MagBlade MaxThrust & SlipStream Propellers Brings Safety to Boat Propellers

MagBlade Propeller

MagBlade Propeller

Recreational Boating Safety (RBS) of South Africa recently announced the new MagBlade boat propellers (MaxThrust & SlipStream) that will fit all outboard and stern drives. Recreational Boating Safety claims the new MagBlade boat propeller is much safer AND provides better performance and maneuverabilty while reducing drag, ventilation, cavitation, and fuel consumption.

Recreational Boat Safety (RBS) accomplishes these things by using aerodynamic principles to harness the potential energy of the water flow. They maximize the use of the surface area of the oncoming “blade face” by reducing the area of the back of the blade. This reduces drag and reduces the area that has high potential for cavitation.

MagBlade Max Thrust also strengthens the impact zone (leading edge of the propeller blade) which increases the life of the propeller.

Mag Blade is manufactured from a keronite (ceramic) coated Thixomolded magnesium alloy. The use of Thixomodling, somewhat similar to plastic injection molding, results in a near net shape product.

By using these materials, they claim MagBlade propellers are lighter, harder, and more rigid than traditional propellers. The more rigid blades do not flex, not even as much as stainless steel propellers, and therefore outperform high performance stainless steel propellers. RBS claims MagBlade propellers are seven times stronger than stainless steel while being four times more impact absorbant than aluminum propellers.

MagBlade Propeller Leading Edge

MagBlade Propeller Leading Edge Insert

MagBlade uses polymer Safety Sleeves on the leading edge of the blade to reduce the chance they will “snag” a human limb and/or cut into the skin of people in the water. As the MagBlade MaxThrust propeller speeds up, it creates a shroud around the propeller “reducing the chances of any object or limb getting in between the propeller blades.” RBS says the safety sleeves are made from an industrial strength, hygroscopic polymer.

MagBlade Propeller Rear

MagBlade MaxThrust boat propeller view of back of blades.

Similar polymer sleeves are used on the trailing edge of the blade allowing them to configure the blade to the desired pitch (different sleeves for different pitches). They claim by offering pitch sleeves from 7 to 23 degrees for 7 different propeller mold sizes will allow them to fit all makes of outboard and inboard marine engines.

The propeller features a patented Anti-drag Lip on the blade face to reduce drag on the back face and to deflect water onto the oncoming blade back. The blades are semi-cleaver, round ear in shape.

RBS also paid attention to the hub. The Vortex Hub System sucks in water and swirls it to produce a secondary jet propulsion. The Vortex Hub System in conjunction with the Anti-drag Lip allows them to utilize 90 percent of the available hydrodynamic flow. Being more efficient allows boats to operate at a lower RPM, burn less fuel, and reduce emissions.

RBS uses a set of Interchangeable Spines to adapt the inside of the hub to all makes and sizes of outboard and stern drive engines (somewhat similar to the adapters used by others).

MagBlade Propeller exploded view

MagBlade Propeller exploded view

RBS claims MagBlade:

  • is salt water corrosion resistant for up to three years
  • is the safest propeller on the market
  • is up to 30% more fuel efficient
  • has higher performance characteristics over conventional propellers
  • reduces the overall harmful impact on the environment
  • is the most durable propeller on the market
  • will be available for sale at the price of an aluminum propeller

Production Status of MagBlade

As of August 30, 2012 RBS website said they were currently completing field testing of prototypes, and hope to commission their manufacture by the end of September 2012 so they can start shipping worldwide by February 2013.

September 13, 2012 Update – Recreational Boat Safety sent us a very colorful newsletter announcing the CFD results are in. TotalSim, a high powered UK, Computational Fluid Dynamics (CFD) consultancy specializing in motorsports, completed their analysis of the MagBlade MaxThrust propeller. The newsletter includes CFD images of the front and back of an aluminum propeller, along images of the front and back of a MagBlade propeller in similar conditions.

The CFD study found MagBlade generates much higher concentrations of thrust on the back of the blade (where it redirects water onto the blade back and the oncoming blade face). The blade back also generates thrust by the anti-drag fin (less drag on the back results in more thrust).

