In this engineering science fair project, you will develop a fin (bilge keel) design that is best at keeping a boat from rolling back and forth.
Even though rolling is a perfectly natural occurrence, it can be pretty tough on people who live and work on ships. A bilge keel is usually a simple piece of steel on the bottom of a ship that is aligned with the direction that the water passes over the hull (see Figure 2, below, for a diagram of bilge keels and other types of keels). In this science fair project, you will learn how different sizes of bilge keels work and how effective they are at reducing the rolling motion of a ship.
You might need an adult's help to understand some of the information in the following books. This book offers a scientific explanation of rolling motion and how bilge keels stop ships from rocking, on pages 269-270. A good explanation of what a bilge keel is and how it works can be found in this book, on pages 116-117. Another good explanation of bilge keels and rolling motion can be found in this book, on pages 245-255. Paint the inside of the bottom of the boat with a thick layer of rubber cement and set about 50-60 marbles in it. Cement the wooden dowel vertically into your empty patch so that it sticks straight up out of the rectangular hole. Using a permanent marker, draw a line near the top of the bottle, from the front of the boat to the back, on either the right or left side. An oscillation is when the dowel rocks back and forth; for instance, if you tilted the boat to the right and released it, the boat would roll and the dowel would tilt to the left and then back to the right, completing one full oscillation. The oscillations will get smaller and smaller, until the boat finally stops, so make sure you count all of them.
Cut the other 2-L bottle completely in half, lengthwise (from the neck to the bottom), using the razor blade or knife. Now attach each bilge keel to the sides of the boat using a few pieces of the padded double-sided tape. Repeat steps 5-6 from the section above, Building the Boat and Performing the Initial Test, so you have a total of three trials with the bilge keels attached, recording all data in your lab notebook. Now, trim 1 cm off the bottom (the part sticking out) of each bilge keel so they each extend 4 cm out from the boat. Continue trimming the bilge keels in increments of 1 cm and test each new length three times. You should have at least three time values and three oscillation totals for each bilge keel length, including when the boat did not have keels. Make a bar graph where the x-axis is Bilge Keel Length (including "0" for the trial without bilge keels) and the y-axis is Average Number of Oscillations. Not all bilge keels are the same—some are shorter or shaped differently (see Figure 5, below). Instead of using only one permanent marker line, try using two or three and test each bilge keel design at each line.
Try using something else besides marbles in the bottom of the boat, such as pouring plaster of paris in there and letting it settle and dry.
Compared to a typical science class, please tell us how much you learned doing this project. The Ask an Expert Forum is intended to be a place where students can go to find answers to science questions that they have been unable to find using other resources. Water covers more than 70 percent of Earth's surface, and marine architects design vessels that allow humans and their cargo to cross through or under those waters safely and efficiently.
Ship and boat captains have the important job of commanding ships and boats through domestic and deep-sea waterways, so that passengers and cargo arrive safely. You may print and distribute up to 200 copies of this document annually, at no charge, for personal and classroom educational use.
Reproduction of material from this website without written permission is strictly prohibited. August 21, 2014 by Jackie Pin5K Share99 Tweet EmailRow, row, row your boat, and see if you can make it float!
What child doesn’t love designing, decorating and trying to float a boat a that they’ve made from scratch?
A childhood just isn’t complete without making a simple but classic paper boat craft. This cardboard sailboat can be made in miniature or large enough for a little one to play in.
A follow up to 'Sink or Float', the activity has children figuring out that shapes can determine whether something sinks or floats.
The author was an ardent boat-builder, and he well remembers how he combed the Children’s Department of the local library in search of a book that would tell him something about boats, and especially for information regarding the construction of models. Building a model boat would be a fantastic project for 4-H, Boy Scouts, or another hobby club. This book starts with the basics of boating- including buoyancy, center of gravity, and other physics.
Full of useful illustrations and instructions on how to make hulls, steam engines, yachts, and much more. Waves can travel in any direction, depending on a lot of factors, like the wind direction, tides, and ocean currents.

Some people get very seasick due to rolling, and some equipment can be affected or even stop working due to roll.
