Safety Factors in Naval Architecture

1. 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

2. 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 “1.02.1 The Safety of a yacht and her crew is the sole and inescapable responsibility of the owner…” Safety at Sea Seminar 2002

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

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

5. Risk Preparation + Training + Cost + Attitude + Routing Risk/Reliability/Safety Trade-Off 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

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

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

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

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

10. 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 2002

11. Do all boats have the about the same basic safety factor for their intended purpose? • No, not all boats are created equal • 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. • How did we get back to gambling? Safety at Sea Seminar 2002

12. What are some safety factors designers use? • Hull Structure = 2 – 6 • Standing Rigging = 1.3 – 5 • Running Rigging = 1.1 - 8 • Engines = 1.2 – 10 • Safety Equipment = 1.1 - 5 • Stability = 1 - 3 Safety at Sea Seminar 2002

13. Stability Safety Factor Issues Safety at Sea Seminar 2002

14. 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: • Choosing a boat suitable for my intended purpose and outfitting it accordingly • Making sure my boat and equipment still have their intended safety factors • Not making any unwise decisions regarding modifying safety factors     Safety at Sea Seminar 2002

15. Do not chose unwisely! Safety at Sea Seminar 2002

16. 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

17. #4 Carrying jerry jugs of fuel on deck • 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/lifelines Safety at Sea Seminar 2002

18. #3 Add stainless steps on mast • Goal: 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 sails Safety at Sea Seminar 2002

19. #2 Cut down rig height • Goal: reduce a boat’s tendency to heel, reduce windage • Results: increases roll rate, decreases options when engine fails Safety at Sea Seminar 2002

20. #1 Buy too big a boat! • Goal: Bigger is safer! • Results: too difficult to reef and steer, higher costs prevented repairs and good equipment, too fatiguing Safety at Sea Seminar 2002

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

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

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