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These differ from the Pacific proas in that they are not double-ended and have a trimaran configuration with two outriggers. These are widely used in the native ships of Indonesia , Malaysia , and the Philippines , and continue to be used today as traditional fishing, cargo, and transport vessels.
Proas are traditionally rigged with the crab claw and tanja sails. The modern proa exists in a wide variety of forms, from the traditional archetype still common in areas described, to high-technology interpretations specifically designed for breaking speed-sailing records. The term "proa" originates from Early Modern English "prow" or "praw".
It probably entered the English language via Dutch prauw and Portuguese parau , similar to Spanish proa , meaning " bow ". Catamarans and outrigger boats were very early innovations of the Austronesian peoples and were the first true ocean-going ships capable of crossing vast distances of water.
This enabled the Austronesian peoples to rapidly spread from Taiwan and colonize the islands of both the Pacific and Indian oceans since at least BC. The first outriggers evolved from the more primitive double-hulled catamarans. There are two types of outrigger ships based on the number of outriggers : the single-outriggers which include catamarans with unequal hulls and the double-outriggers sometimes called trimarans. Single-outriggers evolved first and are the dominant form of Austronesians ships in Oceania and Madagascar.
They have largely been replaced by the more versatile double-outrigger ships in Island Southeast Asia. Double-outrigger forms, however, are absent entirely in Oceania. Catamaran and outrigger technologies were introduced by Austronesian traders from Southeast Asia to the Dravidian -speaking peoples of Sri Lanka and Southern India as early as to BC. Early contact by Austronesians with Arab sailors may have also influenced the development of the lateen sail in western ship traditions, derived from the more ancient Austronesian crab claw sail.
Many of these traditional vessels are now extinct. Either lost during the colonial period or supplanted by in modern times by western boat designs or fitted with motor engines. The Portuguese were the first Europeans to encounter the double-outrigger Southeast Asian ships, initially with derivative vessels from the Malabar Coast , which they called the parau. They applied the same name to similar ships in their colonies in Southeast Asia. Similarly, the Dutch encountered them when they colonized the islands of Indonesia , calling them prauw.
This was rendered as "praw" by the British , later evolving to "proa". In French Sailboat Vector Simple Yupoo territories in the Pacific Islands, they were known by the more general term pirogue. Although technically restricted to outrigger sailing vessels, European sources often applied the term indiscriminately to any native ships of Southeast Asia.
The earliest written accounts of the single-outrigger Pacific proa though not by name were by the Venetian scholar Antonio Pigafetta , who was part of Ferdinand Magellan 's � circumnavigation. They encountered the native sakman ships of the Chamorro people in the Islas de los Ladrones Mariana Islands.
Pigafetta describes the outrigger layout of the sakman , and ability to switch bow for stern, and also notes its speed and maneuverability, noting, "And although the ships were under full sail, they passed between them and the small boats fastened astern , very adroitly in those small boats of theirs.
The accounts of Magellan's crew were the first to describe the Chamorro proas as "flying. During his � circumnavigation , Lord Anson applied the term proa to the double-ended Micronesian single-outrigger ships. His fleet captured one in , and Lt. These accounts fascinated both the British and American public, ushering in a period of interest in the design by sports sailors. Working from the drawings and descriptions of explorers, western builders often took liberties with the traditional designs, merging their interpretation of native designs with Western boat building methods.
In the Marshall Islands , where the craft were traditionally built, there has been a resurgence of interest in the proa. People hold annual kor-kor races in the lagoon at Majuro , along with events such as a children's riwut race.
The kor-kors are built in traditional style out of traditional materials, though the sails are made with modern materials often inexpensive polyethylene tarpaulins , commonly known as polytarp. A loose group of individuals from all over the world has formed from those interested in the proa, including people with a historical perspective and those with a scientific and engineering perspective. Many such individuals are members of the Amateur Yacht Research Society.
