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John Miele

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Top Stories by John Miele

If you hang around naval architects, attend boat shows, or look on various design forums on the Net, you will often see quite the debate about stepped hulls and their relation to speed. Though somewhat “trendy” in boat design currently, stepped hulls have been around since World War II, and they are intended to aerate the hull; introducing a thin layer of air between the hull and the water surface, thus reducing friction and drag, hence, increasing speed. Indeed, a stepped hull design can somewhat drastically increase a vessel’s top speed, when properly designed. It can combine the benefits of a flat hull with a deep Vee. Sounds good, right? Ah, but here’s the rub… Designing such a hull correctly is exceedingly difficult, and many, if not most, stepped designs are not done properly. Get the angles of the steps a tiny bit wrong, and you have just made a very expens... (more)

What is the difference between cavitation and electrolysis?

The following paper was presented by France Helices’ president a while back. It discusses the difference between cavitation and electrolysis and the impact of both on propellers and propulsion. These two phenomena are often confused and it is important to learn to recognize the difference between them, so that the cause of problems can be determined and adequate fixes can be made. We have translated this version from the original French version. We hope you find it interesting. Introduction I have often had the opportunity to see during my career that there was some blurring in... (more)

Welcome to Tier II NOX Regulations

On January 1, the MARPOL Tier II NOX regulations went into effect. From this date onward,  marine diesel engines may emit no more than  7.7~14.4.0 g/kWh of NOX, depending on rating. Tier III goes into effect on January 1, 2016, five years from now, with NOX limits of  g2.0~3.4 /kWh. Though Tier II requirements have been known for a while, very little was written about the implementation date of the regulations. Some vessels are “grandfathered” into the regulations, whereas most other must comply. Some ship owners are letting the engine maker deal with the problem, taking the op... (more)

Two New Patrol Boat Designs from France Helices

We have just made the following designs available for sale: A 22m Patrol Boat and a 28m Patrol Boat. Take a look below and feel free to contact us with any interest. 22m Patrol Boat                                           28m Patrol Boat   Share! (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })(); Tweet Follow ... (more)

A Rational Approach to Engine and Propeller Matching for High Speed Boats

The following paper was prepared by our President, Mr. Paul Bezzi, several years ago. We hope you find it interesting and useful.   Introduction.   I am writing this paper with the aim to help those deciding on which propulsion system to select for their particular application. The majority of yachts and fast boats are targeting speeds in excess of 30 knots. For that purpose, engine manufacturers, boat-yards, and propulsion manufacturers are increasing power, behaviour at sea, and efficiency. Very shortly, problems appear due to the lack of know how; the true reason of failure... (more)