Tugboats have been a long standing theme in my life and I started my tug-affliction at an early age.
To celebrate the spirit of that first tug, I have named these models, in all their sizes, the ‘Amak’ series and I tell you this, in all confidence, that if my ship ever comes in and I reach a time in my life when I want to slow down just a bit, I would like to build one of these boats and do a bit more tugging myself.
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.
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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.
Somewhere in 2005 I was contacted by a customer about the idea of designing a motorsailer suitable for some extended passagemaking. This Camarone (Spanish for Shrimp) design follows close to my heart as the most perfect boat I can imagine. So after some years, along came a new candidate for a boat, this time a couple that was looking for a commuter boat to run from Vancouver Island, specifically Sydney, British Columbia, to their island home located about 34 miles north in the Canadian Gulf Islands. With those requirements set down, I had no hesitation in recommending the Storm Petrel type hull as a good model to choose from. Her overall size was limited to 30ft-6in on deck in order to fit her slip where she will be kept in Sydney and a bow thruster was added to couple with the single engine and give the owner greater control in a tight docking situation.
The fellow on the phone, as it turned out, was looking for a boat design that might be appropriate for his ex-wife to use to commute out to her summer home in the San Juan Islands. The parameters for the design are very simple and uncomplicated with performance expected in the 24 – 28 knot range for top speed and 18 knots for cruising speed with good fuel economy of about a 5 gallon per hour burn. Originally Posted by Chris Ostlind NACA 0000 profiles are very good all-around foil sections and are pretty easy for home builders to complete.
Originally Posted by Chris Ostlind I suggest the use of a set of simple plywood templates for regular intervals down the length of the foil planform to aid the shaping process.
You mention kayaking - would you consider something that would be more of a touring kayak with floats?
I think this is interesting technique - compound bottom piece is joined to plywood topsides .
Secondarily to this topic, the bow of the vaka, as pictured, is probably not going to give the needed buoyancy up front, if you wish to push this boat beyond casual sailing.
We do not know how much sailing experience you have,and you say your BUILDING experience is zilch. Perhaps you should start to walk before you can run and keep this whole first project simple.
With it's self tacking jib and excellent turn of speed it would enable you to get the experience you need and then move on-- without costing you an arm and a leg.
Hmmm OK - but where can I find the profiles themselves (or am I being particularly dim in asking)? Foils are fun to make as there is a degree of sculpture involved in the shaping if you do it by hand.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals.
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. Entering the pilothouse from the spacious cockpit, there is an ‘L’ shaped dinette area with helm forward, allowing the skipper to either stand at the helm for high-attention time or put her in autopilot and lounge back on the settee with legs out in front and reclining up against the rear bulkhead of the house.
Suitable for cruising either north to Alaska or south to Mexico, she is a boat that has spent many fine hours in my dreams.
Lobster-type boat that we built several years ago, and the “Pyladian” is an evolution and direct sister to that design. They needed her to be able to make good and economical speed so that they could spend their time on the island not just going back and forth to it. But the customers wanted a single diesel (not the twin diesels that the Storm Petrel had) and needed the potential for more speed than the Storm Petrel boat had so the Yanmar 6LPA was chosen. A single seat was added across the stern of the boat for passengers on those nice sunny days but the rest of the cockpit was kept as open as possible to carry gear and stores.
As she lived on a small island that had no ferry service, she needed a boat to take her back and forth. Henry and Holly showed us the boat and after a short sea-trial and a lovely lunch, we flew home on one of those February days that shouldn’t happen in the Northwest. A diesel stern drive will keep the engine space and noise aft and maneuvering has to be excellent as she will be single-handed most of the time. At the bottom of this post there is a photo of a centerboard which I built in this exact fashion. Crew weight and placement while sailing are critical as the weight of one adult is very nearly the total weight of the boat itself when ready to sail. I had the first coastal sail in my new 4.4m Weta on the weekend and if you do something half as good as it you will have a great boat. I enlarge or reduce the section drawing to suit the chord at 4-6" intervals along the immersed blade, depending on length of the foil you are making. Please do not use anything on this site without proper attribution and links to the source material.
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.
Unfortunately, he was caught in Hurricane Katrina and his boating plans changed abruptly, but I thought you might like to take a look at what I came up with to address his needs.
A nice counter height chart table is to starboard with lots of space for the charts and tide tables necessary for keeping a boat navigating safely.
With the perspective of about 5 years between the two building projects and with a chance to spend many happy hours bugging about in the Salish Sea in the Storm Petrel, I found her to be, in my opinion, one of the best performing sea-boats that I have ever had the pleasure of running.
