Introduction: The Tarjo - Cheap Guitar Turned Into Guitar-Banjo.

By
About: I'm mainly interested (with occasional digressions!) in working with music technology (crossing over into audio), whether acoustic, electric or electronic. I particularly like upgrading and repurposing basic o…

I liked the idea of owning a Solana 6 nylon-strung banjo when Deering introduced the model a while back, but I really couldn't justify the cost, which was no doubt reasonable for a competent player but really not for a weekend dabbler like me. Noting that the market was awash with cheap but reasonably playable classical guitars, I recalled a variant of the Chinese fretted instrument called the qinqin which had a small guitar-shaped body (more like a baritone uke) with a banjo-like head in the centre, like a resonator guitar with a drum where the resonator would be. Thus was born the tarjo - a name I chose because all the other permutations like 'banjitar' were already in use for other instruments!

Supplies

Here's what I used to build the example shown:

  • A cheap classical guitar. This would be a good way to repurpose a used beginner's instrument, but I found a dealer who was selling some very cheap brand new models fitted with an adjustable truss rod, which is unusual on this type of guitar. It was useful to have a truss rod but it's by no means essential, so don't worry about trying to find a similar example - any classical guitar will do.
  • A pretuned 8" frame drum. You need to be particular about the size and the absence of any kind of tuning mechanism in order to be sure it'll fit. I recommend choosing an example from the Remo range. This one has a Fyberskin head; they have another with a Renaissance head that would probably sound a little brighter. I've found tuning shortcomings with other brands such as Meinl and also the head needs to be synthetic rather than natural to ensure it holds its tension, hence my suggestion.
  • A wooden broom handle and/or a similar (perhaps slightly thinner) length of wood dowel (I ended up using bits of both, but that's probably avoidable).
  • A length of lipped plastic edge trim (often used on shelves) long enough to wrap around the circumference of the drum.
  • A cheap archtop guitar tailpiece.
  • Some ball end nylon strings (these will suit the above tailpiece).
  • (optional) A cheap archtop bridge assembly - there's one shown, but in the event I didn't use it for reasons which will become apparent.

In terms of tools and hardware, much will depend on your chosen techniques, but you need no special equipment other than the usual drills, handsaws, sandpaper etc. used for basic DIY projects. We'll deal with these as we go along.

Step 1: Removing the Strings and Bridge

The first step is pretty easy. Unstring the instrument, then detach the bridge carefully using whatever combination of techniques works. The first things to look out for are one or two small 'mother-of-pearl' (i.e. usually plastic) dots on the bridge assembly. These are often found on cheap (and occasionally not-so-cheap) instruments and are actually covers for bolt heads - the bolts are attached to nuts inside the instrument and help to secure the bridge in place together with some glue. If present, prise the covers out and remove the bolts, then de-glue the bridge. Often the bridge will just pop off if you wiggle a putty knife or similar under one edge; if not, a solvent such as lighter fluid and/or the careful use of a heat gun on a low setting (don't use both methods at once!) alongside your prising will persuade the glue to let go.

Don't worry about the surrounding finish as you'll be removing that whole area of the top in due course. However, try to avoid damaging the bridge when you remove it, as you may want to modify it for re-use later.

Having removed both strings and bridge, cover the surrounding area with self-adhesive labels or masking tape as shown.

Step 2: Cutting the Hole for the Drum

You now need to determine the exact centre of the lower bout between the bottom of the soundhole (we'll assume we're looking at the instrument vertically, the tuning pegs being at the top) and the bottom of the instrument AND the sides of the lower bout, which is a simple measuring task. Having done this, place the drum head down with the exact centre of the head on the exact centre of the lower bout and draw around it. The drum needs to be head down for this purpose to allow for the fabric binding around the edge, which will need to fit snugly in the hole when the instrument is complete.

Cutting the hole for the drum is a process best left to your own particular skills and resources. It's just a matter of following the drawn circle as accurately as possible. I recommend the technique I devised, which is shown in the photo top right. This entails installing a bolt in the centre and using a junior hacksaw blade with a duct tape handle and a length of stiff wire (mine came from a dry cleaner's coat hanger) acting as a guide compass for the circle. Begin sawing by inserting the blade into a single hole drilled at a point on the immediate inside of the circumference.

Once this procedure is complete you'll be able to lift out the sawn-out portion neatly, as shown. You'll notice that you've just cut through the bracing on the instrument's top, but don't worry; you'll be replacing that with something else shortly.

Step 3: Finishing and Checking the Hole for the Drum

Give the edge of the hole a quick sanding to remove any loose debris or obvious irregularities. One or two passes should be enough as the result needn't be perfectly smooth. It's actually better if it isn't, in fact, as you'll be applying adhesive to this edge later and it'll key better if the surface is slightly rough. Take care not to overdo the sanding at this stage to ensure that the drum will still fit snugly. That said, see below! I used a flap wheel for this as I happened to have one handy, but hand sanding would be fine.

Next, cut a length of edge trim to the circumference of the hole with an added extra margin to allow for subsequent adjustment. Tuck the trim into the hole as shown, with the lip on top. Test to see if the drum will fit the hole as it now is (you've just made it slightly smaller by adding the trim). If not, remove the trim, sand the edge of the hole a little more and see if it now fits. Repeat if necessary, but again, make sure you don't overdo the sanding when making any adjustments, as the drum needs to fit closely. When you're confident about this, cut the trim to the exact circumference by removing any overlap.

