Introduction: Army-Navy Mandolin on the Cheap
First Prize in the
Gorilla Glue Make It Stick Contest
A mandolin is a small stringed instrument, traditionally with 8 strings in 4 courses of 2, this means you play it like a 4 string instrument such as a ukulele. The term "Army-Navy" mandolin or "Pancake" mandolin refers to the body shape in that it is flat on both the front and the back instead of domed like an "A" style or "F" style archtop mandolin. A quick Google search will tell you more than you ever cared to know about their history.
This instructable chronicles my progress through making one as cheaply and easily as possible. Please note: this is not a for dummies guide, it is just what I did and how I did it.
The Ultimate Bluegrass Mandolin Construction Manual by Roger H. Siminoff
If you're interested in more details, or want to build the genuine article, I highly recommend getting your hands on this manual. It is a wealth of knowledge by the man who literally wrote the book on the subject.
The attached instructions from Stewmac.com about assembling their campfire mandolin kit. I didn't do things quite the same as they did, but it's handy to read so you get a good picture of what is involved.
basic woodworking hand tools
heat gun & spray bottle or water pistol for wood bending
dremel tool if you want to get fancy
lots of clamps
3/4" softwood scraps, ideally spruce
3/4" hardwood scraps, I used an old floorboard
1/4" hardwood for the fretboard
4mm plywood, alternatively wood planed to this thickness
an 8" piece of 3/16" steel rod, I found mine in an old dead printer
Mandolin hardware (strings, tuning machines, fretwire, tailpiece, nut)
I was able to do the whole thing for under $45, but if you're not a penny pinching cheapskate such as myself, you can find a kit here.
siminoff.net an excellent source of kits, parts, and information
stewmac.com another great place to find parts
Crystal Forest Mandolins a quick overview of the proper process
Chris Williams' mandolin a more detailed review of a 4 string flat top
Step 1: Cut Out
If you followed any of the above links, or if you already know anything about luthiery, you will have no doubt realised that these aren't traditionally made out of cheap plywood. Tradition dictates bookmatched quartersawn hardwoods such as Maple or Honduras Mahogany, and tonewoods like Sitka Spruce or Californian Redwood. However, for me I have found that the 4mm exterior grade 3ply that I had left over from my boat building project fit the bill for both strength and lightness. As a bonus, it's easier to work with, you can cut it with a knife, and it's only NZ$20 for a full sheet. You're more than welcome to use the proper materials, but some of the methods you'll need will be similar to those in the links section than what I'll show here.
Enough talk, lets get down to it. Start out by printing off the blueprints for the neck and the top & back.
Cut a couple strips for the sides, 1 3/4" wide by 20" long. You can do this with a straightedge and a sharp knife, just score it a few times and snap it like sheetrock.
Cut one piece of ply for the top, try to pick a bit with some nice grain, and cut it about 1/2" wide of the line.
Cut another for the back, also about 1/2" oversize all around, making sure to include the bit at the top for the heel of the neck. I forgot that bit and had to scarf on some scrap later on.
For the headblock and tailblock I had to laminate together some pieces of my hardwood floorboard to get 1 3/4" stock. Once you have a block about 6" x 3" x 1 3/4" trace the headblock curve onto it from the blueprint. You can cut the neck heel tab off of the blueprint for this, we won't need it again.
Carefully cut out the headblock making sure to keep the blade square, we'll be needing both halves of it.
Cut out a piece of hardwood for the tailblock as per the blueprint.
Trace & cut 2 or 3 pieces for the neck, it needs to finish at least 2" thick for the neck and about 3" at the peghead end, but you can add ears for that later.
As you'll see later on, my peghead finished to about 6" long, so I ended up cutting off a lot of material from the end. It will depend on the peghead design you choose, but the neck profile blueprint allows for a full F-style scroll peghead length.
Glue up your neck.
Step 2: Bending the Sides
The plywood is easy enough to bend once it's wet, but to make it stay where I wanted it, I put some heat to it with a 1500w heat gun.
Lay out the blueprint and clamp down the tailblock and the inverse of the headblock as in the first pic.
Do the sides one at a time, give the strip a good soaking with the spray bottle and keep it handy because the heat gun will dry the wood out quick.
To do the actual bending process I would clamp the gun to the bench, turn it on and run the wet ply back & forth in front of it, constantly bending it between my hands & spraying it when it dried out.
