How to Make a Banana Telephone (Land-line) and Banana Base Unit

This is it. You've only got a few weeks before Christmas, and you need to find a gift that is truly original and shows off just how much of a maker you are. There are thousands of choices, but the one thing you really want to make is a banana telephone. After all, the only thing better that talking into a banana telephone is giving someone a banana telephone for them to talk into.
But you don't just want to make a banana headset - they are wonderful, but you can do better. Instead, you want to make a household telephone hidden inside a bunch of bananas. You want one of the bananas in the bunch to be the actual handset, and you the others to form the base and charger.
But instead of just hiding a telephone inside some fake bananas you bought in town, you want to go a step further. Because you are giving this present to someone special, you want to make your own bananas. Not just any old bananas, mind; these bananas will need to stand up to a lot of stress. These bananas will need to be strong. These bananas will need to be made from fibreglass.

Don't try and deny it. You know that deep down inside, you really do want to make a banana telephone.
So keep reading.

Step 1: Choose Who the Banana Telephone Is For

Of course, you might just want to make it for yourself. But this is the Christmas season . .

Choose who the banana telephone is for may seem like an obvious, almost subconscious, step, but sometimes it's not. It's lots of fun to make a really awesome project, but it does tend to help if you know who you're making it for.
For example, don't make this project, then realize that the only person you haven't bought a present for is your seven-year-old sister. I'm sure she'll like it, but really, it's like giving a Barbie doll to your dad.
I made the original prototype for my just-married sister and her husband. It's always useful to have a telephone in the house, and (as I told my mum) they're already crazy with love; now they can look crazy, too!

Step 2: Get Your Stuff

Before you start, I would advise you read this instructable. It has a lot of useful hints, and as the method of construction is quite similar (fiberglass on paper), it is a worthwhile read. Thanks, Dr.Professor_Jake_Biggs!

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Get your stuff
Before you clear out the workshop, make sure you have everything you need:

A basic and small phone (I used a Panasonic KX-TG1811, which was NZ$50. However, as long as the phone is small enough, you should be able to use any phone you like). In New Zealand, Noel Lemmings is a good place to find telephones, but any consumer electronics shop should have some.

This pdf and this one and this one of banana patterns - the three pages will make one banana, so you'll need to print each pdf off 5 times.

Epoxy Resin - Along with fibreglass and hardener, this can often be got in small quantities (a jars worth, $20) from a Panel-beating shop (and if not, they will tell you where they get it from) or Surf shop.

Hardener (most usually comes with resin, but not always). When Hardener is mixed with Epoxy resin, the resulting mixture is simply called 'resin'. So if I ask you to resin one face of a banana, that means mix the Epoxy resin with Hardener, then apply it to one face of the banana.

Fibreglass - sometimes called glass cloth. I find that this can often be got for free as off-cuts.

Something to spread the resin with - might come with resin, but if not, any piece of semi-flexible plastic will do. If it's disposable, even better.

Latex gloves (preferably disposable), for fibreglassing. It is also a very good idea to use these when handling the electronics.

Ice-block sticks (for mixing epoxy resin with hardener, can also be used as spreader) - any craft store should have these.

Respirator for when fibreglassing - ask around your friends; quite a few men have one.

Glue - at the very least super glue and hot glue, but PVA is also useful to have as well. Get from craft shops.

Hot glue gun and a spare rod of glue - again, get from craft shops.

Scissors and Stanley knife - again, get from craft shops.

Paint - yellow for body and brown for ends. Actually, test pots for house paint is a good source of cheap paint in the volume we need. I got mine from Resene.

Paintbrushes, both thick (for yellow) and thin (for details/touch-ups). Usually you can get these at the same time as you get the test-pots of paint.

Hair dryer - this is not strictly needed, but just very useful. Get it from your mum.

Both a Phillips and a Flat screwdriver - if you don't have any, go buy some from a home improvement store. Trust me, you should have some.

Drill and 1mm drill bits - get from the same place you got the screwdrivers from.

Some sort of cleaner to remove the epoxy resin. Denatured alcohol is good; acetone is bad, very bad. Supposedly vinegar also works okay - not as well as other things, but at least it's cheap and easy to get.

Sandpaper - Get from a home improvement shop or from your dad.

Something to mix the resin in - paper cups, plastic bags, etc.

Solder and soldering iron - an electronics store should sell these.

Bare wire and Insulated wire- any conductive wire will do, but copper wire would be helpful. Get these from the same shop you got the solder from.

