Introduction: Self-Sailing Yacht

About: I have always loved the feeling of finishing the construction of an object and if I don't have something I need or want I usually give it a go to build it from what I have. Usually though, I look at a boring o…

This yacht model is fun both to make and to use and it is made almost entirely of rubbish. It also has a self-correcting mechanism in the form of a sail-operated rudder. I made and corrected many mistakes while building it but even so, it only took me about 5 hours to make.

A problem faced by uncontrolled yachts is that the sail will blow to one side, so this side catches wind and propels the boat only from that side so the boat will go in circles. To fix this problem, a simple mechanism is used to control the rudder to the same side as that sail so that it causes the boat to rotate towards that side while the sail pulls the boat the other way, thus canceling the uneven force out and allowing the boat to travel in a straighter line. This boat will however, when the wind stops, rotate from the rudder and not the sail. So the boat rotates and when the wind blows again it will travel the other way in a straight line, as it did before but in the opposite  direction. This "Zig-Zag" motion is what allows yachts (and other triangular-sailed boats) to sail into the wind.

To make this yacht, you will need:
- Polystyrene packaging foam (White bubbly kind)
- Kebab sticks (X2)
- Wire (I used wire as well as "un-bent" paperclips)
- A plastic packet
- Toothpicks (X2)
- Glue
- A pen ink-tube from an empty pen
- A fishing weight (or another heavy object of the correct size)
- Soft drink/Beer can 
- Beads (X3)
- Thread/string
-  Glue (First test that the glue you use will not dissolve the polystyrene foam. White, cold glue {wood glue} worked for mine)
- Scissors
- Sharp knife
- Pliers

Step 1: The Hull

For this model I made the hull from foam because it takes very little time, is extremely buoyant, and is cheap because it is free. Using wood to make a framework structure and adding wood or fibreglass as a cover would work well too, but it will cost you more time and money.

On my model, the foam I had was thin so I used 2 layers of it and glued them together. You do not need to do this if your foam is the correct thickness already.

I have added a plan for reference, also for use as a template for the parts. Re-size it to however big you want your boat to be before printing.

There are 2 drawings in the plan for the 2 layers of foam. (If you are only using one layer of thick foam then the best thing I can tell you to do is use the pictures for reference.) Trace the 2 templates onto the foam, then cut them out only on the outline. Bevel the edges of the 2 layers so that the smaller one makes a "V" shape while the larger makes a "U" shape. In the plan, the templates/drawings are from underneath so you can see where the two ends of the bevels should be, from the top(outside line) to the bottom(inside line). This sounds complicated but it is very simple to do, just draw the smaller outline from the plan onto the foam and cut from the one outline to the other (Eg. blue line to red line) and your shaping of the layers should be done.

Poke 2 toothpicks through the two layers but first make sure that they are aligned and symmetrical. Further carve and trim the foam a little bit so that the top and bottom layer meet up nicely. [See the last 2 pictures in this step]

Step 2: Mast

To fit the mast, just poke a kebab stick vertically through the hull, in the place indicated on the plans as a green circle. About a quarter of the length of the whole thing must stick out underneath the hull so that ballast can be added later on. Add glue around the top and bottom of where it leaves the hull, to stop it from sliding up or down.

Add the Bowsprit to the front of the hull. It is another part of a kebab stick and it is stuck into the foam as shown in picture 3. In the plan, it is indicated with green.

Make and add the swinging Boom. For this part, Cut part of another kebab stick off (size indicated in the plan) and add a form of hinge to one end. I first used the same form of hinge as was used in my ornithopters, but then that broke off from adhesion problems so I tried using a pen tube, which broke too. I then resorted to using paperclips which ended up working well enough. [Pictures 4 to 7 show the first attempt] 

[Pictures 8 to 11 show the final attempt] The last (working) try to get the boom to hinge was done with 2 paperclips. My paperclips had insulation on them which I removed. Start by straightening the paperclips with pliers. Then wind one around the "base" end of the boom. Leave a bit of wire sticking out downward at this end [Picture 8].
Wind another paperclip (or piece of wire) around the mast and make sure that the wire leaves enough room at the back of the mast for the wire sticking off the boom to fit into. Slide the wire sticking off the boom into this gap and make sure that the boom can swing from side so side easily. Then bend the end of this wire back and to the boom again so that the boom cannot fall off of the mast. Test the swinging movement again before continuing.

Step 3: Rudder Installation

Clip off the tops of the toothpicks, they will help to hold the hull together, but the parts sticking out are not needed.

