Acoustic Guitar Construction

Kind of late or early where ever you're coming from ..can't sleep of late...have had double pneumonia for 3 weeks and laying down isn't the easiest thing to do...anyway, didn't know where Ken would want to put this info or if anyone would be interested... or not....what ever melts your butter...maybe this info is easily accessed...don't know, it's been hard for me to acquire and I wanted to share...it may or may not make a difference in your end result...but here it is anyway!
My last conversation with Wayne Henderson before Doc Watson passed I ask him if he had any actual measurements that he would share on his bracing and he kind of laughed, not at me...but he actually DOES all of his work by feel and has never actually measured anything...he knows it by heart...folks have checked him many time when he said something measured so and so and he's never been wrong...anyway, to get to the meat of the thing, he told me to give John Arnold a call and talk to him and he was sure John would share his dimensions with me and that they were exactly what Wayne used. In fact, he said that he had worked on John favorite guitar of all time before HE owned it when Wayne was working at Gruhns in Nashville many years ago.
So...for what ever it may be worth, John WAS very kind to share with me and here is what I have:



Borrowed from John Arnold:



One of my favorite guitars of all time is a 1935 D-18 #61033.
All measurements are in inches.
X-brace angle is 97.5 degrees.
Tone bar spacing (C to C) is 1 7/16 @ X-braces, 1 3/8 @ kerfing.
X-braces and tone bars are 0.325 wide.
Bass X minimum = 0.320
Bass X peak = 0.435, 6 5/16 from center of the X crossing
Treble X minimum = 0.300
Treble X peak = 0.565, 5 15/16 from center of the X crossing
Upper tone bar minimum = 0.355
Upper tone bar peak 1 = 0.532, 2 15/16 from the X
Upper tone bar peak 2 = 0.530, 8 3/8 from the X
Lower tone bar minimum = 0.310
Lower tone bar peak 1 = 0.460, 2 3/4 from the X
Lower tone bar peak 2 = 0.500, 8 3/8 from the X
The four short braces (generally called fans) are 1/4 wide, with a peak that is about 1/4 tall. The fans are about 1/16 tall where they intersect the X-braces. The tone bars are about 0.110 tall where they intersect the X-braces.



John


C to C distance from the upper tone bar intersection to the X crossing is 5 1/2. C to C distances from the X to the fans are 2 5/8 and 5 inches.
The angle between the X-brace and the upper tone bar is 62 degrees. Double-check this at the kerfing, where the C to C distance from the X-brace to the upper tone bar should be 1 1/2.

I have found that soundhole locations on 1930's Martins are very consistent. I measure the minimum distance from the brace to the soundhole, which is usually around 0.300". On D-18 61033, that measurement is 0.287.

John.

This is the latest D-18 I'm working on (binding is going on now). Based on a 1937 Martin D-18 which is basically the same guitar. I a discussion I had with John we talked about the addition of the popsicle brace Martin now uses to reduce some of their warranty claims. Instead of that brace and instead of having nothing there a trapezoidal brace is used (John uses it on repairs but thought it was a good idea to include in a new construction). It goes "butted" between the neck block and the transverse brace. Must be butted with no gap. it is the width of the neck block on top and the base extends out to 4". It is felt this gives the support necessary to help prevent those cracks that occur over time in that area (that he so often fixes and that Martin created the the popsicle brace for) but doesn't hinder tone in the same way that the popsicle brace does. So "why" you ask doesn't Martin use it? Because it goes in AFTER the top goes on and has to be accurately measured. It would cost Martin too much in production cost and time to does this so they make up a brace that can be mass produced and put in the same time as the other braces. I would add a pic but I forgot to take one before I put the back on.

Very cool Tim...very interested in that brace...nothing was said about it to me...but that's been a while...if you get an op maybe you could draw out something representative of what you're talking about..I'm sure others would be interested...I can usually visualize something in my mind but I think I misplaced it some where...:>) Thanks for your input.

Ray

Tim...is this something like you are talking about? To me it seems backwards from the way it should be...as I understand it, it widens out to 4" from the block width right? creating pyramid
of sorts with the long side against the top brace. I would think it should fit snug also?

Thanks,

Ray

I believe is been determined that the popsicle brace has zero effect on tone or for that matter nor does any type of reinforcement between the shoulder brace and the neck block ie -- Martin now uses a full cantilivered neck block plus the popsicle brace. It would be interesting to hear what Trevor has to say about this concept. Its great to try and build a clone of a famous instrument, however there seems to be many myths asscociated with the legends -- one John Greven points out is that Martin never used Red Spruce for bracing. And he gets into the HHG thing as well. To me it makes sense that much of the tonal character of the vintage guitars is do to the age of the assembly itself.

Ray, if you took that piece and flipped it around you would have the trapezoidal shape I'm talking about but it is only the thickness of the popsicle brace and no other braces are inlet.

Ken, I agree vintage tone is more likely from the instruments age but I'm not convinced yet (maybe someday) that there is "no" change in tone from the popsicle brace, either good or bad. But I find it intriguing to see and as the brace really is more for structure than sound I wanted to try. Not really making any claims.

Thanks for posting those dimensions Ray. I had certainly never seen them before. Another guy I know online lives near John Arnold and gets his input on guitar builds frequently. I need me a local John Arnold. Or Wayne Handerson. Or anyone who builds and is less than 90 minutes away!

Yeah Tony, I hear that...NOBODY even close to me here except Bill Cory and he seems to be continually busy taking trips to Arizona and around with his daughter...(Good for him...too many people wait too long to retire and the next thing they know...it's too late!) I think he may have gone "Snow Bird" on us...:>)

Tim,
I'm interested to see if you think it makes a difference...let us know when your finished and maybe you could hit us with a sound bite.

Thanks again, Ray