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#16
06-11-2023, 11:24 AM
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There is no way that you will get the back glued so the binding ledge is aligned all the way around. You are going to be setting the neck angle when you glue the back on again whether you want to or not, so you might as well get it right, and then deal with the places where the edge of the back is not right on the edge of the liners. Most likely you will need a thicker binding or to add purfling after you have made the rabbet consistent all around.
Those L-50s have a low bridge to begin with (fretboard extension not raised off the top), and the tone will suffer if you make that worse by lowering the bridge. The dovetail going through the block is usually from the mortise beings sawed rather than routed, although I don't know how Gibson was cutting the mortise in that period. The little bit of neck tenon touching the back wouldn't get in the way of steaming the neck out at a later time if you want to do that, but you could chisel a bit out the bottom of the tenon if you like to preclude there being an issue. The through mortise does make it possible that steaming the neck out would loosen the block from the back--another reason to set the neck angle when gluing the back on. You have the opportunity to get the neck angle right without removing the neck, just by paying some attention to how you glue the back on. Why not take advantage of that?
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"Still a man hears what he wants to hear, and disregards the rest." --Paul Simon Last edited by Howard Klepper; 06-11-2023 at 11:30 AM. 
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#17
06-11-2023, 01:59 PM
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Quote:
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Fred
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#18
06-11-2023, 02:09 PM
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Nice back
redir - I love that pic you posted. That back is gorgeous. I thought about making a form but opted not to as the warping back has mis-shaped the sides where the back needs to be. I figured I'd have to coerce the sides to line up. Not a lot but at least 1/4 inch across the lower bout. I was kind of hoping the guitar would tend to spring back a little when the tension from the back was released. I think it may have as it is sitting right at 14.75 inch which is the spec. If I thought I could make one as pretty as yours, I'd be tempted to put a new one on. I've only made one back for a low-end laminated side martin just for the experience of doing it. I routed the new top for binding but laminate doesn't do well with that. It came out OK but was a bit of a headache. Skipped it for the back. I gave it to the grandkids to play with it when I was done. I was not unhappy but my finishing skills are nowhere near yours. I really want this original one to go back on for this instrument.
Howard - thanks for input. Lots for me to think about. I will have some time while I work on getting the back straight again. Right now I just set it on my dining room table with two panes of thick glass sitting on either side of the center seam brace. I have some weight on it. No heat or moisture applied. I'll have to think about that too if I don't get any movement like this. IMG_7406.jpg soundboard routing.jpg My HD-28 next to my $30 Martin that I put a new back and front on for the practice. The End.jpg
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2010 Martin HD-28 1990 Martin B-40 Acoustic Bass 2004 Taylor 815ce 2018 Taylor 814ce LTD NAMM 2019 Taylor Baritone 8 1937 Gibson L-37 2005 Gibson J-45 Historic 2014 Gibson Les Paul Acoustic Prototype Last edited by wblock77; 06-11-2023 at 02:31 PM.
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#20
06-12-2023, 05:47 PM
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The issues with the sides not fitting the back in outline were not necessarily caused by the back. Often it's the other plate- the one still connected to the sides- that is the primary issue, which is often caused by uncontrolled humidity during the build process.
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bonzer5
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#21
06-22-2023, 08:05 PM
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N23_1161.jpg
Just a feedback note to let you know what I did. As predicted, pressure and a little spritz of water wasn't enough to make anything happen. I had to give it some heat to get good results which I did. It straightened out very nicely. Unfortunately, with that the back finish took a beating. It really comes off easy, probably from the abuse that made it warp in the first place. As for the neck, I chickened out all around. I pulled up on the neck to see how a Cali reset would affect the back alignment and it appeared I would have real headaches getting it to look good even with thicker binding. I thought about a conventional reset but since I'm only a little high. I didn't want to mess anything up. I re-glued in all the braces and buttoned it up. I did buy another aftermarket bridge that looks the same that I can shorten the little bit I was hoping for. Sometime if I get brave, I'll do a neck reset and put the original back on. Truth be told, I think I mostly just wanted to get it to the point I could string it up and see what it sounds like. Ps. That white line in the centerline is a sliver of tonewood I hand shaped to just fit into a crack / gap. I pushed it to see if it would go back together and it felt like I was going to crush the guitar and it didn't budge. I will color match later.
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2010 Martin HD-28 1990 Martin B-40 Acoustic Bass 2004 Taylor 815ce 2018 Taylor 814ce LTD NAMM 2019 Taylor Baritone 8 1937 Gibson L-37 2005 Gibson J-45 Historic 2014 Gibson Les Paul Acoustic Prototype Last edited by wblock77; 06-22-2023 at 08:10 PM.
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#22
06-23-2023, 07:17 AM
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I’m curious to hear your report on what it sounds like. I used to play one of the old Gibson f hole arch top acoustics with a trapeze tail piece that a buddy owned back in the 70s. That was a very cool guitar and played great. I can no longer remember the model #. I just remember it being a super slinky blues machine.
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Gibson and Fender Electrics Boutique Tube Amps Martin, Gibson, and Larrivee Acoustics
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