Friday, March 21, 2008

Loadlines

Maybe you've seen one of these on the side of a ship and wondered what it was:

It's an International Load Line "Plimsoll mark", named after Samuel Plimsoll, a 19th century British MP, who took up the cause of preventing ships sinking by overloading. The mark was adopted by international convention in 1966 and has applied to ships of all signatory nations since then. Of course, it was created to prevent greedy shipowners from overloading large commercial vessels with cargo, but it applies to any ship (other than a yacht or warship) over 79ft in length, including even small, wooden sailing ships like our Spirit of South Carolina.

Unfortunately, Spirit's load line is now slightly submerged. Today, I have to find out why.

- Was the Plimsoll mark placed in the wrong spot?

- Has the wooden structure soaked up a significant amount of water since the orginal stability calculations?

- Is someone storing gold bullion on board?

I suspect it's a combination of the first and the last...well, probably not gold bullion, but sailors are notorious packrats, and I'll wager there are random bits of chain (never know when it might be useful), tackle, tools, packets of Cheetos, etc that weren't there when the vessel was new.

I think we'll be able to fix this pretty easily by adding additional deadweight load items e.g., "crew stores", "bits of chain", "snack foods", to the stability calculations, to account for the general increase in weight, without however, exceeding some of the transverse stability requirements. Not too much, not too little.

1 comment:

Thomas said...

You said you would update the Cangarda page. Where is it?
What happened when she was launched? I was looking for more, current information and came across several newspaper reports saying she almost capsized and sank:
http://www.ebdailynews.com/article/2007-8-25-eb-yacht

Bob McNeil said, when asked to reflect on what he made of his boat almost sinking in a few feet of water, "...it proved the boat is seaworthy. I now know if I go out on the Bay or in the ocean, everything will be OK. She came back from a very steep roll and that's all that counts."

What on earth happened?