The boat needed to be able to handle anything from a few groceries to large units of wood, fuel, and all the myriad of items necessary for comfortable island life.
With 300 horses under her engine box, the hull should top speed out at about 26-28 knots and cruise at 20 knots without difficulty.
The final change was to slightly contemporize her appearance with a three pane forward windshield and twin sliding windows on each of her cabin sides.


It was sunny and almost warm, and Rick made the best of a bright, clear day with a ground and water skimming flight that would excite any of us. Accommodations are simple and neat — an enclosed head forward and double berth with the galley out in the pilot area. The board has a shaped, Sitka Spruce core and was then skinned with two layers of carbon twill cloth in a vacuum bag process.
If you wish to get really creative, take the printed page to a nearby copying machine and scale them accordingly. I do not like to use plywood for the cores, even though the revealed laminates make for really nice guides for sanding to a constant angle.
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. I remember heading north with my good friend George Gray (currently living with his wife on their sailboat and cruising the lovely waters of Mexico) to the Anacortes Trawler Fest show several years ago. The weather would not always be compatible to this lifestyle and so the vessel would need to be able to handle the weather in whatever form that would be presented to it.
With the single diesel layout, the cabin changes considerably in its layout and in the potential layout options for the customers.
She is certainly no traditional appearing lobsterboat like the Storm Petrel was but I really have to say that I like the profile of this new “Pyladian” very much and look forward to seeing how her presence manifests itself on the water. Seating is back up against the engine box for passengers or just lounging about swinging on an anchor. Neither of these foils are going to give you that last knot or two in high speed use, but they will function extremely well in low-to-mid speed work. The top and bottom side of the floats would be like mirror images so that I could make all four hull panels in a single mold. They have made amas for big tris like this - you need to work your design with a scale model as its hard to predict what you can actually do with the method (ie. These boats, especially with assy spinnakers for offwind work, will really want to get tossed over their leeward ama bow. This will give a huge amount of flexibility for the skipper as to how the boat trims when underway in differing wind and sea state conditions. Instead, I prefer to use red cedar or, if you can get it, Sitka Spruce, laid-up from many pieces with the grain alternating from head to tip. She was wood, of course, nicely detailed (though she was a working tug), had a Cat diesel engine and after just a few days on board, I was hooked. 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.
There is a nice standing headroom shower at the aft end which is a very nice feature in keeping the cruise comfortable.
De-emphasized was the need for berthing and a galley with those being way down on the list of priorities and moving up on the list was the need for handling tough waters at all times of the year and keeping a load of people warm and dry while being transported to the island for a visit. 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. When using her for cruising, the inboard steering allows warm, quiet, and comfortable cruising under power and if you are so lucky to have favorable breezes in the afternoon, you can transition to the cockpit and run her very nicely either sailing or motorsailing. With the fetch of Puget Sound and the short steep chop that can develop in those waters, it was a good test of what the Storm Petrel could do. I read issue #1 of WoodenBoat magazine onboard her and made up my mind that boats, indeed wooden boats, were to be my life choice of hobby, avocation, passion, and career. With the following seas and our trying to maintain a pace of 16 plus knots of speed, the Storm Petrel would bound over the top of the crest of one wave and then pitch downward into the trough between the seas burying her bow into the wave just ahead of us till we could see water squirting up thru the anchor roller forward. I always keep my boat eyes open and occasionally, I see an example of a really beautiful and interesting boat.
Without slowing or slewing around in any way, she would then climb at the same speed up the face of the next wave reaching the top before pitching down again into the trough of the next.
After about 30 minutes of this exhilarating ride, I remarked to George something about my amazement of such a remarkable ride to which he replied that he was impressed also.
We chatted for a few more minutes about her amazing performance and no sooner had the words come out of my mouth, “we should turn around and try her head into the wind”, when I started turning the wheel.
We did a good 15 minutes in reverse direction straight into the eye of the wind and those cresting waves with essentially the same results. When so many other boats keep the main cabin cut up with separate cabins, this one feels bright, airy, and large. The boat didn’t slow down and certainly didn’t broach or slew at the bottom of the troughs even when burying her nose deeply into the waves. Really, all in all, she showed remarkable capability for those seas, an incredibly pleasant boat to run on a day when I would normally wish I was home reading a good book by a warm fire. This combination of fine bow lines and entry with her broad and flat exit of run of the hull was literally the perfect example of what one would wish for in this type of boat.



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