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Shaped blade vs Flat blade Comparison

Blade Shape:
Propellers with flat blades (Planar blades) are like a paddle. The flat shape is not efficient at producing thrust. At anything less than max RPM the thrust produced will be greatly reduced. Independent test have shown that at a cruising RPM flat blade propellers produce very low thrust & therefore the boat-speed produced is very low. Lower than a standard fixed propeller.
The Gori propeller blade has true camber and shape (aerofoil) to each blade. Therefore the thrust developed will be greater than a flat blade. This is especially true at the cruising RPM or in adverse condition such as motoring into a head sea. The efficiency will at least match that of a fixed propeller. The Gori produces lower noise due to the twist and camber of the blades reducing the amount of wash off the blade

Drag Factors:
All of the flat blade propellers are feathering propellers, not folding. They have a greater blade area exposed to the water flow, which increases drag. This drag is even greater when the shaft is angled downwards’ presenting even more blade to the water flow.
At higher sailing speeds the feathering propeller will begin to auto-rotate. If the engine is in gear, the propeller can cause the engine to turn over and this would create water problems within the engine. The feathering propellers are prone to catching lines and debris, like bags, weeds, lobster/crab pots etc.
The Gori is a folding propeller and so leaves less area exposed to the water flow….less drag. Blades are “hidden” behind the hub. Tests have shown that the Gori has the lowest drag of all three bladed folding, fixed and feathering propellers.
The Gori will not auto-rotate, as it is a folding propeller. Therefore there is no need to engage the gear to stop possible rotation, even at higher sailing speeds. This also applies to hydraulic transmission installations.
It is for this reason that Gori is always the choice for fast cruising and racing catamarans and maxi mono-hulls.

Reversing:
Again flat blades cannot produce the same thrust in reverse as blades with shape. True, their performance in reverse will be better than a fixed prop in reverse. However it may still have pop-walk.
The Gori blade has the same camber and curve shape of blade and leading edge in reverse as fwd and so therefore increased thrust over the flat blade propellers, and gives a dramatic reduction in prop-walk (almost non-existent).

Installation:
Most all flat blade feathering propellers are delivered disassembled. The hub is installed first and then the gears, blades and pitch setting are re-assembled onto the hub. If the incorrect pitch setting is made it will require another haul-out to make that change.
Gori comes completely assembled, pitched and dynamically balanced at the factory. With the supplied tools there is some minor simple assembly required to install, but there is no re-assembly of blades, gears and pitch settings to choose. No chance of making a mistake. In addition no greasing is required.

Performance:
The feathering propellers have only one pitch setting under power.
Gori has two settings; standard and ‘Overdrive”. Motor-sailing is vastly improved when in “Overdrive”. Increased thrust & speed at lower RPM. Using the “Overdrive” function when motoring in calm conditions gives better speed at low RPM.
Less engine RPM results in lower wear and tear, less noise, increased fuel economy and a greater cruising range.

Design:
The planar blade shape has remained unchanged for 20+ years.
Gori propeller blades have under gone design changes as progressive knowledge of prop design has advanced.
Blade Area Ratio(BAR) %, design etc have all been changed and improved.