Thursday, June 18, 2009
At lunch I predicted that when we got back home everyone would be exhausted from a day just basically laying around, and that someone would blame it on the sun. I was only partially right. Before we even got home Bonnie commented on how tired she was "from the sun and the fresh air."
Because it couldn't be that we have reached that age where even chillin' is tiring.
Everyone was in bed by 11:00 p.m. Even Andrew, who, at 25, can't blame age, so he blamed it on having to get up so early.
Tuesday, June 16, 2009
The replacement zebrawood sides are in a Fed Ex truck somewhere on their way to Walkersville. They'll be waiting for me when I get home.
Pam didn't want me mentioning that we are on vacation because she knows how many questionable characters read this blog and would take advantage of our absences to go rob us. But I was planning on posting while I was on vacation and didn't think anyone would fall for pictures with captions like: "Here we are with our friends Del and Bonnie on the beach...you know, the beach in our backyard. Yeah, that's it, we have a beach in our backyard. We're not in Florida, we're on the beach in our backyard."
So here's the deal:
- If you're a questionable character, stop reading my blog. Go work on your character or something.
- The house is not empty. Austin is still home. He's twenty, he's lean, he's mean, he works out at the gym, and he'll kick your butt.
- Kobi the Wonder Beagle will bite your butt.
- We have snoopy neighbors who will call the cops if anyone with a questionable character even looks at our house.
- We have cheap stuff. No Blue Ray player, no expensive jewelry, nothing worth stealing. Seriously, I'm a pastor, you think I have thousands of dollars worth of electronics? Surely you can find a lawyer or doctor who's on vacation. And who doesn't have a beagle guarding the place.
There. Pam can rest easily now. Like she's ever going to know. She doesn't read my blog. She's a woman of high character. And she's still figuring out this Internet thing. And she still really believes that there is a button she can push on her computer that will destroy Western civilization.
She ain't readin' my blog.
Yeah, so we're at the beach. Beach reading, it's the best. I brought nothing to do with theology, ecclesiology, philosophy, leadership or any of that stuff. Just light reading. Murder, espionage, kidnapping, that kind of thing. Light reading. The good guys always win.
I brought about six junk novels. I don't know what I'll do for the second week, but there's a local library, so I'll figure it out.
Monday, June 15, 2009
What we're looking for is a good balance between structural integrity and flexibility.
The process starts off with marking the minimum heights for the braces of the lower bout. There are minimums for the high spots and minimums for the low spots. I don't want to go lower than the minimums because that compromises the structural integrity. I should be able to hear a good tap tone before reaching that point, and that describes the goal--reaching a good tap tone while leaving as much wood on the braces as possible. Here's what it looks like before I start:
I start with the upper bout and work my way down to the lower bout, carving away with a very sharp chisel. The x-braces I want to just slide under the kerfing of the sides, while the finger braces--the four little ones on each side of the x-braces--and the tone bars--the two lowest one--will end about 3/16" from the kerfing. The upper transverse brace will also be tucked into the kerfing.
Here are the braces after the initial carving.
After each little bit of carving I tap it to hear the change in sound. Not much happens until I get to the lower bout, and then I can really start to hear it. Then I start by sanding each brace, tapping all the while. The changes are more subtle at this point.
Here are all the braces sanded to 100 grit. It sounds really good!
Still a lot of work yet to do. A little more sanding of the braces, then the whole thing, top and braces, get sanded to 320.
Wednesday, June 10, 2009
I've not done any research or any testing, but I find myself in agreement with the latter school. The back is made of hardwood and is not as flexible as the soundboard. It is not designed to vibrate as much as the top. It does vibrate, however. Hold a guitar and strum a full chord and you can feel the sound against your torso. And you can hear the difference between a guitar made of rosewood and one made of maple or some other hard wood, so there is no doubt that the back (and sides) contribute to the sound. But it seems to me that you would want to minimize the vibrations coming from the back. Resonances can cancel each other out, and it seems that this is what would happen if there was a lot of vibrating going on.
