A superyacht with bent or cracked propeller blades might experience severe vibrations while sailing. The classification society might demand a repair before the vessel is allowed to sail on.
Straightening the blades or cropping them underwater can restore the propeller’s balance and result in a green light from the class society allowing the yacht to proceed on its way.
A propeller modification can easily be combined with any other maintenance or repair operation that needs to be carried out on the vessel, as was the case with several of the examples that can be found below. Firms with underwater repair capability like Hydrex allow a vessel to keep to its schedule.
Blade straightening
By taking advantage of the in-house developed cold straightening technique, damaged blades can be straightened underwater, allowing the ship to return to commercial operations without the need to dry dock.
Optimum efficiency of the propellers can be restored by bringing the blades back close to their original form. The cold straightening machine has been in use for quite some time now but the Hydrex research department has been looking into ways to enhance the technique even further to improve our services. A new model of the straightening machine was recently put into service. It is compatible with the existing model and is used to restore more severely bent propeller blades.
Cropping
If straightening is not an option, the affected area on the blade will be cropped to restore the hydrodynamic balance. This is done to achieve the greatest possible efficiency for the vessel. This kind of repair is carried out with the propeller blade cutting equipment that was also developed by the company’s research department. First a detailed underwater inspection is performed by a diver technician team to obtain the exact parameters of the damage which are then used for a detailed calculation of the ideal cutting line. This allows the customer to know in advance what the result of the operation will be. He can then make an informed decision.
On some occasions an entire blade has to be replaced on a variable pitch propeller. This work can also be carried out by Hydrex divers who are trained to perform a wide variety of operations, both above and below the waterline, anywhere in the world and sometimes even in the most extreme conditions.