The front of the MagBlade propeller generates more thrust on its leading edge than the equivalent aluminum propeller (less flexing).

The high pressure of the exhaust gasses prevented the vortex hub from creating as much thrust as anticipated. Minor design changes are underway to counter the high pressure being generated by the exhaust gasses. Reducing the pressure and creating a vacuum that draws water into the vortex hub will create additional thrust.

Some cavitation was detected on the back of the MagBlade propeller (from the abrupt drop off at the Anti-drag fin. Minor design changes are being made to lessen the drop off which should eliminate the cavitation.

Minor cavitation was also discovered on the leading edge of the MagBlade from the barreled edge of the safety sleeve. Minor design changes are being made to eliminate this cavitation.

MagBlade was found to travel faster, further, and use less fuel than an aluminum propeller spinning at the same RPM.

A specific example (90 HP Yamaha two stroke outboard with a 15″/13.5″ MagBlade propeller) was found to use $2.41 less in fuel per hour than a similar aluminum propeller powered boat.

Propeller Guard Information Center Comments

We are excited about any firm developing new boat propeller safety products, and especially excited about companies developing revolutionary products for this market.

When we first posted our coverage of MagBlade on August 31, 2012, I noted we were a bit skeptical, but looking forward to receiving more information about the propeller. I even quoted the Sagan Standard / Marcello Truzzi quote, “Extraordinary claims require extraordinary proof.”

On September 3, 2012 I received an email from RBS along with some copies of portions of their patents, a marketing document, a catalog, and an update on their status that answered many of my questions. We have since been in further communication with them and received even more information. We can certainly say they making considerable progress toward supplying the “extraordinary proof” we spoke of earlier.

Who is Recreational Boat Safety (RBS)?

Recreational Boat Safety (RBS) is a family owned South African firm in collaboration with a USA manufacturer and a UK CFD firm.

At the moment, RBS sells Autotether’s FOB based boat propeller safety device, and says they will also soon release a device called the Skipper Guard Tracker that appears to be targeting larger vessels.

Their official address is:

Recreational Boat Safety (Pty) Ltd.
Design Quaters,
Nicol Grove Office Park,
Leslie Road,

Product Names

At first we were a bit confused by all the company / product / brand names: Recreational Boat Safety / RBS / AirBlade Air Blade, MaxBlade Max Blade, MaxThrust Max Thrust, MagBlade SlipStream, FutureProp, and Future Prop.

RBS explained they started out calling their propeller design the AirBlade but found another firm was using that brand name, so they moved to MagBlade. Future Propeller (Pty) Ltd. is a company owned by RBS that will be used as the trading company to sell MagBlade propellers worldwide. SlipStream and MaxThrust are two variations of the MagBlade propeller. SlipStream will be used on smaller motors and MaxThrust will be used on larger motors.

Previous Designs

The fact that some elements of the Mag Blade Max Thrust & SlipStream propellers are found in other propeller designs lends credence to them holding promise in this design.

The concept of a blunt leading edge to create a safety shroud was been previously developed by the Australian Environmental Safety Propeller which has also seen instances of increased top speeds. The Australian Safety Propeller even created blunt edge prototypes by using “snap in” insert edges of the nature of those used by MagBlade.

RingProp was another instance of trying to create a safety shroud around the propeller that appeared to hold promise.

Veem Engineering Group of Australia sells the patented VEEM Interceptor Propeller that uses high density, color coded polymer strips placed in captive grooves near the edge of the propeller blade to change its pitch. Veem says yachts can even use divers to change pitch for different conditions to reduce fuel consumption.

RBS told us they expect to see Computational Fluid Dynamic (CFS) results this week (week of September 3, 2012) from a well known UK CFD firm that is heavily involved in motorsports CFD. RBS anticipates the CFD analysis will confirm RBS’s analysis of thrust comparisons, drag reduction due to the Anti-drag Lip, the effect of exhaust gasses in the vortex hub, additional thrust created by the vortex hub, and several other calculations. If their calculations are confirmed they will soon be making molds.