If you want to bounce high on a trampoline, you keep your body rigid so that all the energy from gravity is transferred to the springs. When you want to stop and get off, you flex your knees and allow your body to absorb the energy. It seems to me that this is a good analogy for what I want to happen inside the guitar. I want sound waves to jump out of the sound hole, so I therefore want them to bounce off a rigid back. A back that vibrates a lot is a back that flexes its knees, absorbing some of the energy that I really want it to reflect.
The back is made of rigid wood, and the braces make it more rigid. Whereas the braces for the soundboard are there to not only give it structural integrity but also to transfer energy, which are somewhat at cross purposes, the back braces are there to increase structural integrity and reflect energy, which are compatible with each other.
So in shaping the braces I'm not going to remove much material, just on the outsides where the back meets the sides. The sides act as really rigid braces for this part of the back anyway, and the braces needs to taper down to fit under the kerfing. Also, no one likes a heavy guitar, so removing some of the material will help in this regard.
On the top two braces I start the taper about 2 1/2" from the end; on the bottom two about 2".
I put the back in the 15' radius dish so I don't have to worry as much about cracking when I press down. The burlap protects the back from the sandpaper, and I tape two pieces of posterboard to either side of the brace end to protect the zebrawood in case the chisel slips.
The top brace has been done. Here's a close-up of the taper:
Now all of the braces have been rough-shaped by chisel.
By looking at the back more on end you can see the tapers:
150 grit sandpaper removes all the chisel marks and rounds over the sharp edges. The second brace lies directly under the sound hole and so is very visible, so I want them all to look good. Not just good, I want them to make you want to touch them--all of them, even the bottom brace that no one will ever see. So each brace gets a good sanding, moving to 220 grit, then 320 and finally 400 grit sandpaper, which is very fine.
Then the center strip gets the same treatment, followed by the zebrawood back. Start to finish, this takes about two hours. You can't rush good work, and that's what I'm after. Everything is now nice and smooth--the braces are almost polished.
And guess what? The back is done. It's ready to be glued to the sides.
But the sides aren't ready for the back. They're still in California!
Top braces are next, but I have a couple of weddings on Saturday, and Pam and I leave for Florida on Monday, so I don't know when I'll get to them. We'll see.
Here's how part of the conversation went:
Dan: "Yeah, we find that zebrawood can be a little funny when bending. What we find works is to bend slow, use little or no water, and low heat."
Me: "Did you say low heat?"
Dan: "Yeah, and no water and bend slowly."
Me: "Really? That's funny, because I did just the opposite when I bent the other side, and it came out perfectly. I used a liberal amount of distilled water, high heat, and bent rather quickly. In fact, it cracked when I used low heat and bent slowly."
Dan: "Really? That just goes to show you."
Or something like that. I knew what he meant: wood is from a living organism, and life does what it wants to do. Life resists formulas. Each piece of wood is different, and you have to listen to what it's saying.
Water/high heat/bend quickly worked for me, so that's what I'm going to do. In fact, if the sides he sends match the one I already bent into the cutaway, I'm going to use it.
Because for the next set of sides, maybe no water/low heat/bend slowly is what works best.
Or maybe it's what works on the West Coast, and my way works best on the East Coast.
Tuesday, June 9, 2009
Great teacher. Very patient and easy-going. He has a pretty amazing life story that I'll have to share with you some time.
And here's his side-bending machine that I built. Could have bought one for $600; I built it instead for about $100, and most of that was the hardware. The cutaway bending form is in the machine.
This is a front view with the non-cutaway form next to it.
In the center, attached to a press screw, are a series of 1/4" thick slotted leaves. I loosen the bolts in the slots and press the leaves down until they contact the waist of the form. They then take the form of the waist, and by tightening the bolts, they retain the exact shape.
The wood is shaped by heat. It used to be common to soak the sides in water prior to bending, the idea being that this would soften the wood and make it more pliable. However, this also weakens the fibers of the wood, and can lead to cracking in highly figured woods like curly maple. It's not water that allows the side to bend, it's heat that softens the natural resins in the wood. Water just acts as a conductor, but soaking is not needed. When the wood cools, the resins harden again and the wood become rigid.
