Archive for March, 2008

Radiusing the Sides

I’m currently using an old-fashioned, hands-on technique to dimension the sides. The sides (or rim) need to be tapered since the tail of the guitar is deeper than the heel. In addtion they need to be radiused since both the top and back are domed rather than flat. Some makers don’t radius their tops and have had a lot of success using that approach (Kevin Ryan and Jim Olson) but I’m not there yet. I still feel more comfortable with the added strength the domed shape gives.

Sanding dish planes and chisels

I use a block plane to remove stock, taking it pretty liberally from the heel block and a lot more conservatively from the tail.  I own a slew of planes, some of which I acquired years ago when I was a carpenter but most of the ones I use now I’ve acquired over the last few years.  I’m particularly fond of Lie-Nielsen planes.  They’re heavy and really precisely machined.  They’re worth the cost.  Some things you can go cheap on but planes usually aren’t one of them.  A good plane is a joy to use and a bad one is a pain in the butt.  I bought an inexpensive jack plane a few years back and ended up throwing it away.  The mouth was machined a degree or more off square which made the thing useless.  Planes need to be sharp, too.

Anyway, I repeatedly lay the guitar in the radius dish and look for light.  Wherever it’s touching I remove stock.  When it gets close I mark the exposed wood with a big piece of chalk I swiped from my daughter and begin to sand.  When the the chalk is gone you’re there.

I make index marks on the inside of the two blocks on both sides when I start on the back.  The back takes four times as long to do since there is so much stock to remove.  The principle is the same but you have to be careful.  I use a 30 foot radius dish for the top and a 12 foot for the back on all of my guitars so the back ends up being much more radiused or “curvy”.  Some folks will say this radiates sound toward the soundhole which may be true but I just think radiused backs are cool.  They fit in the lap better and just look and feel nice.  Because of the radius, however, you’ll end up taking more stock off the bouts than the waist.  I try not to hurry, using the same technique as the top, putting the sides in the radius dish and using a backlight to check for gaps often.  Also, as I remove stock I periodically check with a ruler to see if I’m taking off stock symetrically.  When I’m close I chalk up the edge and sand away.

Using a backlight to check for gaps Ready for hole filling

This process takes at least a couple of hours, often more.  I’m constantly looking for ways to reduce the time it takes to make guitars and improve the quality.  This is one of those things that can be sped up and I’m working on a jig to do just that.  Anytime you find yourself spending hours removing stock you can probably assume that this might be a good area to innovate (or steal as the case may be).  I was out in Kevin Ryan’s shop last week and Kevin uses a really neat jig to radius the backs of his guitars.  I plan on using his jig as a model to do the same.  Kevin’s shop is really wonderful.  I think he enjoys making tools and jigs more than he likes building guitars. 

Kevin had just finished a “Ghost” guitar which has a redwood top that had been submerged for quite some time giving it unusual tonal qualities.  I got a chance to play it for a while and it was wonderful.  He builds great guitars.  Heck of a nice guy, too.

This guitar uses some old Brazilian Rosewood and, like a lot of the stuff available today, needs some work.  There are a dozen small wormholes and two larger ones that need to be filled.  That’s next. 

(The guitar is further along than the blog so I hope to make several posts in the next week.  Thanks for checking in.)

Bending the Sides

It’s been a few weeks since my last post.  I mentioned in my last post I was going on vacation–I went on a cruise with my wife and 14-year-old daughter. I’ve wanted to do that since I was in the Navy many years ago having always thought going to sea without having to work all the time would be pretty nice.  I was right.  It was too short and it’ll be a long time until I get another vacation.  Oh, well.  Good thing I like my job.

I spent some time when I got back doing some housekeeping chores and building some new jigs, one of which I used for bending the cutaway.  More on that later.

Spraying down the sides Sandwiching the layers Into the Fox bender

Anyway, the first thing I do is choose which side of the side will be up (glued to the top).  I then run the bookmatched sides across the jointer to create a straight, clean side which helps out later when squaring the cuts.  I use my drum sander to thickness to around .092 or .094 inches, give or take a bit.  Bending is pretty easy; I spray both sides heavily with distilled water (to avoid mineral stains) make a sandwich of metal, wood, heating blanket, metal and then put the sandwich in the Fox bending machine.  The machine you see here was invented years ago by Charles Fox and is in use by many, many individual builders and small factories.  It works really well.  I’ve modified mine a bit to fit my guitars–it’s really easy since it’s mostly plywood.  There are two electrical supplies shown in the photo.  Both have the ability to supply full or partial power which is essential.

You can do this by hand with a bending iron but it’s a lot more work.  I still use the bending iron upon occasion to make an adjustment but find the Fox bender usually seems to do the trick.  I like to have the components put together without any tension.  The strings certainly do enough of that and I think the guitar is more likely to stay in one piece longer if all the pieces are well mated before gluing.  I’m striving to have my guitars outlast me hopefully by a really wide margin. 

I turn the heat on full and when the wood begins to sizzle begin to crank down on the waist.  I use a surface thermometer (there’s a picture further along in the post) and begin bending the bouts when the temp gets over 250 degrees (Farenheit).  First the waist, then the lower bout and then the upper.  I usually respray before I do the upper bout since that’s usually the tightest bend and has often begun to dry out by the time I get to it.  The key is to keep the wood damp and supported well by the metal slats to keep the fibers going with the program. Once the wood is bent I let the heat rise to just under 300 for a minute then put the controller on the variable setting, allowing the wood to drop to 200 or so over the next 10-12 minutes.  If I can I’ll let the side sit overnight but I’ll never take it out of the form unless it’s cooled to room temperature, the longer, the better.  Dry is good at this point.

 Marking the cut Cutting the side cleaning and mitreing Into the mold

After cooling and drying the sides are removed and them trimmed to fit in the mold. This is where having a straight side helps out. I then use a belt sander to get the sides as perfect as I can, often putting a small bevel (a mini-mitre) which is really easy with the sander.  This makes binding easier later.

Florentine cutaway bending jig spraying the wood Another sandwich Into the jig Bake 

Bending the Florentine cutaways by hand is a real pain; it’s hard to get a decent grip on something so small and it’s hard to keep enough back pressure on the piece to keep some fibers from breaking.  I stole the design for this jig from Jim Olson (who has made some really amazing jigs.  You can check them out here.)  The bending is the same is for the sides: spray, make a sandwich, heat and then bend.  This jig uses a cool clamp to hold one side in place and another to pull the slats around the jig.  I use the same heating techniques as for the sides and then let sit overnight if I can. 

final form fitting

 After it’s cooled I trim it with the bandsaw and belt sander and then clamp it into place.

 Next step:  gluing the heel and end blocks.

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