Top bracing… this will take a few days

I glued the maple bridge patch on here yesterday and now I’m starting the top bracing. I’m using Sitka Spruce, in an X configuration.

This picture is of the first spar of the X.  This involves a lot of careful whittling, lots of patience, taking only a little wood at a time so it hugs the contour of the top and the patch. Here’s the deal: I want this so well mated that only light finger pressure closes the gap between the 2 pieces of wood. If it closes but you’re using clamping pressure, that means there’s unresolved stress in the top. The glue will be fighting that, the wood will be fighting that, and it will affect how the top vibrates. When it’s ready to glue I do clamp strongly but that’s so I get a good bond. The glue won’t be holding the wood in a configuration it doesn’t want to be in. It will just be holding it together.

This is my constant goal with my soundboards: there should be as few stresses unrelated to actually vibrating with the string as possible. That way they vibrate most freely and project the most energy in the sound frequencies the string is producing. Or: such is my theory. With my theories and 5 bucks you can buy a cup of coffee.

In an earlier post I promised to show you how I support the braces. It’s simple: little posts, glued to the sides, which act like columns. Since their grain runs perpendicular to the grain of the side, they also act to prevent splitting.

 

Notice this brace: it’s Orange Osage. It has to take a lot of stress because the fingerboard will be laying on it, when the guitar is done, and the string tension will be trying to make the neck come up and make that fingerboard collapse the top. The Osage will prevent this.

Orange Osage is a weed tree; it’s hard to find big chunks. It is very hard, very strong, very bright sounding when tapped, very heavy and dense for its volume (so I only use it sparingly, in critical spots like this) , and naturally this color. Some people make tea from it, I believe, but I am not sure which part of the plant they make the tea from. It smells good. I’m the only one who uses it in guitars that  know of. I think some people use it to turn bowls.

A word about the woods I use: I don’t use toxic woods (except a little rosewood).  The wood I use frequently is a food tree– walnut, maple, cherry, osage… on the theory that, If I can eat it or something the tree produces, it’s probably OK to breathe a little of the dust.

 

Various and sundry odds-n-ends

I caught up the maple-bodied boomer while waiting for the fingerboards…

and today those came, so I am putting together a neck too.

The last thing today is making up a rosette, based on a new pattern I have been working with… using a laser engraver. Once it’s engraved I’ll cut it out.

This one turned out too small, so I re-scaled the image. I’ll try again tomorrow…

I think it will look nice when it’s done. I need the soundhole to be 4 inches for the boomer guitar to breathe properly. I’ll save this one for a smaller-bodied parlor guitar sometime.

Top and more bracing, also a little roadblock.

Light duty day. I sanded the top and cut it down on the bandsaw. Also added another brace to the inside of the guitar, after tap testing it and deciding where it would be best.

Discovered I’m out of fingerboards so there will be a pause in the action until they come. Can’t lay out where the bridge will go until I know where the saddle is going to be, and that’s driven by the fretboard.

 

Maybe I’ll work on the Maple Boomer this weekend and get it to this point. It’s always good to have more than one going so you can keep things rolling along if you hit a bump.

 

Gluing up the top, starting to brace the back.

I took the guitar body out of clamps and routed the back flush to the sides. It looks nice. It almost looks nice enough to skip a binding. I’ll have to think about that.

Next, I glued up the Sitka Spruce top the same way I glued the walnut back. This set has been sitting here seasoning for at least a year. It’s nice and dry.

Then, I ripped a plank of Sitka spruce down for bracing. I’ve had this chunk of Sitka laying around for about 2 years now, so it’s also perfectly seasoned.  I cut the first brace for the back, to go across the widest part of the guitar– where the back needs support. I don’t want it to be too bloopy when it’s vibrating; you get a better, more “useable” bass response, if you cut out the loewest frequencies with some judicious bracing. I do not chamfer it yet, nor do I cut grooves in the lining to accept it and secure it. That’s way more work than it’s worth, and if it’s not done perfectly, the result is a brace that comes loose and rattles around at some point. I secure braces differently than some people do; more on that later in a future digest entry.

I will be tap-testing the back and adding braces or chamfering wood away from braces until it sounds “right”.

It’s clamped with a block-n-clamp on each end and some weights in the middle. That brace is going on there strong.

Tomorrow, I’ll add more braces to the back and start messing with the top.