So here's the procedure. I lay out some aluminum foil the length of the side, and lay the side on the foil. I've attached the rosewood bindings to the side so that they can be bent at the same time. I only need two pieces of binding, but these are easily cracked or broken on the cutaway side, so I hedge my bet by taping three pieces to the side, there at the bottom of the picture. At the top are two pieces of the kerfed lining that I want to bend as well, but this makes the whole thing too wide for the stainless steel slats and I take them out. Because of the kerfing they are pretty flexible, but pre-bending them helps them conform to the tight curves of the cutaway without breaking. Breaking isn't a big deal, however, so it doesn't really matter if I pre-bend them or not. You'll see what I mean when we get to that stage.
I spray all of this on both sides with a liberal amount of distilled water, then wrap it all up tight in the foil.
Then it's over to the bender. The side is sandwiched between two stainless steel slats which support the sides and help keep the fibers from lifting up around the tight curves. So a slat goes on the form first:
Then the side:
Then the other slat:
Then I top the sandwich off with an industrial heating blanket:
This is plugged into a variable controller which will allow me to increase or decrease the heat. I clamp the sandwich on either end and plug it in. I have a digital candy thermometer that I stick in the sandwich so I can see when it's time to start bending. When it reaches around 250 degrees I start to slowly press the waist screw down into the waist. The extra clamps are to make sure that the areas that is going to form the cutaway gets plenty of heat.
The temp continues to rise to 300 degrees as I slowly slide the lower bout caul down:
Then the upper bout caul, which can't go very far because of the cutaway ram:
This is the tightest bend, however, so I want good pressure here. Then I very slowly start to screw the cutaway caul down into the form. I take a good ten minutes to go the three inches or so, but this is the critical juncture. I listen very closely for any sounds of cracking, and am grateful that I don't hear any.
When everything is in place I unplug the heating blanket and let this cool overnight.
The next morning I undo everything and open up the foil to see how it all turned out. One of the pieces of binding has cracked a little bit, but nothing major. It is still usable but the other two pieces come out perfect. Good to hedge your bets.
There's a decent amount of fibers that have lifted up around the cutaway curves, but this can often be solved by using superglue and pressing the fibers back down. After sanding everything usually looks good. However, there is a lot of springback, and when I try to press the side into the cutaway form, I find that some of the fibers haven't just lift up--there is actually some cracking that has occurred.
Here are some pictures. I'm flexing it some so you can see the cracks:
The cracks have occurred both across the grain and with the grain. There's no amount of superglue that's going to fix this. I'm going to have to get some new sides.
This is the first thing that has gone wrong with this build, so I shouldn't be too discouraged, but I decide to quit for the day. Not a good idea to be shaping braces when I'm a little frustrated. Frustration can only lead to more mistakes, so I just walk away.
I need some time to think about what might have gone wrong in the process, and what my next steps are going to be. Is it the zebrawood? Some woods are more brittle than others and don't bend as well. If this is the case with zebrawood, I'm better off paying LMI to bend the cutaway. Then it doesn't matter how many sides break, I'm only paying for one more set.
But if it's something I can fix myself, that's better. I'm saving money not paying someone else to do my work, and then I can truly say I did it all myself, which is the point, after all.
The thing that gets me is that the cracking didn't occur in the tightest bend--what I call the horn of the cutaway. It occurred in what I intentionally designed to be a more gentle bend than on the last guitar. This area was tighter on the last guitar, and that caused some problem--more with the binding than the side, but I still wanted to avoid this. Why would the tight bend hold and the gentler bend crack?
Since I can only order sides in sets, I have no other use for the other side, so I decide to bend the cutaway on this one. If it too breaks or cracks, I'll pay LMI to do it; but if it doesn't, then I'll just have to pay for another set of sides.
There are two things that I think about that need to be different. First, it didn't look to me like the cutaway caul was positioned so that it mated perfectly with the form. The ram swings up and down so it can be out of the way (or even removed) when bending non-cutaway sides, so I press the caul into the form and mark on the sides of the machine the exact position.
