The Motorboat Book: Build & Launch 20 Jet Boats, Paddle-Wheelers, Electric Submarines & More (Science in Motion)

The Motorboat Book: Build & Launch 20 Jet Boats, Paddle-Wheelers, Electric Submarines & More (Science in Motion)

by Ed Sobey

ISBN: 9781613744475

Publisher Chicago Review Press

Published in Children's Books/Arts & Music

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Sample Chapter


Start with an Ocean

If you are going to make these models you will need a place to test them and show them off. You need an ocean!

If you have a swimming pool or pond available, you can use either, provided you first give it a suitable name. Since Atlantic, Pacific, and Indian are already taken, come up with a new name for your ocean.

If a body aquatic isn't available, build your own. Here are several size options.

Large Oceans

How big would you like to make your ocean? The limitations are the size of level ground you have and the depth of the ocean you need.

For most purposes I find that a good size for an outdoor ocean is 4 feet by 8 feet. Conveniently, hardware stores sell waterproof tarps and sheets of plastic large enough for an ocean of this size. They also carry larger-size materials, or you can duct tape several tarps together if you really need to.

A shallow ocean requires less support and is a safer option than a deeper ocean. As water depth increases, the pressure pushing your ocean apart will increase and require stronger construction. An ocean with a depth of 4 to 6 inches works well, but you may need more water if your models hit bottom.

Adult supervision required


4 folding tables or similar flat surfaces
Waterproof tarp with grommets, at least 6 feet by 10 feet (larger would be
Nylon string
Hose and water supply
3 wooden boards, 1 inch by 8 inches and 8 feet long (optional)
Adult helper (for optional steps)
Saw (optional)
4 hinges with removable pins or other connectors (optional)
Grid wall, 2 feet by 8 feet (optional)
Plastic cable ties (optional)

Build It

1. Any four vertical surfaces that won't move will support your ocean. For a shallow ocean, four folding tables work well. Lay the tables on edge in a square or rectangle, with the legs extended to hold them up.

2. Lay a waterproof tarp over the sides of the tables and secure it with nylon string through its grommets. Then use the hose to fill the tarp with no more than 4 inches of water. This model takes seconds to set up but will support only a shallow ocean. As the number of people using this ocean increases, the number of random bumps increases — think earthquakes and tsunamis — and soon the ocean will fall apart.

3. A more user-friendly model uses wood planks, set on edge, to form the four sea cliffs surrounding the ocean waters. Get three 8-foot-long, 1-inch-by-8-inch boards, and ask an adult to saw one board in half to create two shorter end pieces.

4. There are many ways to hold the boards together. One is to install hinges that have removable pins at the corners where the boards meet. To take down the ocean, remove the pin from the hinge at one of the short ends and let the water swirl out — hopefully into a drain or thirsty grass. Or you can take a trip through a hardware store to find other ideas of how to fasten the boards together. Screws or nails will work if you won't need to take the ocean apart for a while, and a clever builder could devise a system of pegs (nails or dowels) that fit into holes in adjoining boards to hold them in place. Once it's assembled, use the hose to fill your ocean with water — just enough to float your boats.

5. A radically different approach is to use grid wall instead of wood boards. Grid wall is the display rack material used in many retail stores; see appendix A (page 217) for information on where to obtain it. An ideal size for grid wall is 2 feet wide by 8 feet long. The grid wall shown below is 4 feet wide instead, which makes it awkward to put boats into the ocean and retrieve them. The beauty of grid wall is that it sets up in seconds: one person holds two adjoining pieces on edge while another secures them with plastic cable ties. When all four pieces are secured, drape the tarp over the edges and make sure that it lies flat on the ground. Then secure the tarp grommets with more plastic cable ties, and fill the tarp with water. Don't put in more water than you need; as water fills this ocean, it presses outward and will eventually break the cable ties, creating a tsunami. To drain the ocean, cut the cable ties on one of the ends, let the grid wall fall to the ground, and the water will race out.


How many oceans are there? Not counting the one you are building, there are three: the Atlantic, Pacific, and Indian. All three are connected to each other, but the connections are restricted by land masses.

Although the waters mix with each other, each ocean's water has distinctive properties. Some people lump all three oceans into one World Ocean, and other people will separate the three oceans and add the Arctic Ocean or Southern Ocean or both. So you could answer the question of how many oceans exist by saying the earth has one, three, four, or five oceans.

Whatever number you prefer, the water in those oceans covers more than 70 percent of the surface of this planet and makes this planet livable. We should call it Planet Ocean, not Planet Earth.

Smaller Oceans

If you don't need all the space that a large ocean offers, you can test models in plastic storage containers sold at household stores.


Plastic storage container at least 3 feet long and 6 inches deep
Water supply

Build It

This photo shows a container that is 3 feet long, 18 inches wide, and 6 inches deep. This type of container is large enough to test that a boat works, but not large enough to see how far or how fast it will go. Clear plastic allows you to peer in from the side to see what is going on underwater. This size is somewhat manageable in that two people can pick up a partially full ocean and carry it slowly to a sink to empty it. It requires only a few buckets of water to fill.

