Propeller Guard Information Center

Author Archive for Gary

An NSW Transport Roads and Maritime accident investigation report dated February 2, 2012, “Report of a Special Purpose Investigation: Into a Propeller Strike Injury Involving an Australian Defence Force Academy Vessel on Lake Burrinjuck NSW on 14 February 2010″, found a group of Cadets and Midshipmen were undertaking training for water insertions (leave the RIB while underway) on Lake Burrinjuck NSW. After the training, the Cadets took the 6.3 meter RIB powered by a 115 HP Yamaha outboard for a joyride including high speed turns during which several people were ejected. In one of those incidents, a Cadet fell from the boat and sustained life threatening injuries from the propeller.

NSW Propeller Accident Investigation Report

NSW Propeller Accident Investigation Report

The investigation found:

  • The Defence literature provides sufficient guidance to conclude that a propeller guard should have been fitted unless there were compelling operating reasons not to do so.
  • There is no evidence of any compelling operational reasons for not fitting a propeller guard.
  • There is no evidence that the vessel was previously fitted with a propeller guard.
  • The risk assessment for water insertions did not adequately consider the likelihood and consequences of a propeller strike.
  • There was no assessment for joyriding.

While the report does not identify the injured Cadet, it is obviously Oliver Minchin. This was a very high profile accident in Australia. Senate Leader Nick Minchin is Oliver Minchin’s father. The accident and Oliver’s recovery were prominently covered in the news.

0 Categories : Regulations

ABYC (American Boat and Yacht Council) and CED (CED Investigative Technologies) recently completed a draft of the Propeller Guard Test Protocol. We announced they requested public comment from interested parties by April 11, 2012 on our Propeller Guard Test Protocol Released by ABYC/CED for Public Comment page.

We sent in our comments today (April 11, 2012) and are posting them below. Read More→

As outboard motors began to increase in horsepower, speeds went up, and striking submerged objects became more dangerous. Manufacturers designed systems to handle the loads created from striking logs or other submerged objects, and ways to test those systems.

We (PGIC) cover log strike testing because the industry often uses log strike tests to evaluate propeller guards, most notably as a defense against the use of guards in propeller injury legal cases.

Part 2 of this post, Log Strike Testing Part 2 covers the testing of these systems at Mercury Marine.

Before we cover the history of log strike testing (in Part 2), we will first explain:

  • Variables and Dynamics of a Log Strike
  • Log Strikes With Manual Trim Systems
  • Conventional Shock Absorbers as Log Strike Systems
  • Hydraulic Trim Systems Are Challenged by Log Strikes
  • Trim Cylinder Design for Absorbing / Cushioning Log Strikes
  • Trim Cylinder Relief Valve Spring Rates and Preloads
  • Trim Cylinder and Outboard Shock Absorber Patents

Read More→

A Discussion of the History of Log Strike Testing at Mercury (Kiekhaefer Corporation), Kiekhaefer Mercury, and Later at Mercury Marine, a Brunswick Company

Please be sure to review Part 1 before reading this section. In Log Strike Testing Part 1: Log Strikes and Log Strike Systems we review what happens during a log strike and systems designed to dissipate these impact loads.

Here in Part 2 we discuss methods used to test log strike systems to make sure they are properly designed to accommodate loads generated at maximum design speeds, that production units meet those design criteria, and that accessories (like propeller guards) do not cause issues during log strikes. Read More→

Log strike tests have long been used by Mercury to prove their outboards and stern drives could survive the impact of striking submerged logs and other floating or submerged obstacles. In the original log strike tests, Mercury’s test crew used concrete weights to position telephone poles horizontally in open water, then ran boats over them. One of these early tests is documented in a Mercury (then built by Kiekhaefer Corporation) video prepared for Mercury distributors and dealers.

We (PGIC) cover log strike testing because the industry often uses log strike tests to evaluate propeller guards, most notably as a defense against the use of guards in propeller injury legal cases.

This early log strike test video surfaced when we began doing some research surrounding the Estate of David Paul McFarlin and Jamie Laass vs. Brunswick Corporation (Mercury Marine and Lund Company) and Others case in which a family boating outing ran over a dredge pipe, a Mercury Marine outboard flipped back up into the boat, and a young boy was killed by the propeller. As I started searching for more information about log strike tests, I found this old Mercury log strike test video.

Mercury Log Strike Test

Mercury Log Strike Test

Read More→

Effectiveness of Propeller Guards

CED Propeller Guard Testing @ SUNY

CED Propeller Guard Testing @ SUNY

About 2006 the U.S. Coast Guard began consulting and contracting with some experts to produce a test protocol for propeller guards. The American Boat and Yachting Council (ABYC) and CED Investigative Technologies are now finalizing that process for USCG. CED Investigative Technologies is a forensic engineering and accident reconstruction firm specializing in providing legal support to legal firms, insurers, and manufacturers.

ABYC and CED have completed the rough draft of their propeller guard protocol, titled “The Effectiveness of Propeller Guards” and are now putting it out for public comment before delivering the final draft the the U.S. Coast Guard later this Spring. Read More→

Dr. Lawrence E. "Larry" Thibault

Dr. Lawrence E. "Larry" Thibault

We just became aware of the passing of Dr. Lawrence “Larry” Thibault back on September 10, 2011. He was well know as a biomechanics expert witness for the plaintiffs in propeller strike cases.

Dr. Thibault, a former Chairman of the School of Bioengineering at the University of Pennsylvania, and founded Biomechanics, Inc. at Exton Pennsylvania. As Biomechanics Inc. he represented many propeller accident victims or their survivors. Read More→

0 Categories : Propeller Safety News

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.

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→

0 Categories : Guard Technologies

Prior to mid 2011 we captured technologies with potential applications to virtual propeller guards (sensor based guards) or to conventional boat propeller guards on our Technologies page, now titled Prop Guard Technologies <2011. With the advent of our new site, we are moving future posts of this nature to their own category which we are launching today (March 25, 2012). Our earlier information on potential Propeller Guard Technologies will remain on the old <2011 page.

Some of these technologies may have application to other guarding applications as well.

Vlist Propeller Safety Project

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

0 Categories : Guard Technologies

The Storm Lake Iowa Laass v. Brunswick case has focused attention on boats and marine drives striking submerged or floating dredge pipes / dredge lines. In the Storm Lake accident, a ten year old boy, David Paul McFarlin was killed on May 31, 2010. A 175 HP Mercury outboard struck a submerged dredge pipe, flipped back up into the boat, and the boy was killed by its propeller.

We started looking for a list of similar “struck dredge pipe” accidents and were a bit surprised not to find any such list. We thought it might especially exist over in the dredge safety literature, but found no such list there either. We found some dredge safety studies, but they focused on the safety of dredging employees, not boating safety.

In the absence of a list, we started making one ourselves. Earlier, when we started making a list of outboard motors that had flipped into boats, we jotted down several U.S. Coast Guard Boating Accident Report Database (BARD) accident numbers for dredge pipe strike accidents. We went back and fleshed out those accidents into a spreadsheet format including the basic statistics surrounding those accidents.

We also checked some media (news) reports, boat forums, and other online sources for additional boat or outboard motor or stern drive struck a floating or submerged dredge pipe accidents. We found almost countless reports online, but few of them are well documented, so we left them off our list. It looks like these accidents happen much more frequently than they are reported to BARD.

The spreadsheet below summarizes our findings. You can download a pdf of the spreadsheet that includes additional columns of data by clicking on it. It is best viewed on a 24 inch or larger monitor. Read More→