Lifeline Systems Design Considerations and Lessons Learned Presented by: Paul H. Miller Assistant Professor US Naval Academy IBEX 2000 (sometimes the hard way!)
The Big Picture “Lifeline systems discourage (but don’t prevent) the movement of people or items between the deck and the surrounding environment.” This applies in both directions!
Who Needs Them?
Designers and builders have to ask, “Is a lifeline system appropriate for my design, and if so, what type should I use?”
Factors To Consider: Stability
Function
Aesthetics
Other Factors Maintenance Regulations Legal Precedents Crew Ability Inshore/Offshore Operations (expected weather vs. vessel motions)
If the answer is “yes”… Lifeline systems include: Wire Gates Terminals Toe rails Bulwarks Foundations Deck structure Stanchions Pulpits
Lessons Learned: The US Naval Academy/US Sailing Lifeline Failure Study (The State of Current Designs) ( )
Participants Midn Savery (96) Midn Mendez (96) Midn Keller (96) Midn Hanley (96) Midn Anne Palmer (97) Midn David Dees (97) Midn Cris Neish (97) Midn Thomas O’Malley (97) Midn Patrick Saxton (97) Midn Tawnya Tschache (97) Prof Tom Butler Mr Ralph Naranjo Mr Tom Carr Mr Ron Pitt Mr Tom Stallings US Sailing Navtec Cruising Club of America
Documented Failures Annapolis, MD Key West, FL Block Island Sound, RI Lake Michigan, IL Boston, MA others? In 1998 Sydney-Hobart Race, lifeline systems were the 3rd most common failure, after sail and rig damage.
Project Goals Determine failure modes of Navy 44 lifeline systems Improve reliability and capability of current systems Provide recommendations for lifeline system design
The Navy 44 Sail Training Vessel Used to train Midshipmen in offshore seamanship LOA 44 feet Beam 12.3 feet Draft 7.25 feet Disp 27,654 lbs Ballast 12,310 lbs
Navy 44 Seaworthiness and Safety Paramount Notice the vertical components of pulpits
A Full-Scale Frame Simulated The Deck
Welded of Mild Steel and Instrumented With Load Cells and Strain Gauges
Socket attachment assumed the deck would not fail. Valid for Navy 44’s, but not for all boats!
Test Jig 12,000 pound force 1/4” and 3/16” wire Strain gauges on stanchions and pulpits Load cells and angle meters
Results Stanchions and pulpits failed first (1,000 pounds) Wire terminals failed second (3-5,000 pounds) Wire failed third (6- 7,000 pounds)
Pulpit Results Testing...Reality!
Pulpit Design Critical to overall system design Use diagonals to transmit loads in compression rather than bending Don’t clutter with other equipment! Maintain continuity
Recommendations Use quality, uncoated 1x19 wire Avoid gates Check deck construction for adequate stiffness and strength (add backing and/or top plates if needed) Meet Offshore Racing Council Special Regulations (even for non-sailors) Keep lifelines taut Inspect and maintain
Taut Lifelines Reduce Loads on Individual Stanchions Too Loose!
Extra bracing may be required But it may cause a tripping hazard...
Rule #1 when on a boat... Keep the boat between you and the water!