Offshore Sailboat Attributes: What To Look For 15 April 2005 Paul H. Miller, D.Eng. P.E. Professor of Naval Architecture United States Naval Academy Seaworthiness “To be seaworthy, the vessel must be able to defend itself against the incursion and perils of the sea…”
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15 April 2005
Paul H. Miller, D.Eng. P.E.
Professor of Naval Architecture
United States Naval Academy
“To be seaworthy, the vessel must be able to defend itself against the incursion and perils of the sea…”
A classic example of a seaworthy design.
Low center of gravity, versatile rig, narrow beam.
From “Seaworthiness: The Forgotten Factor”
by C.A. Marchaj
But perhaps a bit impractical?
Question: What percentage of recreational marine accidents are related to design, construction or equipment?
1998 USCG Boating Statistics
Owner and Operator Mistakes
Attitude, Preparation, Weather, Fatigue, etc)
1998 USCG Boating Statistics
“How Lucky Do You Feel?!”
Is this your acceptable level?
Or, is this?
Preparation + Training + Cost + Attitude + Routing
Some great voyages have been made in spite of the boat design and equipment!For your level of acceptable risk…
These requirements often conflict with other goals, such as speed vs. comfort vs. cost vs. draft vs. …
The Rating Rules were changed to encourage stability. (’98 Sydney-Hobart)
Boats became more stable at large heel angles.
Today, many “cruising boats” have wider beams, lighter displacements and higher CG’s than pre-1979 boats…Lessons Learned and Relearned
“Give me a lever and I will move the earth!” (or at least right a boat!)
WStatic Stability When Heeled
This lever, the horizontal distance between the Center of Gravity and the Center Buoyancy is called the Righting Arm (RA)!
= Righting Arm x Boat Weight
Boat Will Capsize
Limit of Positive StabilityStatic Stability Lessons
A Vessel’s Response to Wind and Waves is a function of:
What happened to CG and length?
An increase in length leads to greater comfort, possibly higher stability, higher loads and lower maneuverability.
A boat, although a good design, is only as seaworthy as the condition it is in and the skill of the crew that sails it!
High windage rigging (steps, main furlers)
Boats that rely on crew weight for stability
Small keels and rudders (lack of control at low speed)
Large windowsAttributes that increase risk
Larsson and Eliasson
“Seaworthiness: The Forgotten Factor”
C. A. Marchaj
Safety Recommendations for Offshore Sailing
Safety Recommendations for Cruising Sailboats
And, “Safety From Capsizing; Final Report”
by the CCA
“The Seaworthy Offshore Sailboat”
American Bureau of Shipping Guide for Building and Classing Offshore Racing Yachts
The Elements of Boat Strength by Dave Gerr
Buy the smallest boat you can afford…
And go have fun!