Official Luthiers Forum!

No hesh I don't think you were wrong, after reading all this and thinking I think it is a very gray area. The back will probably be weaker given the orientation grain, but given that the back is holding form I think that the strength of the braces will be sufficient for their purpose. More than one thing went wrong yesterday with the build I guess we all have our bad days. Just gotta keep moving forward and learning from all my mistakes.

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--Kyle Burner--

I'd advise removing and replacing them with quartersawn bracing. It's better to look back
on the guitar and know that you did it right rather than taking a shortcut and having to look
at it....or thin about it in the future.

The flatsawn orientation isn't nearly as strong and you can use lighter bracing if you use
quarterswan stock. Plus, there is much more of a chance of splitting along that runout in
the faltsawn piece than there will every be with quartersawn pieces.

Could they last? Sure, but they could fail much more easily than bracing with the right grain
orientation, too. I'd do them again. Quarterswan bracing stock wasn't arrived at or maintained
as being the industry standard by accident. The strength to weight ratio and the assured longevity
were both considerations when all of this stuff was being settled on long ago.

Everything can be a gray area if we don't feel like going back and doing it again. Every detail
can be let go as good enough and as good as the other guy is doing it if we think that's as far
as we want to go.

As far as Martin using flatsawn bracing......especially in older guitars.....it's unlikely although
not impossible. Even though they now machine all of their bracing from quartersawn stock, they
used to split all of the bracing along the grain and on the quarter. Believe me, if there was a piece
of flatsawn stock on the back of an old Martin, it was because someone made a mistake that wasn't
caught by an inspector or another worker farther along the process path.

Grain orientation is a chief consideration at all of the big houses as well as in all small custom
shops. I'd put some weight on that.

Regards,
Kevin Gallagher/Omega Guitars

Geeze Kyle you gotta feel like Chris in the movie Platoon..........

Heart of darkness stuff - duality of man, etc........

I did the same thing (also accidentally) on a Weissenborn about 6 years ago. It's still fine, no problems at all.

Hesh,
I was just giving Kyle some good reasons for going back and doing it right now before the back is
on the guitar, the body is closed and there's no going back....that's all. He took a class here with
me in May and we touched on the reasons for grain orientations being what they are in guitar building.

Just some advise from a guy who wants him to feel as good as possible about his first projects. It's
always nice to look back and be able to say, "I did the best I could." rather than, "I could have done
better here or there, but I didn't want to take the time."

Even others who have done the same thing have indicated that they did it by accident which gives
me the feeling that, had they caught it in time, they would have done it right. Which is a great idea
in any case.

Like I said in my earlier post. they could last forever, but why take a chance?

Regards,
Kevin Gallagher/Omega Guitars

If it were my first, I would have replaced them for reasons that Kevin stated. It's what I would have intended to do. The end result is: this is what I intended to build, rather than, this is how it turned out. I would still do them QS now, even though some testing I've done with both orientations has led me to believe it makes little or no difference in stiffness in spruce on this scale. Strength might be another matter - I didn't test for that.

If I were slapping together a test mule, I might use flat sawn if I had some waiting around to be used.

That's my story and I'm sticking to it.

Pat

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formerly known around here as burbank
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http://www.patfosterguitars.com

Hi Kevin - I was not being critical of you at all and in fact I agree with you on all points.

My position was to do it over too.

My last comment above was addressing how there are two camps here - the do-it-over camp and the let-it-be-it-will-be-fine-camp.....

Sorry if I caused any confusion.

It just occurred to me that re-doing any mistake is good for the instrument and good for the builder. If there's anything building guitars has taught me, it's that there are times when working wood is humbling when no matter what we put into it - blood, sweat, tears, care, fancy tools - the wood is king. The more mistakes we make right, the easier it will be to stop and fix the ones we haven't made yet.

Pat

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formerly known around here as burbank
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http://www.patfosterguitars.com

No biggie Hesh,

I understand what both sides are saying, but just think that Kyle would feel best about his work if
he took the time to do it the way he intended to rather than accepting a mistake as part of the final
outcome of the guitar overall. I've some disastrous builds from people who claim to have incredible
lutherie skills and I have to assume that all of the things that make them disasters were either intended
or left because they didn't want to take the time to offer the guitar to their customer without them.

I think i'm as uncomfortable as the builders are when I'm flipping a guitar around and admiring their
work....when all of a sudden....my eyes come upon something that should never have been left as it
was or should never have had finish shot over it. I never say anything, but they usually do as they begin
to stumble through reasons why they didn't touch it up or just do it again and why they allowed it to
get to a customer that way.

