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Two of these aspects have been discussed at length. The third I do not recall, but that is the only one I am asking for advice.

1) Brace wood is split to assure least runout for vertical grain braces.

2) Horizontal grain braces are perhaps as good or better than vertical grain.

3) My question is, if you use horizontal grain braces, does the runout matter much?

Lets suppose that
"2) Horizontal grain braces are perhaps as good or better than vertical grain."
Then, if runout didn't matter, I would think that we would all use horizontal grain
for all braces all the time. Just something to think about. But to your question. imo
runout always matters. the less the better.

I think what he's getting at, is that the run out would not be in the load-bearing direction.

Pat

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Pat

"I think what he's getting at, is that the run out would not be in the load-bearing direction."
Ah yes, perhaps.
I suppose one could build a guitar with addi or sitka bracing with no regard to grain and it might survive
just fine... or it might not. It's hard to predict the handling it will receive during it's lifetime. I always choose
the best, most runout free, from my pile for the x braces and UTB because not doing so may lead to the chance of
failure that I am not willing to take. Plus, quality straight grained brace wood is fairly easy to come by. 'Course that's
just my opinion. Others may be able to offer a more scientific answer to your question.

Runout gets us short grain whether the grain is vertical or horizontal. Maybe it wouldn't matter as much for horizontal grain, but I think it would still matter.

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Seems like not only strenght but the sound transmission/reflection properties would be different in vertical vs. horizontal grain on braces. Maybe someone has tested that.

Runout occurs when you cut a log across the spiral. So it exists weather it's flat sawn or vertical grain. But in your 3rd scenario you would be gluing the face with runout to the back or top panel and I would think that would lock it up good at least on that one side. Ideally in any orientation you would not want any runout.

imho, runout in either direction will introduce weakness in your braces. The strength of a split log is the grain running ALL the way through. If your runout is side to side, you are still putting short grained wood in the path of tension, no different than if it was vertical. In fact I might suggest that horizontal runout might actually be worse than vertical in a similar way as a scarf joint with a face plate is stronger than a solid neck with a face plate... again in my humble opinion. Most of this I don't proposed based on having made enough guitars with different brace woods with different grain orientations to have some fail and some not. I say it as a wood worker who has been fiddling with sawn and split woods for various projects for a couple-few decades. I say wood is wood. The only difference between one piece and the next is the density, flexibility/brittleness and stiffness. Once you start tempting the grain fibers to hold together as an insurance policy for your project's strength long term, you are asking for trouble.

Lutes use "horizontally" grained braces.
I don't mind if the grain angles a bit as long as the braces are stiff and don't have much runout.

"Lutes use "horizontally" grained braces."

They probably split them off from the edges of the top when it was rough, as classical makers do with fan braces. A lot of the old ways make sense if you think of good wood as being expensive and hard to get, and labor as cheap. We're spoiled by all the good wood we can get.

I often wonder if the late wood lines running out of the scallops at the brace ends would be stress risers, and prone to splitting. Lute braces were not carved down at the ends, but butted tightly into the ribs instead of being inlet into (nonexistent) liners.

I agree with what you have said above, but would like to add that I don't think the lute makers felt there was any loss of quality by bracing their instruments with the grain oriented this way, and for some reason preferred it.

In boatbuilding, I was taught that 12:1 or greater is sufficient to ignore run out. In other words, for a 12" long brace 1" tall, the runout could connect the two opposing corners

Ed M

So using that as a "rule of thumb" a brace 1/4" high and 15" long shouldn't have runout of more than 1 in 60 ?
That sounds reasonable to me.

I grade each piece of brace wood by flexing it by hand. If it doesn't twist or split or break, if it looks like it will carve without running away, I will use it.
The long X's get more stringent examination, only the best will do.
I'm from the "everything is relative" camp.
If I am building a guitar for the camp any brace wood without actual loose knots will do, and wouldn't you know it, maybe sound better and hold up just as well as your finest guitar.
They are all handmade by a craftsman after all.

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I need to improve at all aspects of material identification and inspection. I come from the tech industry so I cannot fall back on experience with boat building or cabinetry. Can anyone recommend good resources for getting the basics nailed down? I need like some exaggerated images to help visualize it.

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I think the best way to start understanding this is to take a nice piece of brace wood that you bought from a reputable supplier (expecting that will be essentially straight grain all the way through) and cut yourself out a 24" piece about 1/4" to 3/8" square. Then, take a random piece of lumber that was sawn at a lumber mill (like for building furniture, or even a 2 x 4 from the local home center) and cut he same sized peace.

Then break them both with your hands. You should be able to see quickly what the difference is... and likely feel it too.

Brad, Bruce Hoadley's Understanding Wood is an excellent book describing how grain runs (with good diagrams) and also how it behaves with moisture.

Cheers Dave

Awesome, will check it out. Now I have a stocking stuffer.

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Another vote for Hoadley.

In addition to Hoadley, here's another excellent resource for free.
'Wood as an Engineering Material" from the US Forest Service Laboratory.
https://www.fs.usda.gov/treesearch/pubs/37440

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Jim Watts
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