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  #71  
Old 12-19-2010, 07:01 PM
Roddy
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Yeah, instrument repair is not like building a house. Gotta have the right tools to get good results.
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  #72  
Old 12-20-2010, 02:53 AM
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^ true, but there are different ways of doing things. For example, when I joined the two halves of my soundboard and back I used my friend's jointer table. Then when I sanded the thickness of those plates down I used a small drum sander. Both jobs could have been done with a decent block plane and I'd probably have learned more about the wood I was working with as opposed to how to operate two intimidating pieces of machinery. I may yet buy a $15 block plane at Harbor Freight along with several $4 bar clamps. Still, I have to learn to sharpen them though.
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  #73  
Old 01-05-2011, 02:12 PM
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Finally a little progress. The rosette is about 99% done, There's just a little bit of filling to do; the cedar tore out on the outer ring where the bit dug into the grain.



About 3 weeks ago I finally got a chance to glue all the rings and strips in but got crazy with the superglue. My friend emailed me and told me the rosewood had turned white. I was a little worried because if it soaked into the wood it'd show up later as a greenish "glow" once a finish was applied. Fortunately, my friend had done that same mistake before and knew what to do beforehand to prevent that - a generous amount of liquid shellac. That's what you see brushed into the top here, after I'd brushed away all the sawdust and cleaned it with naptha.

There was a LOT of sanding to do because those black and white purfling strips were standing really proud of the cedar but they were seated firmly thanks to all the glue I'd used. It took a good couple of hours or careful application of elbow grease but once I started smelling cedar I knew I was almost done. Now everything is flush and the next step is to do something similar along the centerline of my mahogany back plate. It shouldn't be hard since it'll be a 1/4" strip of rosewood with the similar black and white border. There shouldn't be any tearout this time though; it's mahogany (which is a little more resiliant) and I'll be routing out parallel to the grain, not against it in places like I did with the circular rosette.

BTW, I've also been buying up tools. My mom wasn't too imaginative with regards to gifts so she handed me some cash which I blew at Harbor Freight and Rockler, my two new favorite toy stores! I bought that $10 #33 bench plane, some F-style clamps ($3.50 apiece) and a glass plate sharpening system. Now I need to go back and get some chisels because I have a billet of Adirondack spruce I need to split up and cut into braces here at home. I also have a couple of cheap planks of rosewood that I'm going to try and fashion bridges out of.

Hopefully things will really start to roll soon. My molds are ready to use to shape all this stuff into a guitar body. I can't wait!
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  #74  
Old 01-13-2011, 03:30 AM
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Last week I was given a little homework to study up on, soundboard bracing:



My study aid there is a mockup of a Martin dreadnought model soundboard. There are braces on both sides for illustration in Martin's standard X-bracing pattern but one side's braces have been "scalloped" in places to reduce their weight without sacrificing their strength.


Below that is a billet of quartersawn spruce which is used to make the braces. Here I'm holding up the cross section of the billet with my thumb on the face that will be the base of the brace. Note that the grain is nearly perpendicular, meaning that it's nearly perfectly quartersawn.



That's only part of the equation though. The grain also has to be straight as well. Here you can see that it sort of skews off at an angle to the cut of the billet. Ideally, the grain should be straight along the entire length of the brace, maximizing the strength of the brace:


Not pictured is another issue call runout, which I'm still trying to comprehend. Basically, it involves how the wood is structured perpendicular to the grain. Think of it this way, if a tree grows perfectly straight and perpendicular to the ground there will be zero runout but if the tree leans as it grows then at the point of the bend there will be runout which is to be avoided. The best way to check for that is to place a chisel perpendicular to the grain on the cross-section face in my second picture and split it down the length of the board. Hopefully the cut will be straight but if it takes a turn then that's a point where there's runout and it's best to be trimmed off because that will be a weak point in the brace. The trick is to find a length suitable for a brace with no runout. If you don't check for runout you run the risk of discovering it later on.

So last Sunday after I'd made some good progress with my own soundboard we took a rusty machete and a weathered carpenter's hammer and split it into shards that were fractured along the grain. I took those shards home and have been shaping them into the rough braces following the blueprints:



I haven't checked for runout though, so part of me thinks I'm tempting fate.
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  #75  
Old 01-13-2011, 01:44 PM
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feedthemachine feedthemachine is offline
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this is awesome man....never would have thought there was this much involved.....nice work.....
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  #76  
Old 01-13-2011, 03:59 PM
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Thanks!

I should mention that I'm trying to get my 3yo involved. I bought him a little ukelele kit that is about half-finished and am trying to get him to sand it. If he loses interest that's OK because I'm also going to use it as a guinea pig for practicing finishing and decorative stuff like body binding.
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  #77  
Old 01-13-2011, 05:30 PM
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irie feeling irie feeling is offline
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Nice work, Kwak

Last edited by irie feeling; 01-14-2011 at 01:55 PM.
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  #78  
Old 01-14-2011, 02:12 AM
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I spent a half hour today cutting and planing the remainder of the usable sections of the billet:


I don't know if you can see but the grain on certain parts of the billet were really wavy:


BTW, I still have a lot to learn about gluing! Look at that blotchy job on a sanding surface no less. ;)

I was worried I wouldn't have enough for the upper transverse brace but it worked out. I even got all my finger braces.


... but I fell short for enough usable lengths to brace the back:


Like I said though, the back's still a ways off. Not pictured is the optional X-braced pattern which I was hoping to try but I think fate has told me "not this time." That's OK with me though. I think ladder bracing will do just fine.

...now on to figuring out how to radius all the braces but the upper transverse brace.
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  #79  
Old 02-12-2011, 03:54 PM
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Last night sure was educational. The jury's still out on whether it was successful or not. It was my first attempt at bending the sides for my jumbo and the first opportunity to use my home made bending form and guitar mold.

Getting everything lined up and set up. Sandwiched between two metal slats and wrapped in brown paper is one of two slats of quarter sawn Honduran mahogany. They're each about 38" long and sanded to about .085" thick but one edge is curved so that the width at one end is 4-3/4" while the other is about an inch thinner. That side will be the back of the guitar and it's important that each side is a mirror of the other. In order to bend the wood, the brown paper is spritzed (but not soaked) with distilled water and a heating blanket is draped over the metal and plugged into a cutoff switch. To monitor the temperature, a probe is placed beneath the top slat.


As you turn up the heat you can start to smell the wood cook, so you have to be aware of the temperature at all times. When it gets up to 222 degrees the water will boil and you'll see the steam come out from between the slats. At that point it's time to caaaaarefully (and slowly) clamp everything down, starting with the waist, then the springs at either end:


Once it's bent you let it cook a bit, watching the temperature so that it doesn't fluctuate much between 290 and 300. In order to do this you have to switch the heat off and on four times. After that, unplug it and walk away and do something else:


Then after an hour, take it out and caaaaarefully put it into the mold. Meanwhile get to work on the other side. There was a bit of confusion on this though. More on that later, but as for that success thing - well, I learned the hard way not to fool with things: DOH! *face palm*




Hopefully all is not lost. A little fast-acting CA glue on the part of Mr. Kitchen and he may have pulled my bacon out of the fryer:


...now on to the other side. (to be continued)

Last edited by Kwak; 02-13-2011 at 01:27 AM.
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  #80  
Old 02-12-2011, 04:19 PM
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Awesome awesome stuff man.
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