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

Safety at Sea Seminar 2002

Safety Factors in Naval ArchitectureSafety Factors in Naval Architecture

Paul H. Miller, D. Engr.Paul H. Miller, D. Engr.Dept of Naval Architecture and Ocean EngineeringDept of Naval Architecture and Ocean Engineering

United States Naval AcademyUnited States Naval Academy


What is “Safety”?What is “Safety”?

A dictionary definition:A dictionary definition:““The condition of being safe; freedom from danger, The condition of being safe; freedom from danger,

risk, or injury.” risk, or injury.”

A legal opinion from the Supreme Court:A legal opinion from the Supreme Court:““You cannot legislate complete safety”You cannot legislate complete safety”

From the ISAF Special RegulationsFrom the ISAF Special Regulations““1.02.1 The Safety of a yacht and her crew is the 1.02.1 The Safety of a yacht and her crew is the

sole and inescapable responsibility of the sole and inescapable responsibility of the owner…”owner…”


An Engineering DefinitionAn Engineering Definition

• Acceptable Safety is the minimization of risk, Acceptable Safety is the minimization of risk, or is an acceptable level of “reliability.”or is an acceptable level of “reliability.”

• Reliability is a function of the “probability of Reliability is a function of the “probability of failure”.failure”.

• ““Probability” is another word for “gambling”Probability” is another word for “gambling”


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


Risk/Reliability/Safety Trade-OffRisk/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.


What is an acceptable level of risk What is an acceptable level of risk to go Trans-Atlantic?to go Trans-Atlantic?


Risk/Reliability/Safety Trade-OffRisk/Reliability/Safety Trade-Off

Risk

Preparation + Training + Cost + Attitude + Routing


““Safety Factors”Safety Factors”

Example:Example:• -10 Navtec Rod has a strength of 10,300 -10 Navtec Rod has a strength of 10,300

poundspounds• The design load is a knockdown and the The design load is a knockdown and the

load is 4,450 poundsload is 4,450 pounds• The Safety Factor is 10,300/4,450 = 2.3The Safety Factor is 10,300/4,450 = 2.3

Load"Design"

ComponentofStrengthSF


Some thought-provoking questions!Some thought-provoking questions!

1.1. Should every piece of a vessel have Should every piece of a vessel have the same safety factor? (“the one-the same safety factor? (“the one-hoss shay”)hoss shay”)

a)a) Yes, it is the most efficientYes, it is the most efficientb)b) No, there should be a “weak link” or No, there should be a “weak link” or

“safety valve” that will release or “safety valve” that will release or indicate that a catastrophic load is indicate that a catastrophic load is nearnear

c)c) What’s a “hoss” and what’s a “shay”?What’s a “hoss” and what’s a “shay”?


A quote from Ted Brewer on rigsA quote from Ted Brewer on rigs

““The cruising yachtsman must still The cruising yachtsman must still bear in mind that efficiency is not bear in mind that efficiency is not necessarily safety…If a sloop’s sails necessarily safety…If a sloop’s sails are too large for a small cruising are too large for a small cruising crew to set and reef properly, then crew to set and reef properly, then you may have efficiency but not you may have efficiency but not safety…”safety…”


2.2. Do all boats have the about the Do all boats have the about the same basic safety factor for their same basic safety factor for their intended purpose?intended purpose?

a)a) No, not all boats are created equalNo, not all boats are created equal

b)b) No, a boat intended for inland sailing No, a boat intended for inland sailing could have a higher probability of could have a higher probability of failure than a boat intended for failure than a boat intended for offshore sailing, therefore the inland offshore sailing, therefore the inland boat will have a lower safety factor.boat will have a lower safety factor.

c)c) How did we get back to gambling?How did we get back to gambling?


What are some safety factors What are some safety factors designers use?designers use?

