Introduction: Leather Didgeridoo
A didgeridoo made out of leather and sealed with epoxy.
Leather is a great material for first-time didgeridoo builders, because it's relatively easy to obtain, not too expensive (especially if you keep an eye out for sales) and doesn't require any expensive tools or prior knowledge.
You should expect to spend around 10-12 hours on this project, although it can be done in 6-8 hours after you have already made a couple.
The initial cost for all of the materials and tools is around $200 and you'll have enough materials to make at least 2 didgeridoos, maybe 3. The cost per didgeridoo, excluding tools and re-usable materials, is around $50 - $75.
I got started crafting didgeridoos out of leather because I don't have the know-how, tools or space needed to make "split and hollow" didges out of dried logs, and I don't live somewhere with a ready supply of yucca or agave stalks. After some brain-storming and searching, I found a guy that makes leather didgeridoos ( Marko Johnson ) which inspired me to try my hand at it.
I've made a variety of styles of leather didgeridoos. Hand stiched, "triangle", "triangle spiral", sectional, and the simple "wrap and epoxy" style which I will describe in this instructable. I've added some pictures of some of the other styles of leather didges that I've made, if you're interested.
After a while of building leather didgeridoos, I got interested in the physics of didgeridoos, especially in the area of how the bore shape affects the playability and sound of the didge. I did some reading in some acoustic journals, and eventually made a program to calculate what is called the "acoustic impedance" of a didgeridoo with an arbitrary circular bore shape. I've recently created a user-friendly interface and released the code as open source. You can get it here.
One of the great things about this method of making didgeridoos is that it is relatively easy to construct the didgeridoo so that it has specific bore dimensions. This appeals to me because it allows me to design a didgeridoo before hand, using my DidjImp program, and then build the didge and see how it sounds. This allows me to experiment with different designs and learn more about how to make a didgeridoo with specific playing characteristics.
I hope you find this instructable useful. If you do make a leather didge using these instructions, I would love to hear about it! And I would love to hear any feedback you have.
Note: Some of the images are hard to see at the small size shown on the page. I've uploaded full size images, so you can click on the "i" buttton at the top left of the image and choose to view the original image which will be a lot larger.
Step 1: Tools and Materials
Here are the tools needed:
Razor/Utility knife - $4-$9
For cutting out the leather. My favorite is this
Yard stick - $5
The metal ones are the best. The cheap wooden ones tend to be not very straight. Ideally it should have millimeter markings (1/32in works too, if you prefer the "English" system.)
"2 yard" yard stick (optional) - $15
Again the metal ones are best. The markings aren't important. This is only used in the first step, to draw a long straight line. You can use the "1 yard" yard stick instead, or anything else with a long, straight edge.
Carpenter's square or similar - $5
It's best if it has millimeter or 1/32in markings. If not, you can use the yard stick to measure instead.
Hack saw or PVC pipe cutter (optional) - $4
This is needed if you are going to build a PVC frame
And the materials that that are needed:
1 Leather hide - $90
You want a thick vegetable tanned hide, at least 12oz or so. Tandy's cheap 13-15oz saddle skirting works well. This will be enough leather for at least 2 didges, possibly 3.
Epoxy (at least 12-14oz) - $20
You can buy 64oz of the "Klear Koat" epoxy here for $20 (not including shipping), or you can find a 16oz kit of Envirotex Lite in some local hardware stores for around $20. Other types/brands of "tabletop/bartop epoxy" would probably work too. You'll use around 12-14oz of epoxy per didge, so if you buy the Klear Koat you should have enough for several didges.
Fumed Silica (Optional) - $3.50
Used to thicken the epoxy for the final outside coat.
Latex gloves - $10
For working with epoxy
Pencil - $1
Ye olde wooden pencil
Pencil sharpener - $1
Any cheap pencil sharpener will do
Elastic Medical Bandages - $10
You have a couple of options here. You can get a regular "ACE" type bandages, either the self-stick kind, or the kind with the little metal fastener things. You can reuse this type of bandage, assuming you don't get much epoxy on them. These are $2 a piece for a 2" wide bandage, which is an easy size to work with. You can get a wider bandage, but it's a bit harder to keep "flat" while you wrap it on the didge. You'll need around 5 2" bandages or possibly fewer if you use a wider bandage.
