Skateboard Banjo

I recently completed making a 5-string open-backed old-time banjo from inexpensive parts featuring a neck made from old laminated skate decks.

I'm an eager participant in the Nottingham Hackspace Ukulele Orchestra and there are quite a few great musical instrument projects going on there; to the extent that we have a monthly luthiers' workshop. I've become enchanted with the banjo playing in our old-time jam sessions that we have at the Hackspace, and I enjoy a challenge. So rather than make a ukulele I decided to try my hand at a banjo.

I've been a skateboarder since September 1977 but a luthier since only June 2013 so you will have to forgive the lack of finesse when it comes to my instrument building! Also, this Instructable is distilled from my Skate-Banjo project log on the Nottingham Hackspace Wiki which contains rather verbose text written at different stages of the process; sometimes in the present tense, sometimes in past tense, sometimes as lists of ideas, sometimes as a log of what I did. I have gone through the text to see if it makes sense but I may have missed a few things so apologies in advance dear reader.

For general information about hand-made banjos, banjo geometry, banjo terminology, and luthier workshop techniques I regularly referred to the following online sources: -

http://en.wikipedia.org/wiki/Banjo (obviously!)
http://www.banjohangout.org/archive/179296
http://www.frets.com/
http://www.stewmac.com/freeinfo/a-scalelength
http://www.stewmac.com/FretCalculator

I don't currently own a banjo but I do have access to various banjos, both handmade and commercially available, owned by other hackers at the Hackspace. My initial plan was to work with the limits of my ability and the materials that come easily to hand whilst coming close to the size and shape of commercially-available 5-string open-backed banjos with a scale length of around 26" (e.g. a 22 fret Gibson).

The neck of the banjo will be made of laminated skate decks. 

For the body/pot: I'm going to use a wooden hand drum with tensioners which will give me a basic body for little cost and little work. My long-term goal is to glue up and turn my own rims on the lathe. 

For the bridge: current thinking - just a piece of skate deck (see http://www.acousticbox.com/bridge1.htm ).

The nut: current thinking - just a piece of skate deck.

Tuning hardware: ebay cheapest set of 6 guitar tuners 3x left 3x right.

Strings: whatever becomes available.

Tensioning bars: I'll see how the hand drum and neck come together.

Tailpiece: traditionally a fork is used but there are some cheap ones available on ebay.

Fretwire: purchased by the foot for hackspace luthiers' workshop.

Skate decks are typically 7-ply Canadian maple and, as it happens, maple is often used for banjo neck construction. A skateboard deck has a natural bend at the kicktail for the headstock making the underside of the deck a slightly convex fretboard due to the deck's concave.

I will be laminating two decks together for extra depth and stiffness. At the heel I will use as many layers as it takes. I want to retain the authentic used skate deck damage (within reason) on the fingerboard. From my collection of thrashed decks I have chosen two identical Union blank decks (same pressing, same concave) without too much damage. With the griptape removed and a quick clean up with isopropol alcohol I do the lamination glue-up with Gorilla Glue and I popped in some lengths of bamboo chopsticks as dowels to align the bolt-holes, fill them in, and perhaps add a little strength. As Norm Abram says, "You can never have too many clamps". After 24hrs of curing the first rough cuts are made at the bandsaw.  

The skate deck glue-up has been sliced down to about 95mm wide. The nose and tail beyond the bolt-holes are about 135mm and 125mm long. The truck bolt mountings are 59mm long each and there is 350mm between the innermost bolt-holes. The bolt-holes are 35mm between (46.5mm including holes).

The nut is to be located immediately before the kicktail starts to drop away. A centre line is scribed that also defines the location of the third string. The scale length will be decided when the hand drum is obtained and the neck-body join is decided.

The width of the neck at the nut is 1 1/4 inch on a lot of banjos I've seen but I think I'd like to use 1 3/8 inch to be more like my ukulele. This width will fall almost exactly between the bolt-holes.

* 35 millimeter = 1.377 inch  and 1.375 inch (1 & 3/8) = 34.925 millimeter

The neck at the nut will be slightly offset from the centreline due to the asymmetric narrowing after the 5th string. The width where the neck meets the body is yet to be decided.

