PropellerSafety.com

Archive for Research Projects

A college student in Sweden, Fredrik Helgesson, designed a test stand to log strike test outboard motors (outboard motors impact floating logs).

The report is titled, Konstruktion av “log strike”-testrigg for utomboardsmotorer.

Back in early 2016 Mr. Helgesson, a mechanical engineering student at Halmstad University in Sweden, contacted us a few times for technical specifications on how the industry tests log strike systems. He said he was working on a thesis focused on that topic. We supplied him several publicly available materials, some thoughts on the topic, and told him that if he was not teamed with one of the major outboard manufacturers he would likely not have access to the exact specifications manufacturers use for log strike testing.

A couple months ago we noticed his paper had been published by Halmstad University.

We then learned his project was more of a design project teamed with a manufacturer of diesel outboards, Cimco Marine AB.

Cimco Marine OXE diesel outboard

Cimco Marine OXE diesel outboard

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A few months back we came across a 2015 thesis targeting preventing outboard motors and stern drives from breaking off and flipping into boats when striking submerged objects:

Boat Propulsion Impact Relief System
Baccalaureate thesis
College of Engineering and Applied Science
University of Cincinnati
Mechanical Engineering Technology
Jared Frizzi
30 April 2015

We congratulate Mr. Frizzi for choosing his topic in this field and are glad he was at least partially influenced by our site, even if it was probably later on in his project. However, his work was based on several incorrect assumptions, reducing the contribution he could have made to the field of propeller safety.

Again, we really appreciate him choosing propeller safety related topic, but want to use this opportunity to again encourage anyone choosing a student project off our list to contact us for some guidance. We definitely do not want to take over your project, but we can help point you the right direction, point you to some great resources, help you be successful, and help your work make the largest impact possible. Read More→

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An August 2013 academic study of children water-associated trauma (WAT) advises the boating industry to prevent exposure to boat propellers with this statement:

“manufacturers should be strongly advised to consider redesigning some of the components of watercraft known to induce major injuries in victims in these accidents, including preventing exposure to propellers for instance.”

They go on to state, “the public should be educated on the potential dangers of towed tubing and watercraft associated trauma.”

Children Tubing

Children Tubing
image courtesy U.S. Coast Guard


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Increasing the daytime visibility of water skiers, tubers, banana boat riders, wake boarders wakeboarders, kneeboarders, donuts, tubes, and inflatable tow toy riders being towed by a boat or Personal Watercraft (PWC), especially after they fall can help prevent them from being struck by a boat or boat propeller.

These riders and their implements need to be easily seen and detected both when they are up water skiing, boarding, wake boarding, tubing around the lake AND when they fall from their ride and are awaiting being picked up or to ride again.

Maximizing their visibility can prevent them from being ran over in many instances.

John Mansour and family

John Mansour and family

The popularity of towed tubes and other tow toys has placed many more of these on our waters. Children often ride them. The last few years many young children have been severely struck by boats and/or propellers while tubing. The recent Sunday 14 July 2013 Mansour accident on Sylvan Lake in Michigan (two children dead, one in critical condition) motivated us to action.

John Mansour was on a PWC pulling his three children on a tube when the tube was struck by a ski boat. Alex (11) was declared dead at the hospital, Gabrielle (6) died a few days later, Adriana (10) was in critical condition for several days. Their mother was nearby on shore when the accident happened. The funeral for Gabrielle and Alex is today, July 19, 2013.