You can also buy woven cotton bandages in bulk for pretty cheap, but they're not as re-usable. They tend to get stretched out after a couple of uses.
String - $3 (or $25)
Used to draw the curve at the wide end, and also to hang the didgeridoo from the PVC frame while epoxying. You can probably use cheap cotton string which you should be able to find at walmart on the cheap (froogle.com says $3 or so). However, I like to use a type of string called "lacing tape", which comes in either nylon or polyester (among other materials). It is a flat, braided string, is quite strong, and holds a knot very well. I use this stuff for *everything*. It's around $25 for a 500 yard spool, but it's a bit hard to find. The good thing is that 1 spool will last a long long time. The place I got it from last time isn't selling it any more unfortunately. After a bit of a search, it looks like you might be able to get it here. Either nylon or polyester is fine. You want size 3, with the synthetic rubber finish. White is cheaper, but you can get black if you want :)
Masking Tape - $4
Used to hold the string in place while drawing the curve at the wide end, and also to help seal the mouthpiece end of the didge when epoxying the inside. You don't want to use duct tape or packaging tape, because the tape will stick to the leather too much and damage the leather when you peel it off. I use 3M's blue masking tape.
Plastic Drop Cloth - $3
This is used while working with epoxy, to prevent it from getting on the floor.
3 Plastic graduated mixing container - $1.50 total ($.50 each)
To mix the epoxy
1 package of mixing sticks - $2
To mix the epoxy
Silly Putty - $1
To help seal the end of the didge when epoxying the inside
1 plastic grocery bag - $0
Used to seal the end of the didge when epoxying the inside
Optional - if you want to build a PVC frame to help hold the didge while you
epoxy the inside and outside.
4 10' long 1-1/4" Schedule 40 PVC pipe - $4 each, $16 total
8 'T' connectors to fit above pipe - $1.50 each, $12 total
4 90 degree elbows to fit above pipe - $1 each, $4 total
Note: if you buy the Klear Kote epoxy from U.S. composites, you can order some fumed silica (aka aerosil-cabosil), graduated plastic tubs, wooding mixing sticks, and latex gloves from them at the same time.
Total Cost: $220 - Assuming that you have to buy everything that is listed. There's a good chance you will have some/most of the tools and materials already, and you can leave off some of the optional items to save a bit more. Most of the stuff can be re-used if/when you make more leather didges in the future.
Step 2: (Optional) Build a PVC Frame to Help Hold the Didge While Epoxying
This frame is quite useful when epoxying the didge.
You can use it to
- hold the end of the didge up while epoxying the inside
- hanging the didge to let the epoxy drain out
- support the didge in a horizontal position while epoxying the outside
First, you need to cut the PVC pipe into smaller sections. Each line below represents the lengths to cut from one of the 10' lengths of PVC pipe.
5' | 5'
4' | 4' | 1' | 1'
4' | 4' | 1' | 1'
20" | 20" | 20" | 20" | 6" | 6" | 6" | 6"
Assemble the frame. Each of the legs are made up of a 1' piece, a 4' piece, and a 6" piece (from the bottom to top).
The 2 long pipes along the top are 5', and the 4 pieces of pipe that run between the 2 legs on each side are 20".
See the picture to get an idea of how it all fits together.
Step 3: Determine the Bore Dimensions
The first step is to figure out what shape of bore you want to build. In general, you want a small enough mouthpiece that you can play easily (1.25" to 1.5" diameter or so), and a gradual taper towards the end.
You can use my DidjImp program to help design the bore. You enter the bore dimensions, and then you can see what note that didge will play.
Here are the dimensions for the didge that I will be building in this article. The first column is the distance from the mouthpiece, and the 2nd column is the diameter of the bore at that location.
0m (mouthpiece) - 30mm
.628m - 40mm
1.256m - 60mm
1.78m - 100mm
This didgeridoo should play a "D" (73hz)
Step 4: Calculations
Now that you have the bore design, you need to do some calculations to determine the shape of leather to cut out. The idea is that at each "section" in the design, the leather needs to be wide enough that when you bend it into a circle, it is the diameter that you want.
