Your dictionary tells you that 'hydrophobic' means that it repels water. This is why water droplets shrink up tightly to form beads as they are repelled by the hydrophobic teflon on a cookie sheet or on the waxy coat of a newly waxed car. Teflon and wax are hydrophobic. Conversely, 'hydrophilic' means that it likes water, and that water will 'wet' the surface. If you put water on a paper towel, it will rapidly wet the fibers in the towel and spread out. Go around your home and test various things as to whether they are hydrophobic or hydrophilic. Use an eyedropper filled with water to test such things as your sidewalk, the glass in a drinking glass, a piece of clean wood, some painted wood, various leaves, and even your own skin on the back of your hand. And don't forget to test some wax paper and something in the kitchen that has a teflon coating on it - a frying pan or a cookie sheet (new ones work best!).

    Once you understand what hydrophobic and hydrophilic mean, you are ready to test which type of surface on a boat hull will make the boat move more efficiently through water.

Things you must have or should make:

• A small boat - perhaps only 6 inches long - or longer if you feel wealthy. It can be something as simple as a plastic bathtub toy, or a block of wood that you have carved into the shape of a streamlined boat hull. (You will need only one boat-hull because the bare boat will serve as a "control", and then for "experimentals" you will apply hydrophilic or hydrophobic coatings to that same hull. Thus the hull remains a "constant," and only the coatings become the variables.)
• A way to make the boat move in a straight line with a constant force. (This is the hard part of the experiment and much of this webpage will be devoted to doing this!)
• Some paints that are either hydrophobic and hydrophilic. Maybe not 'paints', but other sorts of coatings that you can apply to the shellaced or painted hull surface. Think about Rain-X^®, wax or even spray-on teflon paint to make various hydrophobic surfaces. Think of bare wood, or some latex paints for a hydrophilic surface. Remember that that both hydrophobic and hydrophilic come in degrees: some a more so that others.
  

A Suggested Way to Measure Boat Hull Efficiency

    The method presented here - you might be able to think of a much better way! - tries to address several of your needs. One is to keep your boat going in a straight line; another is to provide all "launchings" with identical amounts of force; and a third is, of course, to provide you with a means to measure the action. In this case, you can clock how long it takes for the boat to move between the start and finish lines. Ideally, you would want the start and finish lines to be as far apart as possible since this will give you more "stopwatch" time and your measurements will be more precise.

    As shown, the string (a thread might be even better) is connected to the boat by a thumbtack, and passes over a pulley at the other end of the water trough. It would be important to make sure that the pulley is very well lubricated so that it does not become the "limiting" factor in your work.

    Obviously if you used a very heavy weight, the boat would fly across the water faster than you could measure the time. So it is important that you use as small a weight as possible - just heavy enough to get the boat moving (and probably enough to keep the string out of the water - you might need to dry the string between trials). Also, as mentioned earlier, consider using a fine sewing thread instead of string.

    About the water trough: If you live on a farm that has animals, you probably have a very wide watering tank that would be perfect. However, the longer the boat's run, the further the weight must be able to drop. If you are clever, you should be able to figure out how to use a second pulley to allow for this longer drop. (Hint: see picture at the bottom corner of the page!) On the other hand you might not have access to a cattle watering tank. Don't fret! Go to your local building supply store and get a piece of eave trough such as perhaps runs along the edge of your roof. The store clerks will be able to help you fit ends to the trough so it will hold water, and they can provide you with pulleys also. Some larger suppliers such as The Home Depot and Lowes Home Improvement Stores are known to give free of charge supplies for science projects, but you must have drawings and talk to the store's manager. But beware: not all of these large outlets do this. Even if they do, you must be very well informed and "sell" your idea to the manager. AND don't forget to mention their "gift" in your final presentation - they want a little advertising space in exchange for their beneficence. Perhaps they can supply you with one of their bumper stickers for the corner of your poster. (Write something like: "I wish to thank Jane Smith, Mgr, of Howard Lumber of Buffalo Village for the free gift of the trough and pulleys used in this work.")

    There are many different ways you can do the necessary experiments. It would be highly desirable for you to devise a plan and then write to this website outlining your plans. We will go over your plans, make suggestions and perhaps be able to offer you some helpful hints. Please remember to tell us your age or year in school.

Click here to correspond with this website.

IMPLICATIONS

    This is a very large title because what really wins the attention of judges at science fairs is that you understand the importance of your work. Anyone can reinvent the volcano for the zillionth time, but so what? What is the importance other than some momentary excitement? Regarding making boats more slippery so that they can slide through water more efficiently, you can immediately jump right into the middle of an ocean of important uses of your new technology. Let's give a few examples:

1. OCEAN SHIPPING. If you could save a shipping line 1% in fuel costs, you would be saving them millions of dollars per year! (See point #3, below, also.)
2. AMERICA'S CUP RACING. While not as financially important as with ocean liners and cargo ships, this would be a very pretigeous use of your technology.
3. MUNICIPAL WATER MAINS. Cities use a lot of energy pumping water through pipes. If your technology made the water slide though the slippery pipes more easily, you would save taxpayers a lot of money each year. Also slippery pipes (coated - say - with teflon) might not build up mineral deposits and become congested ("piposchlerosis"). The same might be said for the ships, too. "Fouling" of ships is a major concern as barnacles and other sea creatures make the hulls rough and much less "slippery". Perhaps your coating might make it hard for barnacle larvae to grab ahold and start growing there. For advanced students, more about "slippery pipes" can be found by clicking button.

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