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Some building questions
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Author:  Sprockett [ Tue Mar 15, 2005 3:11 pm ]
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So I've built a number of guitars now, classicals are pretty easy to build and setup (except the soundboard bracing takes lots of detail work) and setup is a breeze... But on my steel strings I departed from the norm and went my own way and now I have a couple of questions about some issues that the prototypes have developed (that's what I get for being creative )

First let me explain my mortise and tenon, I run two CF rods down the neck and extend them out to support the tongue, when assembled it looks like this (this is one that is on the workbench and I just tossed these together):



I actually glue the tongue down onto the braces and then they plug in like this:





What's great about this is that I don't have to glue the tongue down, in fact I just did a neck reset on my first prototype, it was a breeze. I unbolted, trimmed the heel and re-bolted it back and Voila!! done..

However the problem I am having is that I need to remove the 'hump' under the tongue from the soundboard, on the one I just finish the upper area of the soundboard (under the fingerboard) is pushing it up a little and I had to file those frets flat. Took me a couple of days to figure out the problem (I'm slow sometimes ). I'm referring to the area in the photo above where you see the two CF rods floating into the top...

So my question is HOW do other builders flatten that area to match the fingerboard?? I want it at about the same angle so the fingerboard will essentially float out over the soundboard (about 1/32 or less)..

Ideas??

Issue number 2 has to do with setting the neck angle, here is a picture of the latest guitars saddle:



Now despite what you may think this think plays like a dream and sounds wonderful, very very full and rich. I'm not going to change it now because it works but the person that finished setting it up is a friend who has done setups for years and he didn't complain about the low saddle but it made me nuts when I saw it

When I set the neck angle what I did was position the bridge and then using a straight edge on the frets had the edge of it just sit on the top of the bridge. What I'm thinking I need to do is a couple of things:

1. Lower the 1st string side of my bridges a little.

2. Set the neck angle back just a little more.

So what are other builders doing to set their neck angle?

The height of the bridge is about 13/32's on average, I might lower that just a little. Since I'm out blazing my own trail I have to figure these things out as I go.

Any advice would be greatly appreciated.

Thanks

-Paul-
Author:  Dickey [ Tue Mar 15, 2005 4:11 pm ]
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Paul, you explained it all perfectly. As we can see, flying by the seat of your pants. Hey, it works, we all do it. And I might add, you do it well.
Author:  Kelby [ Tue Mar 15, 2005 4:25 pm ]
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Paul, I haven't built enough guitars that you should take my advice, but I don't mind telling you what I do (and it seems to work).

First, I use a dovetail neck joint. I set the neck so that, without fretboard on it, a straigtedge on the neck lies 1/8" off the soundboard at the saddle location.

Later, when it is time to install the bridge, I make the bridge thick (or thin) enough that when I lie a straightedge down the fretted fingerboard it sits 1/16 - 3/32" above the bridge at the saddle location. It sounds like this is the point at which your method and mine differ --- you have the straightedge touching the bridge. With my method, your saddle height would be 1/16-3/32" further off the bridge without affecting the action.

My own view is that if the customer is happy, maybe you leave it alone. However, I also think that the low saddle height results in a very low break angle, and you may be able to improve tone and volume with a greater break angle. You could get that by resetting the neck or lowering the bridge to increase saddle height without affecting the action.

I will be curious to hear what the more experienced folks have to say.
Author:  Neil [ Tue Mar 15, 2005 5:16 pm ]
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Nice looking neck joint design, Paul. What is the design purpose of the extended carbon fiber rods? I think the hump in your fretboard tongue might be related to your shallow neck angle. With a greater neck angle, the fretboard will “fall away” (angle down) from plane of the main part of the fretboard once it is glued to the top. The extended carbon fiber rods might not be flexible enough to allow this, however. You may have to build fall away into the tongue by sanding a slight angle into the carbon fiber rods where they are glued to the tongue.