At first, you might think that you just need to calculate the circumference of a circle with the given diameter, but that will actually give you a smaller bore than you want, due to the thickness of the leather.
In general, if you have a piece of leather with a certain width and thickness and you form it into a circle, the inner diameter of the circle will be:
InnerDiameter = (width/Pi) - thickness
And the outer diameter will be:
OuterDiameter = (width/Pi) + thickness
The difference between the two is twice the thickness of the leather, which makes sense, because you go through 2 thicknesses of leather going from the outer edge of one side to the outer edge of the other side.
You need to calculate the width of leather than will give you the bore (inner) diameter that you want. From above, we know that
InnerDiameter = (width/Pi) - thickness
And we need to solve for the width.
width = (innerDiameter + thickness) * Pi
Now you need to find the average thickness of the leather. You can measure it at various places around the edge and guestimate the average thickness. It will typically be around 4-6mm.
I happen to have a custom-made tool that can measure the thickness of the leather anywhere in the middle of the leather, so I was able to get a more accurate thickness measurement at each position (shown below)
Now you just need to plug in the thickness and the diameter for each section to get the width of leather at that position.
0m: (30mm + 5.2mm) * 3.14159 = 111mm
.628m: (40mm + 5mm) * 3.14159 = 141mm
1.256m: (60mm + 4.6mm) * 3.14159 = 203mm
1.78m: (100mm + 3.9mm) * 3.14159 = 326mm
And finally, you need to calculate the curve at the wide end. If this was straight instead of curved, the bell of the didgeridoo wouldn't be flat on the bottom, but it would stick down where the seam is.
The curve that is needed is a circular curve, so you need to calculate the radius of the circle. Later, you will use a string that is the length of the radius in order to draw the curve.
The derivation of the calculation is a bit involved, so I'll skip it and just give the calculation itself.
CurveRadius = (((LargeRadius - SmallRadius)2 + Height2)(1/2)) * LargeRadius / (LargeRadius - SmallRadius)
See the images for this step for a better formatted version of the equation.
In this equation, LargeRadius is the radius of the bore at the bell end, plus 1/2 the thickness of the leather.
SmallRadius is the radius of the bore at the section just before the bell, plus 1/2 the thickness of the leather.
Height is the distance between the bell and the section just before the bell.
For the didge that I am building:
LargeRadius = 50mm + (3.9mm/2) = 51.95mm
SmallRadius = 30mm + (4.6mm/2) = 32.3mm
Height = 1780mm - 1256mm = 524mm
And then plugging these into the CurveRadius equation:
CurveRadius = (((51.95 - 32.3)2 + 5242)(1/2)) * 51.95 / (51.95 - 32.3) = 1386mm
Step 5: Draw the Center Line
Lay out the leather so that it is flat, and lay the 2-yard yard stick onto the leather, where you want the center-line of the didge to be. You want to position it so that the outline of the didge that you are going to cut out is as close to the edge as possible, to minimize the amount of left-over leather on the side.
Once you've placed the yard stick, draw a line along the edge of the yard stick with a pencil, using light pressure. You don't want to press to hard, or it will make an indention in the leather.
If you only have a 1-yard yard stick, place the yard stick and trace a 1-yard line, and then move the yard stick along the line so that the end of the yard stick is approximately in the middle of the line you just drew, making sure that the yard stick is still lined up with the line. Then continue the line. You'll need to do that twice to get a long enough line.
Step 6: Measure and Mark Along the Center Line
In this step, you will make tick marks along the center line for each section in the design.
Start off by placing a tick mark where the mouthpiece is going to be.
Then measure along the center line from the mouthpiece, the distance to the next section of the bore design and make another tick mark.
For this didge, the second section is .628m away from the mouthpiece, so I'll take the yard stick and measure the appropriate distance and make another tick mark.
Do this for each remaining section.
Step 7: Measure and Mark the Width of Each Section
In this step you will draw lines perpendicular to the center line at each section, and measure out the required width of the leather at that section.
Place the carpenter's square so that the long edge is lined up with the center line, and the other edge is lined up with the tick mark for the mouthpiece, and draw a line that is at least half of the width of leather at that position (using the width you calculated in step 3). You can just guestimate, and make sure the line is longer than needed.
