Page 14: of Maritime Reporter Magazine (January 2018)

Propeller Guards

About the Authors

PROPULSOIN UPDATE & Cutters

Matthew Bonvento is the Senior Man- ager for Safety, Security, Regulatory, and Quality Compliance for Vanuatu

Maritime Services Ltd.

By Matthew Bonvento & Jawara Drigo, Intern, Vanuatu Maritime Services

As I was preparing for Thanksgiv- propeller. There have been several cases nets and lines wrapped around the out- ing dinner I put on Indiana Jones and of propeller related casualties. side as their net guards only catch, and the Last Crusade. While Indiana Jones One particular case occurred a in 2017 don’t cut ? shing lines and nets.

and Doctor Elsa Schneider were being and involved a 12 year boy from the Generally, propeller cutters are de- chased by the Brotherhood of the Cru- Centerport Yacht Club in Suffolk Coun- signed for the purpose of clearing any ciform sword through Venice and their ty, New York who was killed by a pro- obstructions at sea that would signi? - boat was neatly shredded by the propel- peller after accidently falling off a boat cantly reduce the speed of vessels or lers of a larger vessel, it had me thinking while taking a sailing lesson. This trag- render them inoperable. Propeller cut- of how much propeller technology has edy is possibly going to force a change ters are designed for marine growth and changed over the years. And how hope- in Suffolk County law forcing all small ? shing gear, which due to their smaller fully Indiana’s boat did no actually dam- vessels to have propeller guards. This diameter can easily be wound around a age that vessel’s propeller. law may even be applicable to smaller shaft causing signi? cant damage, loss of

Jawara Drigo is an Intern at Vanautu

Recently an article passed though my vessels such as ? shing vessels and tugs time and possible environmental pollu-

Maritime Services. Drigo is complet- news feed about the ? rst 3D printed operating in Long Island. Casualties tion.

ing his undergraduate degree in Inter- propeller. This is indicative of the di- such as this drive home the importance The shaft mounted cutter or rotary national Transportation and Trade at rection the industry is taking. With the of installing propeller guards on all types cutter which is made of hardened stain-

SUNY Maritime College. advent of new technology, the methods of small craft for the safety of people less steel, works through a screw action of implementation will revolutionize the aboard as well as any swimmers, snor- which is generated once the shaft rotates. ? xed blade mounted on the strut hub maritime world. However advanced we kelers or other living creatures or struc- At the turning of the propeller, lines, nets and weeds are automatically drawn into with other blades mounted on the pro- become though, certain perils are still tures that may be near a vessel.

peller. During each rotation lines are cut prevalent. The methods of prevention As effective as they are, propeller the cutter blades.

The shaft mounted cutter is used for as if with a scissor, making use of the will be dependent upon the type and size guards will not be ef? cient on larger ves- of vessel as well as the risk that is trying sels due to the excess weight. It would small vessels with shafts of 20mm to ? xed blade and rotating blades to slice the line. If aft seal rupture occurs, it can to be prevented. be interesting to see if propeller guards 255mm and cuts in both the forward and made of lighter weight material could do reverse directions. It is usually used on result in oil pollution and other damage yachts, tug boats, pilot boats and super to the vessel which would require expen-

Personnel Injury the same job effectively.

sive repairs.

Propeller strikes are a concern for ves- The Kort Nozzle is a round hydro-dy- yachts and is currently installed on more

In contrast to the shaft mounted cut- sels with large tonnage down to personal namically designed shroud that encircles than 100,000 vessels. One of the main ters, the propeller mounted cutters are craft. From whales who still bear the the propeller. The concept of the Kort advantages of the shaft mounted cutter is used in medium and large sized vessels scars of a decades old propeller strike Nozzle, also known as the ducted pro- during its cutting action, there is little to and designed for propeller hub sizes to the unfortunate children that suffer peller was originally developed by 20th no reduction in the speed of the vessel.

The mounting of such equipment is a of 300mm to 1000mm. The propeller this risk is one in which life is more at century German engineer Ludwig Kort. mounted cutters are installed on all types stake than property and the environment. Since its inception, the Kort Nozzle has simple process. There are a set of blades of commercial and naval vessels includ-

Think of the propeller guard as a steel been used strictly on vessels that are re- mounted around the shaft rotate with the quired to operate with high thrust at low blade cutting any line that is drawn in ing tankers, OSVs, cruise ships and cage that surrounds the propeller. Pro- peller guards are designed mainly for speeds including tugs and trawlers. With by the propeller suction. Requirements semi-submersible drilling platforms. In vessels of a smaller tonnage down to the Kort Nozzle, a vessel’s speed is kept for shaft mounted cutters is a factor of general, the propeller cutters serve as a recreational to safeguard from potential at below 10 knots. If the vessel’s speed the spacing between the strut hub and huge asset to vessel owners because they the propeller, requiring enough room save them from facing serious penalties accidents that could occur such as an in- exceeds ten knots, water ? ow to the pro- dividual falling off the boat. Due to the peller decreases and therefore, there will between the two so as to not have the such as towage of their vessel by the

Coast Guard as well as eliminating the strong steel structure of the propeller not be enough thrust generated to allow blades come in to contact on each rota- need to send divers down into the sea to guard, it is effective any protecting any- the propeller to rotate ef? ciently. It is not tion.

The propeller mounted cutter has a manually cut these lines, nets and weeds one who would otherwise get cut by the uncommon to ? nd Kort Nozzles with 14 Maritime Reporter & Engineering News • JANUARY 2018

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