I bought a Yamaha C40 to learn guitar/flamenco. It is my first and only guitar. It does not have a truss rod. The action was extremely high even when I bought it -- a bit over 5mm on the 6th string. After lamenting over this for the past few months, I shaved down the saddle using sand paper a few days ago. I shaved off ~2mm (~0.079in) of the saddle so that the action would be lowered by ~1mm. Playability has increased dramatically (especially with bar chords), however I am a bit concerned that the neck might start to bow now, especially since I use high tension strings (not sure if that has any effect though). Are my concerns valid/legitimate? Is there anything I can do that would help me avoid this from happening (apart from using a case humidifier)? Have I ensured my $200-guitar's demise?

I am no luthier by any stretch of the imagination, but from what I know.....
Classical guitars are generally safe to take down to 3mm on the 6th string. High tension nylon strings should have no affect on the neck - although I have heard people say stay less than 100lbs. Whatever, take that for what it's worth.

I admirer your guts, and glad to hear that you feel the playability has improved. I have thought it over, but just cann't pull the trigger. I use my classical for both classical and fingerstyle and just love its sound. Not to mention I think I will prefer a smaller nut width and neck type for my Flamenco than I have on my classical. Maybe someday I will buy a Flamenco guitar - for now I will just plug a long.

Good luck to you!

Chindiana,

I am not a luthier but I have owned several guitars and adjusted the action on most of them. And studied a bit of math and physics.

Lowering the strings should lower the tension on the neck and the bridge.

Let's do a thought experiment. A drawing might help. Assume that the string tension stays the same.

Because the differences of lowering the saddle are so small, let's do the opposite. Make the saddle higher and imajine what happens.

Let's imagine or draw a higher saddle and see what happens. If you put on a higher saddle, let's say 6 inches, if it helps you to visualize it. We are keeping the string tension the same, so the actual tension on the neck (at the nut) does not change. However, the angle and thus the leverage effect pulling (bending) on the neck does increase. Also the stress on the neck to body joint increases. And also, the leverage effect on the bridge increases. And the stress on the sound board (guitar top) increases.

So, by doing the opposite (lowering the saddle), you are lowering the stress on the neck, the neck joint (at the body), the bridge, and the sound board.

Lowering the saddle a few mm will:
1. Make the guitar easier to play. Also easier for the strings to buzz on the frets.
2. Compensates a bit for the higher tension strings. But not noticeable or necessary.
3. Changes the intonation, more so the higher the fret. But should not be noticable.
4. Lowers the tension on the bridge and thus the sound board. Which will change the characteristics of the guitar sound. Which may be positive or negative. But probably not noticeable to most people.