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| Backjoint reinforcement wood type and grain direction? http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=36423 |
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| Author: | WendyW [ Tue May 08, 2012 3:56 pm ] |
| Post subject: | Backjoint reinforcement wood type and grain direction? |
What type of wood do you like to use for your backjoint strips and do you always do grain perpendicular to the grain of the back? If so, where do you get the material? Thanks, Wendy |
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| Author: | Michael.N. [ Tue May 08, 2012 4:03 pm ] |
| Post subject: | Re: Backjoint reinforcement wood type and grain direction? |
It's very common to have the strip perpendicular to the Back grain. I simply use an off cut from soundboard material and have the grain running parallel to the Back grain. That's the way that Romanillos (and others) have the grain direction. I doubt it makes much difference. I've yet to have a Back joint come apart. I even have a multi piece Back, all joints reinforced with parchment paper. Some 12 years later they are all still holding true. |
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| Author: | meddlingfool [ Tue May 08, 2012 4:08 pm ] |
| Post subject: | Re: Backjoint reinforcement wood type and grain direction? |
I also use an offcut of the top, except I go cross grain. Is it necessary? I don't really think so, but a lot of buyers balk when there isn't one..... |
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| Author: | WendyW [ Tue May 08, 2012 4:26 pm ] |
| Post subject: | Re: Backjoint reinforcement wood type and grain direction? |
I guess I should start buying bigger soundboards, since I never seem to have enough to get a backjoint strip and end up ordering them separate. Wendy |
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| Author: | Alexandru Marian [ Tue May 08, 2012 5:07 pm ] |
| Post subject: | Re: Backjoint reinforcement wood type and grain direction? |
Most of the time it is perpendicular grain, but there is a number of highly respected classical guitar makers who use longitudinal grain. Whatever you use, it should match the color of the back braces. Rift sawn works best in all cases. If you make a perpendicular grain strip, it will bend easier into the radius. If you make it longitudinal, rift grain will resist splitting better. |
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| Author: | woody b [ Tue May 08, 2012 5:08 pm ] |
| Post subject: | Re: Backjoint reinforcement wood type and grain direction? |
I made cross grain back strips out of pretty much everything, including the same wood as the back. Since then I've quit using them, except on backs with sapwood, or inlaid center strips. |
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| Author: | SimonF [ Tue May 08, 2012 5:39 pm ] |
| Post subject: | Re: Backjoint reinforcement wood type and grain direction? |
I take a slightly different approach to the centerline reinforcement and use it more as a brace than "reinforcement" of a glue line. But as others have said, when used traditionally for reinforcement purposes, I don't think it matters what the grain direction is. I always use Wenge as I like how it looks. 
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| Author: | DennisK [ Tue May 08, 2012 6:09 pm ] |
| Post subject: | Re: Backjoint reinforcement wood type and grain direction? |
Top offcuts, back offcuts, veneer, whatever. I like mine very thin so they have minimal acoustic effect, and cross grain because parallel to the back grain and very thin would split easily if the back's glue seam ever came apart, defeating the whole purpose. If you can cut a truly perfect joint the full length of the back (or are using a soft enough wood that imperfections can squeeze out), then it's not necessary. If there's any hint of a gap at the ends or anything, then the reinforcement is a good idea. I usually inlay a strip on the outside as well, about half the thickness of the back (parallel to the grain, for appearance), to hold it together there as well, because my joints definitely aren't perfect yet. Oh, and keep in mind that it doesn't have to be a single continuous piece of wood, so you can piece together several top offcuts. Actually, I glue my reinforcements in short segments after the braces are in... although now that I think about it I should try the other way now that I can sharpen a chisel well enough not to muck it up. |
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| Author: | Trevor Gore [ Tue May 08, 2012 6:39 pm ] |
| Post subject: | Re: Backjoint reinforcement wood type and grain direction? |