I'd be a terrible judge at a beauty pageant. I like to look for the wonderful traits in everything and
everyone and have a tough time offering a hard critique...unless I'm very close to the person and we
have gotten to that level of comfort in our relationship. I'd be the guy saying, "They're all so darn
purdy...let's give 'em all a tiara."

I think Pat said it perfectly when he said, "This is what I intended to build, rather than, this is how it
turned out." being the two alternatives for a builder to be able to offer when others see their work.

Thanks for the clarification, my friend,
Kevin Gallagher/Omega Guitars

Kevin, are you suggesting that the brace is prone to split parallel the grain lines where the brace tapers? More so than if the grain were oriented the other way?

If so, I suggest that you go to the shop and mill a few pieces in each orientation and see which one splits easier. My tests and some info I've been finding on-line suggest the opposite due to the way the medulary rays connect the annular rings. And the difference is not small.

I used to strongly believe the same thing too but I'm quite convinced it's not true. It looks so obvious, like the early wood is like a weak fault line but there are lots of fibers that connect accross the early wood.

As for stiffness, Somogyi is the only person I've seen that tested this and wrote it up but I've since been messing with it and trust the he is correct that, in all but very dense spruce, flat sawn is stiffer.

Al's point about glue adhesion to late wood is a good one though and deserves testing.

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http://www.chassonguitars.com

Kent,
I've done loads of tests on various bracing cut to every imaginable grain orientation. I've
never been one to just accept anything simply because it has been the norm for any amount
of time, so I was curious and diligent in my pursuit of the facts behind the choices made by
our guitar building predecessors.

Flatsawn wood may well be as strong as or, in some cases stronger than a quartersawn
piece of the same dimensions and material, but I believe that, if you'll do some of the
tests that I've done to compare the two in the application of guitar bracing and the open
ends that we create as we taper them to meet the sides in our construction, that you'll
find the same things that I have.

I took a few pieces of nice stiff Sitka Spruce and cut half perfectly on the quarter and the
other half perfectly perpendicular to it. This offered the two extremes in the saw and grain
orientation possibilities. I then applied pressure to the brace pieces near the end and at the
same point on each one to allow the load to be borne by the decreasing thickness to simulate
a blow, impact or concentrated load in that area.

In each case, it took approximately 30% more weight or pressure to cause failure in the tapered
ends of the quartersawn pieces than it did in the flatsawn pieces. The flat sawn material may have
equal or even superior load bearing ability in the center portion of the brace stock where the full
thickness is present to work, but it indicated that the quartersawn pieces were able to stay intact
without splitting or breaking under a greater load.

With a good glue joint and the ends of the bracing tucked snugly into the kerfed lining to aid
them in staying put, the obvious area of failure in the event of an impact or concentrated stress
would be those tapered end areas and the flat sawn pieces failed earliest for me.

In a free standing load bearing test, the simulated brace pieces measuring 5/8" high and 7/16"
wide bore their load to failure with the flatsawn pieces breaking along a line in the tapered area
at about 28 pounds and the quartersawn pieces of the same dimensions holding out until the load
reached just under 36 and a half pounds or close to 30% more.

I use a pretty simple method for meausing the load before failure that employs my shipping scale
that has a max hold feature, a support for the bracing stock, an arbor press and a stand that holds
the press above the scale. Once the brace starts to fail, the measured weight is displayed it its
maximum. The bracing is suspend between the two legs of the support and about four inches of material
is offered for the pressure to be applied to.

I've read of similar tests being done by other builders, but these are the numbers I've walked away
with so I tend to favor them since I watched them come about in my own shop and in an environment
that I had control over.

I've read Somogyi's stuff on his performing tests of the same nature and agree that there are plenty
of wood species that may indicate the opposite or varying degrees of performance, but have found, too,
that nice dense Spruce has given me these results....and that is what we're using for our bracing material
...or should be. When he said that he'd come to similar conclusions to what I had when testing Spruce of
the quality we should be using for our bracing, I didn't go any farther with the testing since it was all
that I sought.

I have little trouble with using a nice flatsawn piece of wood for a back or sides on a guitar, but bracing
is another issue altogether, in my opinion. I will never use anything but quartersawn material for them.
If a builder is comfortable with flatsawn bracing in his guitars, by all means build away with it. I just
knew that Kyle had intended to cut his bracing on the quarter and place it in the guitar in that orientation
and wanted to see him go back and get it the way he'd originally intended.

Thanks,
Kevin Gallagher/Omega Guitars

I will definitely agree with the notion that you should always do your utmost to create what you initially set out intending to create. That means if this was not your intention, then do it over again. You want the resulting work to be the fruition of your plans and work as opposed to something you just happened to end up with because that's how it turned out. There are plenty of things in life where we often have to accept the end result regardless of our initial intent... I personally do not believe that endeavors in luthiery fall into that category.