Total cost: anywhere between $75 (only pay for fiberglass, resin, and phone) and $120 (buy everything new). It really depends on what you have lying around.

Step 3: Make an Empty Banana - Making the Paper Scaffolding

Now that you have everything you need, we can start making the first of four 'empty bananas'. An 'empty banana' is what I call the four bananas that make up the bunch - although three of them will eventually hold the base circuit board, they are constructed empty at the start. The only banana that is not an 'empty banana' is the handset.

First, find that pdf you printed off. Choose one of the empty bananas to do first as a test run, then cut it out along the thick lines. After this, any tabs should be folded over.
Glue the faces together, matching the letters together (letter a should be glued next to the other letter a, letter b should be glued next to the other letter b, etc).
I have provided two extra side front faces per banana. This is because I find it easiest to join the front three faces together, then join the back three faces plus the two extra faces together, then join glue the duplicate faces together. Notice that I didn't do this in the photo below, but I was wishing I had.

Step 4: Fiberglassing an Empty Banana

Warning: the fibreglass takes a long time to dry before it can be sanded. For this reason, once I have made my first banana, I try to fibreglass all my bananas at once, then leave them to dry outside overnight.

First, find a well ventilated outside area. Set up shop here, to prevent being knocked out by fumes.
Mix the resin and hardener; the quantities depend on the particular Epoxy resin and Hardener used. The stuff I used was 1:50 (Hardener:Epoxy resin).
When the resin is mixed well, spread it evenly over the area you want to fibreglass. I find it best to fibreglass the front the faces together, and then the back three faces. This allows the banana to rest on the opposite faces while it is drying.
Get the fibreglass cloth and trace the faces to be fibreglassed onto it. Cut the resulting patterns out and place them carefully onto the previous layer of resin. Using a pattern instead of placing a hunk on and then trimming it helps to prevent scruffy, sticking-out edges, which are a pain to sand down. Finally, coat the fibreglass with resin, and leave to dry.
Repeat this process on the other faces. Furthermore, if extra strength is required, the whole banana could be fibreglassed twice.

Step 5: Sanding and Painting

Wait till the banana is fully dried - in other words, wait a loooong time. It may be tempting to sand the fibreglass before it is fully dry, but don't. You will just make a mess.
Sand it fully, and if necessary, resin again, then sand again. Any bumps will show through the paint clearly, so this is perhaps the one step that will most improve the finished product.
Once the banana is nice and smooth, you can begin to paint. At this stage, all that is needed is one base colour; the details will be added later. However, it is a good idea to do quite a few coats, so that the banana is solid colour, without lighter parts.
To speed up the drying process, I find it helpful to use a hair-dryer.

Now that you have completed your first banana and got the process down pat, you can make the other three bananas. However, it would be a good idea to resin and fibreglass all three at the same time, to save drying time.

Step 6: Make the Front Face of the Handset

After making the empty bananas, the next step is to build the front face of the handset (the front face is the face on the inside of the banana's curve).
The first thing to do it to blu-tack the front face of the phone (the face you bought, not the one you're making) onto the window and trace the holes. It does't matter too much at this stage if you are a bit off - you can make the holes a bit bigger before resining, then cut them a bit smaller when you re-cut the holes after fibreglassing, and make them bigger again, and put a bit more paint in the holes to make them smaller. . .

Once you have the pattern, get your Stanley knife and cut it out. Don't forget to cut out the small holes, and try hard not to rip the thin strips of paper separating them.

Next, take one of your finished bananas and cover it with cling wrap. Using tape over the tabs, attach the cut-out face on top of the same face on the finished banana. Doing this means that, when resined, the face will be curved just about perfect.
Before resining, take a small piece of fibreglass cloth and pull it apart. If the cloth you have is anything like mine, you should end up with 'strings' of fibreglass - that is, bundles of glass fibre.
Mix up your resin, apply it, then, when it is set enough, carefully place on the fibreglass 'strings', taking care not to lay fibreglass over the holes. It is a good idea to lay on a lot of fibreglass along the edge of the face, especially on weak points like between the hole for the display and the edge. This gives the face more strength.
Try not to put resin or fibreglass on the tabs. This is because it restricts their ability to flex, and makes them a lot harder to connect the other faces to. Trust me, I'm speaking from experience.

[While the fibreglass is drying, it would be a good idea to do the step on the next page]

Wait for the fibreglass to dry, then sand the face and re-cut the holes. Try fitting the keys into their holes, and trim the holes if necessary.
Paint the whole face, and when the paint is dry, trim the holes again to get the paint off the edges.

