The 5 Myths of Propeller Performance

By June 2, 2015White papers

5 MYTHS OF PROPELLER PERFORMANCE

The vast majority of propeller manufacturers in the leisure and work boat industry have not been completely forthcoming with their customers. Propeller performance and efficiency is surrounded by myth and misinformation, it is time now to set the record straight.

Myth 1 – You can modify a standard or semi-custom propeller to suit any boat. 

The majority of manufacturers in the market offer a standard range of propellers and have only limited options to change principle geometry during manufacture. Generally, propellers made in this manner are limited to changes in diameter and partial pitch, so the design is compromised, may not suit the application and result in less than optimum performance.

Therefore, standard and semi-custom designed propellers miss out on an integral holistic design process, which includes unique design features like cavitation resistance, blade root designs, specialist trailing edge detail and advanced blade tip geometry that all need to be specific to your engine and boat parameters.

These factors directly affect the performance and smoothness of the vessel.

At VEEM, we use patented robotic moulding and CNC manufacturing techniques to obtain a casting specific to your vessel, eliminating human error. Through proprietary blade selections, pitch distribution and vortex cancellation, VEEM Propellers will allow you to achieve the maximum performance and efficiency with a propeller specific to your boat.

Myth 2 – Balancing a propeller will always improve smoothness and reduce vibration.

Balancing a propeller sometimes improves smoothness and vibration but because handmade propellers and those manufactured using simple computer controlled cutting have inherent geometric inaccuracies, the process of balancing will simply address the mass of the propeller.

What is not addressed is the unbalanced lift or thrust characterises caused by inaccurate geometry over each blade and therefore balancing will never completely reduce vibration.

VEEM Propellers are moulded using patented robotic moulding and CNC manufacturing techniques, which eliminate human error and provide accuracy within a few thousandths of an inch, giving the optimal smooth performance for the boat.

Myth 3 – All CNC (computer controlled cutting) machined propellers are the same and manufactured to the same accuracy. 

Only fully CNC machining over every square inch of a propeller and boss will provide ultimate performance and perfection. The majority of manufacturers manually adjust the propellers throughout the production process and will inherently damage the precision of the propeller and it’s accuracy in the process.

Additionally, unless the casting process is accurate enough to provide an even amount of material to be removed during the machining process, the propellers will stress relieve differently across the propeller after machining and no longer be accurate.

VEEM’s patented robotic casting manufacturing method and CNC machining over  every square inch of the propeller delivers the perfect propeller for your vessel every time.

Myth 4 – A propeller can be physically moved to adjust the pitch

The installation and design of a propeller requires a careful balance of primary and secondary geometry to achieve maximum efficiency. This includes blade area, rake, skew, and blade foil sections that are all designed specific to your boat. Taking the vessel out of the water and attempting to adjust the pitch destroys the geometry and can have a severe impact on performance.

Interceptor fitted propellers by VEEM, feature pitch altering strips that can be changed once in the water, allowing boat users to adjust the pitch of the propeller without interfering with the critical manufacturing geometry. And because the interceptor technology eliminates the costly need for lifting the boat and modifying the propellers, VEEM propellers may be by way of comparison, be essentially free!

Adjusting the pitch of propellers through the use of an interceptor strip offers many benefits to boat owners during and after production. These include tuning to suit exact engine RPM requirements, tuning for changed operating conditions (for example temperatures of water) and load conditions.

Myth 5 – Any propeller manufacturers can provide you an identical replacement of your propeller for your boat.

There is a large element of human error involved in manufacturing hand finished or semi CNC machined propellers, as the majority of propeller industry does. It is certain that the propellers other manufacturers make will only ever be one-offs and will not be available to be replicated precisely in the instance of events like replacing a damaged propeller, producing an identical fleet or providing propellers for dual shafted vessels.

Trying to match the principle geometry of two un-identicle propellers leads to expensive and time consuming lifting of the vessel for modifications that will damage the critical geometry and the subsequent performance of the propeller.

VEEM’s robotic casting method and CNC machining over every square inch of the propeller blades and hub, guarantees the propeller produced matches the propeller  perfectly. Side to side, boat to boat, year to year, VEEM propellers will be identical within thousands of an inch resulting in exactly the same ultimate performance every time.