Now flip the carpenter's square over and line it up again, and draw a line on the other side of the center line.
Now use either the carpenter's square or the yard stick to measure half of the required width, from the center line, and make a tick mark, and then measure and mark the same distance on the other side of the center line.
For this didge, the required width of the mouthpiece is 111mm, so I will measure 55.5mm on either side of the center line.
Do the above for each remaining section.
Step 8: Draw the Curve on the Wide End
In this step, you will use a piece of string to draw the curve at the wide end.
Cut a length of string that is a bit longer than the "CurveRadius" you calculated in step 4.
Use the pencil to make a mark on the string near one of the ends, leave enough string past the end of the mark so that you can tape it down.
Measure down the length of the string from the first mark you made and make another mark, so that the distance between the two marks is the "CurveRadius" value that you calculated in step 4.
Take one of the ends of the string, and tape it so that the mark is right at one of the "corners" at the wide end of the didge.
Pull the string tight, and bring it over until the other mark on the string lines up with the center line, and then tape that end of the string down so that the mark is directly over the center line. That is the center of the circle that makes up the curve you're going to draw.
Go back to the other end and untape it, and the move the string a little bit towards the center, while keeping the a constant tension on the string. Don't pull so hard that you pull it out from the tape holding it on the other end. Now make a mark on the leather next to the mark on the string.
Move the string towards the center a little bit more, and make another mark.. and keep doing this until you get to the other corner. If you did everything right, the marks that you made go from one corner to the other, and form a circular curve.
Untape the other end of string and discard.
Step 9: Draw the Outline
In this step you will draw the outline of the leather.
Use the yard stick to draw a line between adjacent pairs of tick marks you made in step 7. Do this around the whole design. These will be the lines that you follow while cutting out the leather.
Step 10: Cut Out the Leather
In this step, you will cut out the leather.
Take the yard stick or carpenter's square ("the ruler") and lay it down beside the straight line at the mouthpiece end of the didge, so that when you cut with the utility knife along the straight edge, it cuts right on the line.
Press down firmly on the ruler with one hand, holding it in place, and then take the utility knife with the other hand and cut along the edge of the ruler. You want to pull the blade toward you, while holding it against the edge of the ruler, to ensure that your cut is straight and on the line.
Don't use too much downward pressure on the utility knife, you are just scoring the leather with the first cut. Once you cut along the line once, keep holding the ruler in place and pick up the utility knife and make another cut. You'll probably need to cut 3-4 times to get all the way through the leather.
Use this same technique to cut along the whole outline, except for the curve at the wide end.
Be careful when you get to one of the sections, where the outline changes direction. You don't want to cut past the end of the line and into the piece of leather that you are cutting out. Stop the cut where the outline changes direction, and then reposition the ruler and start the next cut on the next line.
To cut out the curve at the wide end, you'll need to cut it free-hand. Start at the corner and start pulling the knife towards you, keeping a close eye on the cut that you're making, to make sure that it follows the marks that outline the curve. The key is to not get in a hurry. It also helps if you get close to the leather, so you can see better.
On the first cut, you are just lightly scoring the leather. Once the leather is scored, you can use a little more pressure and you don't have to be as careful, because the blade tends to follow the score.
Once you cut all around the outline, you should be able to remove the piece of leather that you cut out. You may need to do run the blade along some of the cuts again, where the leather didn't quite get separated.
Once you remove the piece of leather that you cut out, you can erase the pencil lines on the leather.
Step 11: Wet the Leather and Wrap It
In order to get the leather in a tube shape, it helps if you wet it down first to make it more pliable. You can let it soak in a bathtub for 5-10 minutes, or go outside and wet it down with a garden hose, somewhere where the leather won't get dirty.
Once it's nice and wet, then bend the sides in towards the center with your hands. At this point you just want to get the leather to start bending, it won't stay in a tube shape without something to hold it.
Take one of the elastic bandages and wrap it around the leather a little ways down from the mouthpiece, a foot to a foot and a half down. Make sure it's tight enough to hold the leather in a near-tube shape. This is just a temporary wrap, so you just need to do 3-4 wraps in the same spot - enough so that the wrap doesn't come off when you let go.