Sailing is no name for it � flying is better. Out into the bay she skipped, boys yelling with delight on the uplifted outrigger, spray from the lee bow and steering oar riven into vapor by the speed blowing to leeward. In the late 19th century and early 20th century, many in Europe and America became interested in the proa. Western boat builders such as R. Into the 20th century, the proa was one of the fastest sailing craft that existed. The proa design is still the basis [14] for many boats involved in speed sailing.
Yacht-design giant Nathanael Herreshoff , a friend of Munroe, may have also had an interest in the project. Over the following years, Munroe built several more.
They were all destroyed by the mids, when a severe hurricane leveled Munroe's bayside boatshop. At least two of his designs were documented in articles in The Rudder , as was one by Robert B. Small proas may have been brought back to the United States in the late 19th century, but documentation is sparse. Munroe and Roosevelt appeared to be the first two builders to adapt the proa to Western building techniques. He used the traditional asymmetric hull, flat on the lee side, and a decked dugout ama.
While no quantitative record was made of its speed, it was noted that the proa would run at speeds that would bury the bows of any other vessel. It carried three times the ratio of sail area to immersed midships section than the fastest yachts in the club and yet drew only 15 inches 38 cm. Since Munroe had no direct experience with proas, all he had to work with was the widely distributed and incorrect plan drawing from about , made during Admiral Lord Anson's circumnavigation of the globe.
This drawing had been circulated in the press, for example in William Alden's articles in Harper's Magazine. These were reprinted in a small book called The Canoe and the Flying Proa. Brett, the draughtsman of the plan, is thought by some to have misinterpreted one key element, showing the mast fixed vertically in the center of the boat. This view as based on the fact that other Micronesian proa masts were raked end-to-end as the vessel shunted and the fact that a raked mast shifts the center of effort of the sail which would influence helm balance.
However, Brett's placing of the mast in a vertical position has found to be accurate when replicas of the "Anson" proa were built and sailed by the Marinas-based organization Sails that found that in many points of sail under many conditions the proa sailed well with the mast in a vertical position.
Munroe, however, was a talented boat designer who was able to work around any problems with the drawings. His adaptations can be seen in successive proas.
Rather than the deep, asymmetric hull of a traditional proa, Munroe created flat-bottomed hulls similar to the fisolera referred to by Pigafetta , [9] with keels or centerboards for lateral resistance. His first iteration had an iron center fin with a half-oval profile. Rather than the traditional crab-claw sail's spars which meet at the front, Munroe's sails used what could be described as a triangular lug sail or spritsail with a boom, similar to the modern lateen sail with a shorter upper spar.
Munroe's first proa was only 30 feet 9. His article in The Rudder describes what can only be planing on the flat hull. As this was before the advent of planing power boats, this proa was one of the first boats capable of planing. This helped produce its amazing speed when most boats were limited to their hull speed �they had too little power to achieve planing speed, and yet were not designed to exceed hull speed without planing. For example, a foot 9. This accomplishment was the nautical equivalent to the X-1 breaking the sound barrier.
Munroe was building a "cheap and dirty" sharpie hull made of two foot 9. By lucky accident he may have been the first sailor to plane his boat. Robert Barnwell Roosevelt , uncle of American President Theodore Roosevelt , also built a proa at about the same time. He used it sailing from Long Island. It was significantly different but equally creative, and at 50 feet 15 m , much longer. From his article in The Rudder , it appeared the main hull of Roosevelt's proa was an open 4-foot 1.
The mast was a bipod arrangement with both masts stepped to windward, with a boomed, balanced lugsail suspended from the apex. It is not clear if the boat predated Munroe's proa. Since Munroe wasn't aware of the raking mast, his model used two daggerboards set fore and aft of the mast, which would allow adjustment of the center of lateral resistance to provide helm balance. From the drawings, it appears the mast is higher as well, allowing a larger sail. The sail design also changed, with the upper spar now being slightly longer than the upper edge of the sail, and projecting past the apex slightly to allow the apex to be attached to the hull.
