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Use the form below to delete this Free Download High Definition Cars Volvo Recharge Hd image from our index. Use the form below to delete this Directions Boat By River From Reedham The Boatyard Is Based In A image from our index. Use the form below to delete this WaterCar Panther Auto Anfibia Con Motore Honda V6 image from our index. Use the form below to delete this Charter Your Own Private Speed Boat Pictures image from our index. At moderate impact speeds, your body just deforms some to accept the impact OR it deforms enough to buy time until the affected segments of your body begin to move to absorb the load. At higher impact speeds the ability of the body to deform is limited by its inertial and viscous properties. Vian and King note chest impacts compress the ribcage causing a tensile strain on the outside of the ribs. To design protective systems, Viano and King say you need to understand injury mechanisms, quantify human tolerance levels, and develop numerical relationships between measurable engineering parameters such as force, acceleration, deformation, and injury. Researchers have found that for chest injuries, the product of the velocity of deformation (V) and the percent of compression (C) is useful in estimating injury type (crushing, viscous, or blast).
Serious blunt trauma viscous chest injuries actually occur at the time of VCmax which is typically at about half the time for the chest to reach maximum compression. At very high rates of loading (rates of compression), such as those seen in blast waves (like roadside IEDs) injury occurs with less than 10 to 15 percent compression. Over many years of study, researchers have developed tables of human tolerances for many chest and abdomen blunt trauma impacts.
Dick Snyder Propeller Guard Patent SketchBack to marine drive applications, imagine an outboard boat without a propeller being towed by another boat.
SUNY propeller guard leg strike at 13.6 mphBack in 1990, Mercury Marine and Outboard Marine Corporation (OMC) conducted a series of tests in the large circular tank at the State University of New York (SUNY) at Buffalo. The testing used cadavers from elderly people that had been frozen and stored a long time, so the speeds corresponding to these types of injuries may not be accurate. If the leg had encountered the sloped surface of the guard and not been across the leading edge the cadaver would have fared much better. Balius Propeller Guard (non-retracting)Back in 1980 the boating industry estimated the increased cross sectional area of a propeller guard vs.
The industry said prop guards are dangerous due to the potential for blunt trauma injuries from all this additional cross sectional area. We cover these claims and the industry’s calculations in our Propeller Guards Increase Cross Sectional Area and Thus Increase Risk of Injury?
The boating industry has long objected to propeller guards claiming the increased cross section area (vs an open propeller) creates a deadly blunt trauma hazard to those in the water.
The industry’s opposition to propeller guards based on increased cross sectional area increasing the possibility of blunt trauma does not hold water.
Now (in 2016) since creating this post we are seeing quints with larger outboard motors (even 400 quints). It seems pretty apparent after seeing the large triples, quads, and quints the industry is not really concerned about the amount of hardware dragging in the water.
The boating industry has often commented that propeller cuts are nice clean, easy to treat cuts vs. We have seen countless stories on propeller wounds being infected from the water and spoken with several victims and family members who have endured those challenges. In addition to infection issues, a recent reference reports propeller wounds are much more blunt and crushing than widely thought.
The Chinese researchers explore the differences between propeller injuries and corpse dismemberment (how to tell if a body found in the water or on the beach was hit by a propeller or foul play such as hit by an axe or hatchet). Propeller strikes to large marine mammals often leave a repetitive chop pattern we are used to seeing in news photos. Forensic Methods for Characterizing Watercraft from Watercraft-Induced Wounds on the Florida Manatee. The repetitive chopping pattern of being struck by each blade as the propeller rotates seen on large marine mammals is often missing on humans. Unlike marine mammals that may have previously been relatively stationery in the water, many humans just fell overboard and are dynamically trying to recover themselves when they are struck.