Take another elastic bandage and start wrapping it around the leather at the mouthpiece end. Be sure to pull it tight enough that the edges of the leather are firmly pressed against each other, otherwise epoxy will leak out the seam.
As you continue wrapping down the leather, you will start getting closer to the "temporary wrap" you made to hold the leather in place. You'll want to unwrap this and move it down another foot or so and make another temporary wrap.
When you get to the end of one of the bandages, just grab another and start wrapping again from the same place.
Once you get it fully wrapped, then you should be able to play it! Pick it up and give it a toot. The sound will be somewhat muffled, but you'll get a general idea of what it's going to sound like. I've added an mp3 file of what mine sounded like at this point, and another that I recorded after the leather had dried.
If you can't play the didge, that's a good indicator that you didn't get the seam sealed up good, which means that epoxy will leak out when you epoxy the inside. Not good! You'll probably want to re-wrap it tighter.
Once you are happy with how it's wrapped, you will need to let the leather dry before you epoxy the inside. If it's hot outside, lay it down on your porch and it should be dry after a day. Otherwise, just lay it down against a wall somewhere out of the way in your house. You'll probably want to leave it at least two days. You can tell if it's dry by feeling the leather on the inside at the bell end. Does it feel nice and dry? You may want to rotate it a couple of times so that the side that was facing downward has a chance to dry.
Step 12: Seal the Mouthpiece End of the Didge
In this step, you will seal off the mouthpiece end of the didge, in preparation for coating the inside with epoxy.
First, you'll want to make sure the leather has dried off from the last step. Feel the leather on the inside at the bell end. If it still feels damp, or slightly cool to the touch, let it sit for another day.
Get a small piece of silly putty and roll it into a snake, and then press it onto the edge of the leather at the mouthpiece end.
Place the plastic bag over the mouthpiece end of the didge, and pull it tight against the silly putty. This should make an air (and epoxy!) tight seal, to keep epoxy from leaking out.
Put some of the masking tape around the plastic next to the edge of the didge, and then cut off any excess plastic.
Then put some more tape across the top and down the side, to hold the plastic in place. You don't want the plastic coming off while you have epoxy in the didge!
Step 13: Epoxy the Inside of the Didge
In this step, you will epoxy the inside of the didge. This seals the leather and gives a hard surface for the sound to bounce off of on the inside, and it holds the seam together.
First, you'll want to lay down the drop cloth, to keep the epoxy off the floor. Ideally, you'll want to work someplace that has good ventilation, so you don't breath in too much epoxy fumes.
Mix the epoxy, per the manufacturer's instruction. You'll need to mix up around 8-10 oz of epoxy. The two types of epoxy I mentioned in the "materials" step use a 1:1 ratio, so just pour out 4-5 oz of each component into a plastic mixing cup, and stir thoroughly with a mixing stick. You want to make sure to scrape the sides and bottom of the container, so you don't leave any unmixed epoxy (or as little as possible at least).
Don a pair of latex gloves (just in case), and pour the epoxy into the wide end of the didge.
Pick up the didge and place the far end (the mouthpiece end) on something, to help hold it up - otherwise your arms will quickly get tired from trying to hold it up.
Hold the open end of the didge lower than the sealed end, in order to let the epoxy run back towards the open end. You'll want to look inside the bore and watch for when the epoxy starts getting close to the open end, and then raise the open end back up a bit so it doesn't run out the open end.
Slowly rotate the didge, letting the epoxy coat the bore as you rotate. You'll probably want to raise the open end back up and let the epoxy run pool in the sealed end, and then lower it again and run back towards the open end (several times), while occasionally rotating.
Note that you don't need to worry about coating the leather at the very edge of the open end - it should get coated nicely when you let the epoxy drain out of the open end.
Once you are comfortable that the entire bore has been coated, you can stand the didge back up and let the epoxy drain out onto the plastic drop cloth. The epoxy doesn't stick to the plastic, so once it has cured, you can peel it off the drop cloth and reuse the drop cloth.
At this point, you can take off the tape, plastic and silly putty on the mouthpiece end.
If you built the PVC frame, you take take some string and wrap it around the 2 horizontal bars on the top, and then take the end of the string and wrap it around the top of the didge, down far enough to hold the didge up off the ground.