As I look back on it, however, I think the problem was not enough heat. I started dialing down the heat when it hit 300, whereas before I let it get up to 350 degrees. I really don't know why I was more cautious this time. It could be that because the zebrawood is overall lighter in color than rosewood I was afraid of scorching the wood and not being able to sand it out. Or maybe I was just chicken.
This time, however, I crank the heat up. I don't start bending the waist until it hits 300 degrees, and I let it get up to 350 before working on the upper bout and cutaway. I actually work a little quicker in pressing the cutaway caul. I hear no cracking, and it's a good, tight fit with the form. Unplug it and leave it alone for the night.
This morning I unwrapped it all and guess what? It's perfect. Not even a single raised grain. It fits in the mold with no gaps.
I don't know why I doubted that heat was my friend. So I'll call my friend Chris at LMI and ask him to pick out a nice set of sides that match the back that he sent me, and I'll be back on track. A new set of sides will cost me about $40, but that's the price of a good learning experience--and the cost for doubting myself.
Thursday, June 4, 2009
The scraper takes a decent amount of material off--less than a plane, more than sandpaper--and leaves a really smooth surface. But it's hard work; hard on the arms, but more than anything it's hard on the hands. The scraper, which is made of steel, must be curved backwards against the thumbs so that the cutting surface is curved.
And the thumbs get tired fast. Added to this is the fact that, when you are doing it right, your are creating a lot of friction, and friction created heat, and it burns my thumbs!
Sorry for the whining.
Anyway, I use the scraper to get it down below .95", and sandpaper to get it the rest of the way down.
I use the jointer to get one edge completely straight, and this will be the side that the top is glued to, since the top is almost flat.
I made copies of sides from the plans, taped them together, and cut it right along the edges. I transfer this to posterboard, and now I have a template for the sides. Using a pencil I trace the template on both of the sides.
I mark all over the sides in pencil so that I know which is the inside, which is the outside, which side is the heel and which is the butt, which attaches to the top and which to the back.
On the way home last night I reminded myself that I need to physically orient the sides to the top and back to make sure I've marked them correctly. This wouldn't make that much of a difference but on the non-cutaway side there is a small flaw that I want to make sure is on the inside of the guitar. When I get home I check it out and sure enough, what I had marked as the inside of the guitar would actually have been on the outside. The butt and the heel need to be reversed.
Glad I checked.
After getting this straightened out, I'll cut the sides out on the bandsaw, leaving plenty of overhang. I'll use the radius dishes to get the sides to their proper depths (a guitar is shallower at the heel than at the butt) and radius.
Then it's time to bend and hopefully not break some sides.
At each stage of creation in Genesis 1, God likes what he has created. He declares that the world is good. When it’s all done, he declares that the creation is very good.
And then something goes very wrong.
First the humans decide that they don’t want to be what God created them to be—humans. They want to be like gods. Well, that’s understandable. Who doesn’t? Specifically, they want to be the ones to decide what is Right and what is Wrong. But that’s above their pay grade. Humans aren’t very good at it. Humans can’t see the big picture. Most of the time, they aren’t looking for what is Right or Wrong, but what is right or wrong for them—that is, what most benefits them vs. what would most get in the way of what most benefits them.
It gets worse. Then humans decide it is their prerogative to determine who gets to live and who gets to die. Once again, that’s way above their ability to judge, and generally it’s decided on a self-centered set of criteria. But violence enters the world and humans begin to use it indiscriminately, to the point where God sees that their hearts are “evil all the day.” So, in a great act of violence and genocide God wipes out all but a few of the humans, and decides to start over. Problem is, when it’s all said and done, the violence didn’t work. At the end of the flood narrative, God swears off the use of violence as a means of achieving a peaceful world, because nothing has changed. Even starting over with the one righteous man, God sees that the heart of the human is still evil all the day. And as if to prove the point, one night Noah gets drunk and passes out naked, and wakes up and curses his own son who had the temerity to tell his brothers, “Hey, Dad’s drunk and passed out naked in his tent.” I guess you’re not supposed to talk that way about your own dad, especially when he’s the only righteous man on earth. Don’t point out the problem, cover it up, which is what his brothers do. And it works; they aren’t cursed.
