first one took damage. I’m guessing prepping the rim for a new top is where I messed up. Right now, a straight edge placed on the upper bout (no fretboard) projects a bout 4 1/4 mm above the saddle location. That’s a fair bit more than Trevor’s 2.5mm (or a bit less) suggestion. As he points out, sanding the top into the proper geometry, taking 0.5mm off the top will get me most of the way there. I’m not sure I am comfortable taking that much but I’ll go as far as I can before I start to lose my nerve. The rest will have to be made up by thinning either the bottom or the top of the FB BELOW THE 12 th fret.
Author:  Bryan Bear [ Sat Dec 02, 2017 3:33 pm ]
Post subject:  Re: How to correct an neck angle that is too high
rlrhett wrote:
Don't scold it. Time for that later. Give it a blanket, turn down the lights, put on soothing music...





Oh, sorry, I guess I misunderstood. ;-)


BTW, I took your advice. I think the time-out was just what the second one needed to be brought back in line. But you know how each child is different. . . The other will need a different approach to correction. :)
Author:  sdsollod [ Sat Dec 02, 2017 5:55 pm ]
Post subject:  Re: How to correct an neck angle that is too high
Bryan, You said, "After letting my frustration subside a bit"... I have also panicked and found that most of the time when I thought I was totally screwed, after I sleep on it (and consult the OLF) I usually find a way to fix things. Sounds like at least for one it will work out. Careful not to sand through the rosette. I assume the binding is not on yet because further sanding could reduce the width of the binding... DAMHIKT...
Page 1 of 2 All times are UTC - 5 hours
Powered by phpBB® Forum Software © phpBB Group
http://www.phpbb.com/