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Hi. I've only built 4 acoustics, and was wondering why the little top braces, next the x brace, have a little space, and don't connect to the x. Is this so the top can vibrate? I'm referring to the Weissenborn style bracing, from the plans. Thanks, Alan.

You talking about finger braces....the little short braces that lurk around the bout area of the guitar?

Yes. Also the bridge plate, and little triangle piece at the x-brace. On the plan I have, it looks like there is a space of about 3/32".

I'm not an expert on Weissenborns but on my steel strings I butt the finger braces (and lower bout tone bars) up against the X brace and also drop a bit of Cyano glue in between end of brace and side of X brace to eliminate any chance of buzzing. IMO stopping the finger brace short of the X brace would affect rigidity of the top in the bout area but how much I couldnt tell you.

Thanks K. I already kept the braces away from the x on this one. I'll keep obsessing about it for now. A.

If things are just lightly in conntact there's the chance that they might buzz. you either want to make sure things are tight, or else that they don't touch at all. If you have a brace that ends before it reaches a liner or another brace, it should probably have the end carved away so that it's no taller than 1/3 the thickness of the top at that point, so that it will be flexible enough to move with the top and not peel up. Otherwise, it should be inletted if possible.

Are those monster-sized caps over the x-brace joint typical for a Weissenborn?

Everything I've ever learned about X-brace joints suggests that a thick cap (as opposed to a thin cap) adds only minimal strength but a fair amount of dampening. I'm far from an expert though, and I'm open to learning differently.

AStass, I agree with Kelby, your cap is really only needed in one direction and should only be about the thickness of the top of the guitar, say .110 inches. Longer is better, but an inch past the joint in both directions is fairly standard, so a 2 3/8 inch by .110 splice is all that's necessary.

Heck, Martin persists in using a glued on cheesecloth.

Being familiar with a violin, there is a tiny tool used for practice called a mute. It's not large at all, maybe an inch by 1/4 inch, with three dual fingers that slip in between the four strings and attach like a clothes pin. That tiny piece of wood is a tone-killer. Of course your monster x-brace cap is a fair distance from the bridge on this guitar and wouldn't be as effective as a violin mute, but it would tend to have that effect.

Good luck on your building. It never hurts to call for pictures from other luthiers who build Weissborns. I know that is spelled wrong....

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Thanks for the input. The "monster" cap is not standard on the Weiss. The plan shows the x brace that would go on after the first one is glued thickened, about 3/16", for about 2 3/8", just like you said. Unfortunately I caught that detail too late, so I will shave them down, and hope for the best. Thanks again. Alan.

 

Bruce:
Your comparision between a violin mute and the patch on that guitar top brace needs to be qualified a bit, I think.

A violin bridge weighs, maybe, 2 grams. It's thin at the top and thicker at the bottom to act, in some degree, as an 'impedance matching transformer', helping the flow of energy from the strings to the top. It only has to be stiff enough in the crosswise direction that the string 'knows' how long it is. The cuttouts in the violin bridge act as 'tuning circuits' to filter out some string frequencies and enhance others. Even a small amount of mass at the top of the violin bridge makes a relatively large change in the way it works, and in the tone produced. In particular, it vastly increases the impedance mismatch, and hinders the energy flow.

The guitar bridge has to be rather heavy and solid by comparison to work well. Ity moves up and down with the top, and can 'feed back' a significant amount of energy to the strings at some frequencies if it moves too much. OTOH, if it doesn't move at all, there's no sound, so the weight and stiffness of the bridge are a compromise. Typically, a steel string bridge will weigh between 25-35 grams. Even the patch in the photo is probably less than 5 grams, and I'd guess much less. It's not very close to the bridge, and not adding significant mass to it. It's heavier than it needs to be, for sure, but I'd hazard a guess that you would not notice a large change in the tone of the guitar if you put it together like that, and then trimmed it down to more 'normal' size.

I'm not trying to come down on you with this. I see a lot of comparisons made between violin and guitar acoustics, and they really are much different systems in may ways. A too literal comparison can be misleading.

I have heard & read that Weiss. style guitars are prone to collapsing at the X brace & "north" of the soundhole.
I have only built one, & I changed the bracing quite a bit. I feel that the top braces are way too thick for optimum tone & not high enough for optimum strength.
My Weis is only a year old now, but so far the top is fine.
I used 5/16" X .650" X braces & reduced most of the rest to 14" or 5/16" wide. I also eliminated a couple of braces from the original plan. The upper transverse brace on my Weiss is built higher & a little thinner than the original to beef up that "problem" area.
Even with all the changes, it sounds just like a Weissenborn.

Oops... Please read 1/4" rather than 14" in the note above.

Thanks guys. I'm going to shave that big ole thing down to an 1/8". I'm building another one concurrent with this, and it's koa. I was going to go with bracing as you recommended, Daniel, thanks for the extra push in that direction. Also, if anyone is still here, do you think I should put some arch in the back? I don't think they originally had that. Another thing I've been thinking about is, how much sound is lost with that guitar sitting on your lap, and stopping the back from vibrating? Alan.

Alan, thanks for chiming in. You are right, these are quite different instruments. Just the look of the heavy bracing cap looks unorthodox. The violin analogy just helps in understanding excess weight in the bridge area can kill tone.

Tone, isn't that what we are after?   

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Hey Bruce, hi. Thanks for your input. I guess what I should do is get a dvd on git building , because I just go by my instincts, and top bracing is very esoteric, and probably the most important facet of acoustic git building. I think the only way to really know what to do is to build a lot of guitars, and see what happens with each one. My original thought, when I came up with the monster-baby x-brace, was that the x can still be flexible where it's important, and more rigid where it's not so important. Alan.

Alan, I'm kind of fly by the seat of my pants too. You are right, building more is good. Having some good guidelines also is good. Take a look at some of the bracing jobs by better builders and you learn a lot.

One thing I've learned is height is strength in a brace, and quartersawn is best for the long haul. I've noticed you can hear music in these tiny pieces of wood before they are even glued. So, the more musical pieces might just transmit sound better once installed.

I can remember a builder of factory instruments who said they build them all the same and every now and then the produce a real dud. It's these subtle differences in materials and execution that make for a great, consistant, instrument.

I really like adirondack red spruce for bracing, which is getting harder and harder to find. Try some sooner, rather than later. You just might like it too.

Okay Alan, we want to see a pic of the revision you make on this top. Good luck building.

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could some one post some of the (YUCK!) math here? that would be helpful...

Yep Bruce. I get spruce from LMI, and get really tight grained pieces, and saw them on the quarter. Funny thing is, when I have a looser grained piece, and do a flex test with my hand, they seem to be about the same rigidity, so I don't really know how important the tightness of the grain is. HMMM? What to do. Robert, as far as the math goes, i really don't know, because each piece of wood is so completely different from the next, that I think you have to deal with each one as you get it. Makes building guitars all the more fun! Alan.