The width of the headstock will be decided largely by the string tensioning hardware and the aesthetics of whatever skate-style I can incorporate (e.g. a rounded head like modern popsicle decks or something more old-school)

The heel is the thicker part of the end of the neck where it meets the body of the banjo (aka the "pot"). The join between the pot and neck  usually involves one or more threaded tension rods in modern commercially-available banjos but in old-time banjos we often see a dowel in use. The pot of a banjo is basically a drum and for my pot I'm using this 10" tunable hand drum: -

http://www.percussionplus.co.uk/products/hand-held/hand-drums/10-tunable-hand-drum-pp877.aspx

I was lucky enough to find this on Amazon as a warehouse returned item for the reduced price of £6.66 with free postage. It may be a bit shallow but it has a finger hole about 20mm in diameter that will hold the dowel stick. The drum head is goat skin which I'm sure is fine but as a friend of animals I'd prefer something like an artificial Remo banjo head - perhaps in the future if this one breaks. I have glued up the heel so it is 5 decks thick. I had no remaining parts or the original 2 decks that had a suitable concave so I used some spare bits of my old Enjoi Rodney Mullen deck that I got back off fellow Hacker Jake who is using it for his Ukelele Bass project (thanks Jake!). I was looking around for 20mm dowel and I found the broken handle from my old Nimbus 2000 pool sweeping brush in the shed. It's just over 21mm and is well weathered so I was able to get a snug fit in the hand drum with a bit of dremel sanding of the hole. The dowel will be embedded in the heel end of the neck and the other end will set the action height with a possibly adjustable/shimable screw-slot end that passes through the far end of the drum rim.

I have marked the fret locations, measuring carefully from the nut position on each occasion. The fret wire I have available at the hackspace is rather fine (for a uke) but we don't expect any real problems to result from it. The 596mm fret scale is 25" in old money so it is slightly smaller than a typical old-time open back banjo.

Using the fret calculator at the Stewart-MacDonald website (http://www.stewmac.com/FretCalculator)...

    fret |   from nut   |   fret to fret
    1  |  33.451 mm  |  33.451 mm  (nut-1)
    2  |  65.024 mm  |  31.573 mm  (1-2)
    3  |  94.826 mm  |  29.802 mm  (2-3)
    4  |  122.954 mm  |  28.128 mm  (3-4)
    5  |  149.504 mm  |  26.550 mm  (4-5)
    6  |  174.564 mm  |  25.060 mm  (5-6)
    7  |  198.218 mm  |  23.654 mm  (6-7)
    8  |  220.544 mm  |  22.326 mm  (7-8)
    9  |  241.616 mm  |  21.072 mm  (8-9)
    10  |  261.506 mm  |  19.890 mm  (9-10)
    11  |  280.280 mm  |  18.774 mm  (10-11)
    12  |  298.000 mm  |  17.720 mm  (11-12)
    13  |  314.725 mm  |  16.725 mm  (12-13)
    14  |  330.512 mm  |  15.787 mm  (13-14)
    15  |  345.413 mm  |  14.901 mm  (14-15)
    16  |  359.477 mm  |  14.064 mm  (15-16)
    17  |  372.752 mm  |  13.275 mm  (16-17)
    18  |  385.282 mm  |  12.530 mm  (17-18)
    19  |  397.109 mm  |  11.827 mm  (18-19)
    20  |  408.272 mm  |  11.163 mm  (19-20)
    21  |  418.808 mm  |  10.536 mm  (20-21)
    22  |  428.753 mm  |  9.945 mm  (21-22)

I also started to work out the arrangement for the 5th string tuner.

