G
Guest
Guest
RE: Yachting Monthly 356 Test
As the manufacturer of the Legend 356, we were quite surprised by the presentation of our position on stability curves featured in the current issue's review of the 356.
While it is true that we declined to provide a GZ stability curve to Yachting Monthly, we did provide Yachting Monthly with concise reasoning behind our position. Yachting Monthly informed us that our statement would be printed. In fact, YM paraphrased the statement, which unfortunately misrepresents our position. For anyone who is interested, the statement we sent them is below.
Further, we are happy to speak with any potential customers of our products about any concerns.
Sincerely,
Luhrs Marine Ltd - UK Manufacturer of Hunter and Legend Yachts
http://www.luhrsmarine.co.uk
info@luhrsmarine.co.uk
Stability Curves
The use of stability curves is a worrying trend as consumers are making assessments and comparisons as to a boat’s safety and seaworthiness by a cursory review of the theoretical curve supplied by a boat designer.
While a stability curve contains useful information, it also is based on a lack of real-life conditions such as wave patterns, wind force applied to the vessel, and other loading factors such as crew/gear size and placement, plus the amount of fluids in water, fuel and holding tanks. Numerous factors affect the actual center of gravity, metacenter, and center of buoyancy and can significantly change the shape of this stability curve. Moments of inertia are additionally affected by rig size and weight, wind force, keel size and shape, etc. These factors are not sufficiently weighted into the stability curve analysis.
The CE certification process now utilizes the ISO standard 12217 to produce a complex formula called STIX (stability index), which is summarized by a numerical rating used in the determination of the design category. STIX reaches far deeper in the stability assessment and may be a more useful indicator of a boat’s true stability. This number, however, is not yet understood by the sailing public, hence its value is limited and its meaning may well be misinterpreted.
At Hunter, we work hard to maximize stability though hull and deck forms, which strongly contribute to stability throughout its range, as well as maximizing the positive range of stability. Our bulb/wing lead keels keep the center of gravity low in combination with our strategy of using heavy laminates below the waterline, and lighter, cored laminates in the topsides. We also concentrate on fore and aft stability and directional stability through hull, keel, and rudder sizing and shaping. All of these factors contribute to a boat that has efficient, controllable and comfortable characteristics.
Luhrs Marine Limited
As the manufacturer of the Legend 356, we were quite surprised by the presentation of our position on stability curves featured in the current issue's review of the 356.
While it is true that we declined to provide a GZ stability curve to Yachting Monthly, we did provide Yachting Monthly with concise reasoning behind our position. Yachting Monthly informed us that our statement would be printed. In fact, YM paraphrased the statement, which unfortunately misrepresents our position. For anyone who is interested, the statement we sent them is below.
Further, we are happy to speak with any potential customers of our products about any concerns.
Sincerely,
Luhrs Marine Ltd - UK Manufacturer of Hunter and Legend Yachts
http://www.luhrsmarine.co.uk
info@luhrsmarine.co.uk
Stability Curves
The use of stability curves is a worrying trend as consumers are making assessments and comparisons as to a boat’s safety and seaworthiness by a cursory review of the theoretical curve supplied by a boat designer.
While a stability curve contains useful information, it also is based on a lack of real-life conditions such as wave patterns, wind force applied to the vessel, and other loading factors such as crew/gear size and placement, plus the amount of fluids in water, fuel and holding tanks. Numerous factors affect the actual center of gravity, metacenter, and center of buoyancy and can significantly change the shape of this stability curve. Moments of inertia are additionally affected by rig size and weight, wind force, keel size and shape, etc. These factors are not sufficiently weighted into the stability curve analysis.
The CE certification process now utilizes the ISO standard 12217 to produce a complex formula called STIX (stability index), which is summarized by a numerical rating used in the determination of the design category. STIX reaches far deeper in the stability assessment and may be a more useful indicator of a boat’s true stability. This number, however, is not yet understood by the sailing public, hence its value is limited and its meaning may well be misinterpreted.
At Hunter, we work hard to maximize stability though hull and deck forms, which strongly contribute to stability throughout its range, as well as maximizing the positive range of stability. Our bulb/wing lead keels keep the center of gravity low in combination with our strategy of using heavy laminates below the waterline, and lighter, cored laminates in the topsides. We also concentrate on fore and aft stability and directional stability through hull, keel, and rudder sizing and shaping. All of these factors contribute to a boat that has efficient, controllable and comfortable characteristics.
Luhrs Marine Limited