Official Luthiers Forum!
http://w-ww.luthiersforum.com/forum/

Cross Brace notching
http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10102&t=3343		 Page 1 of 1
Author:  Dave White [ Tue Sep 27, 2005 2:51 am ]
Post subject: 
Following on from the thread on what order tops get braces put on, here's trivial question number 4568.

What direction do you notch your top X braces? Do you notch the X brace that goes treble upper bout to bass lower bout into the X brace that goes bass lower bout to treble upper bout or the other way around? Or do you do whatever the mood takes you? Does it matter which way? If yes why? If no why not?

Did you understand the question? If yes ... oh never mind.

Yours currently bored and mildly curious.
Author:  Don Williams [ Tue Sep 27, 2005 2:54 am ]
Post subject: 
It doesn't matter. Once you add glue to the joint, it becomes a solid unit. Then, a lot of folks add a thin piece over the top of the X to add further support to the joint.
Author:  John How [ Tue Sep 27, 2005 3:07 am ]
Post subject: 
For some unknown reason, my joint cap is always parrallel to the tone bars. I have no real reason for doing it this way but it happens so I figure it must be right.
Author:  Michael Dale Payne [ Tue Sep 27, 2005 3:14 am ]
Post subject: 
I am like Don and feel it does not matter. I make sure my joint is very tight. Once I shallowed my notch then drilled and pinned the braces togather with a press fit rosewood dowel through a rock maple cap. looked cool but noticed no gain in tone, and it was a lot of work that rarly get seen.
Author:  Rod True [ Tue Sep 27, 2005 12:43 pm ]
Post subject: 
Don't it depend on what hand you are?
Author:  Shawn [ Wed Sep 28, 2005 3:15 am ]
Post subject: 
I dont believe that it matter which way you notch it but absolutely do think that it makes a difference to cap the joint. It is a structural issue that can have a side effect on tone.

If you look at any construction site you will see that the holes drilled into lumber to chase electrical wire will always be about the same size and in approximately the same position. This is a structural thing with standards and rules to govern its use. If you notched the top of a beam the overall load bearing capacity of the beam would be not based on the height of the beam but would be reduced to the height of the beam from the bottom of the notch to the bottom of the beam.

Gluing the xbrace together does not replace the loss of structural integrity that was taken away by notching.

I dont know who many were in Ervin Somogyi's workshop at the ASIA symposium and saw his demonstration of sugar cubes...basically where strength is needed the most is where the X brace takes it away...but

By putting a small cap on top of the joint you can gain back almost all of the structural loss of notching. Judy Threet was there and confirmed that she has used a top cap/patch as small as 1/64th and it still made a big difference in the structural integrity of the joint.

It is not that glue wont hold the notch or that without a cap the joint will fail...it is nothing like that...it is a matter of making sure that by stiffening up the x brace the "drum" of the top is as rigid around the perimeter of the drum so that the top will provide maximum resonance.

Think about the cloth patch over the x brace we have all seen in guitars...it wasnt stylistic, it was to add back some of the support that was lost as soon as the x brace was notched.
Author:  LanceK [ Wed Sep 28, 2005 3:31 am ]
Post subject: 
Here is a shot of that class -



Author:  Shane Neifer [ Wed Sep 28, 2005 8:05 am ]
Post subject: 
SWEEEEETT!!

I couldn't resist

Shane
Author:  csullivan [ Thu Sep 29, 2005 1:25 am ]
Post subject: 
OK guys, for those of us that weren't fortunate enough to make it to ASIA,
could someone describe/explain the "sugar cube" game? Judy looks very
serious and intent, but I can't even begin to venture a guess as to what
she's trying to accomplish. It looks fascinating!
Craig
Author:  Alan Carruth [ Thu Sep 29, 2005 5:24 am ]
Post subject: 
I didn't go to that one, so I'll leave it to somebody else to explain about the sugar cubes (although I think I can guess...).

However, I will second the statement that the notch is _not_ solid until you put that cap over the top. If you look at the vibrations of 'free' top plates (before they're glued down) the way I do you'll soon find that even a tighty fitted and well glued box joint without a cap is much stiffer one way than the other. It's got to have some acoustic effect.

Other than that we could go into the statics of beam loading for a long time. Suffice to say that you'll have a lot less trouble over the long run if you put that little patch on the top.
Author:  Arnt Rian [ Thu Sep 29, 2005 5:59 pm ]
Post subject: 
I was at there. It was a demonstration to show the difference in load bearing capacity along the length of the braces, which differs greatly according to their height. It was an interesting visualization of how scalloping works structurally, the peaks of the scallops turned into towers of sugar cubes! Small difference in brace height = huge difference in brace stiffness.Arnt38625.1264699074
Page 1 of 1 All times are UTC - 5 hours
Powered by phpBB® Forum Software © phpBB Group
http://www.phpbb.com/