Safety at Sea Seminar 2002 Safety Factors in Naval Architecture Paul H. Miller, D. Engr. Dept of Naval Architecture and Ocean Engineering United States Naval Academy

Safety at Sea Seminar 2002 What is “Safety”? A dictionary definition: “The condition of being safe; freedom from danger, risk, or injury.” A legal opinion from the Supreme Court: “You cannot legislate complete safety” From the ISAF Special Regulations “ The Safety of a yacht and her crew is the sole and inescapable responsibility of the owner…”

Safety at Sea Seminar 2002 An Engineering Definition Acceptable Safety is the minimization of risk, or is an acceptable level of “reliability.”Acceptable Safety is the minimization of risk, or is an acceptable level of “reliability.” Reliability is a function of the “probability of failure”.Reliability is a function of the “probability of failure”. “Probability” is another word for “gambling”“Probability” is another word for “gambling”

Safety at Sea Seminar 2002 So, “You've got to ask yourself one question: 'Do I feel lucky?‘”

Safety at Sea Seminar 2002 Risk/Reliability/Safety Trade-Off Risk Preparation + Training + Cost + Attitude + Routing Whether you will accept a high risk or low risk is up to you! Of the 5 major factors, we will look at preparation.

Safety at Sea Seminar 2002 What is an acceptable level of risk to go Trans-Atlantic?

Safety at Sea Seminar 2002 Risk/Reliability/Safety Trade-Off Risk Preparation + Training + Cost + Attitude + Routing

Safety at Sea Seminar 2002 “Safety Factors” Example: -10 Navtec Rod has a strength of 10,300 pounds-10 Navtec Rod has a strength of 10,300 pounds The design load is a knockdown and the load is 4,450 poundsThe design load is a knockdown and the load is 4,450 pounds The Safety Factor is 10,300/4,450 = 2.3The Safety Factor is 10,300/4,450 = 2.3

Safety at Sea Seminar 2002 Some thought-provoking questions! 1.Should every piece of a vessel have the same safety factor? (“the one- hoss shay”) a)Yes, it is the most efficient b)No, there should be a “weak link” or “safety valve” that will release or indicate that a catastrophic load is near c)What’s a “hoss” and what’s a “shay”?

Safety at Sea Seminar 2002 A quote from Ted Brewer on rigs “The cruising yachtsman must still bear in mind that efficiency is not necessarily safety…If a sloop’s sails are too large for a small cruising crew to set and reef properly, then you may have efficiency but not safety…”

Safety at Sea Seminar Do all boats have the about the same basic safety factor for their intended purpose? a)No, not all boats are created equal b)No, a boat intended for inland sailing could have a higher probability of failure than a boat intended for offshore sailing, therefore the inland boat will have a lower safety factor. c)How did we get back to gambling?

Safety at Sea Seminar 2002 What are some safety factors designers use? Hull Structure = 2 – 6Hull Structure = 2 – 6 Standing Rigging = 1.3 – 5Standing Rigging = 1.3 – 5 Running Rigging = Running Rigging = Engines = 1.2 – 10Engines = 1.2 – 10 Safety Equipment = Safety Equipment = Stability = 1 - 3Stability = 1 - 3

Safety at Sea Seminar 2002 Stability Safety Factor Issues

Safety at Sea Seminar 2002 What can I as an owner do to make sure I have matched my acceptable level of risk? Attend a Safety at Sea Seminar Stay awake during all the talks Apply what I learned by: a)Choosing a boat suitable for my intended purpose and outfitting it accordingly b)Making sure my boat and equipment still have their intended safety factors c)Not making any unwise decisions regarding modifying safety factors    

Safety at Sea Seminar 2002 Do not chose unwisely!

Safety at Sea Seminar 2002 My favorite unwise decisions when an owner took a boat that was suitable for the intended purpose and modified it #5 Upsizing rigging or mast wall thickness to increase rig strength Results: reduced stability and increased windage

Safety at Sea Seminar 2002 #4 Carrying jerry jugs of fuel on deck Goal: increase motoring range (is that safety or convenience?)Goal: increase motoring range (is that safety or convenience?) Results: decrease stability, increase weight (reducing light air performance), greater trip hazard (with or without leaks), increase loads on stanchions/lifelinesResults: decrease stability, increase weight (reducing light air performance), greater trip hazard (with or without leaks), increase loads on stanchions/lifelines

Safety at Sea Seminar 2002 #3 Add stainless steps on mast Goal: increase ability to see coral heads, increase ability to untangle or retrieve riggingGoal: increase ability to see coral heads, increase ability to untangle or retrieve rigging Results: significant increase in corrosion, significantly increased windage, more tangled rigging and torn sailsResults: significant increase in corrosion, significantly increased windage, more tangled rigging and torn sails

Safety at Sea Seminar 2002 #2 Cut down rig height Goal: reduce a boat’s tendency to heel, reduce windageGoal: reduce a boat’s tendency to heel, reduce windage Results: increases roll rate, decreases options when engine failsResults: increases roll rate, decreases options when engine fails

Safety at Sea Seminar 2002 #1 Buy too big a boat! Goal: Bigger is safer!Goal: Bigger is safer! Results: too difficult to reef and steer, higher costs prevented repairs and good equipment, too fatiguingResults: too difficult to reef and steer, higher costs prevented repairs and good equipment, too fatiguing

Safety at Sea Seminar 2002 Two Suggestions The Seaworthy Offshore Sailboat John Vigor ISAF/US Sailing Special Regs

Safety at Sea Seminar 2002 Is Sailing Safer than Driving? 1999 Statistics from USCG and NTSB Sailing has about 2 fatalities per 1000 hoursSailing has about 2 fatalities per 1000 hours Driving in the US has about 3.5 fatalities per 1000 hoursDriving in the US has about 3.5 fatalities per 1000 hours

Safety at Sea Seminar 2002 Final thoughts! Choose your boat and equipment based on unbiased technical evaluation rather than marketingChoose your boat and equipment based on unbiased technical evaluation rather than marketing Spend your money on advanced training rather extra equipmentSpend your money on advanced training rather extra equipment Maintain a safe attitude!Maintain a safe attitude!