1953 Gibson LG 1 top and back radius question

[John Yungbluth]

Presented for your consideration...............

I have a 1953 Gibson LG 1 that is in the process of being extensively repaired.  It's missing one top ladder brace and two back braces. Does anyone know what the proper radius would be for these braces? I don't want to remove an mounted one to duplicate the radius unless it's a last resort.

She will never look like new, but she can get her voice back.

Thanks in advance.

[Len Biglin]

I have one from about 63 but how do I measure it ?

[John Yungbluth]

I'm not sure.  I'm working on that with my son.  Conquer the world through math.  But I'm looking for a confirmation or consensus information before going forward.

[John Yungbluth]

Len,

Could you take a few pictures and estimate height of the back braces on your guitar. I can get the width from the glue footprint on the back.

I have:

the first brace behind the neck block

missing the second

have the third

and missing the fourth.

I'm guessing 1,2,3 will have the same profile.  But the 4th brace is an unknown.  It's wider by the glue footprint, but I have no idea of the profile.

Thanks in advance.

John

[Taffy Evans]

Hi John,

not being any good at maths other than adding and subtraction, I use this idea I devised to help me. See the photos.

The following math I don’t understand, but muddle through it.

To calculate the radius:

Once you know the width and the height, the formula for the radius is…….

H/2 + W2/8H

Where W is the distance across the guitar top, Width of the base of the arc

H is the height, measured at the middle of the arc’s base.

Hope this helps if you can understand it.

This will find the radius of the top, but keep in mind that it may not be the makers' original built-in radius as these things change over time.

Cheers Taff

[John Yungbluth]

Thanks!  

I'm going to take a few days and make these two tools.

Now, I'm going to hunt up a few pictures of the missing back braces to get their profiles. 

For the top missing braces I'll duplicate height and width and the squared off tops like the ones still attached.

Thanks again.

[Len Biglin]

John i'm sorry for the delay , i must be the busiest luthier in Australia , Ive noticed that the back is wider than the top , its 14 1/8" on top and 14 3/8 " on back , a straight edge across the widest point gives a 1/4 "gap each side . I'll let you work that out . First back brace is 5/8 in centre , 2nd same , 3rd 9/16 , and 4th 9/16 in centre . Top 1st is 5/8 2nd 9/16 , 3 & 4 are 9/16". This is the model with plastic bridge which was replaced when I bought it in 86 with an ebony copy . i have never loved the sound of it but it has needed a reset for the whole 35yrs lol , its in line for that soon if my work dies down a bit . #149275

[Len Biglin]

So here's some pica of braces .