Official Luthiers Forum!

Hi all, I'm new to the forum.

I'm building my first guitar from the Stewmac Dreadnought kit (bolt-on neck version). I just finished attaching the back and the top to the sides.

I checked the fit of the neck and I'm noticing a slight hump in the body where the fingerboard will attach. The gap is about 1/32" near the neck and less near the sound hole. See the pictures or a clearer idea of what I'm talking about:





I was careful to keep the sides square to the work-board when I attached the neck and tail blocks. I used the sanding stick method to level the kerfed linings (1.5 degrees for the top and 5 degrees for the back).

The Stewmac directions talk about keeping the sides square to the top when the top is glued on, but that did not really make any sense to me. If you have just sanded a 1.5 degree angle all along the top there is no way for the top to stay square with the sides!

In any event, I am wondering if anyone has any advice on how to deal with this?

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--Mark
Webster, NY
http://thecraftsmanspath.com

Hi Mark, and welcome to the OLF.

Regarding the hump, there are several ways to deal with it, as some others will surely point out shortly. Some prefer to "true the upper bout", which several posts are in the archives on how to do this with either a sanding block elevated at the bridge area, set to the proper angle. Hesh should be along shortly, as I think he uses his fingerboard with sandpaper attatched to the area over the bout.

I had the same exact problem with the 000 I am currently building, and I did something similar to Hesh...I took a 1X2 and attatched a piece of sandpaper on one end. On the other end I put tape, the thickness of the sandpaper. I sanded the upper bout, with the non-sandpaper side of the stick riding on the neck (sanded it like a windshield wiper). But first, I made a special straightedge, with the area in the hump cut out of it, to set my neck angle to where I wanted it. After doing the sanding, I sanded with the grain to clean it all up. I am sure there are easier ways to do it, but this worked for me.

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Brad Tucker

By the way, I'd check the neck angle in relation to your bridge first...no need to go through all that sanding just to have to do it all over again. Some people use a flat upper transverse brace to eliminate the hump, but I have found that a brace with a 1/32" arch works out great for me.

You may find that, after you get the neck set just right, a lot of the problem there will be lessened

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Brad Tucker

http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=15321&p=219039&hilit=neck+angle+upper+bout#p219039

hope this helps.

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Brad Tucker

Brad,

Thanks for the info. Looks like a reasonable method to address the hump. I agree on setting the neck first. Any words of wisdom out there about that process?

--Mark

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--Mark
Webster, NY
http://thecraftsmanspath.com

I've preferred to use a tool like the one Todd posted in the linked discussion (though building to a normal radius then sanding the extension area flat has worked fine for me). My difference was that the end was non-adjustable, and the height at the axle adjustable instead. With the sanding block the even thickness of the fret board, you can adjust the height in the bridge area to whatever bridge height you are aiming for. If adjusted straight to the intended bridge height you could actually set the angle just by leveling the extension to the top (though this may not be the most fool-proof method). If you want to design a bit of fall away you could adjust to a lower bridge height.

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Eschew obfuscation, espouse elucidation.

Mark,

The best advice I can give about setting the neck is to keep a close look on the "big picture". Everything relates to everything else, sort to speak. On my dreads, I've got the geometry correct in the fingerboard extension area with a slight arch to the upper transverse brace (UTB). Here is how I go about setting the neck.

First, I don't glue the fingerboard to the neck...it makes for a pain when it comes to setting the angle at the heel. If using a bolt on neck like LMI sells, or handmade, I bolt the neck to the guitar as it would normally be. I temporarily clamp my fingerboard, which has 2 index pins through it and into the neck. I then set my bridge at the scale length + compensation (right where it will be permanantly). I make a light pencil mark at the tail of the guitar at the centerline of the soundboard. I then take a straightedge and place it against one edge of the fingerboard, with the other end extending over the tail end of the guitar and make a light mark, then do the same for the other side of the fingerboard. This gives me some idea of how far off centerline the neck is, and which side of the heel needs sanding. I then place the straight edge on it's edge, on top of the centerline of the fretted fingerboard, with the other end passing over the bridge (or against the front of it if the neck angle is already too low). I prefer to have a small amount of airspace between the bridge and straightedge, maybe 1/32" or so. Some people prefer to have the straightedge rest on top of the center of the bridge. On my dreadnoughts, the length of the heel is approximately 1/3 the length of the distance from the edge of the guitar to the saddle, so whatever the amount is that you need to get the distance right between the straighedge and bridge top is divided by 3, and that is the amount that has to be taken off either the top or bottom of the heel, changing the angle. On a 000, this amount will not be as much, because the heel is not as tall, so you will have to do some math to figure out the right amount, and hopefully someone here can help you with that. If it's quite a bit, you can draw a line which is the figured amount at one end and "0" at other end of the heel cheeks, and pare it down pretty close to the line with a sharp chisel. You have to keep in mind that you may be trying to work 2 different issues at the same time; the heel angle and the centerline adjustment. When I get pretty close, I take a strip of sandpaper and "floss the joint" by lightly bolting the neck in, or slipping in if a dovetail, and slide the sandpaper back and forth between the heel cheeks and the guitar side. One way to make this easier is to undercut the inner part of the heel cheeks so that only the outside 1/16" or so make contact with the guitar sides; it makes sanding much easier, and I do it before I even begin to set the neck.

