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44-457: The RS Tera is suitable for introducing newcomers to the sport of sailing, but is also a good boat to race. The boat is highly robust, and it is built with a self draining cockpit and is easy to right after a capsize, in addition to which it has a floating daggerboard . The boat is fairly small and light, meaning it is possible to transport on a roof rack , and that it is manageable on the water by younger children. The mast comes in two pieces, and

88-432: A and b are distances from the fulcrum to points A and B and if force F A applied to A is the input force and F B exerted at B is the output, the ratio of the velocities of points A and B is given by a / b so the ratio of the output force to the input force, or mechanical advantage, is given by This is the law of the lever , which Archimedes formulated using geometric reasoning. It shows that if

132-485: A toothed belt drive, the number of teeth on the sprocket can be used. For friction belt drives the pitch radius of the input and output pulleys must be used. The mechanical advantage of a pair of a chain drive or toothed belt drive with an input sprocket with N A teeth and the output sprocket has N B teeth is given by The mechanical advantage for friction belt drives is given by Chains and belts dissipate power through friction, stretch and wear, which means

176-426: A clip or pin. Unlike a centreboard, which can be set at different angles to the hull of the boat, daggerboards are generally limited to a single perpendicular position relative to the hull. If a daggerboard is located off center, it is called a leeboard or a bilgeboard . The characteristic which differentiates daggerboards from other centerboards and swing keels is that daggerboards are easily removable, even when

220-477: A counterforce from the wind pushing on the sails. Daggerboards are often long and thin to reduce drag and increase effective lift, thus providing a better lift-to-drag ratio. In 2008, a 55-foot-long (17 m) daggerboard ship was found using deep scan sonar equipment off the southern shore of Lake Ontario , the only such vessel known to have been found in the Great Lakes . Vessels of this type were used for

264-478: A drastic change. Generally, daggerboards are used on smaller rigs such as 10 to 40 feet for racing but there is a large number of custom and semi-custom catamaran builders who offer daggerboards as an option. Daggerboard rigs may be faster than fixed keels because fixed keels have so much hydrodynamic drag by the shape. Some makes which utilize a daggerboard design are: The Mirror Dinghy , Laser , Vanguard 15 . Mechanical advantage Mechanical advantage

308-436: A mechanical power transmission scheme. It is common for mechanical advantage to be manipulated in a 'collapsed' form, via the use of more than one gear (a gearset). In such a gearset, gears having smaller radii and less inherent mechanical advantage are used. In order to make use of non-collapsed mechanical advantage, it is necessary to use a 'true length' rotary lever. See, also, the incorporation of mechanical advantage into

352-433: A pair of meshing gears for which the input gear has N A teeth and the output gear has N B teeth is given by This shows that if the output gear G B has more teeth than the input gear G A , then the gear train amplifies the input torque. And, if the output gear has fewer teeth than the input gear, then the gear train reduces the input torque. If the output gear of a gear train rotates more slowly than

396-409: A sailboat could not sail up-wind and would simply be blown sideways. During a storm, daggerboards can help reduce the tendency of a small boat to tip over ("breach") due to waves. A catamaran in a storm would lift the leeward hull daggerboard and fully extend the upwind daggerboard. If there is no wind and an outboard motor is being used, lifting the daggerboards will ensure the least drag. When

440-438: A short time in the early 19th century. In the early 19th century daggerboards were infrequently being used on American schooners . These schooners were used for nearby coastal trade of cotton, wheat, and apples. A sunken 1833 daggerboard schooner was found in the great lakes with the help of sonar equipment. Knowing this, daggerboards have been around since late in the 17th century. Daggerboards can be found on monohulls which

484-424: A small sailboat flips on its side, the keel can also be used to right the boat. Standing on the keel gives the sailor additional leverage to roll the hull upright. The centerboard, daggerboard, or bilgeboard can be used as a platform upon which to stand, providing increased leverage , in the event the dinghy overturns via a capsize or turtle . Because water is denser than air, the force generated by wind against

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528-450: Is a measure of the force amplification achieved by using a tool, mechanical device or machine system. The device trades off input forces against movement to obtain a desired amplification in the output force. The model for this is the law of the lever . Machine components designed to manage forces and movement in this way are called mechanisms . An ideal mechanism transmits power without adding to or subtracting from it. This means

572-477: Is between 30 kg and 70 kg and it can carry up to two children comfortably. The RS Tera Sport has a reefable Dacron sail (the sail can be reefed to de-power in strong winds / for smaller children) while the RS Tera Pro has a battened Mylar sail which gives improved performance and an increase in power. There is also a Mini-sail for very small children, as young as 5 years old. All specifications fit on

616-428: Is the classic sailboat and multihulls called catamarans. Daggerboards come in all different shapes and sizes, some curved or s-shaped. Curved daggerboards started to appear thirty to forty years ago. The first prototype was made in 1985 by Ian Farrier. The benefits of vertical lift generated by curved daggerboards are nominal. When actually sailing, curved daggerboards - not to be confused with hydrofoils - do not make

