Building a Harp Guitar

I’m back after a three month absence.  Whether that’s good or bad is up to you.  style8

I’ve been helping Scott Burwell Holloway get his harp guitar company going and this is an example of a Style 8 Dyer Symphony that we completed in January for the NAMM show in Anaheim.

First a little background on the instrument.   The first “modern” harp guitar was invented by Friedrich Schenck in Vienna in 1839.  It was a “hollow arm” harp integral with the guitar body.  Schenck was a student of Johann Stauffer, who also taught C.F. Martin.

The turn of the 20th century saw a resurgence of harp guitars in the US. Orville Gibson made four models and although they sold for from $194.03 for the style-R to $354.60 for a U-1, 400 were sold.

Most people consider Chris Knutsen to be the originator of the American harp guitar.  Although it’s similar to the Schenck in that it had an hollow arm it was more integrated into the body.

This brings us to the Dyer Brothers, who contracted Knutsen in 1899 to build harp guitars for them.  By 1906 the Dyers had switched from Knutsen to the Larson Brothers in Chicago (possibly because Knutsen kept changing his instruments).  The Larson’s made very high quality instruments (Prairie State, and Euphonon are two brands) and improved on the Knutsen design giving us the most famous harp guitars made.

When I say we made a Dyer #8, it really is a modern Dyer as Scott owns the Dyer name and has committed himself to building faithful copies of their designs as well as what he thinks the Dyers might have done had they taken the harp guitar into the 21st century.

Scott is a wealth of information on all things harp guitar and has many historic examples of Knutsen’s and Dyer’s in his collection.  He is also a phenomenal concert level player, having studied under the late Michael Hedges and Will Ackerman, founder of Windham Hill Records.  As far as I know this is the first time in recent history someone has considered a factory instrument as all the moderns ones are from hand builders.

Next week the beginning of the build.

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Resetting a Neck on a Bozo Podnuavac Part 2

Now that we have the neck off, and I’ve let it dry for at least a week, we can proceed to the reset.

This guitar will have a fret job as well so all the frets were pulled.The first step in the reset is to determine how much of the heel needs to be removed.  As I stated in the previous post the current neck angle left the straight edge about 1/8″ above the top or about 1/4″ too shallow.   Since the heel is about 4″ and the distance from the nut to the saddle is about 25 1/2″ it takes a fraction of amount taken off at the heel to make the 1/4″ needed to correct the angle.  My usual formula (not scientific by any standard) is to take about an 1/8th of the amount off the heel.  So in this case, I would take off a 1/32″ from the heel or an 1/8th of the 1/4″.  Some people use a file to do this but I prefer a very sharp chisel.  I cut to the line on a bevel, then back cut on a slight angle so that shoulders of the neck “bite” into the body. I may repeat this several times, until I get the angle right.  Make sure you take the same amount of material off both sides of the heel to maintain the correct trajectory to the bridge.

This gets me into the ball park, but I use another method to get the final fit.  For this step I use 100 or 120 grit self adhesive sandpaper with the backing left on.  I put the neck on the body and put the sandpaper between them, slick side toward body.This does the final fitting.  I’ve run across several bodies that are not completely flat, so this works very well for this.  Make sure when you are doing this, you do not pull the sandpaper up because you will take too much off the heel.  Again, care should be taken to ensure both sides are even.  When you are satisfied with the fit you must now adjust the dovetail geometry.

I you have taken more than an 1/8″ off the heel you will first need to take off material off the back of the dovetail to clear the back of the head block.  Once this is done you can now make the shim for the re-fit.In taking wood from the bottom of the heel you will have a lose fit because the dovetail is now smaller at the bottom.  The top should be relatively tight because no material should have been removed (in fact, if wood is taken away form the top of the dovetail, it will effect the intonation because the neck will be closer to the bridge).  I make two wedges, one for each side of the dovetail.  Using .032″ thick veneer 5/8″ wide and almost the length of the dovetail I taper the thickness from the full .032″ to nothing.  A trick for getting this done is to use a piece of double stick tape on one side of the shim so that I can secure it to my fingers while sanding. Carbon paper or lamp black used in between the neck and head block is a good way to test the fit.   I do this until I”m satisfied with the joint.  I have to say that the original dovetail was a very fine fit, a testament to Mr. Podnuavac’s work.

I then glue the neck back on using the same type of glue as the original.  In this case hide glue was used.  NEVER use epoxy, polyurathane or any other glue that can’t be reversed!!!   I touch up any finish issues, such as chipped lacquer around the body or neck.

The 15th fret will have to be replaced, making sure it is in line with the others and doesn’t cause any buzzing (in this case a re-fret was needed).  Finally a new saddle will have to be constructed.

Even if you never do this on your own guitar it will give you some understanding of why this kind of repair costs so much money.

One of my students two week guitar build

This is a slide show from my two week class.  The class is an intensive 12 day course in which up to two people build a guitar from scratch.

I use a “Tell, Show, Do” style that starts by me giving information on how we’ll be building, then follows with me showing them how and finally, they do the work.