Step 7: Extract the Electronics and Secure the Keypad

If you haven't already, take the phone handset out of its box. Open the battery compartment and take out the batteries (don't lose them!). Unscrew the screws.
Next, look closely at the join between the two faces of your phone. You should be able to detect three tabs along the two long sides of the phone, and two on the top edge (furtherest from the screws). Get your flat screwdriver and pop these out.
Unscrew any screws used to hold the circuit board in place. Cut the two wires connecting the circuit board to the batteries, but don’t forget to note which wire goes to negative and which goes to positive.
You should now be left with a circuit board that is separate from its case, and a keypad that keeps on falling off the circuit board. The one last stage is to secure the keypad to the circuit board. I used thread to tie the two together, simply because I was running out of glue. However, a better idea would be to use glue.

Step 8: Soldering

Near the base of the circuit board there should be two curved contact points. These are used for charging. Looking from the top (i.e. the side with keys and display), the positive contact is on the right.
Get two pieces of insulated wire, perhaps 10cm long, and solder one to each of the contacts. Because these contacts connect very quickly to sensitive electronics, try not to heat them up more than necessary for soldering.

The next thing to be soldered is the batteries. Before soldering, however, the two batteries should be taped together, side by side. Make sure the batteries are orientated so that each end has one positive and one negative terminal - that is, the first battery should be orientated - +, while the other one should be + -.
After the batteries have been taped together, cut a short (1cm) piece of wire and solder it so that it connects a positive terminal to a negative terminal. Alternatively, the connection could be made purely out of solder. Next, solder the batteries to the correct wires coming off the circuit board.

The last soldering job - for now - is to lengthen the connection to the ringer (piezoelectric speaker). This is done by cutting the wires up as close to the speaker as possible, then soldering a wire between each of the cut wires as the contact it connected to.

Step 9: Glue on a Cardboard Backing

The next step is to glue a piece of thick cardboard to the back of the circuit board. This has two purposes: it provides an insulated place to glue the batteries, and it is used later to secure the circuit board to the banana. Actually, I used fibreglass for this (as you can see from the pictures), but cardboard is a lot quicker.
The cardboard itself should be a bit bigger (wider and longer) than the circuit board (I didn't do this, but regretted it), and strong. If necessary, glue a few layers of cardboard together. Also, don't forget to make a hole for the two big cylinder things (are they capacitors?).
Once the cardboard backing is secure, attach the batteries. I used PVA glue, but something that dries quicker would be better (hot glue would be good).

Step 10: Attach the Electronics

First, carefully insert the buttons into their holes on the front face. Make sure they fit well - this is your last chance to fix anything!

Once you are happy that everything fits, you have two choices: you can attach the electronics to the two side faces that directly touch the front face, or you can attach all the electronics to the front face (I did this). There is no better way; they are just two equally valid means to the same end.

If you are attaching the electronics to the side faces, the first step is to cut out and attach those two faces. However, don't fibreglass them yet.
Take the electronics and try to place it into the front face. If you've done it right, the cardboard backing on the electronics should either fit snug against the side faces (without having to bend the paper, that is), or hit them. If they hit, trim them. Try again; trim again if necessary.
When you have a snug fit, heat up the glue gun and hot-glue the cardboard backing to the side faces.

The alternative method is to place the electronics in the position you want them to end up, then simply squirt hot glue over the gap between the circuit board and the fibreglass face. Note that I said to squirt glue over the hole, not in it. You don't want any buttons glued in position! After this, the side faces can be attached as per normal.

The last job is to push the LCD up against its hole with your finger, and glue it in place. I find it easiest to use transparent glue, because then I can glue it from the front.

Step 11: Attach the Speaker and Ringer

My first idea (and the one I used) was to place the speaker tight against its hole, and the ringer down at the bottom end of the banana. The plan was to drill a hole through the fibreglass, once it had set, so that the ring could be heard. The advantage of this was that a speaker on the end of the banana should be heard whether the banana was right way up or not. This was fine - until I realized that if I drilled a hole, I would most likely hit and destroy the ringer! Of course, the ring can still be heard, but not as loud as I would like.

Silly me.

So, instead of being silly like me, this is what I advise. Glue the main speaker over its hole like normal, but also drill another hole (or two), further up towards the stalk. Glue the ringer there.