Propellers Historically Require Lots of Tooling to Cover the Market

A well known problem to those in the boat propeller market is the tremendous number of “versions” required to cover the diameters, pitches, materials (aluminum, stainless, composite), and mounting shafts of many the manufacturers and frame sizes of drives.

Over time, universal mounting hubs were developed to allow one propeller manufacturer’s propellers to adapt to various drive manufacturer’s propeller shafts.

The remaining size variables (diameter and pitch) still create almost countless possibilities. While we originally thought RBS’s polymer pitch sleeves solely adjusted pitch. RBS notes they can also be used to change propeller diameter within a limited range.

RBS’s ability to design and manufacturer just 7 sizes of propellers and use polymer pitch sleeves to convert those 7 sizes to the pitch ranges and diameters necessary tremendously reduces tooling costs inventory costs, and distribution costs.

RBS noted they anticipate being able to cover the recreational boat propeller market with 18 molds for all the parts related to the propellers (hub parts, pitch sleeves, trailing edge sleeves, etc.) while their competitors may require more than 300 molds to cover the same market space.

RBS showed us a catalog indicating the specific RBS part numbers required (base propeller, vortex hub kit, shock spline, several pitch sleeves, safety sleeves, etc) to build a propeller to fit each of the common makes of outboards and stern drives by horsepower built over the last many years.

One possible advantage is the ability for a boater to quickly change their prop between a shorter pitch for high altitude lake operations to a longer pitch for normal operation.

RBS’s ability to cover the market with just a few parts would greatly slash the inventory costs of their dealers. The lighter weight MagBlade propellers would even further reduce shipping costs.

Several manufacturers have selection charts or online tools to help you select the best propeller for your boat, but optimizing the performance of your boat may require you to run a few propellers to make sure you found the best one.

We notice RBS encouraging boaters to work with their dealers to select the best propeller (diameter and pitch strip) for their boat and not attempt that selection on their own.

Among the reasons for different materials (aluminum, stainless steel, composite) are performance and price points. Stainless steel performs great, is expensive, not as easily repaired as aluminum, and not capable of being repaired as many times (because it is hard and thin). Aluminum is much more durable, more likely to become bent, easier to repair, lighter, and capable of being repaired more times. Composite propellers are generally more economical, light, and some allow the replacement of individual blades.

Other reasons for the variety of propellers (3 blades, 4 blades, 5 blades, racing props, ski props, props for bow lift, surface piercing props, twin contra-rotating propellers, houseboat props, cupping, rake, props without through hub exhaust, left handed rotation props, variable pitch props, shift pitch propellers, etc.) seem less specifically addressed by RBS at this stage. However, if RBS can really cover the center of the market, they will still have a very large target market, especially if they can offer stainless steel performance at aluminum prices.

Intellectual Property:

RBS supplied us some information on their patents.

  • South Africa patent application 2012/05753 Propeller Including a Discrete Edge Member (Pitch sleeve patent). Russel Hawkins inventor.
  • South Africa patent application 2012/05757 Propeller Incorporating a Secondary Propulsion System (Vortex hub patent). Russel Hawkins inventor.
  • South Africa patent application 2012/05758 Propeller Including a Blade Back Flow Guide (Anti-drag Lip patent). Russel Hawkins inventor.

All three patent applications were filed in late July 2012. You never really know what a patent office is going to allow until you file the patent and walk it through the system. Our rough guess is the first patent application (propeller with discrete edge member) may have some challenges with the VEEM Interceptor Propeller and the early Australian Environmental Safety Propeller prototypes. The patent office might not find the Safety Propeller prototypes, but they will probably find the VEEM propeller. VEEM widely applied for patents on the pitch strips including US Patent Application US 2008/0526176, US Patent Application 2010/0008780, EP2117921, WO2008095259, CN101616839, AU2008213740.

The VEEM patent application is still working its way through the U.S. Patent system. I found it in Public PAIR as application 12/526,176. It received a non-final rejection notice on August 31, 2012. I used USPTO Public PAIR to see what the examiners were throwing at VEEM’s application it to slow it down. I found the U.S. examiner cited U.S. patent 6,467,422 and U.S. Patent Application 2005/0233654 against VEEM. If VEEM filed back in 2008 and is having problems with their pitch strip patent, depending on their specific claims, RBS may also have trouble with their pitch strip patent. The other two RBS patent applications may encounter less resistance.