One of the simplest and most ingenious ways is a feature called a bilge keel, shown in Figure 1.
By aligning it this way, the bilge keel doesn't slow the ship down very much when it is traveling straight ahead. Try skinny or fat, long or short, straight, curved, or serrated bilge keels, and see what works best. Although it uses a picture of an airplane, the movement is the same for a boat—imagine it rocking back and forth like the plane.
It's not as smart as you are, and it may occasionally give humorous, ridiculous, or even annoying results! Cut a rectangular hole in one of the bottles, with the longest edges running from the neck to the base—this will be the top of the boat. You might want to cement some marbles around it to hold it in place and keep it straight up.
Start the stopwatch when you let go of the boat, and stop it when it is no longer oscillating. The ripples will bounce off the tub walls and go back to the boat, so make sure you don't count when those ripples rock the boat some more!
Bilge keels extend straight out from the hull at a 90-degree angle (see Figures 1 and 2 in the Introduction). Check the keels again and bend the bottoms of the keels until they're both pointing away from the boat. Repeat steps 5-6 from Building the Boat and Performing the Initial Test again with this new length and record your data in your lab notebook. If you want to combine the graphs into one, divide each bilge keel's number of oscillations by time, and call that number Oscillations per Second. This can easily be done by placing the boat in a pool where others are swimming some distance away. If you have specific questions about your science fair project or science fair, our team of volunteer scientists can help. Some of their watercraft designs are enormous, like merchant ships, which carry huge loads of oil, cars, food, clothing, toys, and other goods, across thousands of miles of open waters. To do this, they need knowledge of the mechanical and electrical workings of ships, navigation, signaling, national and international legal rules in waterways, as well as strong leadership skills, since they supervise the work of all other crew members. A self-proclaimed glitterphobe, she specializes in easy, affordable crafts and activities for toddlers and preschoolers.
For these reasons and many others, it's important for engineers to design bilge keels (or fins) to keep boats from rolling back and forth. Ships, on the other hand, need to travel in straight lines to get where they are going quickly.
Roll also makes simple tasks, like eating, rather difficult, and it can make hard chores, like landing a helicopter on a ship, almost impossible.
But when the ship begins to roll due to wind and waves, the bilge keels act like a plow through the water.
Think about construction and other reasons why bilge keels are a certain size, and investigate what other things ship designers or naval architects need to think about when designing a good bilge keel.
This line will help you figure out how much you need to roll the boat—it will represent where you want the water line to be when you tilt it before letting it oscillate. You might want to have a helper assist you with the stopwatch since you will be tilting the boat. Finding the average of multiple trials is more accurate than using only one trial, because what if you made a mistake in that one trial? You might have difficulty with the neck and the bottom, so go ahead and cut those off first, as you won't need those parts. If you have trouble with the tape sticking, take it off, dry the boat side and the bilge keel, and re-attach the bilge keel using fresh tape.
See Figure 3, above, for a picture of the full ship assembly, and note the bent bilge keels at the bottom of the boat.
Rather than trimming the bilge keels down, cut a shape or a serration into the keel and test the new design. The waves and ripples caused by the swimmers will give the ship a more realistic environment, and will push the boat around for you so you don't need to tilt it.
Our Experts won't do the work for you, but they will make suggestions, offer guidance, and help you troubleshoot. We are chugging along on the alphabet train learning our letters and phonics along the way.  This week we added the letter D train car. Become an engineer for a day and discover the best way to keep from rocking the boat in this engineering science fair project! Depending on the direction of the waves and the direction the ship is traveling in, the ship can really start to rock and roll! The plowing action of the bilge keels generates a force that acts in a direction opposite to the rolling motion, and this force slows down the roll. Make sure to keep them centered along the bottom of the boat—don't put more marbles on one side of the bottom than the other.
The dowel will make it easier to see the boat rock back and forth, and it will also give you a handle with which to rock the boat.

When they start to get bigger again, that's when you should stop the stopwatch and stop counting. After you've tested each bilge keel design, put an object in the boat on top of the marbles or plaster and test it again.
Take video of the boat in the water for each bilge keel design, and determine which design maintains the greatest stability. When a ship rocks from front to back or back to front, it is called pitch, and when a ship rocks from side to side, it is called roll.
