I've thought about taking apart a vintage Yamaha FG to see what the top bracing looks like (better than my mirror shots) but the thought of wrecking a vintage guitar has always stopped me. I'd also like to document the bracing dimensions, since the bracing seems to be much lighter than you see on modern guitars.
Until I found a FG-160 with a smashed lower bout. Unfortunately it's a rare Taiwan "No Taiwan" model, a label they only used for 2 months. But wrecked is wrecked, so I decided to take it apart. Not only to get a better view of the top bracing, but to prove the top, back & sides are indeed plywood (inner ply oriented perpendicular to the outer plies).
So I removed the neck. And struggled to get the back off. It was much harder than I thought, even though it was already started in one area. I figured with some prying it would just pop off! NO! I ended up having to use a chisel to get it started to separate between the back & kerfing. It tended to want to separate between the plies and make a mess.
The separation. Not pretty. Pardon the messy workspace.
Close up. Notice the midsize dust bunny. Upon closer examination I found the original owner must have had long red hair!!
I wanted to save the label, since it is rare. So I cut out a section of the back.
My first thought was to take the guitar completely apart, saving the braces, etc. But after struggling to get the back off I decided to just cut the sides off just above the top kerfing, making an open demo guitar top. But that seemed it would be difficult and I realized I should just clean up what I have and leave all the original markings intact.
I also have a 1972 FG-75 Taiwan "No Taiwan" label guitar. I bought it because of the rare label but after I received it I found someone had power sanded the bridge almost to nothing and left deep swirl marks in the top. So it needs a neck rest, a new bridge, the top refinished, and other work. So I'm thinking I'll use it for a demo guitar.
I also have a 1974 FG-110 that I paid $30 for. It's a bit beat up, has the lowest saddle I've ever seen, obviously needs a neck reset, a few frets, and other work. Sounds like a candidate for another demo guitar.
These 3 guitars will give me a dreadnought, folk size, and classical size (with ladder bracing). Covering every size Yamaha made.
Aaaand.... I'm having second thoughts about taking apart a working guitar. Last night I took out the FG-110. It is stilled tuned to pitch with the same strings that have probably been on it for a couple of decades. The dang things sounds good. Similar to my favorite one. Lots of resonance and sustain. Obviously new strings will make it sound better. Yea it needs a neck reset, a couple of frets, and has a few dings. Once I fix it up it'll be a great player. I can't kill it. I'll have to keep searching for a damaged one.