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’X-ray vision’ reveals a mystery
http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10102&t=851		 Page 1 of 1
Author:  Dennis E. [ Wed Jan 26, 2005 11:07 pm ]
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I repaired an old Yamaha FG230 12-string for my grandson. I plan to build a small-body 12 one of these days, so I study carefully every one of them I get my hands on. Ok, I admit it, I study every guitar within reach. As part of the process I stuck a flash inside the box and snapped a picture to record the bracing pattern — and discovered something weird.

Look closely at the photo below and you'll notice two rectangular areas that look about the size of razor blades. One of them is located slightly above and to the left of the bridge' and the other is on the right side near the pickguard. At first I thought these were patches or reinforcements on the underside of the top. When I felt around inside, there was nothing there.

"Ok, it's a couple of 'Inspected by No. 4 stickers'," I thought. But no, careful inspection with a light and mirror revealed nothing but bare top in those areas — not even a stain where something used to be. Does anybody have any other theories?

I went on to repair its badly bellied gut with a JLD Bridge System, but I still wonder about those dark patches from time to time.


Author:  Mike Mahar [ Wed Jan 26, 2005 11:13 pm ]
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Perhaps this is a laminated top and the squares are in between the plys.
Author:  Dickey [ Thu Jan 27, 2005 1:11 am ]
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Cool Shot, Don W. told me this might work. I see it does. As to the patches? Hmmmm. Good guess Mike. Look also at the shadows by the tone bars, the look a lot the same darkness. Can you tell if this top is laminated at the soundhole?

Mystery Solved, mystery solved, look closely.

Dickey38380.6593981481
Author:  Jimmie D [ Thu Jan 27, 2005 7:37 am ]
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Neat shot Dennis. I'm inclined to think that it is a solid top. If you look, the spot is mirrored on the opposite side. The shading out toward the edges of the sound board is also identical. This tells me that the top was sawed out of the same piece and then bookmatched. As to the square looking shadow, I think it is some kind of abnormality or hard spot in that particular piece of wood in that specific area.IMHO
Author:  John How [ Thu Jan 27, 2005 9:17 am ]
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They're x-ray detectors and now you've gone and set'm off.
I have an old Yamaha that had a laminated top. Could be something to that theory, I see some other cross grain activity in the picture. Let us know what you find out. John How38379.7230787037
Author:  TomS [ Thu Jan 27, 2005 10:09 pm ]
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Is it a shadow from the flash unit?
Author:  Dennis E. [ Thu Jan 27, 2005 10:28 pm ]
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Hmnnn embedded security tags ... John, I like it ...just try sneaking this thing out of Walmart!

It's definitely a solid top, and it's definitely some kind of artifact. Nature doesn't give us too many rectangles with 90? corners.

The shadows lie along a plane that's exactly even with the end of the flash unit, so I think Tom's theory is the best so far. Now I have to try to figure out the geometry involved.

Thanks everybody for your input on this. I haven't been so stumped since I saw a UFO in Portland, Oregon, back in 1978.
Author:  Brock Poling [ Fri Jan 28, 2005 1:44 am ]
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So just move the flash, take the picture again and see if the squares move. That theory can be tested easily.

One thing I have considered... and I don't place too much stock in this idea... but it might be worth throwing out there. The amount of light that would show through the top would change as the density & composition of the wood fibers in the top changed.

I wonder..... what would a top look like that has had something REALLY REALLY heavy set on the billet before it was resawn and sanded? If it was from the top cut I am wondering if you could still see the ghost of the compression. The spot would be bookmatched and once level sanded you might not be able to see or feel it but the trauma would still be in the wood.

Again... just an idea... and probably not a very good one.
Author:  Pete Licis [ Fri Jan 28, 2005 4:34 am ]
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Hey Dennis, are you positive it's a solid top? Does the grain on the inside run the same direction as the outside? The reason I ask is because in the photo, it appears to me at least that there are some cross-grain streaks where there are no braces. Sort of like there's a cross grain ply in there. I know nothing about plywood tops, but if the grain is the same direction both inside and outside, I suppose it could be a three-ply top. Are any anomalies on the outside grain also seen on the inside grain in the same places?Pete Licis38380.525150463
Author:  Dickey [ Fri Jan 28, 2005 5:03 am ]
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Solved.
Author:  LanceK [ Fri Jan 28, 2005 7:27 am ]
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Bruce! GET BACK TO WORK!
Author:  Mario [ Fri Jan 28, 2005 12:36 pm ]
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Looks to me like a laminated top. The old Yamahas had spruce for all layers, and all of them running the same direction, unlike the newwer ones with the junk wood as the middle layer, run at 90 degrees to the outer layers. Yamaha was also extremely good at hiding the fact that they were laminated, to the point where it is nearly impossible to tell.

My guess is that those rectangles are pieces of veneer tape. The middle veneer would not have its join in the center, as does the inner and outer ones, therefor makingt he whole unit very strong.
Author:  Dennis E. [ Sun Jan 30, 2005 10:05 pm ]
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I like Bruce's subliminal advertising idea. That's about the only good reason I can think of for using a laminated top.

The next time we visit Ohio I'm going to revisit the old Yamaha and check out that top again. The more I think about it the less I lean toward the flash/shadow artifact idea and more toward the laminated top and the veneer tape theory Mario proposed.

I would have sworn it has a solid top from my earlier examination, but I might have been fooled if the laminations are all going the same way. I seem to remember seeing solid grain lines at the soundhole edge, but next time I'll take a 10x jeweler's loupe to it. If I have to I might even sand a tiny spot on the lower edge of the soundhole to be sure I'm looking at an actual cross section of the top. I'll also check and see if I can find any "tell-tales" as Pete suggests.
Author:  Michael Dale Payne [ Tue Feb 01, 2005 5:26 am ]
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Dennis I have an 1970 model Yamaha FG260 12 string. After reading your first post in this string I went and looked. My top is most deffently solid. The FG230 may have been laminated I don't know, but I did the back lighting and I did not have the two rectangular shadows. I don't know but that may be the difference in the two models. Just a bit of useless Info for you to have to process MichaelP38384.5628125
Author:  Don Williams [ Tue Feb 01, 2005 5:35 am ]
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LOL !

Bruce, shouldn't that say "Ea A oe's" ?

Go here for more info on Old Joe's Place...Don W38384.5733217593
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