While we do see humans with many repetitive strikes on their trunk or a leg from time to time, often we see humans with chops to multiple body parts, or a few repetitive chops on one body part. Large stainless steel propellers on larger outboards have more momentum than smaller aluminum propellers.
Much remains to be learned about blunt trauma with respect to propeller guards, especially in terms of developing some typical impact numbers, forces, velocities, CV, and the body’s tolerance of these values when in the water. A related field of blunt trauma study is the study of blunt trauma to large marine mammals (whales, manatees, dugongs, etc.). Some work is being done trying to extrapolate tests done on animals (such as drop impact tests to goat skulls) to humans. We look forward to an era in which similar efforts are applied to better understanding propeller injuries to humans and their long term effects. The Anatomy and Biomechanics of Experimentally Traumatized Human Cadaver Lower Extremity Components. We doesn't provide boat with propeller products or service, please contact them directly and verify their companies info carefully. As lower rotation speed, the MAU Propeller more often used in Giant-scale boats, ROV, RC rescue boat, RC angling boat, etca€¦ 2.
For example: our brain is surrounded by our skull, our heart, lungs, liver, and kidneys are protected by our backbone and ribcage.
Velocity of deformation times the percent of compression is sometimes called the Viscous Response. Meaning, the chest is still being compressed by the blunt object AFTER the major viscous injuries have occurred. Our Diver Struck by Propeller Caught on Underwater Video post shows several stills from that encounter and provides a link to the video.
If a cylindrical body part, such as a person’s lower leg, is suspended in the water perpendicular to the oncoming drive (without a propeller) what happens depends on how fast the boat is being towed.
A portion of that work was striking cadaver legs with the leading edge of the Snyder guard. The cadaver leg, including foot, is suspended across the path of the oncoming outboard and guard.
The investigators said the leg still had a fracture, but it was much less severe than the 13.6 mph run. Similarly, if the Snyder guard had a more bulbous leading edge (broad rounding to the front), or incorporated some shock absorbers to allow some give to stretch out the impact time, the cadaver may have fared better. When their own calculations are used on modern propeller guards the increase in cross sectional area is just a fraction of than their previously exaggerated estimates.
How can they promote the use of three or more outboard motors on the same boat (hanging three or more times as much stuff in the water) while at the same time reject guards due to the risk of blunt trauma from the additional cross sectional area? Some might suggest the industry is more concerned about the money from selling all these large expensive outboards and the additional sales they generate by brand appeal than they are about people in the water. A recent example, On June 8, 2013 Chase Edwards, 12, was on Joe Pool Lake in Texas with his mother.
100 autopsies of boat propeller injuries were performed between 1994 and 2005 in Huzhou district, Zhejiang province. Several researchers have taken to analyzing those repetitive chops to determine the diameter and pitch of the propeller that made them. All the activity of trying to get themselves back to the surface and trying to avoid being struck, makes them a much less stable target than a lounging manatee. From the propeller strike victims we have observed, it seems like smaller horsepower outboards tend to leave classic repetitive chop patterns more often than higher horsepower outboards. Their blades are thicker that stainless steel propeller blades more often seen in larger propellers. As a result, the larger stainless steel propellers deliver more energy and and are more likely to result in amputations before the repetitive pattern can be observed. Its sad that sharp and blunt trauma injuries to large mammals, caused by vessels and propellers have been studied much more than similar injuries to humans.
They also note that blunt impact of our upper abdomen (just below our rib cage) can compress and injure our liver or spleen before our body begins to accelerate from the force. Limits have been established for many situations to prevent the breakage of bones, to avoid compression injuries, and to prevent viscous injuries. Viscous injuries tend to occur when the peak value of VC (VCmax) is equal to or greater than one meter per second (like when the chest is 33 percent compressed and the velocity of deformation is 3 meters per second).

Rib fractures also happen at that time (VCmax), well before maximum compression of the chest. While these limits have been established in air, they provide a guideline for what could be established in water.
The same holds true if the drive had a propeller guard that closely fit the leading edge of the drive, like the Snyder guard. The guard has stuck the leg in the upper shin area at 13.6 mph and obviously fractured the leg. They used a very large bulbous basket type propeller guard (the guard at right) and said prop guards present a cross sectional area to those in the water 2.5 times as big as the area of an open propeller. Plus if cross sectional area in the water is an issue, why are they promoting to twin outboards, triples and quads in their commercials and advertisements? For example compare all the hardware dragging in the water in the two images below to a single propeller guard on a small outboard motor.
The Golden Rule was later in a high profile boat propeller accident after the Mercury tweet below. The boat they were in collided with another boat in the dark, Chase was ejected and struck by a boat propeller. The victims were studied for characteristics of the wounds, abrasions, fractures, and clothing. Tom Pitchford of the Marine Mammal Pathology Lab, Fish and Wildlife Institute, Florida Fish and Wildlife Conservation Commission is among the researchers working this field, including co-authoring the paper below with several other researchers, and Dick Snyder (long time Mercury Marine propeller guard expert witness). Plus humans may be more likely to initially engage the prop with their appendages (legs, feet, arms, hands) than marine mammals.
The thicker blades of small propellers reduces their ability to amputate limbs (thicker blades are harder to drive deep enough to amputate limbs). For example, see Gross and Histologic Evidence of Sharp and Blunt Trauma in North Atlantic Right Whales Killed by Vessels. We can still survive if they are crushed (and we quickly receive the level of trauma care available at many major hospitals). The velocity of the guard in combination with the mass of the leg and the added mass of the leg did not allow the leg and foot to swing back around before it fractured. By 1989 the industry had increased their estimate to three times that of an open propeller. These additional drives add a tremendous amount of cross sectional area in the water, but the issue of creating additional blunt trauma hazards is never raised. Propeller wounds are sometimes left open for several days before sewing them shut to try to kill the infection. Per a 14 July 2013 MyFoxDFW story, Chase is battling infections, suffered a broken pelvis, ankle, and thigh. Their cylinders are so large the added mass alone becomes a huge force when trying to move them in the water.
Boats have enough power to knock humans around a with their propellers, while large marine mammals just stay put for the duration of the strike.
One of my uncle’s had his arm crushed between a dump truck bed and its undercarriage a few years ago. The industry failed to note ring type guards present about 1.25 times the cross sectional area of an open propeller. Chinese researchers found the wounds to be distinguishable due to differences in the amount of force and recoil force, and in differences mechanical cutting (propeller) vs.
Even though he was trapped for several hours before anyone became aware of his predicament, his arm was saved and he has since been been able to recover much of his previous capabilities.
If guards are dangerous, are boats exceptionally dangerous, as seen in this headline from The Star Online? Boat propeller injuries come from high speed props with huge splitting power and mechanical cutting.

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