Tiny Seas

For some projects a one- or two-liter bottle provides enough water. See chapter 6 (page 195) for small-sea science projects.


Build a Hull

To build a boat, you need a hull, the body of your boat. It's what keeps the water out and holds everything else in. It's best to make the hull out of inexpensive and free materials so that any mistakes and do-overs don't break the bank, and you can make lots of boats to try different ideas, technologies, and designs.

Free and Easy Hulls

Collect paper milk and juice containers in the quart and half-gallon size. Using them for motorboats merely interrupts their journey from a refrigerator to the recycling center, and briefly extends their useful life. But one note of caution: if you ask people to save these containers for you, ask them to also rinse them out before setting them aside. The smell of an unwashed milk carton can make a boatbuilder seasick.

Adult supervision required


Adult helper
Milk or juice cartons made of coated paper

Build It

1. Ask an adult to help you cut the cartons in half, lengthwise. Cutting the ridge at the top of each carton requires a pocketknife, but cutting the rest of the carton can be done with sturdy scissors.

2. The result of lengthwise cutting one carton is two flat-bottom boats that are ready to be propelled. The ridge at the top of the carton becomes the stem, or the front most part of the boat.

3. Of course, if one hull is good, two hulls are better! Craft sticks and dowels hold the two hulls of this catamaran together. The motor is mounted on the braces between the hulls.

4. To get a V-shaped hull instead of a flat-bottom hull, cut a carton along two opposing edges. These hulls will require ballast (something to weigh them down, such as stones) to keep them floating upright.

Ship's Log

In the past, wooden sailing ships carried tons of ballast stones in their bilges, or the lowest spaces inside ships. The ballast stones provided stability, especially when a ship was not carrying cargo. One way to identify an old shipwreck on the bottom of the sea is by recognizing the pile of rocks that were used as the ballast.

Modern ships don't use ballast stones, but they do pump water into tanks to weigh down the ship when it is not carrying cargo.

Aluminum Hulls

Aluminum is a great material to use for building hulls. It comes in a variety of thicknesses, is easy to cut, and is strong. Here are two wildly different approaches to using aluminum.

Two-Minute Boats

A fun challenge for anyone is to craft a boat using aluminum foil and test it to see how much weight it will hold before sinking. Galvanized nails, pennies, or metal washers can be the weights. The advantage of having uniform weights is that you count how many pieces you are able to put in your boat before it sinks to compare with the total number of pieces needed to sink other boat designs.


Aluminum foil
Uniform weights: 1 pound or more of identical small objects (e.g., nails,
washers, or pennies)

Build It

1. Tear off a piece of aluminum foil that is as long as it is wide. Decide if you should make a barge, canoe, or ship. Fold the sides to make your model and give it a test.

2. Add uniform weights to your model one at a time, counting as you add each one. Stop counting when your boat sinks or otherwise touches the bottom of the ocean.

3. For a competition, give everyone the same size piece of foil and no other materials. Each player should bend, fold, and shape the aluminum foil to make a boat. Once all the boats are finished, players should place them in water and start loading them with the uniform weights, counting as they go. Everyone will want a second chance and a new piece of foil to test their new ideas on what makes an ideal shape.


Why does a boat sink? Most boats and ships are made of materials that, if compressed into a ball, would sink quickly. The materials a ship is made of are heavier than an equal volume of water. But the ship or boat floats because it is a hole in the ocean filled with air, where the sides of the hole are the ship's hull. The hull keeps water out.

If you replace the air inside the hole with water, which is about a thousand times denser than air, the ship sinks. Since the heavy materials in the ship weigh more per volume than water and there is nothing light inside to buoy the ship up, down she goes. At sea, this is a bad day.

Extruded Aluminum Boat Hulls

A sturdier hull can be made from a disposable aluminum roasting pan. This isn't quick and easy, but it is fun and turns out very nice boat hulls. These hulls are best used with small electric motors or steam putt-putt engines.

The process is to cut a mold out of wood and to squeeze (or extrude) the aluminum into the mold. Once you make the mold, you can create as many identical boats as you want.

Adult supervision required


Adult helper
Wooden board, 1 inch by 4 inches and at least 2 feet long
Wood saw
Coping saw
Cereal box (empty)
Large C-clamp
Wood glue
4 small C-clamps
Aluminum roasting pan (disposable)

Build It

1. Ask an adult to cut a 6-inch length of a 1-inch-by-4-inch board using a wood saw. Your boat's hull will be smaller than these dimensions, so you will end up with a form (the size and shape of your finished boat) and mold (a cavity) you can push the form into.

