OM Nearing Completion

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With its new owner due to visit in a couple of weeks, I've been spending a lot of time lately preparing this guitar for finish.

Here's a shot taken this afternoon after shooting a couple of seal coats of 2lb-cut de-waxed white shellac. Prior to spraying, I inflated a couple of party balloons inside the body of the guitar to seal off the soundhole and the soundport, preventing any contamination of the interior.

Given my limited experience with sprayed finishes, it's a case of "so far, so good". I arrived at what I think was the right combination of spray gun settings more by trial and error than anything else. Setting the correct air pressure at the compressor, then adjusting spray pattern, air flow and material flow at the gun took some patience but, as with anything unfamiliar, the secret lies in constant practice.

Without a dust-free environment to work in my finishes are never going to be flawless but, under the circumstances, I'm pretty happy with the results so far. My hope is that the top coats of KTM-SV are as easy to apply as the shellac seal coats were. I guess I'll find out over the next few days!

Cheers

Pete

The Cautious Approach

The way I see it, pledging the guitars I'm currently constructing to keen players free of charge has a dual benefit. Not only is it a nice thing to be able to do for someone who might otherwise never own a handmade instrument, but I also get to have my guitars road tested under real-world conditions. With instructions to play the hell out of them and subject them to the rigours of everyday use, hopefully they'll take this treatment in their stride and I'll be more confident of approaching guitar building as a commercial enterprise, albeit in a limited way. Were I to keep the guitars for my own use, I'd really be none the wiser; they would see little use and, when they were played, I'd follow past practice and handle them with kid gloves. I'd rather not make the assumption that life for a guitar is always that easy! I have sold several instruments in the past, but I feel I did so in ignorance of the risks and the potential for conflict.

Having built around 15 electric and acoustic guitars over the past 20 years, I know that structurally they'll hold up just fine. The area in which I do need reassurance is with the finish I'm about to use for the first time. KTM-SV, a water-based urethane, is receiving great press from those who've tried it, but I'd like to see for myself how it stands up to use and abuse over, say, 12 to 18 months. I can extrapolate from there and make an assessment as to what the longer-term prognosis is likely to be. The manufacturer, Grafted Coatings, has this to say about KTM-SV:

KTM-SV Spar Varnish wood finish is a waterborne, oil-modified, self-crosslinking urethane system. It features high quality, low film yellowing, excellent chemical, mar and scuff resistance, and is specifically designed for finishing wood. Because of its inherent oil urethane characteristics, the user can expect excellent flow, leveling and penetration into porous wood surfaces. Applied by spray or brush, maintaining high solids in the coating allows for good film build and fewer coats to apply.

In my search for a safe, environmentally friendly finish material, I've found any number of products which sound good on paper, however, the reality is that the demands placed on a finish destined for an acoustic guitar are unique. Tops, backs and sides are in the region of 2mm to 3mm thick and expand and contract unhindered. Not only does the finish need to be wear and scuff resistant, but it must also be flexible enough to withstand these changes in dimension on a daily basis. Add to that the guitar-buying public's expectation that their prize instrument should have a mirror-like gloss and the list of candidates shrinks significantly!

Cheers

Pete

Fretboard Completed

Here are some shots of the completed fingerboard which I've slotted, inlayed and bound.

The benefit of some years of experience is that I've come to recognise and accept my own limitations. A more ambitious inlay design would in all likelihood stretch my patience and there's every chance I'd put off completing the job. The other advantage of a simple inlay design is that it looks so darn good, at least to my eyes! Less is more as they say.

The edges of the fingerboard are bound with black and white veneers and a 1mm outer layer of koa. Once the fingerboard was bound, I ran it past an upturned spiral downcut router bit to form a rebate along the edge that will adjoin the neck shaft. Black and white purflings were then glued into this ledge.

Cheers

Pete

Carving the Heel

Pictured here is the result of a couple of hours spent shaping the heel. This is as far as I'll proceed for the time being; I'll carve the neck and fine tune the shape of the heel after the fretboard has been glued to the neck shaft. I've chosen to rough carve the heel prior to attaching the radiused fretboard as it's easier to secure the neck in a vice or clamp it "heel up" to a benchtop without it.

I use a template to pencil in the shape of the heel where it will meet the sides and a second template to mark the outline of the heel cap. Although the intersection of the heel and the sides is critical to the accurate alignment of the neck with the centreline of the body and is crucial in establishing the correct neck angle relative to the bridge, there's a large degree of latitude where the shape of the heel itself is concerned. It's an ideal opportunity to inject some creativity and there are some wonderful examples where luthiers have done just that. Personally, I prefer to keep it simple and a graceful set of curves and a slim, refined look are my primary goals.

