Building a Harp Guitar Part IV

Now we come to the point where it is looking like an instrument!

IMG-20130108-00229The top and back have been trimmed and the binding channels have been cut.  This is pretty much the same as on any guitar… just more of it!  Any of the systems by Stew-Mac, LMI, Luthier Tool and custom setups etc. will work.  For this set up Scott used the Luthier Tool binding cutter with a bearing bit setup from LMI.  Most of these cutter jigs use some sort of trim router and this is no exception.  luthier tool binding cutterThis picture is from their website http://luthiertool.com/binding%20cutter.html

As with any system, it takes some practice to become proficient.  The jig has two bearings one on the top and the other on the bottom of the leg.  These have to be in contact with the sides in order to maintain proper depth and width.

The neck on this guitar is a conventional bolt on slot head so I won’t go into much detail on that as I’ve covered this on other posts.

IMG-20130115-00234The finish, while pretty straight forward is complicated by the size of the instrument.  Some creative ways of positioning it for spraying are necessary.

I use a length of 3/4″ pipe and attach it to a saw horse and to the body where the neck attaches.

The other issue is supporting the body for fretting when the finish is done and the neck attached.  A Taylor fret buck is worthless because the harp arm won’t support the edge of the buck so it will give too much when it’s in use.  I use an arbor press when fretting and in this case the body has to be supported when fretting over it.  To solve this, I made a jack to support the top.  I used two pieces of wood about 1/4″ thick, one for the top and one for the back to distribute the pressure and put a small scissor jack http://www.stewmac.com/shop/Tools/Special_tools_for_Brace_repair/Scissor_Jack.html
to support the pressure.

In the future, I would probable use a neck joint that would allow fretting before the installation of the neck to the body.

Other than the things mentioned, building a harp guitar in theory is not much different than a standard 6 string.  In practice the larger scale and added strings do add to the complexity above and beyond a 6 or 12 string.  IMG-20130124-01093Photo of Don Alder by Scott Burwell Holloway.

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Building a Harp Guitar Part II

Now that we’ve got a bit of history, let’s move on to the actual build.

Even though it looks radically different from a conventional steel string flat top it wouldn’t be foreign to a builder of the latter.  It has an X brace and size that closely resembles a Martin 000. The difference lies in the extra X morticed into the lower half of the bass side to reinforce the top for the 6 harp strings. The bridge plate is also larger to accommodate the extras strings as well.

This is not to say that it is an easy build.  The hollow arm is essentially a hybrid of neck and body, having a head stock and a sound hole.               SH top

The back is pretty similar to a normal steel string as well.IMG-20121220-00204

The head block for the harp head is also a complicated affair that requires some well thought out jigs to reproduce with consistency.

SH harp head

Everything in the build is bigger, including the forms for the body mold.IMG-20121220-00203

A radius form is used for the bracing and grinding the sides to the correct curve.   Instead of a 2 ft. round form a 4 ft. is needed.IMG-20121220-00206All this can add greatly to the expense of gearing up.  I have to say I get a kick out of people asking why hand built guitars cost so much!

The sides are bent using heating blankets (bigger as well) on specially made molds to accommodate the multiple bends.

Next week, sound hole quirks and getting the back and top on.

Basic Inlay Part Two

Now that we have the positive in mother of pearl, it’s time to cut the negative on the fret board.

While it can be done with hand tools, dental chisels, knives, etc., it’s much easier to do it with a Dremel or Foredom rotary tool equipped with the proper router style base.  Bases are available from several companies or you can make your own.  For much of my time inlaying I used a Dremel but have, in the last two years, switched to a Foredom.  While either will work the Foredom is much more powerful and most important to me the motor is well away from my ears.  I still wear hearing and eye protection but it’s much more quiet having the motor several feet away instead of having the Dremel right in your face.  The downside is that it is considerably more expensive.

I start by setting the inlay on the board and using a lead holderI can keep the lead much sharper than I can a standard pencil giving me better results.  Some people use a white tempera paint and a scribe and while this works fine with ebony, using open grain woods such as rosewood, the paint will be very hard to get out of the pores.

I use down cut spiral carbide bits to cut the channel for the MOP.  I have three sizes 1/8″, 1/16″ and 1/32″.  I use the biggest bit I can to get the job done, saving the 1/32″ for only the finest lines and details (they break if you look too hard).  I also use very good light so that the pencil line is clear.  I start at the center removing the bulk of the wood before I attempt the edges.  Of course, ebony is much more forgiving than lighter woods because the fill is easier to match.  One thing I’ve found comes in handy is a fish tank pump attached to the base so that it blows the dust away as you go.

I now carefully test fit the pieces.  It is very easy to break them at this point.  I often find the first time the piece will not always drop in.  I mark the spot that needs enlarging and route out again.

I use two methods of gluing.  On big pieces, I use epoxy and black coloring, fill the void and wait for the glue to cure, then sand back down.  In this case because of the fragility and the closeness to the fret slot, I place the inlay in position and lightly glue them in place with a small amount of cyanoacrylate.  Then once dry I can use colored epoxy to fill any gaps, making sure to avoid the fret slots.  The final thing is to now cut for the open “a” and “o”.  I do this with the Foredom with the 1/32″ bit.After cutting I simply fill the holes with black enamel and I’m done.

The trick to this is, of course, practice. Most of all have fun.

Basic Inlay Techniques

This will be the first installment of doing a retrofit inlay on a 40’s Martin D-28.  While we’ll be doing a signature, something that on the surface is simple, it is very demanding in technique and execution.

The great thing about doing inlay is that there is very little in the need of tools.  With the exception of big manufacturers’ use of CNC, very little has changed.  A jewelers saw, a rotary tool, such as a Dremel or Foredom and you’re in business. 

The piece of plywood you see in the picture is called a birds mouth and it’s used to support the substance to be cut, in this case mother of pearl.

The customer was having the neck reset and a refret and wanted his stage name inlaid in the fret board.  After we picked out the type style, I made copies for adhering to the MOP.  After gluing the type I start making cuts using the saw with a very fine blade that is .011″ thick.  When you’re starting out I would recommend a heavier blade of .021″.  You will break less of them but are limited in the fineness of the cut.  With practice, you can use finer and finer blades without breaking them.  I can usually do an entire signature without breaking a blade.  The actual “Country” measures about 1 1/4″ so you have to be very careful in placement on the birds mouth, making certain it’s supported on both sides of the cut.  Other important things to remember are to make sure the blade is perpendicular to the piece and to use the full length of the blade.  If the blade is not at a 90 degree angle to the piece you will put stress on the blade and produce a piece that is very hard to fit.  Make sure that you allow the blade to do the work and not to force it.  By using the entire blade you will cut faster and keep the blade from overheating.

You will notice from the picture that I am using my two fingers on top and thumb on the bottom as a temporary clamp.  You might also find a magnifying head band works to keep eye fatigue to a minimum.

Another thing to take into consideration is keeping the dust to a minimum by using a shop vac.  The dust is calcium based and something you don’t want to breathe in.

The thick and thin letters in this can be tricky so I always look to the hardest part first.  In this case I did the bottom of the letters first because they had the most turns and would be the most likely to break.  I don’t stop the blade when I come to a 90 degree turn but keep the blade moving rotating it until I get to the position I want, then continue.  If you’re careful you can cut the entire piece without breaks but if you do simply super glue the pieces together when you’re done.  Small needle files can be used to clean up and rough edges and as you can see, in this case I left the “O’s” and “A’s” closed.  They will be engraved when they are installed into the fret board.

Next week:  Inlaying the letters into the fret board.