Implications of socketing braces

[Craig Bumgarner]

I'm wondering about the implications of socketing brace ends in the linings. In all the good examples of the kind of guitar I build, the bracing scheme is ladder bracing with any where from three to five braces. The ends are always socketed. In other guitar styles, many of the braces are not. What happens if I don't socket a brace? I can imagine that socketing a brace makes its end connection to the sides more rigid and the mere thickness of the brace required to fit the socket stiffens the perimeter of the plate, for better or worse I guess its that better or worse thing that I'm wondering about.

[Allen]

Few things I can think of Craig.

One is that the brace end is supported in the linings so if the back (or top) takes a blow, then there is less chance that the brace will pop loose from excess deflection. This could be considered a positive.

Another is that if the brace is tucked into the linings and does butt up tight to the sides and then the bindings if installed, then there is a possibility down the track that the brace will put enough force on the binding to make it loose. You see this type of repair required on old instruments. This would be a negative.

I've noticed in my own instruments that when tucking the braces or not tucking them, the back on the instrument that doesn't have them tucked in is far more responsive. Can be a good thing if you keep that in mind, or really unhelpful if that style of instrument doesn't lend itself to playing with the back allowed to vibrate freely. Think of a uke that is hugged against your chest.

[Mark McLean]

Hi Craig
There is no rule about this. In a modern style steel-string guitar where you are aiming for a more responsive top (e.g. a "fingerstyle" player's guitar) it is a common practice to taper the ends of the x-brace in the lower bout so that they go down to nothing before reaching the linings. Same with the diagonal braces. Many people also thin out the top at the edges as well. Taylor guitars have a system of routing a thin channel around the perimeter of the underside of the soundboard to make it more flexible at the edge. However, builders who do this will still tuck the upper ends of the X-brace, and the upper transverse brace, into the linings. So, you only want to free up the edges of the top in the lower bout, but keep it pretty stiff in the upper bout. Of course, there are many great guitars that are built with all of the top bindings recessed into the linings. More art than science in this I think. However, Trevor Gore might jump in with some hard science also!

I was going to mention that thing about brace endings occasionally pushing out the bindings - but Allen already covered it.

When it comes to the back you are entering the whole subject of "live backs" versus rigid backs. I see from some of your previous posts that you already have the Gore/Gilet books, where you will find a lot of material on this. I think there is also some information in the section of this forum which is devoted to discussion of said books.

cheers
Mark

[Chris.Conery]

I see in the new Romanillos book that he leaves a 1 mm gap between the end of a back brace and the side. I guess, after building 800 guitars, he has found that humidity/temperature changes can cause problems if the brace is butted up against the side.

[charangohabsburg]

Another is that if the brace is tucked into the linings and does butt up tight to the sides and then the bindings if installed, then there is a possibility down the track that the brace will put enough force on the binding to make it loose.

This possibility is about exactly 100%. To avoid this, braces that are let into the linings should be cut 2mm short of the sides.

I took the following photos of four relatively old guitars in my possession, the "youngest" 87 years old, the other three most likely between 100 and 130 years old.

1606-23.jpg (141.37 KiB) Viewed 16741 times

[charangohabsburg]

I see in the new Romanillos book that he leaves a 1 mm gap between the end of a back brace and the side. I guess, after building 800 guitars, he has found that humidity/temperature changes can cause problems if the brace is butted up against the side.

Romanillos has looked at a lot of old guitars!

According to my observations, the culprits are not humidity and temperature changes, but rather wood shrinkage over longer periods of time.

[Craig Bumgarner]

Thanks for you ideas guys. I too have seen brace ends coming through the sides on some vintage guitars. My take on this is when in a dry environment, the grain of the top and the brace are 90 degrees opposed. As wood shrinks more across the grain than with the grain, if dried out, the top plate shrinks and "pulls" the side into the brace which does not shrink as much and the top. A gap at the end of the socket sounds like a good idea.

