Repair And Restoration
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Replace broken back brace Gibson LG-1
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Replace broken back brace Gibson LG-1
Hello,
This is my first discussion as I am new to this group. I am starting a restoration project on a 1957 Gibson LG-1. The first job on it that I want to tackle is to replace a broken back brace. It appears to be broken in half right on the center line (see pic one before the brace was removed). I have removed it and am gluing in back together (pic 2), just to get it strong enough to use as a template for fabricating a replacement as I figure it won’t be strong enough to serve it’s purpose re-glued. My questions are as follows: I do not have a radius dish, so I was going to attempt to craft the replacement by hand after tracing the shape of the old brace. Is this recommended? Any other things I should consider? If buying the expensive radius dish is the only option, how could I determine the radius of the back of the LG-1? Any input would be much appreciated!
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7 Replies
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I might suggest that it would be a good time to make a “Variable Radius Sander” for yourself. They can be set to any radius and are quite handy for shaping replacement braces. Using a contour gauge on the back of the guitar where the brace needs to go will give you the correct radius for the replacement brace – or copying the current brace with a contour gauge will also work.
Here are a couple of links to Instagram posts I did showing the tool in detail:
https://www.instagram.com/p/Coe4biiOabC/?utm_source=ig_web_copy_link&igsh=MzRlODBiNWFlZA==
https://www.instagram.com/p/Coh6W2NJR2C/?utm_source=ig_web_copy_link&igsh=MzRlODBiNWFlZA==
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Saw this tool on my Instagram feed (from February 23 2023) today, and it lead me here…. Thanks for sharing Doug….
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Doug’s solution is genius.
If you want something easier (but not as permanent and multi-purpose) you could glue the two brace pieces together to recreate the full curve, and use that piece as a routing template for a flush trim router bit. You could double side tape a brace blank to the top, and use a flush trim bit with a bottom bearing on a router table to recreate the curve. You’ll have to figure out a way to clamp this safely to present it to the router bit so you don’t get your fingers anywhere near the cutting surface. Maybe you could leave the brace quite tall and then cut off the excess on the non-curved side after you created the radius.
If you send me the chord length (the x distance of the brace, not along the curved edge, but just the straight line across) and the height of the arc (measure from point to point across the chord length, the height of the arc is the amount of the “bulge), I will do the calculation and send you the radius.
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Hello Doug,
That is brilliant– exactly what I need. I checked out your IG posts and have put together the order for the parts. I have one question that was not specified in your posts: it seems you have two different sized turnbuckles, one for expanding and one for retracting. What are the two different sizes? The one you have on your order list is 7.5″ retracted length– is this the short or longer one in your pics? Thank you for the great reply!
John
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The 7.5″ is the original length turnbuckle I used it allows for both convex and concave radii – however there are limitations – the shorter turnbuckle – I believe it was a 5″ or 4″ retracted length. I have a number of different sizes. The smaller turnbuckle allows you to achieve a very concave radius – I have been able to get as tight as a 5″ concave radius with this tool. The convex radius has limits based on the height of the two legs. The taller the legs, the steeper the achievable radius – I haven’t found too many reasons to make the feet taller than they are.
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Hi John, welcome to the Looth Group. Yes, Doug Proper’s radius-sanding tool is wonderful – he should have invented it 50 years ago, and that really annoys me. However it is one of the most “why din’t I think of dat” tools ever. Here is a 6-year old Gibson Byrdland, that needed: 1) the bridge base fit better to the top; 2) a SMac Benedetto archtop fit to the top (the customer wants a traditonal archtop bridge and an a stock T.O.M. bridge so he can switch them out for tone). Before Doug’s tool, I always taped the top with low-tack sign-painter’s tape, laid sandpaper over that, and sanded carefully north and south and it is a delicate, slow job. This is my favorite new tool except for Ian’s pickguard-gluing cauls, or the Total Vise, or learning how to use a 3D printer, and many more. Thanks Doug!
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Thanks Dan! Yes, I’m really looking forward to receiving the parts and putting this into use. I’ve used the sandpaper on the top for fitting bridges and on the fingerboard for radiused nuts, but this should be much better. I’m new to this group and am amazed at all the interesting and useful information here. I was just reading about the use of the 3D printer for making a pickguard caul this morning. Really amazing stuff!
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