Finally, the humans decide that the earth, which was very good in God’s eyes, wasn’t good enough for them, and they try to build a tower that they can climb to go live where God lives. God destroys the tower and scatters them across the earth. It’s not like God doesn’t want to live with the humans; he does. It’s just that he wants the humans to be content being human, and to be content living on the earth, which, after all, he made for specifically for them.
I don’t know what happened to our theology, but some aspects of it have us repeating the fallacious human thinking reflected in Genesis 1-11. It says that the earth is bad and that heaven is good, so we should just endure our time on earth and use it to make sure we get to heaven, which is where the really good stuff happens. This is actually more in line with Gnostic thinking than anything reflected in Scripture. There’s also a healthy dose of Platonism reflected in that kind of theology. (I’m not going to take the time to define these things right now; there’s not enough space and you can Google the terms and see for yourself what I’m talking about.)
Care for the earth is a part of Biblical theology, but somehow it doesn’t find its way into most of our current theology. If we are going to be Biblical Christians, indeed if we are going to get our lives in line with the purposes and plans of God, we must recover it. And please don’t hear me making a political statement; this is a Biblical statement, a theological statement—and a human statement. God made the world inhabitable for humans; we’ve made parts of it virtually uninhabitable (though there are humans living in these areas, if you can call it living.) It’s our responsibility to fix it.
Care for the poor must include care for the planet; the two cannot and should not be separated from each other. Both are Biblical mandates that Christians need to take seriously.
I started with the opening chapters of the Bible, so I’ll end with the last chapters, which is a vision of a renewed creation, and of God making His dwelling place with humans on earth. So we need to take care of the planet if for no other reason than that God has decided to live here.
And you always clean up when company comes.
Wednesday, June 3, 2009
There are two concerns in building a guitar top. One obviously is musical--you want the top to vibrate like crazy creating sound waves which we hear as music. For this, you want the top to be as light and as thin as possible. As I thicknessed the top I kept tapping it with my knuckle, listening as it changed from a short, dull tonk to a ringing thuuuuuuuuummmmppppp that lasts for about two seconds and has low, middle, and high overtones. It also gave me a sheet-metal-like woof when held by the long edges and gently shaken.
However, once it was thin enough that these tones came out, I had taken it past the point of structural integrity. Add steel strings to the top at this point, and it would break apart probably as soon as I brought the string tension up to pitch. To restore the structural integrity I glued braces to the underside of the top. (I was going to say "back of the top" but that gets confusing.)
Now it just goes tonk again, but even more pitifully than before. The braces just kill the tone. The top is strong, but it ain't makin' much music. So now I have to restore the tone without sacrificing the strength, and I do that by shaping the braces, particularly those on the lower bout.
Before I do that I have to glue the bridge plate onto the top. This is a piece of hardwood--in this case rosewood--that is on the underside of the top directly under the bridge. Steel guitar strings have a little steel ball on the end of them that goes through the bridge to the underside of the top, and the strings are held in place by bridge pins. However, the spruce is a soft wood and the metal balls would quickly tear through the wood and start to wear down on the ebony bridge. So a hardwood bridge plate of rosewood or maple is glued under the bridge, and the ball-ends bear against this.
Here is the bridge plate after it's been cut to fit between the braces:
It gets glued on using the go-bars. And here is the top with all the braces glued on, ready for shaping:
The back isn't quite done either. It gets a center strip of spruce with the grain running width-ways. It's purpose is to reinforce the center glue joint. Sometimes one long strip is glued on before the back braces are glued. This requires cutting notches in the strip where the braces cross the center strip. I did that the last time. This time I tried gluing the braces on first, then cutting the strip into sections that fit snugly between the braces, and gluing them this way. Either way is acceptable, but I find I like this way better. Here is the center strip sections being glued:
Done! Isn't that zebrawood gorgeous? I sure hope it bends well.