Kevin, maybe the difference is in the wood because I was using Engelmann and got very different results. I first made some 1/8" x 1/2" pieces and just broke them by hand. The difference was unmistakable. Not only did the pieces split much more easily radially but when they split, the split continued farther. In looking at the breaks, the radial breaks showed a shiny clean surface and you could clearly make out the flecking of the medulary rays. The tangential breaks were covered in tiny hairy fibers which I assume were the medulary rays as well, spanning across the annual rings. Then I set up a test similar to yours with braces with tapered ends on a span. I set up a tube and dropped a rod down it onto the brace end. The flat sawn pieces withstood higher drops. And they often failed by shearing at the support rather than splitting down the length.

edit: Also, I had a different take on the Somogyi article. I didn't see anything in there recommending dense spruce. He said all samples were within a density spectrum of wood that he had used.

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http://www.chassonguitars.com

Im with Kevin. Whacking off a back brace now (15 minute job) is a lot easier then having to pull a back off and re do braces further down the track.

Kent,
I'd pulled the reference to dense Spruce being stiffer from your earlier post. When you said, "As for stiffness, Somogyi is the only person I've seen that tested this and wrote it up but I've since been messing with it and trust the he is correct that, in all but very dense spruce, flat sawn is stiffer." I was actually just concurring with your findings and realized that Ervin was using wood of the
same quality and stiffness that he would use in his guitars.

I found that one set of braces suffered much longer breaks along a growth line creating more of wedge like separation beginning at the tapered end and reaching several inches into the body of the brace before breaking off. Those were the flatsawn pieces, but the quartersawn pieces, even though they took more pressure to cause them to fail in my case, broke in a more immediate and contained pattern and sheared of in a total break length of about 1/4 inch. The break that occurred in the quartersawn pieces was a more violent failure as it seemed that the entire piece resisted more of a load and then failed completely
while the flatsawn pieces failed along a single line and it sort of peeled back along that weakest point before breaking off inches away from the initial point of failure.

Wood is an interesting medium to work in and offers an infinite set of variables....even in pieces of the same species, dimensions and often from the same raw piece of stock.

Thanks,
Kevin Gallagher

I have flip flopped back and forth on whether or not I would redo the back. After thinking about it and reading everyone's comments I had come to the conclusion that the back would probably be fine and function as it should left as is. Pat's statement of building what you intend to build is very good advice. I want this guitar to be a product of the skills that both my father and I have learned from Kevin's class and our own limited experience, and not the sum of small mistakes that hopefully won't influence the ultimate outcome. So as of right now I will be taking down the braces this weekend and starting over.

That being said, Kevin's last post got me thinking.....when designing structural members they should be designed so that when failure occurs it won't be a sudden "catastrophic" failure. If I read the post correctly Kevin's test showed that QS braces would withstand a higher load, but when the failure occurs it is abrupt and complete. If the braces is completely fractured the portion of the back left completely unbraced and vulnerable to further damage. While the flatsawn wood fails along grain paths, and causes partial separation. The partial separation allows the brace to retain a portion of its original strength and provide some continued support for the back plate after failure. I am curious as to whether the partial strength retention in the flatsawn wood would be a great enough benefit to go in that direction, or if the added initial strength of the QS braces would make them the better choice.

_________________
--Kyle Burner--

Kyle,

The additional resistance to failure presented by the quartersawn bracing should be enough to win
you over since the load necessary to bring either to a point of fracture is far greater (nearly 30% in all
of my tests) than the back itself will ever survive with out catastrophic damage.

If, say, the back braced with flatsawn bracing is struck or flexed to a point within the load bearing
capabilities of the quartersawn braces, but beyond those of their flatsawn counterparts, the brace will
fail and will need repair. If that same force is applied to the back braced with quartersawn braces, the
braces will stand unbroken simply because their load bearing tolerance is higher before any failure to
the point of fracture.

My point is simply to favor the format that provides that most resistance to failure....period regardless
of the type of failure.

Mind you, though, that the force needed to break either brace configuration is far greater than the
back will ever be able to bear before cracking, collapsing or shattering...making necessary of both the
back and the bracing. I opt for the stiffer combination if I'm going to have to repair both in the event
of a failure.

Chances are that you will never have a brace break without the back it's glued to breaking as well.
I'll just keep shooting for the most durable combination. The choice is certainly one that you're free to
make for yourself, your guitars and, ultimately, the people who will own and play them one day. I'm
just a stickler for leaning toward what has proven itself to work and to last longest on the most consistent
basis throughout the industry.

Regards,
Kevin Gallagher/Omega Guitars