Apply the heat to the inside of the curve one part at a time, and check it against the blueprint often so you know when to move along the strip to the next bit.
When you think it's pretty close, whack it in the headblock and clamp it up along the edge down to the tailblock so you've got what looks like the 2nd picture.
Wait for it to dry out, the heat gun can assist with this if you've got heatproof clamps.
When it doesn't feel damp any longer take it out of the clamps and hitch the tips together with a piece of tape so it doesn't straighten out while you bend the other side.
Do the same with your other strip, you should be a pro at this by now.
Remove the clamps and carefully mark the centre lines from the blueprint onto the head & tail of both sides.
Cut the sides to length.
Attach the sides together at the head end with a strip of 2" masking tape on the outside, then put it all back on the blueprint and glue in the head & tail blocks, being sure to get glue in the butt joints between the 2 strips.
While it is drying, print another copy of the blueprint and glue it to some heavy cardboard, double thickness if you can find it. Cut it out with a razor knife at the inside rim line, also cut out the head & tail blocks. Once the glue is dry and the body is out of the clamps, bung the cardboard inside it to keep it in shape, it should be a pretty snug fit.
Step 3: Neck
Your neck blank should be dry by now, true up the fretboard plane on the sander and trace the fretboard plane pattern onto it.
Before shaping out the neck, cut a slot for the truss rod about 3/8" deep on the table saw or router or whatever you have.
Start the shaping process with something fairly coarse. I like to sweep back & forth sideways with a skill saw with the guard pinned back, but I'm not recommending you try that. A belt sander works fine, or a rasp & spokeshave if that's how you roll.
Make sure to sand the curve where the neck meets the body. Check it often against the body and the neck profile pattern to make sure it will fit snugly and you don't loose the angle.
When you get close to the lines and the neck starts to look how you want it, switch to something a little finer like in the 4th photo.
Next comes the truss rod. Cut your rod to exact length & rough it up a little with a file or grinder to give the glue more purchase. It should sit completely below the wood, when it does, mix up some epoxy and fill it in. I put some sellotape on the ends to keep the glue from leaking out.
Step 4: Tone Bars
For the tone bars, use some 1/4" x 3/4" softwood. I had some redwood left over from my last F5, but whatever you've got will do.
Cut the pieces to length from the top & back blueprint and angle the ends at about 30 degrees.
Trace the lines onto the inside of the top & back.
Set up a sanding jig like they explain in the .PDF, you want about a 2 1/2" rise in 16" (an 8' radius).
Sand the bottom of your tone bars, once you do one you get an idea of how much material you're removing and can help the rest along with a block plane to speed things up.
Start gluing with the 2 side bars, when they're dry put a bit of a radius in the ends with a chisel, crown the top and taper the profile a little too if you want.
Do the remaining bars in the same manner, you'll need to notch the cross braces to clear the tips of the side braces.
For a bit of soundhole support, glue a bit of surgical gauze between the bars as in the last photo. Use woven gauze if you've got it, this felted mat stuff is a bit messy to work with. Don't worry if you can't find any gauze, its more important with straight grained soundboards to keep them from cracking, we won't have that problem with plywood.
Step 5: Gluing
You'll need to plane your rim & blocks to get a good fit on the soundboard. Plane more on the left & right than on the head & tail since the soundboard is slightly curved now. Also be sure to get the angle pretty close on the edge of the rim where it mates to the soundboard. The soundboard should touch all around the rim when you set it on, without warping any.
Run a bead of PVA all around the rim & blocks, line up your soundboard centre line with the seams in the rim sides, and clamp all around. (Pic 2)
You may have noticed that we're not using any kerfing in this project. If you ever want an exercise in frustration, hand cut some kerfing. No, I've figured out that Gorilla Glue works just as well and is a million times easier.
Once your PVA dries, lose the clamps & cardboard, bring back our old friend the water pistol from the bending we did earlier, douse the inside corner all the way around, and run a nice fat bead of polyurethane in there. Keep it flat or it will run, and smear it up the sides about 1/4" so it doesn't have to overcome the vertical surface tension as it expands. In fact, you would probably get a more uniform expansion if you put it on a record player turntable and spun it around while it dried. Keep me posted if anyone tries that.
When the Gorilla Glue is dry, plane/sand down the excess on the soundboard. You only have to get it close at the headblock for now.