If you are happy with the thickness of your bridge (13/32” is fine), you need to set your neck back further to allow for a taller saddle. A taller saddle will put more pressure on the top and theoretically transfer more power (vibration) to the top. If you leave it like it is now, you will just have to reset the neck in the future once the guitar settles in under the string pressure and the action rises. You’d be better off to reset it now and lower the new taller saddle in the future. I do a lot of warranty neck resets on old Martins. I also use the straight edge method across the frets. I look for a space of 1/64” to 1/16” between the straight edge and the bridge. It often ends up greater once I have closely fit the heel to the body using the sandpaper method.
Author:  John How [ Wed Mar 16, 2005 1:00 am ]
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Paul, the answer is right under your nose here on the forum. I try to make my guitars so thet the area from the neck joint to the top of the sound hole is completly flat. That way there is no hump and the neck angle (which generally is about the same each time) is what it is and I fit the heel just like you would for a reset. Well when this flat top doesn't cooperate, I pull out this jig from our very own jigs page. Here it is right here.
When you make this jig just be sure that the bottom of the sand paper is aa line that is inline with the angle you want the fret board to sit at. You can do some calulations for you own model too determine how high the pivit point is aat the bridge.

For the neck angle I lay the straight edge on the fingerboard without frets and set it so that is right on top of the bridge or maybe just a hair higher. I want at least an 1/8" of saddle showing all the way across, granted you may have more on the bass side. But I want some adjustment space on a new guitar because it will change down the road. I think maybe you might get better results by increaseing your saddle break angle, you sure can't have much on your treble side on that setup. Maybe others will chime in with their bridge/saddle clearances.

Actually a more important measuement is the height of the string above the top as this is what will determine the torque applied to the top. I shoot for about 7/16 - 1/2" and then I don't want the bridge to be so tall that it interferes with the break angle. My bridge height is 11/32" so I will end up with just over 1/8" saddle exposure in the middle. That allows for some adjustment as the top pulls up a little which it will if you build lightly.John How38427.4388194444
Author:  Sprockett [ Wed Mar 16, 2005 2:31 am ]
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Perfect John, that's EXACTLY! what I was looking for, I know my design works but I never took into account that hump under the fingerboard, once I get rid of that the tongue problem will go away.

I like the way your setting the neck angle too, so I'll adopt that method and see what happens, from the comments here I need to make it a little more which is pretty simple to do.

Neil the CF rods support the tongue so it floats out over the soundboard, somehow I got this right on the first guitar and it works very well, I do think in looking at the design that I need to sand in just a little relief to the tongue because the strings are going to pull the neck up just a little.

Thanks everyone for the feedback, I'm going to make a jig like Johns today and get that hump flat

Cheers

-Paul-
Author:  John How [ Wed Mar 16, 2005 2:33 am ]
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Actually you can thank Lance for that jig.
Author:  LanceK [ Wed Mar 16, 2005 4:09 am ]
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and Ill thank Michael Greenfield

Thanks Mike!

Greenfields Shop tour
Click the shop tour on the right..
Author:  Wade Sylvester [ Wed Mar 16, 2005 4:37 am ]
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Guys, Thanks so much for this post. I have been thinking about solutions for some neck joint issues I have had with some of my builds.
Paul, I like your extended CF rods to support the tongue. Over the past 3 months, my flat fret board seems to have curled up slightly at the tongue causing the middle string notes at about the 14th fret to buzz. It would seem that your extensions would help prevent this. Although I thought I had flattened the aria under the tongue enough and had a nice tight neck set, the migration seems to have happened anyway over time. Is this a common occurrence? Are these one of the things we look for during “break in” of a new instrument before letting it go to a client?
Thanks again and especially Paul for the great pictures!

Wade
Author:  Neil [ Wed Mar 16, 2005 1:57 pm ]
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Paul, I finally figured out that you weren’t gluing the tongue down after my last post. Is there a visible gap between the tongue and the top or does the tongue rest on the top? Have you experienced any buzzing or rattles between the top and the tongue?
Author:  Sprockett [ Wed Mar 16, 2005 5:46 pm ]
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Neil there is a very small gap and no there is no buzzing or rattles at all, that portion of the top does not move much and the tongue is anchored on the CF rods.

-Paul-
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