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.

6 Responses to “Bending the Sides”


  1. 1 Daniel Craig

    Hi, Cool post on the Sides at Kamp Guitar, I’m looking forward to reading more of your site.

  2. 2 Victor Di Paglia

    Hi,

    I am just starting off building my first guitar. I’m ok with most of it as I’ve been reading and studying for a while learning all about it. The only thing that puzzles me at the moment is the Venetian and Florentine cutaways. I see your gig but am unclear on just how they are made. Is it my understanding that on the Florentine cutaway, the right side of the guitar (one of the two side pieces) is continuous with the cutaway, or is the cutaway a separate piece? And if so, how is it joined?

    Thank you so much for sharing your ideas and photos.

    Victor

  3. 3 Seth

    Victor:

    I’m not exactly sure what you’re asking. First off, if you’re making your first guitar you might consider skipping the cutaway. Making guitars is hard enough without complicating it the first time.

    Second, Venetian cutaways are much easier than Florentine since there’s less joinery involved. Having said all that I love Florentine cutaways. I just think they’re cool.

    I cut the side before bending and take the cutaway segment and set it aside, then bend the remaining piece as normal. You can see the photo of all the pieces being put in the mold. The cutaway is held in place at the heel of the neck by the heel block which is carefully shaped to account for the reverse curve. I use a small, triangular piece of mahogany to glue into the point of the cutaway to give it strength; the rest of it is done pretty conventionally. Kerfing is tricky with cutaways but those issues are solved by using Kevin’s A4 kerfing although most builders tough it out and make conventional kerfing work.

    Good luck.

  4. 4 gerald

    ran across you site while searching for jigs. enjoyed all your posting. Gerald in La.

  5. 5 Paul Burner

    Gerald,

    I was doing a search for a better way to do repeatable florentine cutaways and came across your photos on your web site. Thanks for posting these as it is giving me some new ideas on how to do this. I went to your Olson guitars link – but didn’t see any of his photos.

    Can you tell me where you got the short heating blanket that you use for your florentines?

    Thanks! All the best!

    Paul

  6. 6 Seth

    Paul:

    Sorry I didn’t get back to you sooner. I bought the blanket at McMaster-Carr. Their site takes a little patience but it’s a gold mine for builders. I don’t remember which size it it but it should be about 5 by 7 or 8 and it’s the low-wattage, low temp version. I’ve also bought toggle clamps, bits, drill guides and tons of other cool stuff. Kevin Ryan turned me onto them.

    Seth

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