Propeller Guard Information Center

Archive for Our Thoughts on Propeller Safety Topics

Many industries have created “checkoff” programs to generate funds to promote their “produce” or “product”. “Checkoff Programs” originally referred to programs where the manufacturer/producer was presented a checkoff box at time of sale they could check if they elected to participate in the program. Early programs were very successful, and more quickly followed. Some are mandatory, but they are often referred to as “Checkoff Programs” as well. Agriculture produce growers widely adopted Checkoff Programs. Funds are used to promote their produce in general, not a specific brand. Among the more popular agricultural checkoff programs are: “Beef, It’s What’s for Dinner” and “Got Milk”.

Prop Aware Propeller Safety Campaign

Australian Take Care Be Prop Aware campaign logo

Manufacturing industries have also turned to the practice. “Discover Boating” is an example.

We suggest a checkoff program for “Propellers” could be used to generate funds to promote recreational boat propeller safety. Currently, most of the focus on propeller accidents is on the manufacturer of the stern drive or outboard involved in the accident. The entire boating industry is benefiting from stern drive and outboard production, and most notably, those manufacturing propellers would be in a far different situation if outboards and stern drives did not exist. We suggest propeller manufacturers could shoulder at least a small portion of a major propeller safety initiative by voluntarily donating to checkoff funds. Read More→

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The U.S. Coast Guard BARD (Boating Accident Report Database) is a vehicle for driving continuous improvement in boating safety, however, it is not being widely used.

We suggest all boat builders closely monitor their boats in all kinds BARD reported accidents, develop and test solutions where needed, and use those solutions to continuously improve the safety of their products. Read More→

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We recently completed our Developing a Consumer Guide for the Selection of Propeller Guards and Other Propeller Safety Devices post. Part of that project involved creating our Propeller Accident Risk Worksheet. In that worksheet we identify five categories of Propeller Accident Risk:

  • Boat Specifications Risk- some boat types are more likely to be involved in a propeller accident than others.
  • Operator Experience and Environment Risk – inexperienced operators in lakes crowded with inebriated boaters are more likely to be involved in a propeller accident.
  • Water Conditions Risk – choppy water with floating and sunken debris is a recipe for disaster.
  • Activities On and Near My Boat Risk- the more people in the water the more opportunity to hit one with your propeller.
  • Exposure Time and Boater Fatigue Risk – The more time you spend on the water each year, the longer you are exposed to the risks. In addition, people out all day on a small boat in the summer heat suffer boater fatigue, dulling their response times. Boater fatigue also amplifies the effects of alcohol making their boat even more dangerous.

We started thinking about how we could calculate an the actual risk of a given boat (or the people with that boat) being involved in propeller accident and quickly realized that if all the risks were really contained within the five categories we identified (or if we were in a perfect world and were able to identify all the categories of risk and the risk of each category), the risk of a given boat being involved in a propeller accident during a year could be calculated something similar to: Read More→

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This propeller guard selection guide is NOT ready for use. As brightly emblazoned on our documents, they are rough drafts. We posted them to generate a discussion that could improve them as well as provide some ideas to those working on the U.S. Coast Guard’s recently announced efforts to produce a consumer guide to propeller guards.

Our guide also covers safety interlocks, changing boater behaviors, boating safety classes and other boat propeller risk reduction activities.


Introduction to the Selection Guide

Our Propeller Accident Risk Reduction process is guided by three documents: Risk Proofing My Boat Against Propeller Injuries (describes the overall process), Propeller Risk Worksheet (large checklist that collects information to aid in decision making), and the Propeller Injury Avoidance Device Radar Plot (graphical representation of performance of various devices in different propeller injury scenarios).

Risk Proofing My Boat Against Propeller Injuries lays out the process, defines the terms, and identifies many possible actions that could make your boat less likely to be involved in a propeller accident.

