From reversible and folding blades to changing pitch with rubber inserts, marine propellers are more versatile than ever.
At the 2024 METSTRADE Show in Amsterdam, GORI Propeller introduced a hybrid folding propeller for electric and hybrid sailing yachts that can switch between regeneration and sailing modes.
The Danish propeller maker said it has developed an integrated locking system that keeps the blades open when regeneration is prioritized. Through counter-rotating, the blades will release so they fold when the boat is in sailing mode.
“Using the GORI 3-Blade Propeller for regeneration is not new, customers have been using our original propeller for several years now, but it’s not optimized for this purpose,” Lars Østergaard Senior Vice President Sales at GORI Propeller, said in a statement. “Extensive testing has been conducted in Haderslev, Denmark and with a manufacturer of electric propulsion. We are delighted with the results, and it’s time for us to tell the world that effective regeneration with a folding propeller is possible.”
The Gori Hybrid propeller 3-blade is available for sailboats with inboards and saildrive propulsion in diameters from 18 to 30 inches.
While the new Gori prop is the first of its kind, there have been advances with other types of propellers designed for sailboats and trawlers. Propeller repair techniques and equipment have also become more precise, so the prospect of getting a propeller custom-tuned to your boat could save money over a new wheel and improve your boat’s performance and fuel efficiency.
AB Marine in Middletown, R.I., has been focusing on sailboat propellers for more than 25 years. One of the lines the dealer carries is GORI. The biggest advantage of the new hybrid propeller is that it locks in the fully open position for regeneration.
“If you took a folding propeller and try to use it to regenerate, the blades will sit at a 45-degree angle to the water flow,” said Brendan Prior, partner at AB Marine. The difference with the new GORI hybrid is that it is the only folding prop with blades that can lock in the fully open position for optimized regeneration. For lack of a better term, they stay vertical and spin when the boat is under sail to provide more efficient regeneration. Because the blades lock in this open position, GORI is the only folding propeller that the blades flip through 180 degrees, so you get the same leading edge in reverse that you had in forward, giving a boat better maneuverability around a dock.
“With a fixed propeller, it’s not efficient to go into reverse,” said Prior. The GORI hybrid is made of Nibral and will be in production this summer. It can work on any sailboat from 20 to 80 feet. While the hybrid propeller is the newest offering, Prior said the most popular current prop from GORI is the three-blade Overdrive. As more boats start going with electric or hybrid propulsion, he expects the new product to gain market share.
Prior explained that there are three main types of propellers for sailboats and displacement motoryachts like full-keeled trawlers. A fixed traditional prop is as it sounds with two or three blades cast in one configuration with a primary function of pushing a boat forward when the transmission shifts in gear. A feathering propeller works like a CV joint in a car with blades that twist to align with the water flow. They rotate on an axis to align with the water to reduce drag while sailing. Blades on folding propellers collapse when the boat is under sail to reduce drag.
In addition to GORI, AB Marine carries Variprop, Autoprop and fixed sailboat propellers from Michigan Wheel. Variprop is good for applications where the propeller sits in an aperture like a keel or has limited clearance under the hull bottom. It has adjustable pitch so you can tinker with it to try to increase efficiency.
The Autoprop is a self-pitching propeller that adjusts based on boat speed and shaft rpm. “It’s always hunting for the most efficient pitch, but it does have the most drag when sailing,” said Prior.
If your boat has a saildrive, you’ll want to consider that it has a different hub than an inboard prop. Prior also said that a saildrive propeller has a maximum diameter of 20 inches because of clearance to the hull bottom.
If a person is trying to find the best propeller for a given boat, AB Marine has a PropFinder function on its website, AB-Marine.com. The dealer developed proprietary software that lets it take the performance data from a given application and recommend one or more propellers.
Prior said that most displacement powerboats like trawlers have a fixed propeller. An owner could use an Autoprop in this application because it’s self-pitching and provides greater fuel efficiency.
“When we size props for trawlers, we try to get history and backload from the owner and how they’re using it and try to come up with a prop that’s optimized to their speed,” said Prior.
AB Marine also carries Hundested Controllable Pitch Propeller that are primarily for lager yachts. They have controllable pitch design propellers that allow the pitch to change while the vessel is underway. A pitch control unit mounts on the shaft and adjusts the pitch based on engine rpm and load.
General Propeller in Bradenton, Fla., carries inboard propellers from Michigan Wheel and Australia’s Veem for trawlers. Sales manager Pablo Soto said that advances in propellers for displacement boats include increasing the number of blades from the traditional three-blade design that was popular in the 1990s.
For a trawler, he wants to run a calculation based on the boat’s displacement, gear reduction, blades and more. With lower gearing, like a 3:1 ratio, you want more blades to generate thrust. A higher ratio like 1:1, which is used in higher-revving applications like a tournament ski boat, has a smaller propeller.
Another characteristic of propellers that Soto said is getting more attention for displacement boats is disc-area ratio. This is the ratio of the total blade area of the propeller to the area of a circle with the same diameter as the propeller.
“If you have a 60-foot boat, going to the right blade configuration and disc-area ratio is going to make a big difference,” said Soto.
Blue Ribbon Propeller
Another intriguing propeller design that has created serious buzz since it was first introduced in 2012 is the Sharrow Propeller. Greg Sharrow, the founder and CEO of Sharrow Marine, was working in video production and wanted a drone that operated without the humming blade noise.
He came up with a ribbon or loop design and then realized that it might have an application in boat propellers. It’s called a ribbon or loop because the blade looks like the center section has been cut out, creating a loop shape. Initially, the propellers were tested on outboards and stern drives with noteworthy results.
One reason for this is that early Sharrow propellers were custom designed for each boat and for specific rpm ranges. This led to high prices for the propeller, but plenty of people decided the investment was worth it.
More recently, Sharrow partnered with Veem to create the Sharrow by Veem propeller. It is targeted for inboard-powered boats ranging from 33 feet to 98 feet and owners who want to save fuel and experience reduced vibration.
Work With What you Have
Another way to improve the performance of your boat is to have its current propeller customized. Randy Hale is the founder of Hale Propeller in Old Saybrook, Conn., and the inventor of the Hale MRI (Measurement Recording Instrument), a three-dimensional propeller measurement device.
The Hale MRI uses an arm-mounted device that rolls across the face of the blades of a propeller, measuring pitch, rake, track, angular spacing, section face camber and more. Permanent records of pre- and post-repair data are stored in a PC that can be transferred to another MRI user via email or data storage devices. More than 250 propeller repair shops worldwide use the MRI.
If a propeller doesn’t need repairs, Hale can customize a propeller for a boat including a trawler.
“They’re not looking to gain speed,” Hale says of his trawler customers. “It’s usually, at 1500 or 2000 rpm, I want to burn 2 gallons per hour and run 10 knots. It’s all about fuel burn and range.”
He explains that they need to start with a sea trial that includes spending time at full throttle. Many times, a potential customer will reveal that he’s never run his boat at wide open. Hale recommends doing so at least twice a year because it can reveal maladies like a clogged injector or dirty filter.
Once he has the baseline data, Hale can use MRI to customize the propeller to what the client wants. He estimates that 50 percent of the time a boat that comes to him is not propped correctly. “We make the adjustments to make sure you’re burning the correct amount of fuel,” said Hale. Veem propellers have plastic interceptor fins that can be installed on a blade to change the pitch measurement.
The best part is that on a 30-inch diameter Veem propeller, Hale said the typical custom work will cost a boat owner between $500 and $1,000. He gets about $10,000 for a new 30-inch Veem wheel. ν