Those in the performance end of the propeller market know propellers are still a bit of a black art. It takes a lot of “hands on” knowledge, experience, skill, and trial and error to design, build, and polish a line of propellers for the performance market. Performance prop manufacturers they have learned a lot of tricks over time.

IF RBS’s MagBlade MaxThrust propeller is equal to stainless steel performance at this early stage of its development, even more potential might be tweaked out of RBS’s props later by those highly skilled in the art.

We also always wonder about performance in reverse. When you start making modifications to conventional propellers, sometimes they create problems in reverse. Will MagBlade backup a boat like normal AND provide protection to those in the water when in reverse? Time will tell.

IF MagBlade MaxThrust propeller lives up to its claims, it might find use on large vessels (ships) where a small change in efficiency can result in thousands of dollars in fuel savings.

Mixing applications (large industrial mixers) are another possible application for MagBlade technologies.

Comments on the Business Development of MagBlade

We note Recreational Boat Safety (RBS) is in South Africa. The government of South Africa has long provided a very friendly climate for inventors and those developing new products. Assistance from government and university sources can provide a great boost to those developing products like the MagBlade.

The Tech Park in which RBS is housed is an example of the favorable environment there for development of technical products and services.

South Africa is a country with much of its boundaries defined by water. Boating, work boats, and fishing boats abound in this environment.

We have assisted others developing products in South Africa and been pleasantly surprised at the assistance and support they receive. The country backs innovative efforts because the are trying to create jobs.

A somewhat similar boat propeller safety invention, RingProp, was known for its handlers almost constantly focusing on fundraising, being listed on AIM (the London stock exchange), and frequently generated press releases to stimulate investment. It seemed like they may have spent more time on raising money than on developing the technology.

In contrast, RBS told us that MagBlade is currently funded by the inventor’s family, and they are in process of bringing on an investor with marketing and export experience. RBS notes they anticipate seeking additional investors for a second round of financing as global demand increases.

Recreational Boat Safety is housed in a large, well known tech park similar to the one that housed RingProp in the U.K.

Repairing MagBlade Propellers

RBS says the MagBlade cannot be repaired, however at 7 times stronger than stainless steel AND 7 times more rigid than the most hardened steel, the chances of failure are slim. RBS includes a Shock Spline (breakable insert) in their design to prevent the additional strength of the propeller from damaging the drive. In addition, they will be shipping a spare Shock Spline with each MagBlade.

The existing propeller repair market is a significant force in propeller sales. Prop Repair Shops make recommendations to customers and many sell propellers as well. It would be good for RBS to make friends with the National Marine Propeller Association (predominately U.S. propeller repair shops) and similar organizations around the world as MagBlade gets closer to launch. The prop shops are also often a market for custom repair tools to repair specific brands of propellers.

Field Testing

It sounds like much of the testing to date has been on paper and by CFD (Computational Fluid Dynamics). While that is a great place to start and hone in on optimal designs, the real world often has some effects and nuances we fail to include. We suspect RBS’s CFD optimized designs will need at least limited tweaking after running in the field AND after encountering the manufacturing / assembly problems that always seem to show up.

After endlessly hearing the boating industry tout the advantages of unguarded propellers in going through weedy areas, that is an area we expect some challenges to MagBlade. Its blunter edges may not cut weeds resulting in MagBlade props being stopped in heavily weeded areas.

Prop blades strike sticks, logs, floating debris, rocks, and all kinds of stuff. Some of these impacts may be a challenge for MagBlade’s polymer strips.

The Magnesium alloy is coated for hardness and corrosion resistance. The resistance of that coating to sand (like coming off a sand bar) and other particles suspended in the water may also be a challenge.

We did not notice any left hand propellers in RBS’s catalog. With something of the nature of 25 percent of larger boats having twin drives, that will create several additional parts for RBS to design, build, and inventory.

We are thrilled to see this new propeller entering the market and certainly do not want to be seen as a naysayer, we are just raising a few points that may need some attention.


Recreational Boat Safety says MagBlade MaxThrust propellers will sell at aluminum propeller prices.