And here are the back and the top, bracing complete, ready to be shaped.
Before I do that, I'm going to start the process of bending the sides. Each side is done separately and there is a couple of hours of downtime while I have to wait for the side to cool after bending, so I'm going to use the downtime to shape the braces. So it'll be bend one side, shape the back braces and start on the top braces, then bend the other side and finish shaping the top braces.
But more on that later.
Monday, June 1, 2009
I put the back on the 30' dish in the go-bar deck and from the plans marked out the position of the braces, and put them in place for radiusing. Unlike the x-braces, which are symmetrical, the back braces run parallel to each other on different places on the dish. Therefore they will each be radiused a little different.
The bottom two braces are a pain because they are long and wide but not very high. It takes a lot of sanding to get the 30' radius on them, and there's not much to grip. I ended up sanding a jagged edge on one of my fingernails. But after some hard work, they are ready for gluing.
So that's what I did.
I woke up early this morning, so this was all done before going into the office. This evening the back braces will be dry and I'll be able to install the center reinforcing strip.
The last few days I worked on building the forms that will be used for bending the sides and the spreaders that will hold the sides snug against the mold. I finished them and looked at my hygrometer and the humidity was 45%--perfect gluing conditions.
So I got the jointer and joining jig out and got the back joined.
I put that aside to dry overnight and decided that I had just enough time before going back to speak at the 7 p.m. Refuge service to maybe get the x-braces glued on the top.
Steel-string acoustic guitars are sometimes called "flat-tops", and originally they were and sometimes are. The first two guitars I built the tops were flat, but it has become pretty standard to give the tops a very slight arch, which adds a little bit of strength. Whereas the back has a noticeable curvature--I use a 15' diameter arch for the back--the arch of the top is only a 30' diameter. On a finished guitar you wouldn't notice this unless you laid a straight-edge across the lower bout.
I have a couple of radius dishes with low-grit sandpaper affixed to achieve the arches, and I use them to radius the braces. Here's one of the x-braces on top of the 30' dish, and you can see that small gap under the middle.
After sanding the brace for just a couple of minutes it is radiused. The gap is gone.
I do this for both x-braces. I won't radius the braces in the upper bout; I want this area to be flat so that there is a good gluing surface for the fretboard extension. Some people radius all the braces on the lower bout, but apparently just doing the x-braces is sufficient, and that's what a lot of builders do.
Before I can glue them on the top, notches have to be cut in the braces where they cross.
After drawing the brace positions in pencil on the back of the top, I place the x-braces in position and mark on the lower brace where the upper one crosses.
I also mark about halfway up the height, and then place the brace in my vice at this mark. I use a small saw to cut the sides of the notch and a chisel to remove the waist. When it's even with the top of the vice, I know it is the right depth.
I repeat the process for the upper brace, creeping up on the depth of the notch so that the gluing surfaces are perfectly even. I want a tight fit, and I get it even though I actually cut the notch in the bottom brace a little wide. The top notch is tight, however, so after everything is glued I'll glue a wedge of brace material in the gap and sand it flush. This is more for the transference of vibrations than it is for structural integrity.
To clamp the x-braces would take some clamps with really deep throats--like around 8". I'm not even sure they make clamps like this. To get around this, someone invented a contraption called a "go-bar deck." This is just two thick boards held 2 feet apart by pipes. The clamping pressure comes from flexible fiberglass rods or "go-bars" that are a couple of inches taller than the deck. One end goes on the brace, and the other on the top of the deck, and you are able to get even pressure along the length of the braces.
The big factories like Martin and Taylor use rubber seals and vacuum pressure to glue all their braces. The vacuum actually speeds drying time. But this is how it was done for years and how most of the little guys still do it. A vacuum system would cost a few hundred dollars; I built this deck for maybe $30. At Vermont Instrument we used the bamboo stakes that are used in gardening as go-bars, and that's what I did for the last guitar, but they vary in thickness and tended to break, so I sprung for the fiberglass rods for about $2 each.
These are important braces, so they get an overnight dry. Next I'm going to work on the back braces so I can stabilize the zebrawood.