A more-or-less copy of a Martin OM

[Diane Kauffmds]

This afternoon I glued in the bridge plate I carved out out a piece of maple firewood. Cutting a flat piece of wood 0.10" thick out of a random log is a lot of work! I split off a slab as a starting point so it would be quartered and have perpendicular grain. That part worked quite well.

Carter curves the back and front of his bridge plates; based on what he's seen doing repair work, he believes a straight back or front edge on a bridge plate acts as a stress concentrator and becomes a line of weakness. Curving those edges better distributes the forces, or at least that's the theory. Sounds good to me....

My bridge plate is larger than most that I've seen. I hope it's not too large!

I put a larger than usual plate on my project guitar and it sounds great. It makes me wonder if a larger bridge plate conducts the vibrations from the strings more efficiently.

I love the look of the bridge plate.

[MaineGeezer]

Today I brought the top braces down to final dimensions, with Carter's supervision and explanation of what to listen for when tapped. I may sand them a bit more to clean up the appearance, and clean off the glue ooze-out with Zip-Strip. My 3rd attempt at a bridge plate was approved.

I also glued the braces on the back and started shaping them with a chisel and block plane. The back will have a 12' radius -- Carter has a preference for somewhat more curvature than many builders do. His theory is, when the wood expands and contacts, the curvature gives the movement a place to go. His guitars sound extremely good, so the curvature certainly doesn't hurt the sound any.

[Diane Kauffmds]

Looking good Steve. You're guitar "guru" has some interesting ideas that I may incorporate into my next guitar.

[MaineGeezer]

The back has warped. The back braces have warped. Instead of the 12' convex radius I cut into the braces, it's a slightly concave radius -- it's warped so much it's gone past flat and is curving the other way.

So what do I do about that? I assume it's due to uncontrolled humidity changes before, during, and after assembly. First step is probably to get it into a controlled 50% humidity space and see what happens to it.

[Kevin Sjostrand]

Yep, humidity.
Put a hair dryer to it, on the concave side and see if it starts to move, then put it in a place with lower than 50% humidity for a few days.

[MaineGeezer]

The problem isn't too much moisture -- it's too little. With a wood fire going 24-7, the house gets really dry. I've been humidifying it, and it's gotten better. It still has a way to go.

[MaineGeezer]

Some more visible progress. The end blocks are glued to the sides, and the tail wedge installed. It's another piece of quartersawn dogwood that echoes the headstock cap.

[MaineGeezer]

I just made the end pin out of dogwood to match the bridge pins. I hope I go the taper correct.

[Diane Kauffmds]

Gosh, your end pin looks so nice! So does your end wedge.

Isn't it amazing how the lack of humidity affects guitars so quickly? It takes a very short time to do real damage to an acoustic guitar when the air is dry. The addition of humidity fixes things quickly. I started seeing small changes in the OM while I was building it, that indicated it was drying out. I started storing the box in the guitar case with the Oasis humidifier, while I was building, which stabilized it.

I'm obsessive compulsive about guitar humidity.

[MaineGeezer]

As soon as I get the back and top glued to the sides and trimmed so they will fit the guitar case, I'll be storing the in-progress guitar in the case with a humidifier too.