The back goes on.

I sanded the back after it came out of the clamps, laid the guitar body down on it, marked it with a No.2 Ticonderoga pencil (very important) and cut it out on the bandsaw. I sanded it with a drum sander.

 

I chamfered the edges of the tail block and head block with a sharp chisel and hand-sanded everything inside, just so it’s nice.

 

 

Then I glued it. If the surface is dead flat, it doesn’t take much clamping pressure to mate it up.

 

I laid this big heavy tabletop thing on it and micro-slid the sides on the back plate until it was exactly where I wanted it. then I added just enough clamping pressure to get consistent glue squeeze-out all around. It’s a good visual cue that clamping pressure is even. If there’s a lot more coming out in one spot and another spot is looking dry, it’s a sign of a problem. You need to pay attention to these things.  In this case the ribbon of glue was consistent all the way around and left me feeling good.

Sides nearly done; time to make the back

I pulled all the clamps off the sides today and started sanding them. I have about an hour more of working the surfaces that the back and top will attach to.

But it takes a day to glue the back up, and the same to make the top, plus time spent on making braces… so while I’m sanding the sides, its time to start gluing the back. Thing need to go down multiple tracks if you don’t want to spend a year doing this. I’m always waiting for something to dry/cure as it is.

First you mate the edges by running them through an edge planer. Fiddly work, that; multiple passes, taking only a little at a time. I stop and check after each pass. You hold the 2 halves together against a bright light and when simple hand pressure mates the halves well enough that you can’t see light, it’s ready to glue. If you can see light, it’s not good enough.

I lay the wood down on top of a bar or stick, so it’s in triangle configuration, and secure the sides; I apply glue to the seam; then I pull out the bar and push the wood down so it’s lying flat. It’s the simplest way to put clamping pressure all along the seam, evenly.  Wax paper underneath (and on top) if you ever want it to come free again!

 

Then I clamp a bar down across the top of the seam, so it can’t pop back up:

And I leave it alone for a day.

Walnut sides, Walnut back. It’s going to be a beautiful thing if I don’t screw it up.

Tapering and Lining the back

Today I tapered the sides so the body will be shallower near the neck and deeper near the tailpin, by marking the sides and cutting this slice away.  I love the weird looking objects one generates as a biproduct of guitar building…

Then, I glued the bent linings in to what will be the bottom of the guitar– where the back gets glued on. I clamp the sides down to a true-n-level surface at the head and tail blocks so that, as the linings dry to the sides, they will tend to hold the sides (you guessed it) true-n-level.

Tomorrow I’ll be sanding both upper and lower edges with a long plank with sandpaper stuck on so the edges are all square to each other and the top and back will lay flat on them. There must be no stress on the top or back besides what the string tension imposes. Gluing the top or back to a wavy set of sides will not do, acoustically.

Next step: linings. How I do this is unusual.

Tonight I put linings in the first side of the guitar. I do this differently than anybody else I know: I use bent wood strips, instead of saw-kerfed linings like the big makers. The big names all use those notchey cut-through strips and it’s what everybody else does too.

Above: strips readied.

I don’t. I bend a slat of wood on the bender (or use a side that cracked, so it isn’t wasted), cut it into strips on the bandsaw, and then glue them in. I’m sure somebody somewhere must do it also — there is nothing that hasn’t been tried in luthiery — but so far I haven’t encountered any guitars but mine that do it. The only really tricky part is getting the slats the exact right length– it’s harder than you might think.

The only reason I can think that other people don’t do it that way is because bending wood is always a dicey process.

 

Above: the strips dry fitted.

The result looks great (I think), and I can state of a certainty that the guitar winds up with more longitudinal rigidity than a guitar with saw-kerfed linings. I have had 2 side by side , one body with kerfed linings and one with bent linings, and the bent lining guitar body deflects a lot less in compression. Since I want to prevent as many different types of stresses from affecting the top/sound board, this is valuable.  I don’t want the top under compression OR tension when it’s strung up. I just want it to vibrate up and down at the bridge, like the membrane of a reflex speaker moves at the magnet.

I sometimes alternate the colors on the linings (dark with light sides, light with dark sides) and it looks awesome. On this guitar, everything inside will be walnut.

 

Above: glued up. Tomorrow I’ll flip it over and put the linings in the other side.