PROPELLER NOISE

Propulsion propellers are a serious source which can cause annoying noise and vibration problems. It is strongly recommended to look into the following topics in an early stage of the project:
1) Vertical clearance
2) Blade area ratio
3) Tip speed
4) Skew back design
5) Number of blades and blade frequency
6) Tip unloading and class of the propeller
7) Pressure Fluctuation and cavitation for suction and non-suction side
 

An “overloaded” propeller can cause serious cavitation, noise and vibration problems along with loss of performance.

 
The lay-out of the nowadays Yachts do have a Beach Club area located above the propulsion propellers or Storage while in the “old days” Guest and VIP areas where located aft of the engine room and close to the propulsion propellers. The nowadays design offers a benefit as the ship-structure reduces (dampens) structure- borne noise emitted by the propulsion propellers.

Vibrations due to pressure fluctuation equal to the propeller blade frequency or nodes (harmonics), must be studied in an early stage of the project (Design Stage). Finite Element Analysis is strongly recommended in order to avoid serious vibration problems.
 
By means of the afore-mentioned propeller studies we are aiming to achieve “low pressure fluctuation levels” which is very important. Still the propeller blade frequency can be close to or equal to a natural frequency | mode shape of a deck structure. This means that we can to modify the structure by adding pillars (this will affect the interior design) or increase the number of propeller blades.

These are important and significant changes to be made and only can be done in the Design Stage (prior to the build). This kind of problems on an excising Yacht are not easy to solve and the cost involved is significant.

Silent Line has the experience and know-how to carry out these analyses and supply you the best tailor-made Innovative Engineering based solution.
Contact us at info@silentlinegroup.com for additional information or if you require a tailor-made quotation for your applications.