Now is a good time to test the handset. Plug in the base and ring up your grandma. Have a good chat, then tell her you're ringing from a banana. The wonders of technology these days . . .

Step 12: Making the Charger Contacts and Closing the Handset

Print, cut out, and glue together the three back faces. However, do not glue them to the front three faces. Instead, resin and fibreglass the back face only. Wait for it to dry. Sand.

Now you make the charger contacts. First, take a good look at the first picture - in this case one picture truely is worth a thousand words. Then get a drill and a 1mm drill bit, and drill four holes in the places indicated on the first picture below. Get a length of wire, and thread each end through one hole, so that the wire is running along the edge of the face, like in the picture below. Do the same with another piece of wire and the other two holes.
Next, take the insulated wired that you soldered to the contact points on the circuit board, and solder one insulated wire to each of the wires you just threaded through the back face. See the second picture for details.

Finally, glue the two sides of the banana together, then resin, fiberglass, sand, and paint. Excepting the ends, you've finished the handset!

Step 13: Extract the Circuit Board From the Base

Now that you're finished the handset (for now), the next step is to get the circuit board out of the base, so we can put it in the bunch of bananas.
The first step is to turn the base upside-down and take out the two screws in the back corners. Switch to a flat screwdriver, and pop out the three tabs that are evenly spaced along the front join. With a little bit of wiggling, the two halves should now pop apart. Once you have cut the two wires leading to the charger contacts (taking note of which one leads to which side), you can place the base in a static free bag (if you don't have one, ask your computer geek friend - most computer parts come in them), and get on with the next step.

Step 14: Making the Cavity

The next step is to cut holes in three of the empty bananas so that, when they're placed together, there will be a cavity under them for hiding the base in. Also, the holes are necessary for making the other half of the charger contacts.
I will leave the exact positions and sizes of these holes up to your own judgement. Honestly, the actual dimensions are not very important, just as long as the circuit board will fit in.
If you are using a different phone (and hence a different base), simply cut a larger or smaller hole for it.
Also, don't forget to test the cavity's size when the power and telephone cords are plugged into the board - they will have to be in the final product, so get it correct now.

I have to apologise about the picture below - the picture I wanted to use got corrupted while still on the camera, so this is second-best. Hopefully you can see what the cavity should look like. And no, you are not meant to have the circuit board glued in yet.
Also, notice that in this photo I have already covered up the third hole. No, you're not meant to do that at all - just cover the holes all at once with one piece of paper.

Step 15: Making the Contacts for Charging

First, figure out which two of the three bananas are going to be the ones with charging contacts in them. As shown by the picture below, it will be the centre one and the rightmost one.
So, when you have the two bananas, go right ahead and drill the holes for the wire to go through. A 1mm drill bit worked fine for me, but it really depends on the size of your wire. No, I'm not going to tell you where to drill your holes. The precise location is not important, and you can figure out roughly where they should go without me telling you.
Next, get a length of wire (30cm? you can always trim it later) and thread it through, so that it looks like the picture below.

The next step is to glue the three bananas together. Trust me; it's best to do it now, even though we're halfway through making the charger contacts.
To glue them together, first balance them upside down in the right configuration - making sure the centre banana isn't on the edge, or vice versa. I tell you to glue them together when upside down, because then it means that the blob of glue is more hidden. However, if the bananas just won't balance, then feel free to glue them while they are right-side-up.
Next, heat up the hot glue gun and deposit a blob on each of the two points where two bananas connect. Nice and simple.

Now, we need to finish the contacts. Place the base circuit board into the cavity so that the cords are coming out at the back of the banana (i.e. towards the end where the bunch of bananas angle together). The black insulated wire (negative) from the circuit board should be soldered to the centre banana's contact wire, and the red wire to the outer banana's wire.
Now is a good time to test if the banana works. We already know the handset works, but try it again. More importantly, see if the handset will charge when placed on the contacts.
If it does, then glue in the base circuit board with hot glue, and celebrate - you now have the essential components of the phone in place!