• Hull Structure = 2 – 6Hull Structure = 2 – 6

• Standing Rigging = 1.3 – 5Standing Rigging = 1.3 – 5

• Running Rigging = 1.1 - 8Running Rigging = 1.1 - 8

• Engines = 1.2 – 10Engines = 1.2 – 10

• Safety Equipment = 1.1 - 5Safety Equipment = 1.1 - 5

• Stability = 1 - 3Stability = 1 - 3


Stability Safety Factor IssuesStability Safety Factor Issues


What can I as an owner do to make What can I as an owner do to make sure I have matched my sure I have matched my acceptable level of risk?acceptable level of risk?

Attend a Safety at Sea SeminarAttend a Safety at Sea SeminarStay awake during all the talksStay awake during all the talksApply what I learned by:Apply what I learned by:a)a) Choosing a boat suitable for my intended Choosing a boat suitable for my intended

purpose and outfitting it accordinglypurpose and outfitting it accordinglyb)b) Making sure my boat and equipment still Making sure my boat and equipment still

have their intended safety factorshave their intended safety factorsc)c) Not making any unwise decisions regarding Not making any unwise decisions regarding

modifying safety factorsmodifying safety factors


Do not chose unwisely!Do not chose unwisely!


My favorite unwise decisions My favorite unwise decisions when an owner took a boat that when an owner took a boat that

was suitable for the intended was suitable for the intended purpose and modified itpurpose and modified it

#5 Upsizing rigging or #5 Upsizing rigging or mast wall thickness mast wall thickness to increase rig to increase rig strengthstrength

Results: reduced Results: reduced stability and stability and increased windageincreased windage


#4 Carrying jerry jugs of fuel on #4 Carrying jerry jugs of fuel on deck deck

• Goal: increase motoring range (is Goal: increase motoring range (is that safety or convenience?)that safety or convenience?)

• Results: decrease stability, increase Results: decrease stability, increase weight (reducing light air weight (reducing light air performance), greater trip hazard performance), greater trip hazard (with or without leaks), increase (with or without leaks), increase loads on stanchions/lifelinesloads on stanchions/lifelines


#3 Add stainless steps on mast#3 Add stainless steps on mast

• Goal: increase ability to see coral Goal: increase ability to see coral heads, increase ability to untangle or heads, increase ability to untangle or retrieve riggingretrieve rigging

• Results: significant increase in Results: significant increase in corrosion, significantly increased corrosion, significantly increased windage, more tangled rigging and windage, more tangled rigging and torn sailstorn sails


#2 Cut down rig height#2 Cut down rig height

• Goal: reduce a boat’s tendency to Goal: reduce a boat’s tendency to heel, reduce windageheel, reduce windage

• Results: increases roll rate, Results: increases roll rate, decreases options when engine failsdecreases options when engine fails


#1 Buy too big a boat!#1 Buy too big a boat!

• Goal: Bigger is Goal: Bigger is safer!safer!

• Results: too Results: too difficult to reef and difficult to reef and steer, higher costs steer, higher costs prevented repairs prevented repairs and good and good equipment, too equipment, too fatiguingfatiguing


Two SuggestionsTwo Suggestions

The Seaworthy Offshore Sailboat

John Vigor

ISAF/US Sailing Special Regs


Is Sailing Safer than Driving?Is Sailing Safer than Driving? 1999 Statistics from USCG and NTSB1999 Statistics from USCG and NTSB

• Sailing has about 2 fatalities per 1000 Sailing has about 2 fatalities per 1000 hourshours

• Driving in the US has about 3.5 Driving in the US has about 3.5 fatalities per 1000 hoursfatalities per 1000 hours


Final thoughts!Final thoughts!

• Choose your boat and equipment Choose your boat and equipment based on unbiased technical based on unbiased technical evaluation rather than marketingevaluation rather than marketing

• Spend your money on advanced Spend your money on advanced training rather extra equipmenttraining rather extra equipment

• Maintain a safe attitude!Maintain a safe attitude!

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

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