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Archive for Guard Technologies

Kill switch preventable accident after kill switch preventable accident is stacking up this summer. It is long past time for the industry to investigate alternative methods to prevent Circle of Death accidents. Outboard powered recreational boats from which an operator has been ejected, circle repeatedly striking those in the water.

This post opens with a discussion of the ineffectiveness of kill switch lanyards because almost nobody uses them, then reports on a special control lever created by Vermeer to detect operator presence with potential application to passive (fully automatic) boat kill switch applications.

Vermeer OPS patent application

Vermeer OPS patent application

Read More→

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National Highway Traffic Safety Administration (NHTSA) issued its final rule 31 March 2014 requiring backup cameras on all new vehicles less than 10,000 pounds by May 2018. The rule includes trucks and busses.

Field of view must include the 10 foot by 20 foot zone directly behind the vehicle.

Many automobile manufacturers are already installing the cameras.

FMVSS-111 Rear Visibility Final Rule is anticipated to significantly reduce the number of children backed over.

2010 estimated costs were $132 to $142 per vehicle, or $43 to $45 for camera only installations (vehicle already had a display). Read More→

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Propeller guards on the market in early 2013 are not the optimal solution for all recreational boats and applications. In addition to propeller guards several other propeller safety devices and approaches can mitigate (reduce the frequency and severity) of boat propeller accidents.

We created a chart to illustrate these approaches and their relationships to one another. The chart is very large and best viewed on a large monitor. It is currently a work in progress and will continue to be updated from time to time. Read More→

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Contrapel Water Jet

by Gary

Two New Zealand inventors (Barry Davies and Paul Paterson) have spent nearly twenty years developing a contra-rotating water jet. Like contra-rotating propellers, the Contrapel waterjet uses two impellers turning in opposite directions.

The original efforts were by a firm called ContraJet Ltd. After that effort stalled, it became PropellerJet Ltd. The water jet research and development operation is now called Contrapel Ltd.

Contrapel Boat

Contrapel Rescue Boat

The technology is now running in a 10 meter rescue boat built by Stabicraft Marine. Read More→

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RingProp

RingProp safety propeller

Several years ago, a UK firm tried to commercialize a ringed propeller from Australia called RingProp. The propeller was said to be safer than traditional propellers because human limbs could not easily enter between the blades. When the propeller was spinning it created a shroud around the blades.

Efforts to develop RingProp were spread over at least two decades, two continents, several firms, and one stock exchange. We previously covered the history of RingProp hoping other firms might learn from their efforts and avoid their mistakes.

Liquidators have now placed the intellectual property behind RingProp for sale at Edward Symmons, a UK property and asset consultancy. Read More→

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U.S. Patent 8,240,609 “System and Method for Reducing Viscous Force Between a Fluid and a Surface” invented by Parazzoli, Tanielian, and Greegor (three Boeing researchers), was issued on August 14, 2012. Boeing’s drag reduction patent may hold promise for reducing the drag of conventional cage type or ring type propeller guards.

Viscous drag (the fluid stirring up near the surface) is a significant component of the total drag of many aerodynamic and hydrofoil surfaces. Previous attempts by others have tried to keep the fluid away from the surface. Examples include the Russian Shkval high-speed supercavitating rocket propelled torpedo, Riblets, and the use of suction or a blowing force through pores in the surface.

Boeing’s approach is highly technical but the basics involve the use of a metamaterial (an artificial, manmade material) that generates a magnetic repulsive force between the surface and the fluid.

While Boeing is obviously targeting aviation applications, they specifically note the material could be bonded to a hydrofoil, a boat hull, or a propeller blade. It looks like Boeing is contemplating the use of nanomaterials, or more specifically nanorods for the metamaterial.

Some ways the repulsing forces might be generated include reversing the Casimir-Polder-Lifshitz force between the material and the fluid. Or the repulsion forces might be generated by reversing the van der Waals force between the material and the fluid.

While this technology may still be a ways off, it is certainly worth watching and might one day find widespread use in boating, and might be applied to reducing the drag of propeller guards.

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On June 5, 2012, Volvo Penta was issued U.S. Patent 8,195,381 for a Safety System for Marine Vessels. The patent focuses on detecting people in the water in conjunction with digital anchors. UPDATE note – on September 18, 2012 Volvo Penta was issued another patent, U.S. Patent 8,271,155 for technologies surrounding this same concept.

GPS anchors, also known as digital anchors, are computer systems that keep a boat or vessel in place on the surface of the water. They first gained popularity in drilling rigs and have since spread to recreational boats, and more specifically to larger, twin engine recreational boats. The boat operator can punch a button (or touch a touch screen) and the vessel will stay in place based on GPS signals.

In recreational craft and smaller working vessels, sometimes operate with only one person on board. That person might launch the digital anchor then leave the boat and get in the water to tend to the vessel, to tend to nets, to perform a dive, or for other reasons.