I carry out the initial shaping using a variety of chisels, then move to rasps and files. As the heel approaches its final shape I switch to scrapers and sandpaper. Shadows cast on the heel while holding the neck up to a bright light help identify any remaining lumps and bumps. Although I'm aiming for symmetry, I'm not obsessive about it - I'm happy to rely on visual cues such as this to highlight any inconsistencies.

Cheers

Pete

An OM for Maurice

As a music lover as well as a guitar builder, I can imagine no greater reward for my efforts than getting my instruments into the hands of great players. With that goal in mind, here's one of the instruments I'm working on which I look forward to sending to friend and musician Maurice McGovern in Melbourne.

Soundports like the one pictured are becoming commonplace on custom instruments and, having added one to an old guitar of my own, I can vouch for their effectiveness. US builder Matt Mustapick has this to say about soundports:

This concept came originally from the great classical maker Robert Ruck, who puts two small holes on each side of the guitar, very close to where the neck joins the body, rather than one larger hole. The main advantage of the soundport is that it gives the player a "front row seat" to enjoy a strong direct signal from the soundbox. This feature takes nothing away from the forward projection of the instrument. From 20 feet away the guitar is just as loud. For anyone closer to the guitar, it adds a great deal of richness to the sound, owing to the dual sound source which creates a stereo field.

The combination of rosewood with koa trim is one of my favourites and I can't wait to see the effect when a finish is applied; the rosewood will darken considerably and the curly koa will really come alive. The small clamps I use when gluing kerfed linings came in handy for pre-gluing the purfling lines to the koa bindings prior to bending them in my Fox bender. I used Titebond 3 for this job and there was no sign of delamination which can happen with regular Titebond.

The purflings around the perimeter of the top and back are comprised of black-dyed maple and natural maple veneers with a 1mm mahogany centre piece. The five veneers were glued up as a sandwich using Titebond 3. I then cut the sandwich into strips on the bandsaw (a table saw with thin-kerf blade would be better) and ran them through my thickness sander prior to bending. On future guitars I'll substitute black fibre for the black maple; the maple gave way on the outside of some of the tighter bends. Luckily, I took the precaution of bending a few spares at the same time.

The overlay on the rear of the headstock strengthens the splice - not that it really needs it - and also obscures any glue line where the headstock joins the neck shaft. It's a much cleaner look as well as another excuse to use more of that beautiful koa!

Cheers

Pete

What's on the Workbench

Never one to complete a project before moving onto the next one, I currently have a number of instruments at various stages of completion:

• 14-fret 000 - Australian Blackwood back and sides, Sitka Spruce top
• 14-fret 000 - Claro Walnut back and sides, Sitka Spruce top
• 14-fret OM - East Indian Rosewood back and sides, Engelmann Spruce top
• 12-fret 00 - Claro Walnut back and sides, Engelmann Spruce top
• F5 mandolin - Maple back and sides, King William Pine top

My excuse? As a hobbyist luthier, my choice of finish materials is limited due to lack of access to a spray booth with an explosion-proof fan, etc. I've been down the nitrocellulose path before in more reckless times, but I've had time since then to contemplate the health and safety issues associated with use of that material. As a result, the unfinished instruments have banked up while I explore the alternatives best suited to my hobbyist status, more cautious approach and limited workspace.

I used Birchwood-Casey Tru-Oil successfully on several earlier instruments - it's very forgiving and can be brought to an attractive sheen - but, ideally, I'd like to find a finish I can spray safely and ticks all the boxes where ease of application, appearance, durability and repairability are concerned. A tall order perhaps, but I've finally bitten the bullet and ordered some of Grafted Coatings' KTM-SV, a water-based urethane which I've heard encouraging reports about. Luthiers Mercantile now stock it in addition to Grafted Coatings' KTM9, a water-based acrylic lacquer which promised much but, despite the best efforts of any number of talented builders over a number of years, has not delivered dependable results. Although it still has its advocates, I've read enough negative reports now that my own unopened tin of KTM9 will be thrown out in favour of the KTM-SV I'm currently waiting for. For an excellent discussion of KTM-SV, have a look here.

I hope to post a few pictures of works-in-progress from time to time, as well as share methods and jigs which have helped take the guesswork out of a particular process or have contributed to a more consistent outcome. And, who knows, perhaps this blog will chronicle the completion of my first F5!

Cheers

Pete