A Dingy, a Dory or perhaps a Door. Lift Boat Hazards

You don’t have to have naval architects’ degree to realize these special vessels stretch the definition of the term seaworthiness.  Let’s imagine this scenario for a moment. Suppose you had a choice of two “vessels”, which would you choose?

A dingy, a typical row boat , that may hold one or two adults. They are very small, typically not much larger in length and breadth  than a sheet of 4 x 8 plywood but their hull is designed properly to includes some freeboard, a defined keel and perhaps a slightly raised bow to take the small chop they are designed to be used in.

The second vessel is a 4 x 8’  watertight flat bottom box made of plywood (like two waterproof doors sandwiched together), imagine it to be thick enough (perhaps 4 inches) that when a man sits on it, it has about 25% (or 1” remaining) of the sides height as freeboard.

Now both these vessels can support the adult, but how well do you think each can handle the sea. The man rowing the dingy is continuiously moving as he strokes his oars. If we give the man on the 4 x 8 box a paddle and let him row, his movements will easily cause the edges of the box to dip under water due to the “box”  pitching, yawing, and rolling.  If the mans weight shifts at all, the effects are great.

Perhaps both could make it across the bay or pond, albeit one more easily than the other. Now let’s add the wind. A sail on a dingy is no problem because of the hulls shape and the fact that it has some freeboard which offers up reserve buoyancy, the sailor can also shift his weight to the opposite side of the boat. The “box boat” is a whole other story. Having no reserve buoyancy the force of the wind would cause a side to go deeper in the water further exposing more area for the force of the wind to act upon.

The force of the wind and its calculations on different shaped surfaces is very complicated, yet one thing is common, as the wind speed increases the forces increase exponentially against the surface the wind is acting upon.  The surface area of exposed legs of the Seacor Power along with its house superstructure was roughly the equivalent of 10 roadside billboards. The wind that tragic day, created a tremendous force upon the vessel causing her to turn turtle. The concerns regarding this effect on lift boats can be examined and are noted by the different requirements in both ABS and USCG documentation regarding the lift vessels and their unique operational modes.  These regulations have been changed several times due to different events and casualties.

It is also interesting to note that in the USCG licensing examination modules for Captains and Mates of Offshore Supply Vessels there are only 10 questions regarding vessel stability out of 375 questions in the combined modules. Should this be reconsidered given the vessels unique characteristics? 

Only time will tell if any changes that effect the safety of the men who go to sea on these vessels, will come out of this sad event.  In the meantime, let’s continue remember those lost and offer prayers of healing to those left behind.

 

#seacorpower #unitedcajunnavy


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  • Stacey Minick op

    My question would be, compared to chemical/supply/mud/crew boats, how many lift boats are there? Is there another test specifically for loft boats? If not, then yes…more questions should be added, or a separate test for those looking at going to lift boats


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