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| Classical back - 3 braces or 4 ? - http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10101&t=29271 |
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| Author: | John A [ Tue Sep 28, 2010 8:58 pm ] |
| Post subject: | Classical back - 3 braces or 4 ? - |
Hi everyone - Today I was laying out my 4 braces for my back on my first classical - I am following the Cumpiano/Natelson book - for their guitar they have 4 back braces - While laying it out I noticed that the 2nd brace is pretty close to the first brace - (closest to headblock) can I just omit the 2nd brace and make 3 brace back ? The 3rd brace is in the lower waist - and the 4th is in the midle of the lower bout. Thanks !! |
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| Author: | douglas ingram [ Tue Sep 28, 2010 9:04 pm ] |
| Post subject: | Re: Classical back - 3 braces or 4 ? - |
I thought that 3 was pretty much standard! On smaller bodies, such as the FE17, I've gone down to 2, leaving out the one just before the heel. |
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| Author: | Alexandru Marian [ Wed Sep 29, 2010 1:05 am ] |
| Post subject: | Re: Classical back - 3 braces or 4 ? - |
Sounds odd to me. Look at the GAL plan thumbnails to get an idea for where they normally are. A 4 brace back works better for a large shape with a thin back, with the lower two packed relatively close across the lower bout. Or, a few people reach for 4 braces instead of 3 when using a low density back. |
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| Author: | Howard Klepper [ Wed Sep 29, 2010 1:35 am ] |
| Post subject: | Re: Classical back - 3 braces or 4 ? - |
4 |
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| Author: | John A [ Wed Sep 29, 2010 7:06 am ] |
| Post subject: | Re: Classical back - 3 braces or 4 ? - |
Two guitars I have on my wall have 3 braces - 4 braces seem like too much - I am using maple and it is pretty stiff as it is. I will just omit the 2nd brace - It seems like it is a judgement call - if my back is loose and soft - then go with 4 - or stiff and thick - go with 3 - right ? In the Cumpiano/Natelson plan it shows a brace by the heel, then another just a couple inches below that - that looks like it would be at the middle of the soundhole. Then another below the sound hole and a lower bout brace. Howard - you simply writing of the number 4 - leads me to believe that you feel strongly about 4 back braces - why ? |
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| Author: | Alexandru Marian [ Wed Sep 29, 2010 8:00 am ] |
| Post subject: | Re: Classical back - 3 braces or 4 ? - |
If you do omit the "soundhole brace" you should move up the lower two a bit. The last should cross the whole width of the lower bout and the middle should be a inch or two below the waist. |
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| Author: | jfmckenna [ Wed Sep 29, 2010 2:40 pm ] |
| Post subject: | Re: Classical back - 3 braces or 4 ? - |
For me it depends on the stiffness of the back. One of my personal older guitars with three braces showed some deformation in the dry months that could have been controlled better with four braces. Well it could have been controlled better with a humidifier too  I like to build very light classical guitars so I try to omit that brace but on the larger ones it's tempting to put one in, then you can lose a bit more weight on a thinner back and perhaps gain some volume IDK? |
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| Author: | Mike Collins [ Wed Sep 29, 2010 5:03 pm ] |
| Post subject: | Re: Classical back - 3 braces or 4 ? - |
Leave the back as thick as you can . I use a X brace. with one transverse brace just a few mm from the neck block! Stiff box & sides with flexible top ! KILLER Guitars ! Mike 
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| Author: | JoeUlman [ Wed Sep 29, 2010 7:13 pm ] |
| Post subject: | Re: Classical back - 3 braces or 4 ? - |
Quote: While laying it out I noticed that the 2nd brace is pretty close to the first brace - (closest to headblock) can I just omit the 2nd brace and make 3 brace back ? Hi John – Not sure if you are leaning toward a traditional design but FWIW – Courtnall’s book shows representations of several traditional makers: Torres, Santos Hernandez, Hermann Hauser, Hernandez Aguado, Fleta, Bouchet, Friederich, and Romanillos; 650mm scale, all have 3 back braces. The 604mm Torres has 2. I’m just working on my first and followed Brune’s 650mm Hauser plans which show 3 back braces. When creating the arch in the back per Cumpiano it seems to me that it would be somewhat trickier to get the arching even, both across and longitudinal, and also profile the sides to perfectly match when using 4 braces; but maybe it’s not difficult, or maybe flexing the back/braces into position a millimeter here and there isn’t a big deal. Joe |
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| Author: | douglas ingram [ Wed Sep 29, 2010 7:25 pm ] |
| Post subject: | Re: Classical back - 3 braces or 4 ? - |
JoeUlman wrote: When creating the arch in the back per Cumpiano it seems to me that it would be somewhat trickier to get the arching even, both across and longitudinal, and also profile the sides to perfectly match when using 4 braces; but maybe it’s not difficult, or maybe flexing the back/braces into position a millimeter here and there isn’t a big deal. Joe I found the arching of the back far easier to achieve once I started fitting the braces to the body first. Then I can use a template to set the basic shape, and then a large sanding board set to the correct arc for the back radius to refine the shaping. |
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| Author: | JohnAbercrombie [ Wed Sep 29, 2010 10:05 pm ] |
| Post subject: | Re: Classical back - 3 braces or 4 ? - |