I use cross-grain soundboard off-cuts like this. The cross-grain orientation makes more sense in terms of strengthening the joint, but with a good glue line, it isn't necessary at all. For example, the back in the picture is four pieces, with only the centre seam reinforced, mainly due to deference to tradition. This guitar has a centre seam inlay, which was inlaid with the body assembled. I wouldn't have liked to do that without there being a centre reinforcement strip. (Full story here: The Shed Guitar). There's no need to match the brace wood. I frequently make cedar topped guitars with a cedar centre strip on the back, spruce back braces. They look fine. There always seems to be plenty of wood off the soundboard blank for centre strips. I get two or three out of some, which makes up for the rare occasions I can't get one off the current build. |
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| Author: | LaurieW [ Tue May 08, 2012 7:30 pm ] |
| Post subject: | Re: Backjoint reinforcement wood type and grain direction? |
Attachment: Mad RW GA - Low Res Copy.JPG I buy usually buy the spruce ones from LMI for about $5 each. Although I do have a couple of tops that I wasn't crazy about, so I sliced them up to use them for future builds. |
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| Author: | Corky Long [ Fri May 11, 2012 9:23 am ] |
| Post subject: | Re: Backjoint reinforcement wood type and grain direction? |
DennisK wrote: Oh, and keep in mind that it doesn't have to be a single continuous piece of wood, so you can piece together several top offcuts. Actually, I glue my reinforcements in short segments after the braces are in... although now that I think about it I should try the other way now that I can sharpen a chisel well enough not to muck it up. +1 |
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| Author: | WendyW [ Fri May 11, 2012 10:43 am ] |
| Post subject: | Re: Backjoint reinforcement wood type and grain direction? |
I've always wondered why I'm going to the trouble of gluing the backstrip first and then chiseling it away for the braces. It would be so much quicker and easier to glue the braces and then glue pieces of backstrip between them. What is or was the reason behind that? Wendy |
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| Author: | WaddyThomson [ Fri May 11, 2012 11:01 am ] |
| Post subject: | Re: Backjoint reinforcement wood type and grain direction? |
I do the back strip after the braces too. |
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| Author: | Don Williams [ Fri May 11, 2012 1:22 pm ] |
| Post subject: | Re: Backjoint reinforcement wood type and grain direction? |
I've seen enough edge joints fail to feel like I wouldn't want to do one without reinforcement. I've used both cross grain spruce as well as cross-grain wood cut directly from the back. Frequently I've incorporated the little piece that has a center seam inlay into the section right at the sound hole and leave it there to be seen as a (corny?) design element. I sort of like the look. |
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| Author: | Trevor Gore [ Sat May 12, 2012 7:36 pm ] |
| Post subject: | Re: Backjoint reinforcement wood type and grain direction? |
callyrox wrote: I've always wondered why I'm going to the trouble of gluing the backstrip first and then chiseling it away for the braces. It would be so much quicker and easier to glue the braces and then glue pieces of backstrip between them. What is or was the reason behind that? It really depends on the rest of your process. If you're sourcing stock from soundboard off-cuts, it's easier to glue down in rectangular section and shape to "half round" on the panel (well, it is for me), and that's a whole lot easier when the braces aren't there. If you're sourcing "half round" stock, there's probably not much in it. Either way, it's fitting a joint and getting things lined up. |
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| Author: | Mattia Valente [ Mon May 14, 2012 5:41 am ] |
| Post subject: | Re: Backjoint reinforcement wood type and grain direction? |
Cross-grain spruce, most from off-cuts from tops. I have a whole pile from a top that was stiff but had some sap/defects that could not be worked around. Sliced up, that's several years' worth of backing strips right there (possibly decades at the rate I'm building right now!). I glue cross-grain first, then smooth/round over the top (basically radius it smooth) with a block plane, then mark (marking knife) and fit the braces. This is completely trivial with a good, sharp chisel and results in a perfect fit that I can't get as easily by fitting the strips between the back braces. I just glue the cross-grain strips in slightly overlong so they require only a bit of trimming. Most pieces aren't that long. |
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| Author: | Chris Ensor [ Mon May 14, 2012 8:13 am ] |
| Post subject: | Re: Backjoint reinforcement wood type and grain direction? |
Cross grain spanish cedar. Before bracing. |
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