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Fretboard extension - tension? HELP!
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Author:  Dave-SKG [ Wed Apr 27, 2005 5:39 am ]
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Does anyone know how much tension is actualy placed on the extension section of the fretboard. It seem to me that that part of the fret board is relatively thin and made even weaker by the fret slots. Looking at the jazz boxes we see that while the fret board is supported in that area they don't attach the FB to the body. Their support on the extension seems only to be there to strengthen the area that might be played on (rarely) by a player.

I would realy appreciate all input as I Recently (today!!!) dropped an otherwise finished neck and the ebony fretboard snapped/cracked right off at the 14th fret. I repaired the break. It is undetectable as it split lateraly and long enough that some ca covered and rejoined it without detection. I am now, of course, very reluctant to use the fretboard any longer but dread removing it and replacing this one if I don't absolutely have to. I truely wonder if the structural integrety has been comprimised since I don't think there is that much tension at this portion of the neck. THANKS FOR ALL RESPONSES!!!!!
Author:  crazymanmichael [ Wed Apr 27, 2005 5:56 am ]
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fret board extension is supported by at least the heel block and the upper transverse brace, some times more in some designs.

it was also not unknown to cut the fingerboard off at the neck body join to effect some repairs, so i don't know that it is so much a matter of strength.

if this is a new build for sale to me ethics says put a new one on. if its a repair, give the client the option of accepting a discount.
Author:  Don Williams [ Wed Apr 27, 2005 5:57 am ]
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It's very difficult to remove a FB without damaging the neck in some way. The fretboard extension is under some small torsional load, but most of that is carried by the upper braces and rim. Not "tension" technically, but some could argue for compression. Mostly it's torsion though. Just don't ask me to calculate the Moments of Inertia around it. Those days are long gone.
Author:  rick s.r.g. [ Wed Apr 27, 2005 7:51 am ]
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Dave, If it's one of your new builds, why not add 2 graphite rod extensions to strengthen it. Just drill 2 holes in the end of the neck right against the fingerboard. C.a. or epoxy them into place then wick some glue to the fingerboard. You will have to rout channels in the top to accomodate the graphite but the fingerboard wont move. I would agree however with Crazyman that if it is a repair to give the client the option. I dont know if I would replace it especially if the repair is undetectable and you can strenghten the break area.
Author:  Dave-SKG [ Wed Apr 27, 2005 8:32 am ]
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The repair is invisible...I mean completely. I like the rod idea...I think I will do that...except instead of length wise I will do them like screws...sort of like Taylor does when he bolts on his fb to the top. THANKS EVERYONE!

p.s. Don when you say "torsion" that makes me think "twist". Is that correct?
Author:  EricKeller [ Wed Apr 27, 2005 9:27 am ]
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The way I see it, the fb and neck are under bending load. Thus the fret side is under compression (good, don't want the frets to get loose and fall out) and the neck/soundboard side is under less compression. The neck is taking up pretty much all the tension that balances the compression in the fingerboard.

There are a couple of factors that could make the two pieces of soundboard want to seperate, so very small reinforcement between them at the soundboard side might be a good investment.

I did the same thing to the fb of my gibson j50 after I took the neck off. Actually did it twice, because I glued it back together and then broke it off again. That's what I get for not finishing projects.
Author:  Dave-SKG [ Thu Apr 28, 2005 12:05 am ]
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Thanks guys!
Author:  Mario [ Thu Apr 28, 2005 1:27 am ]
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It's very difficult to remove a FB without damaging the neck in some way.

Huh? A fretboard, unless glued down with something it shouldn't have, will come up readily and cleanly. It's relatively thin and flat, and is easy to heat it.

I've pulled about a dozen of mine with not even a splinter to speak of.

The reason I had to pull a dozen fretboards? Not all truss rods are created equal <sigh>

Anywho, it can be replaced easily enough. If you plan to sell the guitar, you should replace it now. If you are keeping it, then trying a repair is not a bad idea. Also, remember that until recently, it was normal to cut the fretboard off at the 14th fret and remove that section to steam a neck out to reset it. The extension was just glued back on the top in its place afterwards. Thankfully, that practice is nearly dead(though I know of some repair folks still doing it, to vintage instrumnts, no less <arghhhhhhh!>, but it does show that it works.
Author:  Dave-SKG [ Thu Apr 28, 2005 1:40 am ]
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Mario,
Thanks for chimming in. What that tells me is that the extension doesn't realy do a whole lot structurally since as you said "some repair folks still doing it...".
I was worried about that...I don't have a problem pulling the fret board. I just was being lazy, I guess, and didn't want to unless I absolutely HAD TO!

Thanks Mario, THANKS EVERYONE WHO CHIMMED IN!Dave-SKG38470.4462268519
Author:  Don Williams [ Thu Apr 28, 2005 1:43 am ]
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Dave,
Torsion, in layman's terms is a force that rotates around a given point. Not a twist per se.
Author:  Dave-SKG [ Thu Apr 28, 2005 1:50 am ]
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gottcha! thanks!
Author:  Michael Dale Payne [ Thu Apr 28, 2005 3:55 am ]
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Strings impart torsin, compresion and sheer on a a tendon. Torsion as Don said is constent for the whole length of the tendon, compression is in the upper half of the joint (pulling of the strings want to force the tendon onto the mortise) and sheer in lower half.( the compression of the upper half. (caused by the strings tension wanting to pull the lower end of the mortice out of the mortise) A vastly simplified explanation.
Author:  Dave-SKG [ Thu Apr 28, 2005 5:56 am ]
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Thanks MP,
My necks are bolt on. The problem I was facing was whether or not to put a new fret board on after cracking the end of one off. I repaired it and it is undetectable visualy. My concern is whether or not the guitar is structurally disadvantaged as a result. From what Mario has said about repair people and what I vaguely remember hearing the extension doesn't realy amount for much. Even structurally I don't think my instrument is compromised because my neck block is shaped like a flattened "c" ( sort of like Hanks with a bottom half as well) so I already have a good deal of extra support in that area.
I really do appreciate everyone chimming in ... helped me greatly!
Author:  EricKeller [ Thu Apr 28, 2005 8:38 am ]
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typically, torsion is thought of as a twist. Sort of like   a motor driving an axle. A structural engineer would look at you funny if you said that the strings impart a torsion on the neck, the neck is loaded in bending. Of course they are all kind of mixed up. For example, since the bridge twists forward, you can think of the strings imparting torsion on the top at the bridge.
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