Marine Technology Group

Surface Piercing Propellers

 
 
SURFACE PIERCING PROPELLER STYLES

Today there are a variety of propeller styles for surface piercing applications to choose from.  In addition, there are numerous manufacturers that claim to have the best propellers available.  Be cautious when selecting propellers – It is easy to get swept up in the enthusiasm of a new project and allow a vendor to sell you a product that isn’t the best fit for your application.  Months later reality catches up in the form of a vessel that will not perform, or can’t even get on plane.  We are frequently involved in the problem solving of these situations after the fact.  Many times a propeller supplier will make recommendations based on what they have on the shelf or have patterns for.  Sometimes gear ratios are compromised for the same reasons or to stay under a torque rating to use a smaller ASD unit.  These issues almost always lead to a disastrous application.  If you are considering using the ASD system, please contact us at H/RI before finalizing your equipment.  We will perform an analysis on your application and make our recommendations at no charge.  We offer this service to enhance the successful use of the ASD system..  

Cleaver

The propeller that readily comes to mind for most people when discussing Surface Drives is the cleaver propeller.  This is understandable as the ASD system was born in a racing environment.  The cleaver propeller is typically manufactured out of stainless steel, with some larger configurations made out of NiBrAl Bronze.  Heavy cambered wedge sections, similar to super cavitating propellers, are standard with a blunt, squared-off trailing edge.  Up to 8-blade cleaver propellers have been used to allow smoother operation and an increase in efficiency with reduced propeller submergence.  These propellers typically are used for vessel speeds in excess of 50 knots.  Depending on the size of the craft, the performance gains fall off using cleavers for the slower speed applications.  As a general rule, there are better styles for the slower speed applications.

Low Rake, Round Ear Propellers

Low rake propellers have a very similar appearance to conventional propellers.  Typically blade areas range from 0.75 for a 4-blade to 1.25 for a 6-blade.  These propellers have a cambered blade section with a trailing edge cup.  Sometimes, for slow speed applications, the cup is extended forward of the maximum radius on the propeller.  The design and application for this style of propeller has come a long way recently.  This is the propeller of choice for most applications under 50 knots.  Propeller geometry can be altered on these propellers to enhance the slow and mid speed performance.  Many propeller shops can undertake the repair of this style of propeller.

High Rake Propellers

The high rake propeller was developed primarily as a "poor man's cleaver."  This is a propeller that is easily manufactured and has evolved from the standard wedge-shaped cleaver propeller.  These propellers generally are for use on the light, high-speed, small vessel applications.

Photos of Surface Piercing Propellers