Now we look at fitting with a dowel stick and start to consider the neck shaping and heel carving. Some pro tips at http://blog.boymeetsbanjo.com/2011/10/14/carving-the-neck/ and inspiration at http://www.deepcreekstrings.com/p/instruments.html

I had a bit of a weird mental crisis when it came to shaping the neck - it felt too horrible to start to cut into what is just a throwaway blank at the end of the day! I got quite wound up thinking that I needed to CNC it in order to get it "right" and make laser cut templates and jigs so I could get good lines with a router. It took a day or so to get my mind straight and get to work shaping just by hand with rasps, files and sandpaper. I found it very absorbing and I put in a crazy amount of time observing the ply layers and grain, working at the imperfections and getting a pleasing shape that felt right.

For the tuning head I wanted to place the tuning pegs in the standard (new-school) skateboard truck bolt-hole pattern and shape the end a little like a miniature deck. The holes need to be 2.1" x 1 5/8" apart (== 42.1mm x 53.3mm). I need to leave enough tail to wear down like a used deck -- the existing worn-down nose/tails had to be cut off to avoid massive voids when laminating.

In order to lighten up the headstock, and to accommodate the (cheap, nasty) standard sized tuning pegs I cut a scoop out of the back side to about 13 ply thick (griptape side of the decks!). This brought some much-needed elegance to the shape and exposed the natural beauty of the skate ply(!) and the grain of the wood after some meditative hand-sanding.

At this stage I also temporarily fitted the nut. The nut blank I bought from a local guitar maker: it's a traditional bone nut blank costing £3.99. Personally I'd prefer not to use animal products (ethical human bone is _so_ hard to find!) and make mine from hardwood or some interesting plastic. I've already involved some poor goat in the drum skin so I'm damned already - plus I fear that the sound over the horizon is a large number of traditional luthiers spinning in their graves. I'm gonna go traditional here!

My design has 9mm between the string centres giving a 36mm span between strings 1-4. I had already "fitted" the nut width and length (along the neck-wise) but not set the depth -- little point until the height of the frets was established. I marked the basic fret height with a "half-pencil" that I had made for just this job. Then I set feeler gauges to a depth of 2.5mm to mark the initial depth of the strings (to be refined later) and cut guides for each string down to this level using a "zero-kerf" pullsaw. I then removed the nut and ground down the basic height and roll-over on the bench sander. When I refitted the nut I used a few drops of superglue. I don't have, and am unlikely to obtain, a set of nut files and so I intend to hack some tiny abrasive strips with exact tolerances. The nut will remain rough until I have the strings in place.

The tuning gear is cheap and nasty! No excuses here - it was a simple gamble on the lowest ebay price that included enough pegs to go round: i.e. 2x left-handed, 2x right-handed, and a choice of LH or RH for the 5th string.

Drilling the holes for the tuning pegs was simple enough. I agonised slightly over the 5th string tuner but I think I came up with a nice solution that didn't require me to fork out £12 to obtain a specialised peg. I decided on a deep-set peg almost the depth of the neck.

I chiselled out a little recess about 2 ply deep so that the string winding part was just high enough (the 5th string nut will also be quite low profile). A little hand-sanding and it looks acceptable. The full fitting of the 5th string tuner gear will require a bend for that second screw to sit against the neck.

The mounting of the pot to the neck required a mating curved surface on the heel which I cut on the bandsaw, but also rebate to accept the tuning rim. After a lot of thought I made a simple circular router template for this more accurate job. The first pass brought out the beautific green laminate but unfortunately it was slightly too shallow and I had to chisel it out a little further.

The structural aspect of the join comes from the dowel stick. I spent a lot of time setting up to drill the dowel hole in the neck, creating a makeshift jig to ensure that the hole was exactly vertical... and then finding that the pillar drill was not exactly vertical! Thankfully I discovered my assumption before making the cut. The dowel had to be sanded to fit the hole then glued and screwed. Additional screws might to be necessary to give additional strength to the heel ply layers.

The dowel stick was then cut to exact length and slightly rounded to fit the inner radius of the pot. A half-machine-screw-half-woodscrew lag-bolt thing (I think that's the correct term!) provided the fixing to secure the dowel stick in place and also to set the angle at which the neck meets the pot, which in turn sets the string action to a large degree.

I started off with a single hole in the rim with an action that was set up by eye and cut on the pillar drill with a bit of scrap wood sanded to fit the inner rim of the pot.