While Thixomolding (also called Magnesium Injection Molding, or MAG) offers many benefits and opportunities. Thixomolding’s downsides are the high cost of raw materials, high die development costs, and the need for higher trained machine operators. It will be interesting to see if RBS can really offer products at aluminum propeller prices.

Propellers being priced like prescription drugs may give them enough headroom to reduce their markup and meet aluminum prop pricing.

Reduced shipping costs due to lighter weight raw materials and reduced inventory by using polymer strips to adjust pitch and diameter at point of sale will help as well.


I suggested RBS be sure and comply with any existing boat propeller standards. After discussion with RBS it appears that as long as they stay under .8 meters in diameter there are no standards for propellers.


RBS reports magnesium is recyclable and environmental friendly. They also note it requires 50 percent less electricity to mold MagBlade vs similar die cast aluminum propellers (have to melt the aluminum all the way to a slurry).

Estimating Market Size

We noticed RBS attempted to estimate the world wide market for recreational boat propellers in units. It was interesting to see them using some surveys we posted several years ago on propeller replacement frequency by material (aluminum or stainless steel) and encountering the same lack of data we have previously encountered (boat park / boat population data world wide, propeller sales world wide, etc). They resorted to IBI (International Boat Industry magazine) boat park estimates for several developed countries, including the U.S. RBS estimated about 36 million boats in the countries for which data was available (including 17 million in the U.S.).

RBS estimated 95 percent of those 36 million boats were less than 40 feet in length (their target market). RBS then estimated about 25 percent of those boats had twin engines, and that 50 percent of those engines would need a propeller within the next three years. Their calculations indicate about 21.5 million engines would need a new propeller in the next three years (or a rate of about 7 million propellers per year).

Several years ago RingProp estimated worldwide annual recreational boat propeller sales at 5 million propellers per year.

We have made a few estimates/guesses of annual propeller sales as well. But that is all they are, guesses because:

  • Boat park / boat population data is lacking from many countries and the available data is often not specific to power boats or by size.
  • Little data is available on the frequency at which propellers are replaced.
  • Propeller replacement frequency is known to be related to propeller material (aluminum or stainless) and little data is available on the distribution of propellers by material.
  • Data from major recreational boat propeller manufacturers is confidential.
  • Some of the available data is very old
  • Boat usage rates (hours per year) and the environment of that use is not available for most countries
  • Many small boats outside the U.S. are fishing boats, work boats, or small ferry boats. The replacement frequency of propellers in those environments is unknown.
  • Propellers tend to move through stages in life (put on a boat as a new propeller, repaired a few times, then moved to being stored on the boat as a backup propeller, then stored in garage for possible repair or eventual sale as scrap. Just like the unemployed or underemployed, more propellers get pressed back into service at some times and taken out at others. Several years ago we created a Boat Propeller Life Cycle chart showing the path of a propeller through the system that acknowledges many propellers are carried as replacement propellers.
  • Other unknowns.

We will make a couple comments about RBS’s estimate of 17 million U.S. boats. We are used to seeing the 17 million number. It includes power boats, sail boats, personal watercraft, rafts, and about anything that will float. In addition it includes boats that have not been used for several years.

Boating Industry Market DataBook 2012 places the U.S. boat population at about 8 million outboard boats, 1 million inboard boats, and 1.5 million stern drive boats for a total of 10.5 million power boats. That 10.5 million power boats still includes a lot of boats that have not been used in the last year.

While 10.5 million boats is significantly less than the 17 million boats estimated by RBS, it is still a huge market for propellers.

We are used to seeing business plans estimate market size, then create a spreadsheet showing them getting a small percentage of a large market (like 5 percent of the 7 plus million propellers RBS estimates being sold annually), and then calculating how much profit they would make off that share. We salute RBS for not doing that at this stage. It is often much harder to acquire even a small market share of a fractured market like boat propellers than newcomers anticipate. On the other hand, MagBlade may become wildly successful. We just do not like seeing business plans insert a percent of the market without explaining exactly how they could conquer that market share. RBS did not do that and we salute them for it.


