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I've built several guitars now, and have had mixed results on the geometry of the fretboard, angle of the neck etc. I'm wondering how you handle the issue of the fretboard "gap" when gluing fretboard to neck on a steel string. Somogyi's book describes his process, but it doesn't help much (at least in my interpretation of his description) since he builds a "coplanar" neck - my read on this is the neck is attached dead-on straight.

The design I'm following is built to have the neck on a slight angle - as members of this forum have taught me to do.

Specifics - steel string, 000 sized, 25 foot radious on the top (15 foot on the back, although I'm not sure that's relevant.) Neck is attached to the body using an M&T with bolts - I've learned to love this method as it allows me to attach and remove the neck at will while flossing the neck and checking neck angle, etc.

Here's the question. I'm about to tackle the fretboard (slot it, cut to size, glue to neck and hammer frets in). As I look at the fretboard, placed on the top of the attached neck, quite logically, the fretboard sits flat on the neck, then theres a wedge shaped gap between the fret board and the top of the guitar, increasing as it gets closer to the soundhole. I have sanded the top flat, at the point where the fretboard will be touching it.

How do you accomodate this? Will the string tension bring the top up to the fretboard? By clamping and gluing the fretboard to the top, will the fretboard "bend" at the proper point?
For what it's worth - I plan to follow the instructions that Frank Ford posted on refretting, expecially regarding sanding the fretboard, at a slight angle, from 12th fret down, to attain the slight "fallaway" that we're looking for.

Thanks for the help - apologies if this is not clear.

Corky-
Just to give readers a bit more info on the 'geometry' you are working with....
How thick is your fingerboard?
How big is your 'wedge-shaped gap'?
If you place a straightedge on the 'bare' neck (without fingerboard), what's the distance between the straightedge and the soundboard at the bridge location?

Thanks
John

Hey Corky,

The quick answer to how I avoid the 14-fret hump is by not radiusing my fretboards till after the neck is attached to the body. I do all my finish work with the neck and body separate. Then once the neck is attached I radius and fret.

I don't really understand the gap you are referring to. I build with a flat upper transverse brace above the soundhole. I sand a slight angle into the portion of the rim above the soundhole before attaching the top. Once the top is on I sand the portion above the soundhole to fine tune the angle until I've got a 2.5mm gap at the saddle position when a strightedge is placed on the top above the soundhole. When cutting the neck joint I make sure the angle of the joint matches the top angle exactly. That way it is a smooth transition off the neck blank onto the top of the guitar. When the fretboard is glued onto the neck blank there is no gap over the body. This ensures that when the neck is finally attached there should be no gap and no hump to deal with. By radiusing the board after it is attached it ensures that the hump will not be an issue.

There are many different ways people go about dealing with this problem and it took me a while to figure it out. This works very well for me, but I'm sure there are a number of other ways that might be just as good or better depending on your set up.

Josh

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Josh House

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Hey Josh

That's seems like a great idea.

How do you hammer in the frets over the body?

Neil

With the neck in place as is, with the gap, is the neck angle where you want it? In other words, does a straight edge on top of the neck project to the correct height at the bridge?

That relationship is primary, everything else follows.

If that angle is correct, the next question is how much of a gap there is at the soundhole end. If it's about 3/64", you're probably good to go. You can flex it down to glue it and string tension will rotate the neck up to flatten it back out.

The reason to have fall-away from the 14th fret to the soundhole is so the neck can rotate up a bit with string tension without creating a rise past the 14th fret. The amount you need depends on the rigidity of all the parts involved.

One way to estimate how much fall-away you need is to bolt the neck on and flex it to simulate string tension.

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Hey Neil,

Hammering the frets in over the body isn't too hard. You just have to make sure you are supporting the fretboard. A tool like the

Fret dolly http://www.lmii.com/CartTwo/thirdproduc ... Fret+Dolly

or just a chunk of steel is all you need. I need to buy a Taylor Fret Buck but I haven't wanted to spend the money.

Josh

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Josh House

Canadian Luthier Supply
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House Guitars - Custom Built Acoustic Instruments.
http://www.houseguitars.com

I hope this is not a hijack. I am nearing closing the box on two guitars that are warm ups and refreshers for my 12 string slope dread build. I am counting upon the flattening of the portion of the upper bout 25' radius at the fretboard attachment zone to avoid the hump-done to the appropriate straightedge-hover above the bare bridge-per Hesh's tutorial(I also built the bridge pivoting sanding board as a method to flatten). I have been setting up fretting for pressing. Back when I learned fretting I hammered. Now, I am set up to press and have done practice runs fretting the FB before any attachment-using gauged nut files and a couple of saws to adjust fret slots (and the "Fret Barber" which is really effective) for backbow control.(some of the variety came about because I have made some ebony with inlay FB's for already built Les Pauls-custom dress-ups-I have to deal with the necks as built and the inherent backbow/relief already there and one-way trussrods).