The jig in picture 6 is for holding everything in place while you glue the neck joint, but really any flat surface will do if your clamps can accommodate it. The jig has a centerline scribed down the middle, as well as the outline of the body & neck, and a support to simulate the bridge. The support should pretty closely match the curvature of the soundboard and be 3/8" high in the middle.
Lay everything up dry before you get the glue out to make sure you'll be OK with clamping. When you're all set, wet down the joint and apply the Gorilla Glue. Once everything is in place, double check your centre lines to make sure everything is still in a straight line. When that was dry I put a great big wood screw through the headblock into the neck heel for good measure.
This is your last chance for personalisation on the inside of the instrument, so if you want to name & date the headblock or put anything on the backboard where people will see it though the soundhole, now is the time.
To attach the backboard, test fit it and scribe a line all the way around. Douse it with water, then run a glue bead just inside the line, not forgetting some for the blocks. Since we won't be able to get our fingers in there once we close it up, run another bead of glue around the inside of the rim as shown in the 2nd to last photo. Make sure to keep the mandolin face up until this dries.
Assemble according to your scribed line and clamp it up.
Step 6: Fretboard
You can get your fingerboard pre-slotted from stewmac.com, and for $14 its hard to go wrong, but if you've got some 1/4" hardwood, its pretty simple to do yourself.
Firstly, build a little box jig like you see in the first picture. To make the guide cuts in it, put a piece of perfectly square cut scrap wood in it and run your saw along it to get the cuts straight down.
Your piece of 1/4" hardwood should be about 2" by 10", leave it square for now, it'll be a lot easier to get your fret cuts straight that way.
Transfer the fret positions to the wood, making sure you've got a square end at the nut before you start. Then its pretty straightforward, cut a slot at each mark, to a depth not quite halfway through the fretboard.
Now its time to test fit it to the neck, remembering to put the nut in place for a spacer. Scribe the neck lines onto the back of the fretboard and then plane it down to shape.
This is where you would install fretboard dots if you wanted them, I chose not to on this project.
Installing the fretwire is pretty simple, snip it to length with some wire cutters, tap it into the slot with a light hammer, and once you've done the lot, file the pointy ends down.
Now you've got a fretboard! Pretty flash, eh?
We'll also need to cut a little wedge called the fretboard extender that fills the gap between the bottom of the fretboard and the soundboard of the mandolin.
Step 7: Bridge
The bridge is another item that is readily available to buy, but just as easy to make. I printed out the below diagram, it took a couple tries to get it to scale, and then glued it to some hardwood and cut around it.
I found some machine screws in my random screw jar, I think they were either M3 or 6-32 thread, about an inch long. I couldn't find any thumbscrews, so just used some nyloc nuts.
Drill the top half of the bridge for through clearance, and the bottom half for screwing in clearance. Don't drill all the way through the bottom half, otherwise your screws might gouge your soundboard. Turn the screws in and then cut the heads off. The top half slides over the screws and should sit on the nuts.
To match the bridge to the soundboard, place a piece of sandpaper face up on the soundboard, and rub the bridge back & forth across it until it can sit perfectly flat, exactly 13 7/8" from the nut.
Step 8: Peghead
There are tons of mandolin peghead designs out there; from the classic Gibson F style, to something simple like mine. You can get creative here, because it really doesn't matter what you do. I thought I would try a slotted peghead since I hadn't done one before, and because I could fit it all on the the blank without gluing on any extra "ears". Whatever you do, just make sure that your tuning machines fit, so it would be good to have them on hand before you start cutting.
My process for getting the slots went something like this: drill, dremel with router bit, chisel, file. Its generally standard practice to veneer either the face or the face and back of the peghead with hardwood. I wouldn't have, but I needed just a little extra thickness to fit my tuning machines on. That and it covers up the end of the truss rod which would have looked a little funny otherwise.
Once I had the slots roughed out, I made the holes. To get the centres marked I turned all the tuner knobs until the string holes were parallel, and then very carefully with a mechanical pencil, marked the dots on the edge of the peghead through the string holes in the tuners. I clamped a bit of wood for a fence to the drill press to make sure the holes bored true.
Step 9: Inlay (optional)
If you've got a Dremel tool and a bit of spare time, you can try putting some decorative inlay on the peghead. True inlay involves cutting your design out of sheets of Paua shell or similar with a jewler's saw and then routing out a cavity in the peghead veneer for it to slot into exactly. I've done this before with an actual Paua shell I found on the beach, but its a bit beyond the scope of this instructable. If you're interested I'd recommend reading Siminoff's chapter on the subject in his manual, its very informative.