We suggest a College Senior Design Project or Capstone Project or Design Team Project would be an excellent means to develop some possible High Visibility towed sports solutions. Engineering students, safety students, recreation students, textile design, clothing design, and industrial design students are among those with useful skills for this project. Read More→

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Recreational boat propellers often strike swimmers, divers, snorkelers, tubers, people ejected from the boat, logs, driftwood, dredge pipes, debris, marine life, or other floating or submerged objects. A model of those risks would be useful in crafting:

  • Boating safety tips
  • Regulations
  • Propeller safety products
  • Design and marking of swimming, snorkeling, and diving areas
  • Boat and boat entry and exit design
  • The place of alcohol, life jackets, and boating safety training
  • Boat designs

We encourage college math and engineering students looking for a senior design project, capstone project, senior thesis, masters thesis, or similar project to consider modeling the risk or probability of a propeller strike in a given area. Read More→

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The boating industry has long been aware that marine drives can strike submerged or floating obstacles. In the early days they conducted on water log strike tests. In more recent times, some have moved to dry land impact tests (log strike test stands), and even considered virtual log strike tests (computer simulated log strike tests).

Old Mercury Outboard Log Strike Test

Old Mercury Outboard Log Strike Test

They moved from on-water testing to the dry-land impact testing shown below.

Log Strike Test

Mercury Marine Log Strike Test

As we understand it, the progression from on-water testing to dry-land impact testing was primarily verified by adjusting the dry-land impact masses to achieve similar failures to the on-water tests with the standardized logs at similar speeds. Dry-land impact facilities cannot be quickly dialed up to achieve a collision with a different kind of log, length of log, diameter or log, geometry of log, log submerged to a different depth, etc. The actual force X time profile may be quite different for a dry-land impact test than for an on-water log strike.

This progression (on water testing to test stands, to considering using simulations) was made without a total understanding of the science and mechanics behind log strikes.

We encourage Senior Design Projects, Sr. Thesis, Masters Thesis, Capstone, and Masters Degree projects on the science behind log strikes (the striking of driftwood, stumps, dredge pipes, and other floating or submerged obstacles by recreational boat outboards and stern drives). A better understanding of this science will allow more accurate designs and testing, resulting in safer boating. Read More→

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We have seen some great student propeller safety research projects through the years. In an effort to encourage more college students to consider propeller safety projects for Senior Design Projects, Project Classes, Senior Thesis, Capstone Projects, and Thesis, we created a post to attract them, Research Projects for Senior Design Classes, Masters Thesis Projects, & Other Researchers. We followed up that post with a series of posts providing additional information on several of the suggested recreational boat propeller safety projects.

Vlist Propeller Safety Project

Vlist Propeller Safety Project. Eindhoven University of Technology. Netherlands. 2005.

The next step to landing more student researchers is to make the projects more attractive by providing funding, hardware, test equipment, access to facilities and engineers, mentors, internships, software, access to boats, test equipment, fast computers, travel / trips, company tours, branded apparel (caps, shirts), a ride in a fast boat, and related incentives.

Free pizza is always good too.

If your are interested in sponsoring any of the projects listed in any way, please contact us (see contact tab in the menu). If you are in the industry and have another related project you would like to list or sponsor, please contact us as well.

Please step up and help the bright minds of tomorrow take on propeller safety issues today! Read More→

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Propeller Guard Design: An Investigation Using CFD. Oliver Lee. University of Sydney (Australia). November 2011.

Mercury CFD mesh

Mercury Marine CFD mesh

We are thrilled to welcome this Computational Fluid Dynamics (CFD) analysis of propeller guards into the library of academic research studies on propeller guards by college students around the world. We also proud to have been a small part of it as it developed. A huge thanks to Oliver Lee for his efforts, to Dr. Steve Armfield his supervisor, to Julian Todd (an Australian propeller safety advocate who assisted with the project), and to the University of Sydney for all their support.

We first heard from Oliver Lee back in late March 2011 as he was getting underway on his Senior Thesis and were able to point him to some information and other studies he found helpful.