Otherwise, you can try and find something else to hang the didge off of. Put a hook in the ceiling.. Use an existing light fixture (with the light turned off!)... etc.
Or you can just lean the didge against a wall or something. The only downside is that the epoxy will be thicker on the side of the bore that is facing downward.
Now just let the epoxy drain and cure. It will be dry to the touch in 4-5 hours, and it will be fairly hard in about a day. It takes a week or two to reach full hardness, but it's "good enough" after a day.
The attached sound file is what it sounded like the next day, after the epoxy had cured.
Try not to get any epoxy on you. If you do, just wash as best as you can with soap and water.
If you get epoxy on something that you don't want it on, you can clean it up before it cures with some mineral spirits, denatured alcohol, or something similar.
Step 14: Unwrap the Didge
Once the epoxy on the inside has cured, you can remove the elastic bandages from the outside. The epoxy will hold the seam together and the leather in the same shape.
At this point, you can take the utility knife and trim off any excess epoxy off the bottom end of the didge. There will usually be several places where the epoxy was dripping. Or if you happen to have a dremel, a flap wheel is an easy way to remove the epoxy (wear a dust mask!).
Step 15: Epoxy the Outside of the Didge - First Coat
In this step you will coat the outside of the didge with epoxy.
First, you need to figure out how you are going to position the didge while applying the epoxy.
If you built the PVC frame in step 2, then hang some string from the two horizontal bars on the sides of the frame, and then run the 1/2" pvc pipe through the didge, and hang the ends on the string.
Otherwise, you can use the 1/2" pvc pipe and let the pipe rest on something on either end, or just let the didge stand up vertically while you apply the epoxy - just don't let it fall over while you're applying the epoxy.
Mix up another batch of epoxy, you only need about 2oz this time (1oz of each component).
(Optional) It tends to be a bit easier if you pour the epoxy out onto something, instead of trying to dip your hand into the plastic mixing tub. You can put down some wax paper and pour the epoxy onto that. This lets you move the epoxy as you move along the didge.
Don some latex gloves.
While wearing the latex gloves, dip your fingers into the epoxy, and then spread the epoxy onto the didge. You don't want to apply it very thick, so spread it out good.
Continue applying the epoxy to the outside of the didge. Once you get to the other end, the leather will probably have soaked up some/most of the epoxy on the end that you started on, so go back and apply more epoxy to the whole didge. I usually keep applying epoxy until I've used up the entire amount of epoxy that was mixed up.
Once you are done applying epoxy, you'll want to remove the pvc pipe and let the didge stand up on its own, to prevent the didge from being bent in the middle.
Now wait a day for the epoxy to cure. The leather will soak up nearly all of the epoxy that you applied, so once it's cured, you will have a hard, rough leather surface.
Step 16: Apply Second Coat of Epoxy on the Outside
Once the first coat of epoxy on the outside has cured, you can apply a second coat.
Use the same procedure to apply the 2nd coat as the first coat. Be sure to spread the epoxy nice and thin, so that the epoxy doesn't run. Since the first coat of epoxy soaked into the leather and sealed it, the leather won't absorb the 2nd coat, so you won't need to go back and keep applying epoxy as it soaks it up, like you did with the first coat. You won't need to use much epoxy, just mix up about 1oz (.5 oz of each component). You probably won't use all of it.
(Optional) You can add some fumed silica to the epoxy to thicken it. This allows to you spread it thinner and prevents the epoxy from running, and from "bunching up" - Like when you try to spread water thinly on a piece of glass - it won't form a uniform film, but it will separate and bunch up. The epoxy will sometimes do this to a small extent if you apply it too thinly without a thickener.
You should thoroughly mix the epoxy first, and then add some fumed silica to the mixed epoxy. Add small amounts at a time, to make mixing easier. Keep adding fumed silica until you get something like a "snot-like" consistency. Note that the fumed silica will make the epoxy a translucent white color. Don't worry, when you spread it thin enough it will still be quite clear.
Step 17: Enjoy the Didge
Once you've applied the 2nd coat of epoxy, wait a day for it to cure. Congratulations! The didge is finished. Enjoy!