Performance boaters are used to having a gleaming stainless steel propellers on the back of their boat when the drive is raised or when their boat is being trailered. Some magnesium alloy with a what could be perceived as plastic ears on it, might be a bit hard for some of them to stomach. However, if MagBlade can really deliver significant fuel savings, many of them may forget about its appearance.

The polymer “ears” will provide some level of safety when the boat is at rest in the water, being trailered or being stored. Several unreported propeller injuries occur during those times.

In addition, if the polymer strips are bright orange they will provide a strong visual indication of the presence of the propeller blades and the need to avoid them.

The Response of the Competition

Some major players have been making huge profits off the propeller segment for many decades. They will not stand still while a competitor seen as a threat attempts to enter their market. Some of the same players have strongly opposed other propeller safety devices claiming the did not work, were unsafe, saying their use would void the warranty of their marine drives, etc. We would anticipate similar responses if RBS is acknowledged as a significant threat to their cash cow.

In addition, if MagBlade is proven to be a “safety propeller” the industry will be challenged for not creating one earlier. Propeller injury cases will have new fodder against the industry in propeller accident trials. The industry does not want that to happen. They are already having enough trouble in court (Mercury Marine settled three prop cases this summer).

If anybody out there thinks the major players in the boating industry will accept a “safety propeller” with open arms, we suggest they study the reception the Australian Environmental Safety Propeller received, beginning with the 11 February 2010 Miami, Florida USCG Propeller Injury Avoidance Meeting.

We would anticipate opposition to rise in proportion to the level of excitement RBS is able to raise in the marketplace. Many feel the industry has frequently employed technology suppression techniques to block or delay other propeller safety devices.

Interestingly, at least one company no longer in business will may join in the fight (or at least their insurance company). Outboard Marine Corporation (OMC) is still represented in propeller guard cases by their insurance company. They too may well have a stake in trying to prevent MagBlade from being successful in the marketplace.

The boating industry is well known for constructing tests and operating them in a manner that guarantees the failure of propeller safety devices (litigation testing). We would anticipate those tactics being used here as well.

Also among the industry’s objections will be MagBlade’s absence from the previous round of Propeller Guard Protocol on-water testing and tank testing at the State University of New York (SUNY) at Buffalo CRESE (Center for Research and Education in Special Environments).

If the new MagBlade technology really works (increases safety, improves performance, and increases efficiency) and is profitable, and the existing players are unable to block the new technology, they will try to copy it (get as close as possible without violating any patents), license it, or acquire it (buy RBS).

I visited with RBS about the possibility the industry might oppose them or try to suppress their technology. They mentioned they had anticipated those possibilities and shared a plan with me of how they anticipate minimizing and countering those efforts. Their plan sounds like a reasonable approach to me.

In Conclusion

Our review is a little skeptical as could be expected at this early stage. We thank Recreational Boat Safety (RBS) for answering many of our concerns and supplying a wealth of information about their MagBlade propeller.

The Propeller Guard Information Center especially thanks RBS for making the efforts to invent, design, develop, and launch a new propeller safety product. We look forward to MagBlade proving itself in the field and in the marketplace.

I was especially impressed to see RBS’s responses to our comments that were not always positive. I particularly liked this response to our posts:

Russel Hawkins RBS September 5, 2012 email to PGIC

“In conclusion please don’t misunderstand me but all your comments are respected and I am sure that many of these challenges are going to come our way to test us along the way but resolute we shall attempt to stay and grow our business one baby step at a time.”

That is a much more realistic approach than we often see from inventors. We have seem some inventors that think they will capture 50 plus percent of a long existing market almost immediately. RBS anticipates there will be challenges and is preparing to overcome them.

We hope RBS becomes wildly successful and their example encourages others to develop boat propeller safety products as well.


  1. Good day, an interesting write up, do you sell these? Is it possible to put me onto some one who does.please mail me a quote on some of your props for a 90 hp mercury, what size n pitch would you recommend.?

    fa ebrahim

    • They are not yet on the market (October 2013). We heard they may be making some timing announcements at a major trade show by the end of the year.

  2. Hey. Have magblade start selling this propellers now.
    Best regards.from Norway.

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