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I have my two top panels nearly ready to be glued up, but as they were one of the lower grades, they aren't exactly quarter sawn and there is the hint of a knot on one side. As far as I can tell, they are bookmatched panels that go together like this:
https://www.dropbox.com/s/reincj1shpy17yg/100_2925.JPG
Here is the knot:
https://www.dropbox.com/s/emo05asyqtjd5v0/100_2927.JPG
So does it matter having this in the top (I can get rid of it, but then the top wouldn't be quarter sawn in the centre). Should the grain run in opposite directions on each panel, or the same direction?

2nd question - Which way does the grain run on bracing - vertically or horizontally? (when looking end on)

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"I am always doing that which I cannot do, in order that I may learn how to do it."
Pablo Picasso

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Peter, the way you have sketched that in the first pic is not a book matched joint. It's flip-matched. Nothing wrong with that (and it hides the long-grain run-out), just pointing it out. For a book-matched joint, off-quarter shows as a continuous set of parallel oblique lines, with no change in angle across the joint when you look at the end grain.

Personally, if I had that piece of wood, I would probably be looking for another. Working around its shortcomings is, of course, possible (full thread here) but takes a fair degree of effort and know-how. If you really want to use that piece, see if you can get the knot in the sound hole and cut it out.

The bracing grain is usually placed perpendicular to the plane of the soundboard.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

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To get what you see in the drawing you would have had to spin around one of the pieces 180 degrees showing the same face. Those are not actually book matched in that orientation. None the less I think I know what you are saying, that it is off quarter towards the outside (or the inside) of the boards. BUt the knot is placed in the more on quarter section. Is the knot also present on the other board? It's a bit nasty looking but beauty is in the eye of the beholder. I'd probably go for the slightly off quarter to get rid of the knot unless the knot is book matched and of course is not a structural problem.

I have received better quartered sets as shipping protection. You can get a better quartered set if you don't mind streaking for good prices. Even on your early builds use the best wood you can afford, a few more $ will get you a much better top.

I don't believe in saving the good wood for later projects.

Fred

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Thanks for the replies. The knot only shows on one side apart from some irregular grain and is not on the other board at all. I don't know if they are bookmatched panels, but they both had the same number written on them so I assumed they were. They came rough cut, so it's hard to tell until I get a good surface on each side. Which orientation is more stable for the wood - if the grain is continuous (bookmatched) or if the grain switches direction at the join.

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"I am always doing that which I cannot do, in order that I may learn how to do it."
Pablo Picasso

https://www.facebook.com/FenskeGuitars

I agree with Fred. You can, I can, and we all can build great sounding guitars from crappy wood.
It no longer needs to be proven that the cosmetics of the wood don't limit the sound producing quality.
But you'll spend the same amount of time on a great guitar if it is poor looking wood or superior wood.

That being said, I love to build a quick and dirty guitar every other year or so. I call them "river guitars", to take in the canoe.

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If the knot is only on one side of the top I would plane the other side until I had a good surface then thickness the soundboard by removing the rest of the wood from the side with the defect. The knot might disappear. If the knot is still evident I would keep it to the inside of the guitar, make it fall under the fingerboard, or cut it out of the soundhole area.
For a book match the face grain should be "mirrored" on both sides of the joint - like putting your hands together and then opening them out flat (palms up, pinky to pinky) The end grain would appear to all go the same direction.
If the small knot can be eliminated or hidden, and the top is otherwise good, I would use it. I can not tell from the photograph how well quartered the top is. The growth rings vary in width a fair amount but that doesn't necessarily make it a bad top. Buying a more expensive top might solve cosmetic issues more easily, but may not give you a better soundboard.
For guitars the grain generally runs vertically in the brace (perpendicular to the plane of the soundboard ( For lutes it runs the other way, so this may not be as big a deal as some folks think!).

Finally got around to taking a photo! The grain's almost 45° in places. Do you think that qualifies for returning it? It was a first quality top. I've already planed the faces, so I don't know if they'd accept it back (Touchstone tonewoods).

https://www.dropbox.com/s/laku5fo44t1p3 ... dboard.JPG

At least the knot would be cut out in the soundhole.

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"I am always doing that which I cannot do, in order that I may learn how to do it."
Pablo Picasso

https://www.facebook.com/FenskeGuitars

That's a bit off quarter for my taste but if it feels stiff when you flex it then you'll be ok. And you should spin that piece on the right around so that your ring lines are symmetrical to those on the left, i.e the one on the left points towards 10 o'clock and the ones on the right point to 2 o'clock and that your closer more quartered lines are in the center.

Wow, tonewood grading really is silly. I was about to bad mouth them for selling that as 1st quality, but I just checked the site and apparently their "1st quality" is actually 6th quality out of 8 levels...

I'd send it back and get a better one. I don't think long grain stiffness is affected too much by quartering, but cross grain stiffness is lowest at 45 degrees, right about where that one is. It goes back up as you approach perfectly flatsawn, which I believe is due to the cross sectional shape of the cells.

On the other hand, I'm not necessarily convinced that low cross grain stiffness is a bad thing, since my harp ukulele sounds great and has a significantly off quarter, floppy cross grain top. But for a first guitar, you might as well go with something more "normal". At the very least, it will keep you from blaming the wood and forming a bad opinion of off-quarter wood if it doesn't turn out to be the absolute best sounding guitar you've ever laid your ears on

If you can, place the defect in the soundhole, or under the bridge. It is not a knot. This type of defect is usually caused by injury, and can separate under certain conditions.

Flipping the top end-for-end does not change the runout.

Nor am I. One of my best vintage Martins, a 1937 D-28, has a red spruce top with 45 degree grain in the center. That top is about 0.130" thick.

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John