Since then he took on a broad swath of propeller guard topics in addition to performing the CFD analysis:

  • Surveyed the types of propeller guards and other propeller safety devices available
  • Investigated the history of propeller guards and the debate surrounding their use
  • Investigated the accident frequency of propeller guards
  • Investigated the relative costs of propeller guard designs
  • Investigated the Australian Safety Propeller and how it fits within this arena
  • Developed a propeller guard rating system based on the protection provided
  • Developed the model and the equations for the CFD analysis

You can download the full pdf document from the link below the thesis. Read More→

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Marine drive companies have long employed damping / cushioning technologies to protect marine drives, most typically trim cylinder log strike systems that allow the drive to swing back, up, and over underwater obstacles. Recent years have brought several through hull drives to the market, most prominently Volvo Penta’s IPS, and Brunswick’s / Cummins Mercruiser Diesel (CMD) Zeus Pod Drive.

CMD Zeus Drive

Cummins MerCruiser Diesel (CMD) Zeus Drive

These thru hull drives, typically used on larger boats, are no longer able to be protected by the trim cylinder log strike systems because the drives do not trim. Volvo Penta and Mercury Marine / Brunswick have been issued several patents for break away drives and other techniques to protect the drive and especially to prevent the boat from sinking if the drive strikes a major obstacle, like a large rock.

In November 2011, Brunswick was issued U.S. Patent 8,062,082 for a “Marine Drive With Staged Energy Absorption Capability”. Targeting through hull drives, the patent describes a drive with a long, crushable nose cone. Depending on the amount of energy to be expended when a drive strikes an obstacle (speed of boat and mass of the boat), the nose cone can crush to absorb the energy, or the drive can “breakaway” from the boat. At lower energies (lighter boats and slower speeds) the nose cone crushes to absorb the energy, slow the boat, protect the main part of the drive, and prevent the boat from stopping so fast that people would be ejected. At higher energies (heavier boats and faster speeds), the drive breaks away in a manner that maintains the integrity of the hull and prevents water from entering the boat. The patent includes several charts showing the deceleration capabilities of varies designs. Brunswick introduces the idea of not only crushing the nosecone to absorb the energy, but also of allowing water to fill the nosecone, then forcing it out through one or more orifices during a collision, of filling the cone with an impact absorbing structure, filling the nosecone with an energy absorbing foam, and review previous approaches by others.

The industry is identifying technologies that can protect the boat, and the drive, and do so in a way that does not cause sufficient rapid deceleration to eject people from the boat.

Some of the earlier technologies, and the some of the more recent developments appear to hold significant promise for being able to reduce the impact / blunt trauma felt by humans when struck by a propeller guard. Anything that can reduce the rapid acceleration felt by humans when struck by a marine drive or guard AND the duration of that acceleration is a candidate for reducing injuries and their severity.

We anticipate publishing a post on the science behind blunt trauma injuries in the future which should also be a helpful reference to those pursuing this project. For those not familiar with blunt trauma injuries or who just think of them resulting from being whacked or hit with something, blunt trauma injuries result from sudden accelerations or sudden decelerations. Our organs, tissues, and even bones are damaged when they are accelerated or decelerated too quickly. Blunt trauma injuries can be reduced by reducing the peak accelerations and decelerations of humans struck by propeller guards.

We propose students consider Cushioned Propeller Guard design projects for their Senior Design Projects, Sr. Thesis, and Capstone projects to better protect humans and marine life from being struck by a propeller guard, and provide further information below. Read More→

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Safety professionals turn to the U.S. Coast Guard Boating Accident Reports Database (BARD) to find the total number of recreational boat propeller accidents reported to USCG.

USCG acknowledges some propeller accidents go unreported. The boating industry claims the more severe an accident it is, the more likely it is to be reported, propeller accidents are severe, so they must almost all be reported.

Propeller safety activists point to countless unreported accidents and previous studies showing thousands of propeller accidents going unreported.

Without an estimate of the total number of propeller accidents, injuries, and fatalities it is difficult to decide how best to address the problem. This same problem exists in accident frequency studies in automobile crashes, industrial accidents, and other fields. We propose encouraging students searching for Senior Design Projects, Capstone Projects, Sr. Thesis, Masters Thesis, and similar projects to consider applying the techniques used to estimate actual accident frequencies in other fields (like automobile injuries and fatalities) to recreational boat propeller accidents. Read More→

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