Official Luthiers Forum!
http://mowrystrings.luthiersforum.com/forum/

Fixing Flawed Wood
http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10102&t=13755		 Page 1 of 1
Author:  Brock Poling [ Sun Sep 23, 2007 12:49 pm ]
Post subject: 
I have a couple of sets of wood that are just outstanding, but they have a couple little flaws and I wanted to get some ideas about how you would attempt to fix these?


The first is a ABSOLUTELY killer set of black & white ebony that I got from Bob. This is just really over the top, but it has what appears to be a compression crack all the way through both plates on the back. It almost looks like it was struck with a sharp blow.

The crack is about 1" long. Outside of this damage the set is perfectly clean. It looks to me like this may have happened during shipping.

I have arranged this about every way I can, and no matter what I do this is going to end up in the pattern. So I have to fix it. But, my plan was to make this a show guitar, so the fix has to be invisible.

I am interested to get your opinions.





And just to give you a little context, this is the whole back.





The second flaw is a split knot in a pair of macassar sides. The goal is to use this on a commission of a dread size guitar so I need to go clear to the edge.

Most of this will come out with the binding, and I am confident that I can seal this up with dust and epoxy... but given that it is right on the edge and I am unsure about what heat will do to this much glue. Would you attempt to fix this now (before thining and bending) or later (after thinning and bending.)



Author:  Michael Dale Payne [ Sun Sep 23, 2007 1:00 pm ]
Post subject: 
Fix it and move on that stuff is so awesome that small fill a and a fix will never catch the eye

Nice eye candy
Author:  Dennis Leahy [ Sun Sep 23, 2007 2:08 pm ]
Post subject: 
Hi Brock,

This is just from fine woodworking experience, and instinct, not from my vast treasury of tricks of a master luthier that has built one guitar.

OK, with that disclaimer out of the way,

I'll start with number 2: That Macassar side will probably go right through the bend without problems, but this is what I would try, for insurance: I would edge-glue a small piece, maybe 6" long and about the size of a piece of binding to the edge of that board, bridging the knot crack. I'd use Titebond III (to take the heat and water of bending.) I would use something easy to bend for the edge reinforcement strip, like Walnut or EIRW or even something like Aspen. If you believe that might unduly stiffen that one area of the side and cause trouble with the bend, then you could straightline that edge first, and edge glue the entire edge with a piece of banding. (That is, if that edge is not to be tapered to meet up with the back - I can't see a taper in the photo.)

Number 1: First of all, yes, it will be difficult to get anyone's eye to roam to that spot, with the incredible black spider lines near the center grabbing their eyes. However, knowing that light wood dust gets darker with glue, I would be inclined to try something other than filling with surrounding wood dust and glue.

Idea 1: Use slivers from the board that match as well as possible. There is a small area between 6:00 and 7:00 outside the pattern that looks like a donor candidate. There's even a thin black line.

Idea 2: Use wood dust that is even lighter than that area, so that wood dust plus glue equals the correct shade. Maybe some of the sap at 6:00 outside the pattern.

For either idea 1 or 2, I would experiment on waste pieces from this set, make a crack/gouge, and try to fill it, then shellac the test. That's the only way you'll know how close you got.

Idea 3: I built a curved reception desk of figured Sapele veneer. After it was lacquered and delivered, someone ran into it with a fork lift, right in the front. The company I was working for hired a touch-up guy with a very good reputation. I saved some of the Sapele veneer for him, but he said "no, thanks." I went on-site and examined his repair. It took a minute to even find it! He filled it with Bondo, and hand painted in fake grain, with artists acrylics, to match.

So, whatever you do to repair this, you still may need/want to touch it up after the sealer coat of epoxy or shellac or whatever you plan to use.

Best of luck, and skill. That really is some fine wood!

Dennis
Author:  TonyKarol [ Sun Sep 23, 2007 11:00 pm ]
Post subject: 
Not too sure abou the B&W ebony Brock, but on the macassar I would fix with dust and CA first, then thin and bend. Where on the side pattern is this - if its lower bout, you should have no worries at all - the bottom of the waist or top of the upper maybe - oops - dread, waist is not an issue. It should be fine.
Author:  Pwoolson [ Sun Sep 23, 2007 11:33 pm ]
Post subject: 
Brock, on the B/W Ebony, can you simply flip the pattern over so the upper bout is in that area?
If that doesn't do it for you, my fix would be to flood with epoxy. You would then have to do some sort of painting to retouch the color issues.
Author:  Bob Garrish [ Sun Sep 23, 2007 11:45 pm ]
Post subject: 
[QUOTE=TonyKarol] Not too sure abou the B&W ebony Brock, but on the macassar I would fix with dust and CA first, then thin and bend. Where on the side pattern is this - if its lower bout, you should have no worries at all - the bottom of the waist or top of the upper maybe - oops - dread, waist is not an issue. It should be fine. [/QUOTE]

No experience with bending glued stuff, but be really careful if you're going to bend something with CA in it. I've had some 'eye opening' (actually closing very tight with absurdly painful burning) experiences with the fumes when CA gets hot.
Author:  GCote [ Mon Sep 24, 2007 1:29 am ]
Post subject: 
I agree with Paul.
I just had a Braz 000 at Tony's. On the sides right at the top of the cutaway there was a white mineral line on the wood that would not sand off so I had Tony do some magic on it and it went away...

Gary
Author:  Brock Poling [ Mon Sep 24, 2007 5:12 am ]
Post subject: 

Thanks for the ideas guys.

To make the whole thing even more complicated there is a decent amount of curl in this set.

Author:  Larry Davis [ Mon Sep 24, 2007 5:59 am ]
Post subject: 
Brock, that black and white ebony fracture is not from an impact suffered in shipment, but a common defect in brittle woods. I find it in ebony, ziricote and some high figured bubinga among others. An impact would have left dented wood fiber also and the package would have been clearly suffering a traumatic impact point.

Bad news is if you can't trace it into the other side and find an exit to define the defect it may continue for several inches hidden inside. You might try lifting the separated fiber with a knife point to get a feel for it's depth. I can see darker lines coming off the ends of the shake that might indicate weak fiber beyond what's allready visibly cracked. It's possible to saturate with CA and press it back together. Most important is to define the scope of the defect.

I'm not a big fan of using knot sweep wood fiber due to it's instability and extra brittleness. The wood fiber sweep is defined by the knot shape around the cracked, loose knot down to where the grain becomes straight again.

Author:  James Orr [ Mon Sep 24, 2007 6:14 am ]
Post subject: 
Brock, I had a crack like that in my flamed mahogany from Bob (from my
own doing). I used the red label Special T CA glue and a clamp. It might
be luck, but it's undetectable, and I couldn't see any evidence of the CA
under the finish the first time I tried finishing it.
Author:  James Orr [ Mon Sep 24, 2007 6:14 am ]
Post subject: 
The CA would also wick itself to the far reaches of the crack.
Page 1 of 1 All times are UTC - 5 hours
Powered by phpBB® Forum Software © phpBB Group
http://www.phpbb.com/