Propeller Designs

The Aquafoil with it’s cambered pitch face, continues to be one of the most sophisticated standard propellers available anywhere, which is why it is used as standard equipment by the most discerning manufacturers of high speed craft.The Aquafoil ’55 has 3 blades, whilst with 4 blades and 73, 80 or 87 % DAR it is ideal for applications where high horsepower is being transmitted or where the propeller is running in a tunnel.

The Aquaquad has been developed to solve the vibration problems encountered in large pleasure craft when fitted with today’s high horsepower engines. The four blade design gives this finely engineered propeller the acceleration and ‘bite’ of a 3 blade propeller, with a smoothness that can only be bettered by the Aquaquin. The Aquaquad is offered in High Tensile Manganese Bronze or Nickel Aluminium Bronze and should be ordered with 1’’ less pitch than the equivalent 3 blade propeller to maintain the same engine loading. It can also be cupped on the trailing edge.

Surface-Piercing Propellers. This type of propeller was mostly used by offshore power boat racers, but now builders of fast motor yachts fit surface-piercing propellers as standard equipment. The scimitar-shape leading edges are designed to cut through the water with the minimum drag. This type of propeller is subject to very high stresses and must be manufactured to very fine tolerances. Surface-piercing propellers are always dynamically balanced and made from high strength Nickel Aluminium Bronze or Stainless Steel.

The Aquapoise 55 is considered the ‘Industry Standard’ for medium speed inboard cruisers and it is designed for applications where smoothness and performance are essential. The blade design gives less slip then the old-fashioned round blade or turbine propeller. With a Disc Area Ratio of 55% it can be used on displacement craft when the power is considered too high for the Aquapoise 45. The 55 can be manufactured from either High Tensile Manganese Bronze or Nickel Aluminium Bronze.

The Aquapoise 65 is usually cast in Nickel Aluminium Bronze due to its very fine sections and is used on high powered vessels. The ‘65’ is used as standard equipment on high performance pleasure craft, customs, police and patrol launches. With a Disc Area Ratio of 65% it can be cupped on the trailing edge, which has the effect of reducing slippage and cavitation whilst increasing the jet stream volume and therefore the speed of the boat. Although initially more expensive then the ‘45’ and ‘55’ the life expectancy of the Aquapoise ‘65’ more than compensates.

The Aquaquin was designed for the quality end of the fast pleasure yacht market, the Aquaquin is fitted to those high powered vessels where smoothness and vibration free performance is more important than instant acceleration and ‘top end’ speed. The extra blade also makes it ideal for installations where the propeller tip clearance is limited. Many manufacturers have tried to copy the Aquaquin but build refinements such as aerofoil sections, anti-singing edges and ‘high-skew’ blades make duplication impossible.

Highly Skewed Propellers. A relatively new innovation in the propeller industry, highly-skewed propellers are now standard equipment on luxury motor yachts, fast ferries, patrol craft and other high speed vessels where low noise and smooth operation are an essential feature demanded by today’s sophisticated vessels. Particular care must be taken when designing this type of propeller to achieve the correct balance between the sectional thickness and the degree of skew. Usually manufactured in nickel aluminium bronze, the highly-skewed propeller is specially designed to suit the customer’s requirements. This type of propeller is often designed to comply with the rules of classification societies.

The Aquastar is designed to give optimum performance and manoeuvrability on all types of displacement craft. The blade sections and generous hub dimensions impart exceptional strength and damage resistance. As standard, blades are raked aft and have a certain amount of skew, which assures smoothness, even when operating close to a wide sternpost. Finely balanced and supplied as standard with a high quality disc finish, the Aquastar is manufactured from high tensile manganese bronze as standard but is also available in aluminium bronze.

The Kaplan propeller is designed for use on trawlers, tugs, and other vessels where a nozzle is fitted to give greater thrust than a conventional open screw. This type of propeller will typically give 25-30% greater thrust on trawlers, whilst on certain applications up to 50% more thrust has been recorded on tugboats. The Kaplan’s flat pitch face facilitates easy, inexpensive repair whilst its aerofoil sections near the root impart enormous strength and resistance to impact damage.