What I chose to do this time instead is something I saw on supersoftdrink's instructable on how to make wooden rings.
First I printed out the text I wanted, pasted it in place, and routed it out to a depth of about 1mm. You'll need some sort of router stand for your Dremel, don't try it freehand. I used a 1.0mm reverse twist end mill from stewmac.com, but there are probably a variety of bits that would work depending on your design.
Practice on scrap wood before you go gouging into your peghead. If I had taken that advice myself on this project, I would have realised that this doesn't work so well on softwood, especially not when routing to the exact depth of the first lamination of the plywood. If I had known that I probably would have flagged the whole exercise, but you can't do these things halfway.
Once you've got your holes dug, mix up some epoxy and add some crushed rock or other pretty material. I used some greenstone dust from some core drill cuttings I was doing anyway. Unfortunately for me, that didn't turn out very well either, it came out a sort of murky grey instead of jade green. Perhaps I didn't use enough dust, but it was getting pretty thick. Yet again, testing this would have told me that.
Once it was set but still soft I shaved it off with a razor knife and when it was fully hard I smoothed it down to the wood with a fine flat file.
Step 10: Finishing
To prep for finish, make sure everything is finish sanded. Bring the soundboard and backboard right down to the rim with a belt sander, then go over the whole thing with #220 then #400 hand sandpaper. Put a large screw or similar into the tailpiece for holding/hanging while the finish is drying.
Now it's time to put a finish on the instrument. I chose some antique mahogany wood dye that I had and followed it up with quite a few coats of clear acrylic lacquer. You can install the fretboard first and then mask it off, but I figured it was easier to leave it off since I didn't want it painted.
The first thing I did was put down a strip of masking tape where the fretboard goes. Then I applied the dye according to the instructions on the bottle. I made an attempt at a "hand-rubbed sunburst" design which involves applying more dye around the rim and edges of the soundboard & backboard than in the middle. It didn't turn out looking like a Lloyd Loar original because the goofy plywood grain just wanted to be real dark in places and real light in others, but its pretty unique, so I don't mind.
If you're lucky enough to be using some nice fiddlebacked curly maple, you can get really good contrast between the different parts of the grain by rubbing it down between coats of dye with 000 steel wool dipped in meths. I didn't bother because my grain was too contrasted to begin with.
Once you've got it the way you like it, start in with the clearcoat. I put on 4 or 5 coats separated by 5 minutes, and then let it dry for 24 hours, wet sand, and repeat. You can get it looking like a mirror this way, it depends on how fussy you are.
Step 11: Final Assembly
Before gluing on the fretboard, check the plane of the neck with a straightedge to make absolutely sure it's true, the last thing we want is any high or low frets. Also check the side clearances on the fretboard, this is your last chance to make sure its flush with the sides of the neck.
For the nut I used a white bone blank from Stewmac. I cut it down to the width of the neck and shortened it to about 1/8" proud of the fretboard, and glued it on at the same time as the fretboard. To ensure even clamping pressure across all the frets I used a chunk of angle iron on top. Double check that everything is where it should be and don't let any glue runs dry on your nice new neck finish.
I made my own tailpiece, but it was a lot of trouble and didn't turn out quite as nice as I would have liked. If you're keen to build one, you don't need me to tell you how to do it, but I will tell you that it would probably be easier to buy one.
If you want a finger rest, cut one out of the ply using the finger rest pattern. I attached mine with a couple rods salvaged from a dead PC CD drive, but anything ~1/8" will work. I bent the rods at right angles, routed channels for them to sit in on the back of the finger rest, and epoxied them in place. To attach it to the instrument, transfer the rod locations to the edge of the fretboard/fretboard extender and drill appropriate sized holes. You'll also need a little block of wood glued to the back, and fashion something to attach it to the edge of the rim with. I found everything I needed in my screw bin.
When everything is all dry you can put your tuning machines in if you haven't already, file some string notches, and string it up. Transfer the marks from the string spacing diagram onto the nut & bridge, and put some notches in with a V shaped needle file. You want the angle of the notches in the nut to be between that of the fretboard & the peghead, which I am attempting to illustrate in the last photo.
And you're done!! There are plenty of resources on the interweb for tuning and learning to play the mandolin, and if I can do it, anybody can! Enjoy!
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