Wednesday, August 20, 2014

Crossing A Crucial Bridge

Well, Bruce Roper and I have reached the last couple of visits on the Buildmyguitar project, and I'm happy to say one of the most complicated parts of them all comes just about last. Take a look at the guitar as it sits right now:

It's all but finished. What's missing is the bridge, the tuners, the nut and the saddle. The bridge and the saddle are the reasons the neck isn't attached yet. We're moving into that frightening world that is a mix of math and geometry, and the calculations Bruce uses will determine exactly where the bridge should sit on the body of the guitar, and then how the neck should be placed to make certain the intonement is just perfect.

But we didn't start the day at Bruce's shop. Instead, we went to Guitar Works in Evanston, where the folks in charge let us peer into this guitar:



This is just the top. I put it here like this to show you the name, "Greven", which is an important name for Bruce. Greven works by himself in his shop in Portland where he turns out just about 40 guitars a year. That's a lot for one person. What is amazing is that they are of such high quality. Here's the rest of the one from Guitar Works (the room was too small to get a good shot).


Bruce and I went to Evanston because we had dropped in last week, saw and played this Greven, and decided to go back and look inside to see what made it so special. And it is special. Finger pick on it, thump it hard, wham it with your fingernails, whatever you do it feels and sounds great. Bruce put his mirror inside and used his flashlight to light it up. He looked around and concluded "damn" it's just like any other guitar, maybe even a little heavy inside in some ways. But the sound is wonderful. The only thing that kept me from buying it is I already have too many good guitars, Bruce is building me another and it would be crazy to add to the pot, especially when I'm not playing them out and making money.

"I don't know how he can do that," Bruce says of Greven's output and high quality. But he does. Greven explained it all at a Luthiers Convention workshop in 2011. It sounds simple. You just line up a whole bunch of wood, form it, glue it, finish it in stages and there you have it, a guitar! If you read the transcript from that workshop, what you learn is that Greven has been making instruments for 50 years and spent a stint running the repair shop at Gruhn Guitars in Nashville. Gruhn Guitars is like Mecca for acoustic guitar players. It's where failed country stars can sell their best stuff, where the biggest names got their instruments tweaked or repaired, and so on. Greven learned a lot there and built it into how he constructs his own guitars.

Bruce has an immense respect for Greven and he bows to the man and his processes even as he builds my guitar. Back to the bridge story!

Using a fret tool to measure distance

Because everything has to be just right after this point, Bruce uses a fret measurement tool to find out where he is going to place the saddle in the bridge on this guitar. He marks the spot with a white grease pencil. Then he brings in the bridge to position it over that spot. It has to be square and lineup with the center line on the instrument.

Positioning the bridge
When that's done, he has to find a way to cope with the fact that the top of the guitar has a gentle arch and the bottom of the rosewood bridge is absolutely flat. To accommodate that curve, he tapes a piece of rough sand paper to the top of the guitar. Then he slides the bridge up and down on the sandpaper, creating the same arch in the bridge as the one that defines the top of the guitar.

Sanding the bridge to match the guitar top.
 Every few minutes, he vacuums the dust from the paper and watches closely as he starts the sanding process again. He is looking for the point at which everything is sanding evenly, which means the shaping of the bridge is complete.

Scraping an area for the bridge
When that is done, Bruce takes a very sharp chisel and scrapes the finish from the part of the top that is covered by the bridge. (He used an Exacto knife to create an outline just inside of the edges of the bridge. This is because you never glue wood to finish. You can only glue wood to wood if you want it to hold. He creates the clean space on the top of the guitar for the bridge.

Putting glue on the bridge and the guitar
See the holes in the guitar top? Those are the holes that will ultimately hold the big and little "E" strings. But for now, they will serve as guide posts and anchors to glue down the bridge.

Posts and bridge clamps in place
It's almost finished now. By the time Bruce is done, every fraction of an inch of the bridge will be glued tight. It's sitting just above the bridge plate glued on the underside of the top way back in March. The edges of the bridge are glued directly over the x-braces that run diagonally under the top of the guitar. Put it all together and it's a very solid package to hold a couple of hundred pounds of string pressure.

The last step
After the bridge glue dries, Bruce will be setting the neck. If you look at his bolts and the joint above, you can see there are spaces to trim face wood and bottom wood, which will give him the set he needs to make sure the neck and the bridge are in alignment.

We're just about there.

Come back.


2 comments:

  1. So exciting, so worth the wait, as with all good things in life!

    ReplyDelete