660-449: The actual mechanical advantage (AMA) is defined by a factor called efficiency , a quantity which is determined by experimentation. As an example, using a block and tackle with six rope sections and a 600 lb load, the operator of an ideal system would be required to pull the rope six feet and exert 100  lb F of force to lift the load one foot. Both the ratios F out / F in and V in / V out show that

704-472: The IMA is six. For the first ratio, 100  lb F of force input results in 600  lb F of force out. In an actual system, the force out would be less than 600 pounds due to friction in the pulleys. The second ratio also yields a MA of 6 in the ideal case but a smaller value in the practical scenario; it does not properly account for energy losses such as rope stretch. Subtracting those losses from

748-494: The IMA or using the first ratio yields the AMA. The ideal mechanical advantage (IMA), or theoretical mechanical advantage , is the mechanical advantage of a device with the assumption that its components do not flex, there is no friction, and there is no wear. It is calculated using the physical dimensions of the device and defines the maximum performance the device can achieve. The assumptions of an ideal machine are equivalent to

792-403: The boat is underway. Centerboards and swing keels, common alternatives to fixed keels, can pivot up and down but are fixed to the hull. The freedom of movement of dagger- and centerboards allows them to swing or slide up into the hull of the boat, which is advantageous when sailing in shallow waters. The pivoting centerboard or swing keel can swing up when it strikes an object which helps prevents

836-476: The boom is padded. Furthermore, the RS Tera can be rowed and has oarlocks. Built with a Comptec PE3 hull, the RS Tera has been described to have a modern look. The RS Tera is available in 3 specifications: RS Tera Mini, RS Tera Sport and RS Tera Pro. The RS Tera Sport is designed with beginners and training centres in mind while the RS Tera Pro is more suitable to older, more experienced sailors. The weight range

880-424: The chain or belt is the same when in contact with the two sprockets or pulleys: where the input sprocket or pulley A meshes with the chain or belt along the pitch radius r A and the output sprocket or pulley B meshes with this chain or belt along the pitch radius r B , therefore where N A is the number of teeth on the input sprocket and N B is the number of teeth on the output sprocket. For

924-429: The corresponding backward-directed reaction force on the ground is indicated). A block and tackle is an assembly of a rope and pulleys that is used to lift loads. A number of pulleys are assembled together to form the blocks, one that is fixed and one that moves with the load. The rope is threaded through the pulleys to provide mechanical advantage that amplifies that force applied to the rope. In order to determine

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968-458: The design of certain types of electric motors; one design is an 'outrunner'. As the lever pivots on the fulcrum, points farther from this pivot move faster than points closer to the pivot. The power into and out of the lever is the same, so must come out the same when calculations are being done. Power is the product of force and velocity, so forces applied to points farther from the pivot must be less than when applied to points closer in. If

1012-443: The distance a from the fulcrum to where the input force is applied (point A ) is greater than the distance b from fulcrum to where the output force is applied (point B ), then the lever amplifies the input force. If the distance from the fulcrum to the input force is less than from the fulcrum to the output force, then the lever reduces the input force. To Archimedes, who recognized the profound implications and practicalities of

1056-416: The end of the rope, which is A where the input force is applied. Let R be the distance from the axle of the fixed block to the axle of the moving block, which is B where the load is applied. The total length of the rope L can be written as where K is the constant length of rope that passes over the pulleys and does not change as the block and tackle moves. The velocities V A and V B of

1100-408: The front and rear sprockets The ratio of the force driving the bicycle to the force on the pedal, which is the total mechanical advantage of the bicycle, is the product of the speed ratio (or teeth ratio of output sprocket/input sprocket) and the crank-wheel lever ratio. Notice that in every case the force on the pedals is greater than the force driving the bicycle forward (in the illustration above,

1144-443: The fulcrum, or pivot. The location of the fulcrum determines a lever's class . Where a lever rotates continuously, it functions as a rotary 2nd-class lever. The motion of the lever's end-point describes a fixed orbit, where mechanical energy can be exchanged. (see a hand-crank as an example.) In modern times, this kind of rotary leverage is widely used; see a (rotary) 2nd-class lever; see gears, pulleys or friction drive, used in

1188-462: The ideal machine does not include a power source, is frictionless, and is constructed from rigid bodies that do not deflect or wear. The performance of a real system relative to this ideal is expressed in terms of efficiency factors that take into account departures from the ideal. The lever is a movable bar that pivots on a fulcrum attached to or positioned on or across a fixed point. The lever operates by applying forces at different distances from

1232-420: The input gear, then the gear train is called a speed reducer (Force multiplier). In this case, because the output gear must have more teeth than the input gear, the speed reducer will amplify the input torque. Mechanisms consisting of two sprockets connected by a chain, or two pulleys connected by a belt are designed to provide a specific mechanical advantage in power transmission systems. The velocity v of

1276-413: The law of the lever, has been attributed the famous claim, "Give me a place to stand and with a lever I will move the whole world." The use of velocity in the static analysis of a lever is an application of the principle of virtual work . The requirement for power input to an ideal mechanism to equal power output provides a simple way to compute mechanical advantage from the input-output speed ratio of