2. Draw the shape of the hull that you want on the inside of an empty cereal box, and then draw a straight line through that shape, from the stem to the middle of the stern, the back end of the boat. Cut out the hull shape, then cut along the center line as well so you have two half-hull shapes. From these two pieces of cardboard, pick the one you like best; you'll use it to draw the full hull shape on the wood.

3. Measure the center of the two short sides of the wood your adult helper cut so you can draw a center line. Align the cereal box shape along the center line, making sure that you are leaving enough wood (more than ¼ inch) all the way around the shape so the mold won't break. Trace the outer edge of the cardboard form. Flip the cardboard over and trace it (now upside down) on the other side.

4. Clamp the wood firmly to a workbench and ask your adult helper to cut out the shape with the coping saw. This inexpensive saw allows the user to turn corners easily. Your helper should keep the blade vertical while he or she cuts, starting from the outer edge of the wood and sawing into the hull shape you have drawn, following the line all the way around. To make the cutting easier at the far end, he or she can cut the mold through to the end of the block of wood. It doesn't matter if the mold ends up in two parts. When your helper has cut around the shape you have drawn, you will have a piece of wood in the shape you designed — the plug (or form) and a mold that has either one or two pieces.

5. Lay the one or two pieces of the mold on top of another 6-inch-long piece of the 1-inch-by-4-inch board. Glue the mold to the new piece of wood. Use wood glue and four small C-clamps to hold it while it dries.

6. While the glue is drying, use scissors to cut a piece of aluminum from a disposable roasting pan. The piece must to be larger than the plug since you need additional material to form the sides of the boat, not just the bottom.

7. After the glue has dried, place the piece of aluminum on top of the mold. Put the plug on top of the aluminum so it is aligned with the shape of the mold and can fit into it. Use a large C-clamp to force the plug into the mold. If the plug isn't going in evenly, release the clamp and reposition it to the high spot — where the wood sticks up the highest — and then clamp down again.

8. When the clamp has pushed the plug down evenly into the mold, unscrew the clamp and remove the hull. Trim the hull with scissors, but to eliminate sharp edges, leave some excess material as you trim. Then fold this excess inside the boat to leave a folded edge around the top of the hull.

Other Hull Materials

Many other materials make good boat hulls. You can use styrene meat trays, which you can purchase in bulk at restaurant supply stores. If you only need a few, a friendly butcher at the grocery store will likely give them to you, or you can wash and recycle trays that your family might have left over from a meal.

Meat trays are easy to cut with scissors and float well. On the negative side, they don't have much free board (height from the water level to the top of the edge of the boat), they aren't easy to attach things to, and the styrene doesn't have much strength or ability to bend. For many projects, you will use a hot glue gun, and this will melt the styrene, making it more difficult to hold pieces together.

Styrene and coated paper plates work for some models. The model shown below is a gravity boat, and the large symmetrical surface of a disposable plate works especially well as it spreads the weight evenly. The symmetrical shape, however, is difficult to steer and is slow moving through the water.

Other materials also work. Rubber ducks are fun but are difficult to cut and more expensive. For most "messing around" projects, less expensive materials are more desirable.


Ship and boat hulls are made of a wide variety of materials. We think most often of boats made of wood and ships of steel. But fiberglass, aluminum, and plastic are also used in boats, and concrete and ferro-cement are used in ships.


Propel That Boat

How many ways can you think of to propel your boat across the ocean? Lots! As you build these models you'll think of variations to these designs or even brand-new ones. That's part of the fun of messing around with boats.


When people think of making a sailboat, most picture square sails rather than the fore and aft sails more commonly used today. (Fore means that something is toward the forward, or front, part of a ship or boat, while aft means it's toward the after, or back, part.) Scraps of fabric work well for fore and aft sails. For square sails, plastic bags or even sheets of paper will do.

Adult supervision required


Milk carton hull (page 10) plus additional pieces of milk carton
Dowel, 6 inches long, ¼-inch diameter
Hot glue gun
String (optional)
Plastic bag, paper, index cards, or cloth
Battery-powered fan

Build It

1. Start with the quick and easy hull cut out of a paper milk or juice carton.

2. Attach a dowel mast to the hull. The biggest challenge is how to hold a mast upright. Simply gluing the bottom of the mast to the hull won't provide enough strength to withstand a breeze, let alone a gale. However, you can stabilize the mast by either tying strings (sailors call these stays and shrouds depending on where they attach to the boat) or using pieces cut from a milk carton. The first way is difficult and requires nimble fingers and patience. Bracing the mast with a piece of milk carton that is glued to the side of the hull is fast and easy.

3. A plastic bag, as shown at the top of the next page, is an obvious material for sails. So is paper or an index card.

Excerpted from "The Motorboat Book: Build & Launch 20 Jet Boats, Paddle-Wheelers, Electric Submarines & More (Science in Motion)" by Ed Sobey. Copyright © 2013 by Ed Sobey. Excerpted by permission. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher. Excerpts are provided solely for the personal use of visitors to this web site.
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