Once this is done and the drum fits in neatly as shown in the photo bottom right (it should squeeze in with gentle but firm pressure, with the fabric trim on the drum acting as a seal), remove the drum and the plastic edge trim in preparation for the next step.

Step 4: Adding Internal Supports and Fixing the Trim

You now need to cut two sets of four pieces of broom handle or dowel. The first set are supports which brace the front of the instrument against the back and compensate for the removal of the top bracing earlier. These should be installed as shown above, one on each corner (insofar as circles have 'corners') of the hole. This will entail measuring the internal depth of the instrument as carefully as possible for an exact fit. If in doubt, cut the supports fractionally oversize then adjust their length by sanding the ends. The supports can just be glued in place with ordinary PVA (white) wood glue. You may need to sidestep some of the remaining internal bracing when you do this, but that's fine - the supports needn't be exactly equidistant. Allow the glue to dry before proceeding further to avoid nudging the supports out of place.

The second set of supports are used to hold the drum in the correct position. Again, this will entail careful measurement and adjustment. The objective is to have the bottom edge of the drum shell sitting on the uppermost ends of these supports, with the drumhead exactly level with the top of the instrument. You can arrive at their approximate length by measuring the depth of the drum shell and subtracting that figure from the internal depth of the instrument as measured earlier, but again I recommend cutting them slightly oversize and adjusting them by sanding the ends. The drumhead needs to be level and the drum must be stable on all four supports, without wobbling in any direction. A couple of 'dry fit' tests will ensure this. The drum supports can then be glued in place, again using PVA wood glue and again sidestepping any bracing as required; the supports don't have to form the points of a perfect square and will work perfectly well in a stable trapezoid arrangement provided the diameter of the drum is taken into account. Again, allow the glue to dry before proceeding to avoid accidentally nudging them out of position.

(I used sections of broom handle for the drum supports, as the relatively large surface area of its cross-section allowed for any small positioning inaccuracies. I used slightly thinner wood dowel for the body brace supports in the hope that this would give improved acoustic results, but I think the difference this made was marginal at best and that using broom handle for all eight would work equally well.)

When all the woodwork is complete and the glue dry you can remove the label/masking tape covering. You can now install the trim permanently using a trace of all-purpose contact adhesive around the cut edge of the hole and/or the trim, following the manufacturer's instructions regarding joining porous and non-porous surfaces. The adhesive may not stick to the trim with complete efficiency but it'll stay in place, which is all it has to do. Install the drum while the adhesive is drying, carefully removing any excess; the drum will hold the trim in position. Positioning the trim's end join at the bottom will make it as unobtrusive as possible, while a dab of black mastic would hide it even more (I've yet to get around to this!).

Step 5: Adding the Tailpiece, Bridge and Strings

Nearly done! The tailpiece is just screwed into position in the usual way; take care to locate it at the exact centre of the lower bout. If in doubt, just attach it with a single screw in the first instance as shown in case you need to adjust its position. This guitar already had a strap button but it was slightly off-centre and thus unsuitable as a positioning guide.

I experimented with a couple of bridge ideas but ended up just cutting down the existing bridge assembly as shown and filing the saddle down to suit.

As this is an archtop tailpiece the string spacing is slightly narrower than that of a classical guitar, so I filed notches in the bridge saddle to guide the strings into the correct spacings. The easiest way to do this is by putting the bridge assembly in place, then cutting notches for the outer two strings (low and high E) initially. Install these two strings, then determine the correct position for the bridge by intonating them using the octave vs. the octave harmonic (or any other method you prefer); it's easier to do this at least roughly at this point rather than when all six strings are in place as the bridge will slide more easily on the drumhead without the pressure of all six strings. You can then copy the remaining string spacings from the nut by marking them on a piece of paper, as shown. Once this is done, install the remaining four strings and your tarjo is complete!

Step 6: Further Ideas, Variables and Caveats

This is a design that lends itself to various modifications. There are any number of alternatives regarding the bridge design, including shaping one from scratch from either wood or indeed metal. One observer has suggested that the bridge isn't in the best location on the drumhead and that moving the drum further towards the fretboard would allow the bridge to sit off-centre on the head. The bridge may indeed have a slight damping effect in its centre position, so I may well try this on a future version. I also plan to add a side soundport to the existing instrument and have identified a bass drum port of a suitable size that will provide a neat finish (it'll match the black trim) when installed.

It should be noted that this instrument was mainly created because I thought I'd enjoy playing it, which I absolutely do. As a performance instrument its sound isn't as bright as either a conventional guitar or banjo, which is unsurprising given that the various internal supports and the drum frame will inevitably detract from the instrument's resonance, Adding a transducer and then applying EQ has a transformative effect and is well worth trying. I'll let you work out your own tarjo technique, but I've found that the sound is closer to a guitar near or over the soundhole and more banjo-like the closer you get to the bridge, This actually enables you to play both parts of the intro to 'Dueling Banjos'! A hybrid of banjo and guitar picking styles gives good results, as does a soft plectrum; a hard felt ukulele plectrum works in an interesting way on strummed chords.