Frequently Asked Questions
Frequently Asked Questions
WHAT PROPELLER SUITS MY BOAT ?
Not all propellers work for all boats. Propeller dimensions and features vary among boats with different parameters such as
- Boat main particulars
- Engine specifications
- Gear box specifications
- Mode of operation
- Desired speed
Since boats differ in those parameters, it’s usually complicated to achieve a proper propeller design which would give the optimum speed and efficiency. A propeller manufacturer could help you with the best possible combinations of propeller variables for the optimum propeller, from their theoretical as well as practical aspects. Please feel free to write to us. We would give you the best propeller quote.
WHAT IS OVERLOADED PROPELLER ?
If your engine is not achieving its rated RPM while running, an overloaded propeller could be the reason. You could see the sign of black smoke from the engine exhaust. An overloaded propeller could cause severe damage to your engine parts in long run ad that would eventually result in higher fuel consumption.
Too high pitch would be the primary reason for overloading. Too large propeller diameter would also be the reason rarely.
WHAT IS UNDER LOADED PROPELLER ?
If your engine revolutions are higher than its rated RPM while running, you have an under loaded propeller. You are not using your engine’s full capabilities. This may cause engine parts damages in long run, as the engine is not designed to revolve beyond its recommended RPM.
Insufficient pitch and diameter of propeller are the reasons.
WHAT IS CAVITATION ?
Cavitation is a phenomenon of water vaporizing or boiling due to the extreme reduction of pressure on the back of the propeller blade. The low pressure tends to generate bubbles which would implode due to the pressure of surrounded water. This implosion causes a pitting on the surface of blades. Over time this would cause a severe damage to the blades. The eroded blades would result an unbalanced propeller with poor surface finish which would affect the propeller efficiency.
There are different types of cavitation. They may be grouped as :
- Tip vortex Cavitation
- Sheet Cavitation
- Cloud Cavitation
- Bubble Cavitation
- Root Cavitation
- Face Cavitation
- Boss Vortex Cavitation
WHAT ARE THE CAUSES OF CAVITATION ?
Causes for cavitation:
- Heavily loaded propeller
- Pitch / diameter ratio too high
- Thicker blade and blade tips
- Insufficient blade area
HOW TO PREVENT CAVITATION ?
Propeller manufacturers would have a clear picture of how to keep the cavitation minimal, from their theoretical aspect as well as practical experience. All propeller designs would be particularly checked for cavitation.
Here are some remedies to reduce cavitation:
- Proper loading for the blades
- Increasing blade area ratio
- Keeping pitch/diameter ratio under the limit
- Using high strength alloys such as Nickel Aluminium Bronze (Cu3 grade), which has a better resistance to cavitation due to its high strength characteristics, thus improving the thickness profile for minimal cavitation.
- Keeping the propeller free from fouling due to marine organisms , which may induce cavitation
- Reconditioning the blade damages in period and keeping a smooth defect free blade surface
- Increasing the no.of blades