Just work and judiciously remove wood, checking the fit often. Take your time. I have set a neck in as little as 15 minutes, and as long as 8 hours, getting to the point where I wanted to toss the whole guitar out the back of the shop!

Another thing, if you have the hump there, you have to take it out of the equation. I have a straightedge made for just this. It has the fretboard extension area sanded away, and it is notched on the bridge end the thickness of the fingerboard with frets. I can use it to set a neck without using the fingerboard if the hump is and issue.

There are several other ways of doing the neck set, and I am sure other folks have better ways, but this is what works for me. One thing I became quickly aware of on the 000 I just finished. It being a 12 fretter, there is a LOT of fingerboard extension area and I have been cruising the archives here, soaking up some good info on dealing with it! This forum is as good as any book on the subject. A lot of stuff is in the archives, but can be a pain to find.

I really hope this helps, and maybe some others will give you their take on the neck set.

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Brad Tucker

I always find it interesting to hear how others set a neck .. some with the FB on, some off, some flattent he upper bout area, some use a flat UTB, some change the radius (like to 60').

Anyway, I do mine with the FB on, and with a 28' UTB radius. The math seems to work out fine with this, I simply flatten out the slight curvature of the top under the FB ext (this is almost nothing, about 7-8 thou) and then set the neck such that the FB lies FLAT on the top - I dont pay any particular attention to what the neck angle is cut at - it doesnt matter, its cut to whatever it needs to be to get the FB ext lying flat. I actually under cut it a couple hairs such that the neck it pitched FORWARD to begin with, then by flossing the joint with sandpaper, it not only brings the neck back into correct alignment, but tightens the heel/side joint at the same time - if you build a guitar with a curved neck joint area, this is essential. The neck heel angle is cut flat on the table saw, and the body is curved - so somehow this needs to mate up. Floss it till it does. I find that there is always a slight gap at the top of the heel that requires a slight shave about 1/2 inch down on the heel edge with a sharp chisel - this usually brings the heel in tight all the way down.

While flossing the neck back from its pitched forward position, when it gets close I stop, and then put in the neck inserts for my heel bolts. I bolt the neck on, and check for centre line, then adjust one side or the other as required. Keep on flossing evenly now until the neck and FB ext sit tight, and flat respectively. I am now done setting the neck. Using a 1/4 thick FB to start, I find that a straight edge will lie about 1/32 to 1/16 above my test bridge as I call it - its an old bridge thats too thin . about .315 inches - thats where I want the FB plane to sit above once the FB is radiused, with no frets. Once the board is then fretted, I will need a true bridge height of about 0.350 or so.

On a 12 fret guitar, I will sometimes taper the FB from nut to 20th fret when radiusing to get the bridge height I am after. Maybe use a bridge thats slightly higher as well - depends on how it all lines up.

Hope that makes sense, and helps out some.

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Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

Tony's process is very well explained and that's pretty much the way I do it, except I use 220 PSA sandpaper instead of "flossing" (I slide the neck back and forth until I have no gap). I've used as steep as a 15' radius for the top and had no problem, neck angle ends up being 88.5º or so, it needs to be addressed/calculated before building the radius onto the rim obviously.
One more detail: it's much easier to get a perfect fit between the neck heel and the upper body when the rim is dead flat (vertically), a slight curve there makes things very difficult.

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Laurent Brondel
West Paris, Maine - USA
http://www.laurentbrondel.com/