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Build #2 - upper transverse graft question
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=26191		 Page 1 of 1
Author:  Gtrman13 [ Mon Feb 22, 2010 1:08 pm ]
Post subject:  Build #2 - upper transverse graft question
I'm in the midst of my 2nd, 3rd, and 4th builds (all the same design) and I have a question regarding the bracing. My first guitar was based on an OM design and I did not include an upper transverse graft. The fingerboard went all the way over the upper face brace and up to the soundhole edge. The guitars I'm building right now are based on a gibson L-00, and the fingerboard does not stretch as far onto the body. I like the idea of not putting the graft on the guitar, but I feel that it may be more important on these guitars for structural integrity. On the other hand, the kind of neck block I use is probably a bit larger than a normal one, so that may give a little bit extra support. I really don't know. I've finished up all of my other bracing and am ready to glue my sides on, so I guess I need to get this figured out before I take that step. Any opinions here, folks?

Here's a picture of the underside of the soundboard with the fingerboard placed to show where the end of it will be.

Image
Author:  Edward Taylor [ Mon Feb 22, 2010 1:18 pm ]
Post subject:  Re: Build #2 - upper transverse graft question
What about cutting the neck block down and putting a piece on top to extend it almost to the brace?
A lot of guitars are built like this.
Author:  Michael Dale Payne [ Mon Feb 22, 2010 1:25 pm ]
Post subject:  Re: Build #2 - upper transverse graft question
A fretboard the fall short of the sound hole will likely cause as much or possibly even more chance of inward rotation leading to top splitting. And more so if the end is not well supported by a UT brace. If you use a cantilevered "L" shape neck block you greatly reduce this problem but if you use a straight neck block I suggest you have the UT graft.
Author:  Tom West [ Mon Feb 22, 2010 2:58 pm ]
Post subject:  Re: Build #2 - upper transverse graft question
Not sure I've seen a guitar with the fingerboard end this far from the sound hole. Is this a 14 fretter neck on a 12 fret plan..?
Author:  Hesh [ Mon Feb 22, 2010 4:24 pm ]
Post subject:  Re: Build #2 - upper transverse graft question
What Tom (Westca) said - why is the fingerboard extension ending so far from the sound hole?

There are a number of options here including the paddle on the neck block as mentioned. Brian Kimsey (Google him and check out his excellent site) has been involved in hot-rodding guitars where part of the treatment is to remove the popsicle brace and free up the upper bout more.

Brian also is known to use a patch instead of the popsicle brace and I personally like this idea better than using nothing at all.

Another option IIRC is that John Hall will cut down the popsicle brace to about 6 inches long. I like this idea too.

Then there is A-frame bracing which a lot of builders also use with seemingly good success.

I have a great picture of what can happen to a guitar when the popsicle brace fails but it's on one of my other computers and I will try to remember to post it later. Anyway this guitar has a popsicle brace, a Guild, and .... well when you see the picture you will understand that the popsicle brace as we know it is not all that effective anyway...

Lastly and it may be the perspective of the pic but your UTB looks a little on the smallish side to me and from here. This brace, unlike the popsicle brace, is very important and needs to be dimensioned for the forces that act upon it.

I'll be back with the pic I mentioned.
Author:  Alan Carruth [ Mon Feb 22, 2010 4:29 pm ]
Post subject:  Re: Build #2 - upper transverse graft question
As far as I can tell, the purpose of the upper transverse graft is to keep the neck from shifting inward when the top splits on either side of the fingerboard, either due to impact or fingerboard shrinkage. It's not tall enough to present much resistance to downward movement: that's the job of the UT brace. The graft simply has a lot of gluing surface to prevent shifting.

The problem is that it might not work, depending on the glue you use and how well it's done. I've seen guitars that were put together with white or yellow glue shift, even when the glue line was not broken. That stuff can 'cold creep' a surprising amout without ever letting go. The issue becomes worse if the top is not really smooth, and the surface has not been freshened up just before gluing.

In this case, I'd be inclined to put as wide a patch in as I could fit, prefferably filling in the whole area between the block and the UT brace. With the 'board ending at the UT brace, there's a lot of force concentrated in a small area.

Withal, I'm not a big fan of the patch: I find that A bracing from the upper arms of the X through the UT brace and inletted into the block works much better. Kind of late for that here, though.
Author:  Jeff Highland [ Mon Feb 22, 2010 4:55 pm ]
Post subject:  Re: Build #2 - upper transverse graft question
I'm with Alan on this, especially with a narrow UTB like you have used, there is not much glue area to resist shear from the top of the block and the section of the soundboard attached to it being pushed into the soundhole.
Author:  TonyKarol [ Mon Feb 22, 2010 6:12 pm ]
Post subject:  Re: Build #2 - upper transverse graft question
Easiest fix IMO .. add another UTB ... it cant hurt.
Author:  Hank Mauel [ Mon Feb 22, 2010 7:03 pm ]
Post subject:  Re: Build #2 - upper transverse graft question
Check out this post in the Video and Picture Tutorial section of the Forum:
viewtopic.php?f=10117&t=24866

Solves all your potential problems! ;)
Author:  Pete Brown [ Tue Feb 23, 2010 7:35 pm ]
Post subject:  Re: Build #2 - upper transverse graft question
Gtrman13 wrote:
I'm in the midst of my 2nd, 3rd, and 4th builds (all the same design)

A little off-topic I'm afraid, but I question the wisdom of a building more than one instrument at a time when one is "learning the ropes". I travelled the same path myself, but came to the realization that in doing so, I was reducing what could be learned from each instrument along the way, for a given expenditure of effort. If the designs are truly the same, it's likely that their strengths and weaknesses will be similar too.
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