The bilge keel only works when the ship is rolling and doesn't hurt the straight-ahead speed very much. Use the dowel as a handle and tilt the boat until the water line is at the line you drew with your permanent marker.
Make sure you place the boat in the tub so that the front and back are perpendicular to the longer walls; that way the ripples have farther to travel before hitting the walls and bouncing back, so have less chance of interfering with the oscillations. Since it is just a simple piece of steel and doesn't have any moving parts, it is fairly inexpensive to build, too. Let the rubber cement dry for about 15-20 minutes, and don't be tempted to touch the bottle to check it—it could dislodge the marbles and cause you to have to cement them down again.
Let go of the dowel and record the number of oscillations it makes in a data table, like the one below, in your lab notebook. One by one they fall down and the children can’t stop laughing when they see or hear one fall to the ground. We are busy drawing the peanuts characters on to poster board so wwe can have our own Great Pumpkin patch for the wall. So far we have Snoopy, Woodstock, Linus, and Charlie Brown.The tomatoes are taking over the garden. The children like eating the cherry tomatoes for lunch especially Gideon and Harper, who think they are the yummiest treats.Thanks to Jonathan’s Daddy for picking up our huge bale of hay for the yard. The children gathered the hay to make their own scarecrow just like Curious George’s scarecrow, No-Noggin. They can’t wait to use their feathers they brought to make their Indian hats and turkeys for ThanksgivingMusic and Movement: The autumn leaves action song. The months in the year and the holidays we celebrate in each month of October, November, and December.
By introducing the days of the week, months of the year and the meaning of yesterday, today, and tomorrow we are helping the children to understand the abstract concept of time which they will later apply to math and science learning.
Understanding time and the tools that help us tell time like a calendar or clock are part of the Kindergarten and First Grade Common Core State Standards. But we teach in such a way that learning becomes a natural process for the children and once that is instilled in the children learning becomes not only fun but easy for them. Soon their knowledge base grows and grows as does their capacity for knowledge.  Where most places take the children to the pumpkin patch one day to pick out a pumpkin we have spent many days out in our own little pumpkin patch watching first hand just how a pumpkin grows from a little seed, to a yellow or green pumpkin, and finally to an orange pumpkin.
The children have been watching it finish turning orange in the warm sun.  I will be sending out photos of the children sitting in their pumpkin patch proud as can be of the little pumpkin they helped grow. Overheard this week. The children were asking each other where they thought their lunch food came from.   “Where do apples come from?” Trees “Where do grapes come from?
This week the children learned that Columbus set sail across the ocean with three ships in search of new land. Our little explorers pretended our clubhouse climber was their boat and used their hands as telescopes to search for distant lands.
They shouted taking turns guiding their “ship” to shore.  At art they painted an ocean in water color.
We did counting activities all week as we learned the words to our new counting song, The Five Little pumpkins. We are learning about the ordinal numbers 1st through 5th as we sing.  Ask your child to show you the movements that go along with their song. Thank you to Cole’s family for the yummy watermelon they grew in their garden, and thank you to Trinity’s family for all the delicious tomatoes you brought.
A sprinkle of glitter and the web and spider “magically” appeared before their eyes.  We put up a big spider web banner and the children decorated spiders with googly eyes and shapes to stick up on the web. We gave them all the ingredients: tortillas, tomatoes, lettuce, organic ground beef, and shredded cheese. Music and Movement: Itsy Bitsy Spider, and 5 little pumpkins songHappy Halloween 2013What fun we had this week getting ready for and celebrating Halloween.
The children have been practicing trick-or-treating all week with the felt pumpkin and cat treat bags we are using for pretend play.
This week the children put on a spider costume and turned into an eight legged arachnid for the spider and fly game.  They took turns being the spider and chased the flies, their friends, to catch them in their web. There was toilet paper webs all over the house but they had so much fun with the hands on learning. The children painted their wiggling feet white at Art to make little ghosts and painted everything orange when they made jack-o-lantern masks. The children loved wearing their costumes and were excited to see what everyone was wearing.