The sail was loose footed, with the boom attached to the upper spar near the sail apex, and to the clew of the sail. His article in a issue of The Rudder included more details on the construction of his second proa.
A book of sailboat plans published by The Rudder includes the following specifications for the proa:. From the drawings, the distance from the center of the main hull to the center of the aka is about 12 feet 3.
Western designers often feel the need to tinker with the proa. They are attracted by the minimalist nature and amazing speeds that proas are capable of they may still be the fastest sailboats per dollar spent for the home builder but they often want the proa to do more; adding cabins, different sailing rigs, and bidirectional rudders are common changes made. James Wharram was greatly influenced by the Proa design.
For example, unconventional boat and yacht designer Phil Bolger drew at least three proa designs; the smallest one 20 ft has been built by several people while the larger two, including his Proa 60, have not been built. For additional examples, see here. The terms ama and aka have been adopted for the modern trimaran. Since trimarans are generally designed to sail with one ama out of the water, they are similar to an Atlantic proa, with the buoyant leeward ama providing the bulk of the stability for the long, relatively thin main hull.
Some modern proa designers have borrowed trimaran design elements for use in proas. Trimarans often have main hulls that are very narrow at the waterline, and flare out and extend over a significant portion of the akas. This topheavy design is only practical in a multihull, and it has been adapted by some proa designers. Notable examples are the designs of Russell Brown, a boat-fittings maker who designed and built his first proa, Jzero , in the mids.
He has created a number of proa designs, all of which follow the same theme. One of the design elements which Brown used, and a number of other designers have copied, is the lee pod. The akas extend past the main hull and out to the lee side, and provide support for a cabin extending to the lee of the main hull. This is similar to the platform extending to the lee on some Micronesian proas.
The lee pod serves two purposes�it can be used for bunk space or storage, and it provides additional buoyancy on the lee side to prevent a capsize should the boat heel too far. Crew can also be moved onto the lee pod to provide additional heeling force in light winds, allowing the ama to lift under circumstances when it would not otherwise.
The Jzero also used water ballast in the ama to allow the righting moment to be significantly increased if needed.
One of the issues Western designers have with the proa is the need to manipulate the sail when shunting. Even Munroe's early sails discarded the curved yards of the traditional crabclaw for the more familiar straight yards of the lateen and lug sails. Munroe's designs likely lacked the tilting mast because he was unaware of it, but many designers since have use a fixed mast, and provided some other way of adjusting the center of effort.
Most sailboats are designed with the center of effort of the sails slightly ahead of the center of area of the underwater plane; this difference is called "lead. Put together your model rocket, paying special attention to the engine mount and fins, then giving the completed vehicle a drag-reducing finish.
Apply the science of aerodynamics to calculate the required diameter of the parachute. Then check the rocket's stability by determining its center of gravity and center of pressure locations. Your creation is now ready to fly Get a taste of electrical engineering by designing and building an electric launch controller that will ignite your rocket engine safely.
Design a circuit that meets all code requirements. Use Ohm's law to determine the number of batteries and type of resistor required.
Also, get a lesson in proper soldering technique for assembling the circuit Finish your launch preparations by building a theodolite to measure the altitude of the rocket's trajectory, building a launch pad, packing the parachute, choosing a safe launch site, setting up the site, and coordinating the activities of the mission control team. Once all systems are go, conduct the countdown and press the firing button Delve into the history of the most potent artillery weapons in the era before gunpowder: catapults.
Examine the workings of the ballista, onager, and trebuchet. Then get started on a model ballista capable of hurling a golf ball feet. Analyze the machine's nylon torsion springs to ensure that they can store enough elastic energy to achieve the required foot range Build your model ballista.
