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About Marine Propellers

6/20/2013 1:41:42 PM | by Anonymous

Marine Propellers

A type of fan, marine propellers moves vessels by transmitting power which converts rotational motion into thrust. The rotating propeller creates a water pressure to its rear causing the boat to propel in the opposite direction. The invention of marine propellers is considered a great advancement from the old ways of propelling boats which are manual rowing and reliant to wind power. The concept behind the creation of propellers came from the paddling or rowing movement that Venetian gondoliers make. Their trademark J-stroke paddle movement involves a regular stroke with turning the canoe creating a J stroke for final act.


There are different types of marine propellers which size and construction type vary depending on their application. The variation in the construction of marine propellers can be distinguished on how they are attached and the number of blades. Marine propellers are usually designed with either three or four blade configurations, though five or more blades are also constructed for larger vessels. For reduced noise in boats, multiple blades can be applied. Three and four blade forms have their advantages and disadvantages. The cost of three-blade propellers is lower and their top speed performance is good. Four-blade propellers, on the other hand, are costlier but feature improved handling which is especially useful in rough seas. A blade’s performance can be measured by how far forward it can move the boat through the water in one rotation.


Marine propellers are attached in the boat where they can be submerged in the water to perform their function. Since this is the case, they have to be made from materials which they would not get easily destroyed. Painted or powder-coated steel could be used but they cannot be considered as effective as aluminium and stainless steel which are the popular materials to use when dealing with rust. These metals are not only known for being corrosion resistant but also for their durability which great features can justify their being expensive. Blades made out of metal are also considered as the ones easy to repair but the easiness would still vary depending on the metal. Doing repairs on aluminium parts are usually simpler to perform and less costly than those made from stainless steel.


Attaching the blades to the marine propeller can be done by either welding or forging in one piece. Blades that are forged are more durable and perform better compared to welded blades but can be purchased in a higher cost. When it comes to repairing the blade, welding and soldering is applied. Damages to blades usually occur to light and cheap metals. The blades could be bent, chipped our completely broken beyond repair and would require replacement. Some bent blades can still be straightened. Meanwhile, torn blades can be repaired through welding and soldering. Among the two, soldering is a cheaper way to fix blades but welding can give more powerful bond. After repairs are initiated on the blade, check if the marine propeller is balanced to make sure that it would not vibrate when it spins as this could damage the lower part of the unit.

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