The photos were taken by the student so most of them show me executing the procedure.

Replacing a bridge

Unlike neck re-sets this is not a repair that every guitar will need.  Some can go their entire lives without needing a bridge replaced.  A bridge can need replacement for many reasons.  Left in a car the glue can soften and the tension of the strings can pull the bridge up. The piece of wood used for the bridge can have an undetected crack and split.  In the case of some Gibsons from the 60’s, the plastic (yes I said plastic) bridge is bolted to the top and usually warps over time.  I’ve never been shy about what I think of a high priced guitar with a dime store bridge.  This goes for bridges with adjustable saddles.  These have no place on any acoustic!  Older guitars using hide glue can pull off because of fatigue.  Hide glue, being organic, can deteriorate over the years.  The bacteria present can break down the glue.  Some repair people shave the bridge down instead of doing a neck reset and this can weaken the bridge as well.  This type of “repair” has fallen out of favor for obvious reasons.  I just worked on such a guitar.

Now first we must evaluate whether or not the bridge is salvageable.  If it’s not then we must find a suitable replacement.  If it’s a bridge that’s common, such as a Martin, I just use that but sometimes, in the case of the plastic Gibson, you will have to make another one out of rosewood or ebony.  Make sure that the pin holes are the same spacing and the saddle slot is in the same area.  Of course if the intonation was off on the original, now’s your chance to correct that.  If I’m making a new bridge, I will make it about a 1/16″ bigger all around to cover any damage that has occurred or can take place taking the old one off.  Martin even sells such bridges.  I start by planing or sanding a blank to about 3/8″, cutting to shape with a bandsaw, then drilling the holes for the pins and finally cutting the slot for the saddle.  This is accomplished using a simple jig with fence attached to the router.

If the top has a dome shape (my tops are a 25′ radius) I usually sand that in before I cut it to shape.  That allows me to get rid of any rolled over edges from the sanding.  I do this by making a positive radius sanding block from my bigger forms used to radius the braces.

Once the bridge is completed, I make a heavy cardboard template for the top of the guitar, so that only the bridge is showing.  This is covered in aluminum foil to shield the guitar from the heat source needed to soften the glue holding the bridge.  I then use a silicone heating blanket with a timer and temp controller to heat the top of the bridge.  You can also use a heat lamp for this but I find the blanket does a quicker job of heating just the bridge area.  The blankets can go to 500 degrees so set the heater at about 250 degrees.  I use a block of wood clamped to the bridge to ensure good contact and I usually let it sit for about 10 to 15 minutes.

Once the heat is on I use several palette knives and a thinned putty knife to get under the bridge.  If It’s not budging, I put it under heat again.  I’m cautious about too much heat because I don’t want to break the joint combining the two top plates.  I’m also very careful of how much pressure I use with the putty knife.  I don’t want to take the top with the bridge, so slowly is the rule.  The bridge usually has enough mass to keep the heat sufficient to separate the bridge from the top.

If you’re going to use the old bridge, make sure you clean up any residual glue and splinters from the top.  You must then do the same with the top under where the bridge was located.  I use a sharp chisel to scrape away the glue.  This is also a good time to check the bridge plate underneath the top for any repair there as well.  The ball ends of a steel string can be tough on wood.  If it’s a mess you can simply glue a small piece of rosewood or maple on the bridge plate or spend $150.00 on a bridge plate repair tool from Stew-Mac.  While expensive the repair is almost undetectable.

I like to get my clamps ready at this time.  Deep throat “C” clamps work well provided they have a block of wood attached to the stationary part of the clamp to clear the “X” brace.  You can also buy clamps specifically designed for the task.  I’ve made a clamp that is similar to one that Charles Fox designed that consists of an aluminum plate with two threaded rods that go through the outside bridge pin holes and mate with a top piece of aluminum.  Once bolted together, there is no clamp to get in the way for cleaning up the glue.

Make absolutely sure both the surface of the top and the bridge are completely free of glue.  Fresh glue will not stick to dried glue!  Put a generous amount of glue on the bridge and don’t worry about squeeze out at this point.  If you’re not using the Fox system you can use plastic bridge pins to locate the bridge and make sure it doesn’t move while you’re clamping.

Now, you can clean up the glue before it dries.  Don’t worry if you find that some glue has escaped your notice as it will come off a finished surface when dry by using a soft cloth dipped in hot water.

Two more things have to be done the next day after the glue is cured.  You have to ream the bridge pin holes to the correct taper of your pins (usually 3 or 5 degrees, depending on the pin).  This is accomplished with a pin reamer (yes, yet another specialized tool) but in a pinch I’ve used the tapered end of a file by sharpening the tang.  Lastly, the bridge pin holes have to have a slot in them to allow for the strings to seat.  Saws are available for this but I like to use a Dremel and three different sized cutters to make the slots.  The slot must be rounded over in the direction of the saddle so that the string does not break at a sharp angle.

Now you’re ready to string up and play.

Cheers