Then construct two other types of catapult-the onager and trebuchet-designed such that they store the same amount of energy as your ballista. Field test all three to determine which throws a golf ball farthest. Will the winner be the weapon from the Hellenistic ballista , late Roman onager , or medieval era trebuchet? You may be surprised! Plunge into hydraulics, learning how force is transmitted from actuators to hydraulic cylinders through fluid-filled lines.
Then use this knowledge to design and build a hydraulically powered mechanical arm that can grasp and manipulate a concrete block-controlled by four hand-operated syringes. Along the way, use 3D printing to fabricate several crucial parts Harness the power of moving water by building an impulse turbine capable of lifting a 2. First, use Bernoulli's equation to determine the required height of the water reservoir.
Next, focus on the turbine, plotting power versus load to determine the turbine diameter that will produce the required power output optimally. Then build! Test your water turbine, comparing its performance to the theoretical ideal. Next, modify it by adding a set of spur gears that will allow the machine to lift a 6-pound weight, which is well beyond its ungeared capacity.
Calculate the optimum gear ratio, use laser-cutting to fabricate the gears, install them, and watch a modest stream of water lift a disproportionately heavy mass The pendulum clock was the standard for precise timekeeping for centuries.
Plan and build one using your newly acquired knowledge of gears. Start by exploring why a pendulum keeps accurate time. Then calculate an appropriate pendulum length for the clock. Design the escapement mechanism and gear train, then add a suitable power source to keep the pendulum swinging Test the limits of small, inexpensive, off-the-shelf hobby motors by building a motor-driven crane capable of lifting pounds-a tall order for a motor that weighs only a few ounces!
First, construct the world's simplest electric motor to gain insights about how they work. Then calculate the torque requirements for your crane, and add gears and pulleys to achieve mechanical advantage Your final DIY project is a tribute to cartoonist Rube Goldberg, famous for sketching machines that perform the simplest tasks by the most complicated means.
Accordingly, combine twenty design elements from this course-from airfoil to electric circuit-to create a machine that will click a computer mouse. Professor Ressler offers a solution that produces a surprising outcome Master the principles of engineering with 17 hands-on projects you can do yourself taught by a West Point engineer. In over two decades as a teacher, I've never experienced anything quite like commitment of The Great Courses to rigor in the course development process and uncompromising production quality in the studio.
This upgrade requires that you change your password. We've sent a link and instructions to your email address to help you easily reset your password and start exploring the new Great Courses Plus immediately. Become a Plus member today to create your Watchlist and enjoy our courses. Do-It-Yourself Engineering is rated 4. Add Course To Watchlist. Sign In or Subscribe to Watch. Do-It-Yourself Engineering. I own all 4 of his courses and hope that he does more. I will probably never build any of the projects that he does in this course but I really enjoyed watching him do them and learned a lot about the science and engineering involved.
I was very much impressed by the level of his craftsmanship and now I know how he built those wonderful models in his previous courses. I love to build things but they generally involve 2x4s! Date published: Rated 5 out of 5 by Architect from Great teacher. Great at visually helping people understand basic engineering. Rated 5 out of 5 by spankeycat from The great-nephews love it!
I bought this course for them and I have not seen any episode myself, but they sent me a photo of the trebuchet they built -- very cool! I hope to reverse engineer some of the projects for my elementary school STEM classes. Rated 5 out of 5 by Jermey from This title leaves no guessing as to expectations Excellent presentations of subjects. Rated 5 out of 5 by Frank from Professor Ressler is a great instructor Watched this with my 15 year old grandson.
He was fascinated, as was I. Ressler uses his creativity to demonstrate engineering concepts. The course is not for everyone, but for the mechanically inclined it is a winner. Rated 5 out of 5 by LarsTheBear2 from MythBusters with math -- great fun Is it just me, or was anybody else struck by how similar the content of this course is to MythBusters? We have rockets, unusual aircraft, concrete boats, Rube Goldberg machines There are no completely gratuitous explosions, for better or worse, but there's a lot of similar themes.
For the avoidance of doubt -- a favourable comparison with MythBusters should be taken as flattery.
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