Fretting -- it really is worrysome! I nearly had a breakdown over this. Without a separate replaceable fretboard I had no real room for error but the errors kept-a-comin'! Using the Japanese pull saw with depth gauge was quite a trial - the grain of the fretboard top ply goes lengthways so I had to use the cross-grain cutting edge. The cuts were easier to make and more accurate than with the cheap pull saw I used for the test frets. Getting the fret wire to go in and stay in was a bit of a challenge. I gave up after 3 frets and returned home to read up on the subject. It was clear I needed a way to safely bend the fret wire to fit the convex deck.

With some trial-and error I found that the best way to get the fret wire to sit nicely was to put a serious amount of over-bend in the wire, use plenty of superglue, hammer in and then clamp the fret down while the glue dried. I can't properly recall the number of hours I put into the frets but it was ridiculous! Some of the frets I had installed just looked plain wrong and I had to remove them and begin over. I filled the cuts with superglue and some of the red sawdust produced by previous cuts. The fretboard for the next banjo will be done in a completely different way (hint: frets cut way before the neck is shaped when the sides can be parallel and using a laser-cut jig for guiding the pull-saw).

I worked out a good method for safely pre-bending fretwire using a convenient groove in he thread of a machine vice to hold the profile vertical. Later I found a pair of hefty long-nosed pliers at the Hackspace that had a handy gnurled section that could hold my fret wire for bending by hand (see photos).

In some of the photos there can be seen the luthiers' neck stand I made out of some scrap wood with a protective neoprene surface.

I had been obsessing for weeks about mechanisms to properly secure the pot to neck connection (the dowel stick only serves to align the neck). For all the fancy brackets I had drawn on paper I finalised on a simple pair of bolts... well, I was sure it would be simple but it turned out to be a long day of problem solving! Firstly now the dowel stick is glued and screwed in place there is no way to get a drill chuck, from pillar drill, cordless drill, hand-drill, or otherwise, close enough to drill the very necessary pilot holes for the screw ends. The solution devised was to use the flexible "snake" Dremel extension which has a very narrow chuck/collet (see photo).

Next I found that with the bolts installed in the heel it was really difficult to work out the exact positions for the associated holes to be drilled in the pot rim because, although the bolt ends could mark indents in the rim, they could not easily be positioned exactly because the bolt at the far end of the dowel was the exact same length and could not be located in its hole to give the dowel the right alignment. With some assistance I was able to position the first hole in round about the right place and thankfully I was able to make enough adjustment on the second hole to correct the slight error. I was very pleased with the final result: straight and true, a good solid connection.

The final part before stringing for the first time was to fit the tailpiece: this part holds the looped ends of the strings in a fixed formation and also tensions the strings down against the bridge to set the scale-length. The true banjo hacker tailpiece is made from a fork! However, I went for convenience when I found a very cheap "Elton" style chrome-plated 2-part tailpiece from an ebay seller China for £3.72 (free postage). Some creative bending provided a good means of sitting the fixed part of tailpiece on the metal rim of the pot. I ground off two locating tangs to make it sit right and used a small angled piece of Meccano provided an adjustable connection with the dowel end bolt.

= Stringing and first setup =

The set of stings I have is D'Addario J61 medium gauge set that I bought from Dave Mann Music in Nottingham for £4.99.

Strings in the D'Addario J61 medium gauge set: -
     Item # Note Inches mm lbs kg
     LE010 D 0.0100 0.2500 13.900 6.300
     LE012 B 0.0120 0.3000 14.100 6.409
     LE016 G 0.0160 0.4064 15.800 7.181
     LE023W D 0.0230 0.5842 12.100 5.490
     LE010 G 0.0100 0.2500 13.600 6.150

The last job before stringing was to finally affix the tuning pegs. I pre-drilled shallow 1.5mm holes to guide the little screws slightly. They're rather cheap and nasty and the screw heads can't take much torque before failing as I learned with the first screw. I was sort of expecting this and I had a couple of spare screws so no worries. I couldn't really wait to make the full alterations to the 5th string peg which involves bending one of the screw tabs down so I just bent it a little using some molegrips. There isn't really room to get a hammer in there to finish the job as I imagined I would so I just left it for the time-being as it is just non-functional eye-candy!