[jeffhigh]

In a ladder braced Selmer style guitar in particular, there is a fair shear load between top and sides at the ends of the two braces carrying the bridge load.
I would not be keen on feathering out these two ends to nothing before the lining.

[charangohabsburg]

I too have seen brace ends coming through the sides on some vintage guitars. My take on this is when in a dry environment, the grain of the top and the brace are 90 degrees opposed. As wood shrinks more across the grain than with the grain, if dried out, the top plate shrinks and "pulls" the side into the brace which does not shrink as much and the top.

If it was only the humidity-loss related shrinking, this would occur much earlier. I have never seen braces pop through the sides of a relatively new guitar (50 years or less). Also, these popped-through braces are pretty much locked in their position, they do not retreat with higher RH. Thus, it must be wood shrinkage that happens in addition to the humidity related issues.
The good news is that most of us will not have issues with customers coming back to us complaining about braces self-destroying the guitars we built!

[56nortondomy]

If it was only the humidity-loss related shrinking, this would occur much earlier. I have never seen braces pop through the sides of a relatively new guitar (50 years or less). Also, these popped-through braces are pretty much locked in their position, they do not retreat with higher RH. Thus, it must be wood shrinkage that happens in addition to the humidity related issues.
The good news is that most of us will not have issues with customers coming back to us complaining about braces self-destroying the guitars we built!

Speak for yourself Markus, i'm still gunna be here when i'm 110. Wayne

[charangohabsburg]

If it was only the humidity-loss related shrinking, this would occur much earlier. I have never seen braces pop through the sides of a relatively new guitar (50 years or less). Also, these popped-through braces are pretty much locked in their position, they do not retreat with higher RH. Thus, it must be wood shrinkage that happens in addition to the humidity related issues.
The good news is that most of us will not have issues with customers coming back to us complaining about braces self-destroying the guitars we built!

Speak for yourself Markus, i'm still gunna be here when i'm 110. Wayne

And still taking on guarantee repair work!

[Kim]

If you don't inlet braces it's important to tapper down the ends so they feather out to nothing where they abut the linings. The thicker you leave them at that juncture the more susceptible they will be to breaking the bond with the top under impact.

Cheers

Kim

[charangohabsburg]

I made a drawing of Romanillo's method. Yes, he makes the bars thinner towards the center. Antonio de Torres left the braces at full height throughout the whole length, rounding their top over except at the ends where he let them square so they could rest on the consoles glued to the sides.

Romanillo's method

[Nick Payne]

I would not be keen on feathering out these two ends to nothing before the lining

I've actually done that a few times. Doesn't seem to adversely affect either the structural integrity of the guitar or its tone. Here's a photo of one of the back braces on an instrument that I made in 1976 - still in my possession, still played most days, has never had any structural problems in spite of the hard life it has led.

[Kim]

Feathering braces to nothing at the ends allows the brace to flex a little should there be impact with the top. Taller braces being more rigid are more susceptible to damage from that same impact. The glue is crystalline, the centre of the brace is taller and often thicker and being furthermost from support, is less restrained against downward movement. If there is no give at the ends, impact with the top, particularly at the centre, can work via leverage to break the bond at the brace ends...The only un-let braces I've ever had to re-glue were those left taller at their ends than a 16th of an inch.

[jeffhigh]

I would not be keen on feathering out these two ends to nothing before the lining

I've actually done that a few times. Doesn't seem to adversely affect either the structural integrity of the guitar or its tone. Here's a photo of one of the back braces on an instrument that I made in 1976 - still in my possession, still played most days, has never had any structural problems in spite of the hard life it has led.

braces.jpg

Nick, my negative opinion on feathering to nothing (which you have quoted in part) was specifically for the two ladder braces supporting the bridge on a Selmer/Macafferi style guitar.
I was not expressing an opinion on Back Braces or any other form of Top Braces