Am I barking up the tree of a totally different topic? My gut said this is the same topic and I want as many alternative methods available to me as possible-my reaction to the OP's question was to immediately think of the flattened upper bout zone as the simple answer;refined by fret fit and its effect upon neck relief. Comments? Thanks, mt

John - thanks.

The fingerboard isn't to final thickness yet. Some more to take off yet.

When laying a straightedge on the neck (without fingerboard) at the bridge location, the straightedge is about 140 thousandths above the top.

As for the gap between the fingerboard and top, at the top of the soundhole, tough to measure with precision, but it's about 50 thousandths. (With no tension, or weight on the top, to simulate tension.) Thanks!

I'm thinking that when the fingerboard is at final thickness it will be possible to glue and clamp and it will create the "fallaway". Your thoughts?

If not wanting to put the frets on when the neck is attached to the body, Wouldn´t it be a soluthing to simply screw the neck on (bolt on neck) then radius the neck, then take it off and fret it !. ???

Lars.

I do not know what thickness you shoot for your fretboard and bridge, but assuming it's going to be what it is in the centre now, you should be in good shape for the usual dimensions. If I understand correctly, the gap is at the end of the fretboard extension at the soundhole? So it sounds your neck is overset and you need to take some material off the heel right under the fretboard. Closing the .050" down to the top will lower the position at the bridge of more than .050", but not much more. Bridge thickness is usually between .300" and .350", fretboard .180" to .250". Just make sure the top right under the fretboard extension is flat, and not domed.

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West Paris, Maine - USA
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Again, the starting point is getting the neck angle so that the strings are the correct height above the top at the saddle. If you don't know your final fretboard thickness, you don't know whether your neck angle is correct. You don't need to know to the thousandth but within .010" would be helpful.

Second, it's good to have some fallaway from the body to the soundhole without string tension. The neck block will rotate as you tighten the strings and it's helpful to account for that. Frank Ford suggests .020" if I remember correctly but that's for a re-fret. I use more than that on a new guitar because it will continue to distort over time. How much depends on the overall stiffness of your rims, plates, and bracing.

Third, humps at the neck/body joint can also arise from improper clamping. Since you are clamping two surfaces at 90 degrees to each other, it's important to add clamping pressure incrementally. In other words, you want to tighten the bolts snug, then clamp the fingerboard ext snug, then fully tighten the bolts, then add full clamp pressure.

Good luck.

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Corky-
As Laurent and Kent have pointed out, you need to decide on a fingerboard thickness and preferred bridge thickness and saddle height before you will know if your neck angle is correct.
If it were my project, using a 1/4" thick (at the centre) fingerboard, I would be leaving quite a lot less than 0.140" clearance over the soundboard at the bridge, with a straightedge on the 'bare' neck. You should get more opinions on this, I think.
If you just clamp your fingerboard to the body, and lay a straightedge along the FB, how far above the soundboard is the straightedge at the bridge location? By eliminating the .050 gap between the FB and top at soundhole, you may be in the right 'neighborhood' with clearance at the bridge.
Some builders fit the fingerboard to the body, tapering the FB underside if necessary, and then set the neck angle to 'fill the angle' between the FB and the side, at the heel. Several different approaches will all work for this stuff.

Taking some time with some thread to simulate string height, toothpicks for fret simulators, etc at this point will be a good thing to do. I find it easier to do a 'mock up' rather than getting too buried in numbers and diagrams, sometimes...

Cheers
John

Would someone please tell me if I'm talking the "apples and oranges?" Does the flat upper bout minimize potential fretboard to top gap and provide the means to get the fretboard thickness to bridge(and potential saddle height)relationship correct? For a "conventional flat-top"(domed) is 1.5 degrees a common neck set angle, subject to fine tuning?

On the two I have going, my 25' dishes have produced an upper bout with subtle dome and most significant part to level being the neck block(it goes from aligned with "flat" at the outer portion glued to the sides, tapering up to about 1/16th" high at the block edge going "south," in the interior of the body. My pivoting sanding block(or my piece of 1/2" thick, dead flat 6061T6 aluminum with sandpaper) will give me a flat rim and neck-block including the "north" 3 1/2" to 4" approximately-from soundhole to outer edge of neck mortise. I cannot grasp needing built-in fallaway with this neck to top to bridge relationship.(typically my FB will be .210 +.010/- 0 thick at the soundhole end).

Please keep in mind that I first started building when Sloane was all we had-no radius dishes, and "cut and try" to close the FB to top gap and at the same time maintaining relationship with bridge thickness-carefully planing in some fallaway clearance-hit or miss- and spot sanding a flat in the top under the FB extension. Less "rim profiling" information than Cumpiano. Thanks, mt

http://www.youtube.com/watch?v=QYHPCeVRUA4 this video may help explain what you have to do to control that hump. This is done using a 1 1/2 degree neck angle on a dred.

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John Hall
blues creek guitars
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