The basic stringing technique used was as described at
http://www.frets.com/FretsPages/Musician/Banjo/BanjoStringing/banjostr1.html

This was kind of fiddly and a bit exciting as the anticipation of hearing the thing approaches! The tail-piece assembly seemed to be working well but it was clear that it would require some adjustment.

The immediate issue was the height of the action: crazy-high! Some serious adjustments would be required of the join between the neck and the pot although I always knew that this would probably be necessary. The bass string (4th) was unable to stay in the initial nut groove so I had to file it out slightly. Remember: at this stage the nut finishing is still on the TODO list!

To make the action easily adjustable the dowel fixing hole at the tailpiece end needed to be turned into a slot. To avoid the need to  remove all the strings when removing the tailpiece a temporary clamp made using a RapStrap (as invented by a Nottingham Hackspace member!) can be rigged as shown in the photos. The strings are loosened and the bridge dropped. Then the tailpiece can be dismantled and the strings put out of the way of any works on the pot. The slot is carefully made and filed smooth and after a little sanding on the heel join between the neck and pot we have a good adjustable action.

After a few reassemblies and a lot of tuning we have a nice playable banjo; playable by those who can already play -- i.e. not me! The learning process has begun though and I'm working on old-time clawhammer style as taught on YouTube by rpeek (http://www.youtube.com/playlist?list=PLD8B12621CCAB1A11).

The route of the strings on the peg head was annoying as the outermost strings which are not pulled down enough at the nut have a tendency to pop out of the nut when hammered. The innermost two strings were quite low but also splaying out and cutting into the nut. I fashioned some little string tree hooks from some clipframe clips. They seem to work rather well!

Whilst "playing" I find the head tensioning hardware on the back of the pot is kinda harsh on my ribs and right arm so I want to provide some protection on the back rim and maybe an arm-rest. This needs to be done without sacrificing the aesthetic, adding too much weight or affecting the sweet sound.

The frets and nut still require work and I've ordered a set of tiny nozzle cleaning files from ebay to assist. I'm told these are close to useless but I don't really care.

I have ordered a 99 cent (!) capo from ebay and I'm looking into making some some railroad capo spikes for the 5th string.

I also need to make myself a lightweight travel bag and I have found some good examples, (both here on Instructables and elsewhere) in this department.

I got a little plastic toy skateboard from a pound shop; I want to make use of the trucks somehow - perhaps just decoratively - maybe even functionally!

OK, so how much did I spend in the end? 

Item: Union Blank skate decks x2
From: my shed
Cost: Originally £20 each (with griptape!) but essentially free repurposed scrap

Item: Percussion Plus 10" tunable hand drum
From: Amazon marketplace
Cost: £6.66 (spooky price but free postage)

Item: set of 6 guitar tuners
From: ebay seller, China
Cost: £2.99 (free postage)

Item: dowel-stick
From: my shed
Cost: repurposed scrap - free

Item: D'Addario J61 strings
From: Dave Mann Music, Nottingham
Cost: £4.99

Item: fret wire 30cm x4
From: Nottingham Hackspace luthiers' supplies (thanks Jake!)
Cost: £4.00

Item: bone nut blank
From: Dave Mann Music, Nottingham
Cost: £3.99

Item: "Elton" style chrome-plated tailpiece
From: ebay seller, China
Cost: £3.72 (free postage)

Item: misc. assorted screws bolts and other hardware, use of tools, electricity, lighting, excessive coffee, access to knowledge, advice, and emotional support
From: Nottingham Hackspace
Cost: included in my membership (pay what you like)

Total: £26.35

Sounds pretty cheap but if I were to include labour costs at my usual hourly rate then this would be one of the most expensive banjos on the planet :)

Here we see the "Skanjo" with its kinfolk at the Hackspace: skateboards, Toby's Canjos, an antique Banjolele, Altoids Canjolele, a "real" banjo, etc.