1320-442: The leeward push of the sail . The theoretical centre of lateral resistance is on the trailing edge of the daggerboard. A daggerboard is a removable vertical keel that is inserted through a "trunk" in the center of a vessel's hull, usually amidships. Daggerboards are usually found in small sailing craft such as day sailers , which are easily handled by a single person. Daggerboards are not usually ballasted but are locked in place by

1364-404: The mechanical advantage of a block and tackle system consider the simple case of a gun tackle, which has a single mounted, or fixed, pulley and a single movable pulley. The rope is threaded around the fixed block and falls down to the moving block where it is threaded around the pulley and brought back up to be knotted to the fixed block. Let S be the distance from the axle of the fixed block to

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1408-422: The moving block. Let F A be the input force applied at A the end of the rope, and let F B be the force at B on the moving block. Like the velocities F A is directed downwards and F B is directed upwards. For an ideal block and tackle system there is no friction in the pulleys and no deflection or wear in the rope, which means the power input by the applied force F A V A must equal

1452-408: The moving block. Mechanical advantage that is computed using the assumption that no power is lost through deflection, friction and wear of a machine is the maximum performance that can be achieved. For this reason, it is often called the ideal mechanical advantage (IMA). In operation, deflection, friction and wear will reduce the mechanical advantage. The amount of this reduction from the ideal to

1496-399: The much larger surface area of the sails can be equalized by the force of a relatively small daggerboard pushing in the water below the hull. A daggerboard fits into a trunk that runs through the hull of the rig. When the board is in the trunk it keeps the water out while in use due to how tightly wedged it is. It is held in place by a pin on the forward end or a shock cord. The daggerboard puts

1540-426: The points A and B are related by the constant length of the rope, that is or The negative sign shows that the velocity of the load is opposite to the velocity of the applied force, which means as we pull down on the rope the load moves up. Let V A be positive downwards and V B be positive upwards, so this relationship can be written as the speed ratio where 2 is the number of rope sections supporting

1584-429: The power out acting on the load F B V B , that is The ratio of the output force to the input force is the mechanical advantage of an ideal gun tackle system, This analysis generalizes to an ideal block and tackle with a moving block supported by n rope sections, This shows that the force exerted by an ideal block and tackle is n times the input force, where n is the number of sections of rope that support

1628-438: The power output is actually less than the power input, which means the mechanical advantage of the real system will be less than that calculated for an ideal mechanism. A chain or belt drive can lose as much as 5% of the power through the system in friction heat, deformation and wear, in which case the efficiency of the drive is 95%. Consider the 18-speed bicycle with 7 in (radius) cranks and 26 in (diameter) wheels. If

1672-403: The problem with wood is that wood rots over time. Alternate materials for daggerboards are metal (aluminum/steel) and fiberglass . A daggerboard boat can be costly to manufacture. If not well-made, the daggerboard will transfer vibrations from the trunk through the hull. The purpose of the daggerboard (or any keel) is to balance the force of the wind on the sails. Without a daggerboard or keel,

1716-423: The ratio of the number of teeth on each gear, its gear ratio . The velocity v of the point of contact on the pitch circles is the same on both gears, and is given by where input gear A has radius r A and meshes with output gear B of radius r B , therefore, where N A is the number of teeth on the input gear and N B is the number of teeth on the output gear. The mechanical advantage of

1760-420: The same hull and same mast meaning that the same boat can be used for children of all ages and all abilities. Hull: Rig: Options Daggerboard A daggerboard is a retractable centreboard used by various sailing craft. While other types of centreboard may pivot to retract, a daggerboard slides in a casing. The shape of the daggerboard converts the forward motion into a windward lift, countering

1804-605: The sort of damage to which fixed keels or daggerboards are subject. Daggerboards can be raised and lowered as needed but will generally be damaged if not retracted before impact with the bottom or with floating objects. Many small sailboats use a daggerboard instead of a fixed keel. This allows these boats to be more easily moved on trailers, sailed in shallow waters, and easily beached. Daggerboards also afford an opportunity to reduce drag when racing because they can be retracted when not needed (i.e. when sailing downwind or in very light winds). Daggerboards are often made of wood;

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1848-418: The sprockets at the crank and at the rear drive wheel are the same size, then the ratio of the output force on the tire to the input force on the pedal can be calculated from the law of the lever to be Now, assume that the front sprockets have a choice of 28 and 52 teeth, and that the rear sprockets have a choice of 16 and 32 teeth. Using different combinations, we can compute the following speed ratios between

1892-419: The system. The power input to a gear train with a torque T A applied to the drive pulley which rotates at an angular velocity of ω A is P=T A ω A . Because the power flow is constant, the torque T B and angular velocity ω B of the output gear must satisfy the relation which yields This shows that for an ideal mechanism the input-output speed ratio equals the mechanical advantage of

1936-399: The system. This applies to all mechanical systems ranging from robots to linkages . Gear teeth are designed so that the number of teeth on a gear is proportional to the radius of its pitch circle, and so that the pitch circles of meshing gears roll on each other without slipping. The speed ratio for a pair of meshing gears can be computed from ratio of the radii of the pitch circles and

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