It also teaches about five categories of Propeller Risk Reduction Activities: Read More→

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After reading the negative comments left on hundreds of propeller accidents reported in the media, we see some common themes. We thought we would make a check list so readers could just select the ones they want by topic. We have seen all these before. The phrases in quotes are direct quotes from their posts. Read More→

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The boating industry has long objected to propeller guards. One of their frequent objections is the possibility that someone might become entrapped in the propeller guard (physically caught on the prop guard). We find their objection interesting considering we frequently encounter reports of boat propeller accidents in which people were entrapped in open propellers.

Swimmers and those who fall overboard can have their clothing or life jackets caught in the propeller. Others have their bodies impaled by the propeller and remain caught on the propeller somewhat like a fishing hook with the propeller embedded in their leg or trunk. Still others have been trapped between twin propellers.

These accidents are sometimes referred to as propeller entangled, propeller entanglement, propeller entrapment, entrapped by a boat propeller, and a host of other phrases.

A list of some of the occurrences of boat propeller victims being caught on propellers, entrapped by propellers, impaled on propellers, or having their leg embedded by a propeller follows: Read More→

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Following up on Hydrodynamics of Propeller Accidents Part 1, we now share some research work that looks very applicable to future hydrodynamic studies of human body / swimmer / man overboard interactions with boats, drives, propellers, and propeller guards.

Whale Model

Whale Model

We recently came across some hydrodynamic studies of whale interactions with ships, ship hulls, and ship propellers. One study was done at Carderock (the U.S. Navy lab facility we earlier suggested as a possible location to do full scale interaction studies with small boats). In the whale ship interaction study, they used a scale model of a huge containership with an elliptical bow bulb along with an instrumented model of a right whale.

The study is cited below.

Hydrodynamics of a Ship/Whale Collision.
Gregory K. Silber, Jonathan Slutsky, and Shannon Bettridge.
Journal of Experimental Marine Biology and Ecology.
Vol.391 (2010) Pages 10-19.
an Elsevier Journal.

Several quotes in the journal are strikingly similar to the needs of propeller guard hydrodynamic studies. The abstract contained the quote below:

“Factors influencing the incidence and severity of ship strikes are not well understood, although vessel speed appears to be a strong contributor. The purpose of this study was to characterize the hydrodynamic effects near a moving hull that may cause a whale to be drawn in or repelled from the hull, and to assess the acceleration exerted on a whale at the time of impact.”

Read More→

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Little research has been done surrounding the hydromechanics of people / swimmers/ man overboard encounters with propellers or propeller guards. We will now explore this field, some of the opportunities it presents, and some recent research that looks very applicable to studying the hydrodynamics of human / boat / propeller / propeller guard interactions. We will begin by exploring the history of what has been done to date. Read More→

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We have been promoting the use of Computational Fluid Dynamics (CFD) in the development of prop guards for a long time. It’s been on our Help Us page for several years, we mentioned CFD in our January 2009 post on a Propeller Guard With Reduced Drag, and just a few days ago we briefly discussed the use of CFD in our The Emperor Has No Boat: SUNY Propeller Guard Testing post. In addition, our efforts to encourage engineering and design students working on student projects, thesis, and dissertations to consider studying propeller guards has a student that looks like he is going to be working at least in part, on propeller guard CFD.

Computational Fluid Dynamics (CFD) is a natural fit for propeller guard design. It allows sorting through the design variables to optimize the propeller guards to reduce drag, minimize their impact on boat handling issues, make sure cavitation issues do not cause a problem, and even test the interaction between propeller guards and humans (human factors issues of being struck by a guard, being entrapped, or being pulled into a recreational boat propeller). Read More→

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Emperor

The Emperor has no boat.

CED Investigative Technologies, Inc. has been testing the human factors of propeller guards at State University of New York (SUNY) Buffalo at their Center for Research in Education and Special Environments (CRESE) facility. Some may recall, this is the same facility used by Mercury Marine and Outboard Marine Corporation to test a propeller guard back in late 1990. CRESE has a large circular water tank resembling a doughnut from above. Read More→

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