Archive for the 'Kamp Guitar' Category

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.

Joining the Back and Top

The first step for me is to join the back and sides. Most of the techniques I use are detailed in Cumpiano’s splendid book Guitarmaking with a couple of exceptions, most notably the power jointer.  I decide which sides I’m going to join, trim them to align the grain if needed or desired using a band saw or my table saw, square them up against the fence of the joiner and then tape the board to keep them from moving.  I then run both sides through the jointer so they’re straight.  They don’t need to be parallel.  This keeps the ends I’m going to cut flush when they’re put into the shooting board (the second photo).

Squaring Edges Shooting Board Jointer Plane Candling

The power jointer creates a long straight cut but it’s not as smooth as it could be.  The spinning blades create tiny gaps which just aren’t good enough for luthiery.  I use a long Lie-Nielsen jointing plane to clean up the cut from the jointer.  I try to get it ready for joining using as few passes as possible since you can run out of wood pretty quickly.  Also, the more passes I make the more “wavy” the edge begins to get–the blade of the plane takes varying amounts of wood as the grain of the piece changes direction along the joint.  If I can’t get it right in three passes with the Lie-Nielsen I put it back on the power jointer and start over again.  The power jointer takes off 1/64″ per pass.

The fourth photo shows me “candling” the joint i.e., holding the joint up to a light source to look for gaps.  It works really well.  A joint can look absolutely perfect until you hold it up to a window or bright light (or candle) and a .001″ gap shows up.  If the joint here is really tight the likelihood of the joint failing is really small.  After the glue dries the joint is stronger than the surrounding wood.

Joining jig Glue up Glue Cleanup laying protecting newspaper strip Tapping in Wedges

The jig I use for gluing is really simple and came from Cumpiano’s design shop.  I put the dry pieces in place, slide a piece of newspaper underneath (important) clamp little blocks of wood in place on the side using c-clamps and then glue the side using Titebond.  I then push the sides together, clean up the squeeze-out and lay another strip of newspaper on top.  Over that goes a heavy straight-edge and then sand bags to keep the joint from popping up when clamped.  I use little wedges I made from some ebony scrap and gently tap them between the side and the blocks.  Not a lot of force is needed. 

After an hour or so (if I’m gluing more than one set and need the jig) I’ll remove the wood from the jig and set aside to dry overnight.  I always undo the clamps before I remove the weight to keep the thing from popping in the middle and making me swear a lot.

One of the luxuries of working by myself is that when I make a mistake I can swear and no one can hear me.  When I was learning carpentry back in the mid 80s I was working with a friend of mine who had been in the business for 15 years.  I goofed up something and said an expletive.  He said, “Shhh!  Don’t swear!”  I was surprised by his prurience and asked him why.  He told me that if you don’t swear the client won’t know you’ve screwed up. That was pretty good advice. No one wants to hear their heart surgeon say, “damn!”

Anyway, these photos show the top being joined but the back is identical.

The next step is thicknessing which I do on a drum sander.  I’m going on vacation for a week so it may be a few days before my next update.   If you have any questions feel free to post them or email me.

Component Selection Day

The first day is a lot of fun as I begin to visualize the guitar I’m going to build.  Since the guitar is going to a raffle winner rather than a client involved since the beginning I get to pick out all the components as I would with a spec guitar, which I enjoy.  This guitar will be auctioned in the second week of Kaufman Kamp during the flatpicking session so we decided that it should be a dreadnought.

Back Back Back Sides

 I have some very old Brazilian rosewood that I imported last year which I think is perfect for this guitar.  Like most of the Brazilian on the market these days it is either flawed in some way or extremely expensive.  A mint quartersawn back and sides set can run in excess of $2,500.  Much of the wood available now comes from other sources, either stumpwood which is being harvested, logs which might have been submerged for years or wood salvaged from other projects like furniture or building materials. 

This rosewood looks like it may have come from a stump; some of it is quartersawn and some flatsawn so the grain is changing direction within the piece.  It also has a couple of small cracks, several knots and wormholes which you can see in the photos. 

Despite this it’s still Brazilian, is old, dry and stable with a very “glassine” taptone and should make a gorgeous guitar.  This stuff will be fun to work with and fun to fix the flaws.

Top Sides close up

The top is from LMI and their grade is AA.  It has a couple of slight discolorations in the top and the grain varies in width from one side to the next.  As I’ve said elsewhere, the more it looks like Formica the more expensive it is.  This stuff looks like wood.  The top is nice and stiff, the “imperfections” small with no impact on acoustics. 

These are the components that were used by Martin during the “Golden Era” of dreadnoughts, those made before the second world war.  While a new guitar has fewer overtones and presence than a 60 year old guitar does, at least this one is on its way.




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