Step 16: Hiding the Electronics

We have a working banana, but there's one problem - we can still see the electronics. What kind of a shoddy, man-made banana would be left with the electronics exposed? Not us; we are building an aesthetically pleasing bunch of real bananas here!
The first step is to cover the gaping cavity we just finished making. Get a piece of paper large enough to reach across all three bananas, trim it to size, and glue it on. You should end up with something like the picture below, except it will look even better when finished.
Next, take two roughly triangular pieces of paper and cut them so they nicely cover the gaps between the three bananas (see picture). Their wide end should extend at least as far as the large bottom piece of paper does. As you can see, mine go a bit further, but that is quite fine. When you are happy with their shape, glue them on. I find PVA glue good for this, because as it dries clear.
The next two holes to cover are those between the large bottom piece of paper and the two triangular pieces. I don't need to tell you how to do that - just glue them in.
If you want, you can also put a piece of paper over the back end of the bunch, where the cords come out. I chose not to, both because I was running out of time before Christmas and because I expected most people wouldn't look behind there. However, if you plan to display your bunch of bananas somewhere where the back may be seen, it would be a good idea to cover it.

Step 17: Stalks and Ends

Your bananas look good, but all five still have gaping holes at each end. We need to fix that!
The bottom end, near your mouth, is easy. A simple piece of paper can be cut to shape and glued across the ends. Alternatively, if you want more rounded ends, cover the hole with successive thin strips of paper(I did this on the handset but didn't like it). Each piece of paper should start on one side, go across the centre of the hole, them be glued to the side opposite where it started from.
Whichever technique you choose to use, make sure you apply lots of resin. However, as the ends aren't structural, fibreglass is not needed (but feel free to use it if you want).

Making the stalk is a bit harder. In fact, I can't accept responsibility (or blame) for this part of the project - because I was running out of time before Christmas, my brother offered to make the stalks. Thanks, Cameron!
As far as I understand, the first step is to make 'paddles'. Each of these is essentially equivalent to one face of the banana. Think of them like wooden spoons - the paddles are wide for a short distance at the base (just long enough for us to stick them to the actual banana), then they angle in, and finally they are thin for most of their length. For a visual explanation of their shape, see the second image below.
Anyway, six of these paddles are taped together (their wide bases should be overlapping, but their thin tops should be just touching) around a pen, in such a way that the thin strips form a stalk. Next, the wide ends of the paddles are bent out and attached to the banana, one to each face. However, this usually leaves gaps between paddles. The easiest way (though not necessarily the best way) to fix this is to get little strips of tape and cover the gaps with them.
Resin the stalks, then paint them solid yellow. Fibreglass can also be used (especially on the handset's stalk) because the stalks are a lot more fragile that the ends. But again, it doesn't matter too much.
At the same time you are and fibreglassing the stalks and ends, don't forget to also fibreglass and paint the paper you glued on in the last step.

Step 18: Painting and Final Assembly

By now, your banana should look nice, and be functionally complete. However, it most likely just won't look finished. The next step is to paint the ends brown so they look more convincing.
I found that the exact shade of brown wasn't so important - in fact, my stalks are a different shade of brown to my bottom ends. It really depends on your taste.

The bottom ends are easy enough to do. First, paint the end a solid block of color (For four of my bananas, I could just paint the end face). Next, paint a little way up the joins between two faces, then paint a line that curves down across the face to the end, then curves up again to the next edge. It is very hard to explain, so perhaps a better idea would be to investigate the pictures below.
Alternatively, feel free to paint the ends your own way. If you have a better idea, go for it!

Believe it or not, there is even less of a defined technique for painting the stalks. Dab a bit of brown paint on until it looks good. If you don't like it, just paint over with yellow and start again. Also, don't forget to use a hair dryer to speed it up a bit.
Once the ends are done, it would be a good idea to check over the bananas for any areas that need touching up. I found that some areas were not as thick as I thought, and needed another coat of paint. You might also want to paint around the drill-holes for the charging contacts.
When you've done that . . . you are still not finished. The final job is to glue the fourth empty banana onto the base. It should be positioned so that it is sitting on both the center banana and the left-most banana. Hot glue works well for this.

Step 19: Final Words

Now you finally have what you've always wanted - a true DIY banana telephone. Try it out, show it off, bask in the glory, think about all the hard work you put into it . . . and then give it away for free.

It is Christmas, after all.

Step 20: Credits

I would love to be able to say that this project is totally original and has never been done before, but that is just not true. I have to acknowledge a heavy debt of inspiration to the original banana-phone, found here. Great job, Scottredd!
Another person I owe thanks to is Dr.Professor_Jake_Biggs, for his excellent article on making a Master Chief costume - it taught me heaps about fibreglassing.
And, of course, thanks to mum, dad, cristelle, and cameron for putting up with the mess and strong smells while I was making this project!
Finally, a thanks in advance to all who make this bananaphone themselves or, even better, improve on it.