douglas ingram wrote: I found the arching of the back far easier to achieve once I started fitting the braces to the body first. Doug- How do you glue on the back? Do you glue the braces into the rims then glue on the back, or you you have a trick for getting the braces correctly positioned on the back before closing the box?? Brian Burns described to me how he 'picks up' the (fitted but unglued) braces from the body with a small amount of hide glue on each brace center... Cheers John |
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| Author: | Alexandru Marian [ Thu Sep 30, 2010 1:28 am ] |
| Post subject: | Re: Classical back - 3 braces or 4 ? - |
Yes the braces are fitted on the rims (I use a 1/4 chisel, and it is one the parts I love the most, along carving the top bracing), then glued in their pockets, then more trimming and tuning can be performed. In my case it means checking there are no low spots - there should always be some rocking when I touch a brace with a straight edge. If anything, getting a nice fit between brace and lining is probably much easier than having to fiddle with the entire plate (just guessing, i never did it the normal way). The fit really can go beyond nice or acceptable. I have often seen only approximate fittings through the soundhole, and together with shredded spruce around the rosette it makes for serious frowning on my part. I did not do one with 4 yet but apart from more work, i do not see why there should be problems with getting the doming right. |
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| Author: | John A [ Thu Sep 30, 2010 6:52 am ] |
| Post subject: | Re: Classical back - 3 braces or 4 ? - |
How do you then accurately cut the space for the brace on the center strip ? How do you clean any glue squeeze out ? |
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| Author: | Alexandru Marian [ Thu Sep 30, 2010 7:18 am ] |
| Post subject: | Re: Classical back - 3 braces or 4 ? - |
I carefully measure the distances and it works fine. I actually glue separate strip pieces instead of a long one. For squeeze out you just need to learn the right amount of glue. If I still get a few beads here and there (in the photo too by the upper brace) I do not mind it. I don't try to please all squeezeoutfreaks 
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| Author: | WaddyThomson [ Thu Sep 30, 2010 8:33 am ] |
| Post subject: | Re: Classical back - 3 braces or 4 ? - |
I use a bit of a different procedure. My braces are full height at the wings of the brace, rather than scooped at the ends, so i use brace supports on the sides which are glued in first. Then I set the braces in place un-glued, and install the linings around them. Then I use double stick tape on the ends of the braces after sanding the dome in them, and position the top, and press down the edges to catch the tape I then work the top off with the braces attached, and carefully clamp the ends down, and position tape dams at the ends and edges to lock the position, take off the d/s tape, and glue them in place with HHG or Fish Glue or LMI White, depending on how long I want to wait. When dry, I make sure it fits back into position on the box. If it's right, I glue in the back strip in sections between the braces, then glue it on the box. I do it this way, because I have twice had a brace hang on the back strip when gluing it to the already braced body. So far this way has worked really well. There is a good series of pictures in Waddys #5 build album, page 7. Link below to Photobucket albums. |
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| Author: | douglas ingram [ Thu Sep 30, 2010 9:45 am ] |
| Post subject: | Re: Classical back - 3 braces or 4 ? - |
I lay out the back brace positions, then glue in the kerfed lining to the layout position, fit the brace, then continue fitting the lining. I find this easier that gluing in full length lining and then cutting notches for the brace. I first use my arced sanding board to establish the final heights of the ribs. My back braces are full height to the end and are supported by small blocks. I set a template from heel to butt and fit the back brace to this height, thus establishing the curve of the back along the length. Once all the braces are set in, I take the template and establish the curve from side to side by tracing a line off of the template onto the brace. Then the brace is rough cut to the line, replaced into the brace pockets along the lining, and then using the arced sanding long board, the final shaping is established. To fit the back is easy. The back is laid over the guitar body and the brace end locations are marked. Lines are drawn on the back to identify the brace location on the center strip, which is then fitted to the braces. Having the braces keep the back properly located, I can then fit the center strip to the slipper foot and the butt block. Once satisfied that all lines up just right during the dry fit, glue it in place. Arcing the back over the braces ensures that pressure is applied for a good fit. I used to do it the other way around, glue all the back braces to the back first and then try and fit it to the rims with the linings all glued in, but I find this way much easier. And, of course, the photos show up in reverse order... |
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| Author: | JohnAbercrombie [ Thu Sep 30, 2010 11:32 am ] |
| Post subject: | Re: Classical back - 3 braces or 4 ? - |
Alexandru, Waddy, Doug- Thanks! A couple of 'wrinkles' I learned from Brian Burns: If you use kerfed linings and aren't overly concerned if a brace is a few mm 'out of place', you can glue in a section of lining, space for the brace, glue another lining section, etc. . (Avoids part-blocks of lining...) You can make a jig to check the action at the 12th fret and do a final 'neck angle adjustment' before gluing on the back (with the body and neck held in the jig). Cheers John |
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