Make a hole where shown in the plan and widen it so that it is just a little bit smaller than the pen ink-tube you will be using. This hole must go through to the bottom of the hull. Clip a part off of the empty ink tube the same length as the height of the hull. Slide this part of the tube into the hole you just made.

Bend another paperclip (or piece of wire) into the shape shown in the plan as a brown line. Don't bend the bottom-most bend yet though.
Slide 2 beads onto the long part of the wire and then drop the wire through the hull with the bent part on top [See picture 3].
Slide another bead onto this wire, only this time underneath the hull. Bend the last bend into the wire now.

Cut a rectangular piece of metal from a drink-can of the size shown in the plan as a grey rectangle. Fold this rectangle in half along the dashed line also shown in the plan. Round the bottom edges and trim as shown in the side-view of the plan. Slide this piece of metal onto the wire and glue it in place. Squeeze the rudder metal around the wire part. Check that the rudder can swing round the pen tube.

Step 4: Keel / Ballast

Without a keel or ballast, this boat would simply capsize if wind blew its sails. The purpose of the ballast on a boat is to keep the centre of gravity low down so that it has a resistance to rolling to one side and actively stabilize the boat.

I tried adding ballast in the form of wrapping wire around the bottom of the mast pole but I found that it was not heavy enough after some testing so I had to add some more weight. I did this with a fishing sinker and some more wire. To do it like I did, wrap some wire around the bottom part of the mast pole and thread this wire through the eye of a lead fishing sinker and continue to wrap wire around the two to bind them together.

To test if the ballast is heavy enough, put the yacht in water and tip the mast to an angle of about 30 degrees and let go. If it pops straight back upright, the ballast is heavy enough.

Step 5: Rigging and Rudder Limits

The first picture in this step is chronologically last, I moved it to first so that I could label the parts.

The second picture shows how to attach the rigging to the mast, boom and bowsprit. Just put a drop of glue on the end of the stick and wind thread (or string) around it.

Most of the rigging is done with a single thread, on my model this thread was about 35 cm long.

Start at the bowsprit. Attach the thread as described above and pull the long end up to the top of the mast. Attach it here in the same way and make sure that it is taught.
Bring the long end down to the back end of the boom and attach it there. Leave about 5 cm (2 inches) of thread and then tie the end of the thread off on the hook part of the rudder wire. The slack in this line will allow the sail to swing and correct the rudder while accelerating the boat.

Bend a paperclip in half [Picture 5] and spike it through the hull where shown in the plan, just in front of the mast. Bend the bottom ends of the wire outward to keep the wire from being pulled out. The hoop above the deck will be used for rigging.

Clip a paperclip in half. With each half, spike it through the hull in the places shown and bend the bottom end outward and then upward again. Then push it back up into the hull so that it hooks itself in place. This will be a rudder limit, its purpose is to stop the rudder from spinning all the way around. The Rudder should be now able to rotate about 70 degrees left and right, but no further.

As shown in the last picture, tie and glue one end of another thread onto the hoop on the deck. Bring it up to where the other thread is glued on the mast, but do not glue it there as you did with the first thread. Leave about 2.5 cm (1 inch) of thread as slack before tying off and gluing the thread to the top. It should look like the thread in the first picture.

Step 6: Sails

Trace the two sails from the plan onto a plastic packet but make them a little bit bigger so that you can fold the edges of the sails around the rigging, boom and mast. Cut both sails out of the packet.

Start with the Mainsail. On one side of the mast and boom (I chose the starboard side), add some glue. DO NOT get any glue into the hinge part. Place the plastic sail over the glued side and move your fingers over the packet where there is glue underneath so that good contact is made. Wrap the straight edges of the sail around the mast and the boom to make it stronger and neater.

For the jib, put glue along the 2 longer edges of the sail and place the front edge onto the Forestay. Pull on the bottom of the thread behind the Forestay to make it taught, then let the back edge of the jib (and the glue on it) touch this thread. The part touching the sail must be straight, but the part of the thread under the sail must have slack in it. Wrap the forward-most edge of the sail around the forestay and the back-most edge around the back string.

Both the Jib and the Mainsail should be able to move left and right if you blow at the boat from either side. This type of boat works when the wind hits it side-on and this is what enables it to sail into the wind unlike a square-sailed boat.

This boat is lots of fun to make and use and it is very satisfying to see it sail. I do, however suggest keeping a line attached to it so that you can get it back if it sails too far away. Bon Voyage!

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