Volvo Penta Patent 8,195,381

Volvo Penta U.S. Patent 8,195,381 sketch

If the digital anchor fails, the boat might leave the area stranding the boat operator. The digital anchor might decide to make a correction just as the boat operator is approaching the stern and they could be struck by the propeller. Read More→

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Yanmar D27 & D36 Diesel Outboard Service Manual cover

Yanmar D27 & D36 Diesel Outboard Service Manual cover

Back in 2000, Yanmar was offering a special lower leg on Model D27A and D36A outboards (27 and 36 horsepower) that came with bolt holes for installing a propeller guard.

The boating industry has long claimed that all marine drive manufacturers are united in their stand against propeller guards. Drive manufacturers say their united stand is an example of how unsafe propeller guards are, the problems they create, and of the impossibility of designing a safe, functional propeller guard. Some marine drive manufacturers have voided the warranty of drives due to propeller guards being mounted on them.

Yanmar may not have installed them, but they set their drives up to use them. Yanmar Service Manual. Diesel Outboard Motor. Models D27A & D36A. Manual # A0A5055-JC03. Model Year 2000. The cover page, and page 141 are reproduced here.

It is obvious from these images that Yanmar built drives with the full intent of them being used with propeller guards AND did so at the request of their customers.

Yanmar Preforms Propeller Guard Mounting Holes

Yanmar preforms propeller guard mounting holes in diesel outboard lower legs

Those objecting to propeller guards sometimes claim the holes drilled for mounting some guards could cause the drive to corrode. Yanmar solved that problem by pre-forming the holes.

Others have claimed that outboards and stern drives were not designed to support propeller guards or the loads they might generate in use. Still others have claimed the drilling of mounting holes could weaken drives and cause them to break.

Long ago, we suggested marine drive manufacturers beef up the drives most likely to have guards mounted to them if necessary, and supply “knock-outs” that could be easily punched out to create mounting holes for propeller guards.

Propeller Guard Paradox Defeated by Ant Farm
Propeller Guard Information Center

“Drive manufacturers could design their drives in advance to accept their own propeller guards by beefing areas needing reinforced and by incorporating any necessary mounting holes either as pre-formed holes or as “knock outs” that could be easily removed.”

Yanmar took that approach one step further (even before we suggested the idea). They went ahead and drilled or formed the holes in an optional lower leg.

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Deer Crossing sign

Deer Crossing sign

Many areas of the country, including ours, are know for large animals being on the road from time to time. In our region, the problem is most often deer at dusk, just after sunset, or during the night. Many drivers become oblivious to the ever present Deer Crossing signs (often with a few bullet holes in them), just like some boaters become oblivious to instructions to check to make sure nobody is near the propeller when the engine is started.

The Propeller Guard Information Center was born from an idea to detect people near the propeller and automatically take actions to prevent boat propeller injuries (shut off the engine, blow the horn, turn on a light, or whatever the best action would be for the particular situation detected).

From time to time we write about new sensors being developed to detect people, and specifically sensors developed to people in the water, such as our recent post on A Survey of Human Sensing Methods published by researchers from Yale and MIT.

Recently, I was pondering similarities in warning drivers of the dangers of striking large animals on roadways to warning boat operators of the dangers of striking swimmers with boat propellers. In both instances we know they (people in the water or large animals on roadways) may be out there somewhere, we do not know exactly where they are, sometimes visibility is bad, sometimes they (swimmer or large animal) appear at the last second too late to successfully avoid striking them at our current speed, and we have some idea of what happens if we hit one (swimmer or large animal). While considering these similarities I came across some interesting research that may be useful to those trying to detect people near propellers.

Several researchers at Montana State University conducted a multi-year study of existing large animal detection systems for roadway use. The study is titled, The Reliability of Animal Detection Systems and Reliability Norms. Read More→

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A paper by Thiago Teixeira and Andreas Savvides from Yale and Gershon Dublon of the Massachusetts Institute of Technology surveys methods used to detect the presence of humans. This work could be very useful for those designing virtual propeller guards (propeller guarding technologies based on sensors).

The paper, A Survey of Human-Sensing: Methods for Detecting Presence, Count, Location, Track, and Identity, creates a taxonomy of observable human properties and physical traits (what can be sensed to detect human presence) along with the methods that can be used to detect them. The paper is available online sometimes.

Their work is a considerable enlargement of the work done by a European college student we helped back in 2005, Human Body Detection Methods: A Literature Review.

The current researchers also discuss the use of sensor fusion (the use of multiple types of sensors in the same system) to reduce false positives and improve overall accuracy. We first encouraged the use of sensor fusion in virtual propeller guards in response to an April 2002 NASA article discussed on our Technologies <2011 page. Brunswick later followed by suggesting the use of multiple sensor types in their infrared virtual propeller guard patents by Staerzl (U.S. Patent 7,476,862 and U.S. Patent 7,511,276). Read More→

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