Archived

This topic is now archived and is closed to further replies.

woodreau

Flexing Container Ship

Recommended Posts

Help AVSIM continue to serve you!
Please donate today!

They are designed to do that (as scary as that thought might be). If they didn't flex, you would have a real serious problem. I once stood on the transom of a research vessel and looked forward to the wheel house; a distance of about 200 feet. We were operating in the Atlantic about 120 miles east of Cape Cod in a sea state of 4 - 5. We had a quartering sea running (the worst when it comes to longitudinal flexing). I was amazed to see the wheel house flexing in the totally opposite direction as the transom. It was as if a child had put a hand on the bow and a hand on the stern and started twisting. I am not talking about minor flexing... this was distances of feet. The chief engineer spent a considerable amount of time that day trying to convince me that this was normal and that I should wear my survival suit 24x7.The R.V. by the way, was the G.W. Pierce based out of Ft. Lauderdale at the time.

Share this post


Link to post
Share on other sites

Tom,Aren't there expansion joints for dealing with this kind of thing? The ship "working", I mean.

Share this post


Link to post
Share on other sites

Think of it much like an airplane wing - the joints, the design, and indeed perhaps the metal itself - all engineered to have a degree of flex in it to absorb the changing dynamics of the environment it's travelling in.The airplane wing is a "solid" form, with no distinguishable expansion joints, but it's construction allows it flexibility. I think the ship is the same way... no designated expansion joints, but engineered to absorb the loads of high seas without snapping in two. -Greg(NOT a mechanical engineer)

Share this post


Link to post
Share on other sites

greggerm,Yours was a good analysis. I'm persuaded by it.

Share this post


Link to post
Share on other sites

Greg and Mike,Greg's explanation is spot on. Flexure allows the ship to survive whereas rigidity could make for a very bad morning after. An expansion joint (ala the U2 spy plane) is not a particularly good idea in a hull design for a ship. Today's steel and aluminum designs allow for light weight, but very strong structure that can be put under tremendous at-sea loading and survive. Mike, sorry for not getting an answer back to you sooner, but Greg's response is much better than I could have come up with. :)

Share this post


Link to post
Share on other sites

Tom- I've read of crew on an aircraft carrier, sitting on the flight deck and cracking walnut shells with the steady movement of deck expansion joints as the ship ploughed into a heavy ground swell. Any truth to that tale? I suppose one should be cautious with his fingers as the bow reaches the trough of the swell and starts to lift once more!Alex Reid

Share this post


Link to post
Share on other sites

On the old Lexington class(FDR)carrier I was on,Rain water used to pour threw the expansion joints in the passageways right below the flight deck.

Share this post


Link to post
Share on other sites

Joke Alert! I repeat, this is a Joke Alert!xxxxxxxxxxxxxxxxxxxxxxxxSo okay, folks,Some ships may have expansion joints. And guess what? Some Southwest Airlines aircraft may also have expansion joints, though these were not a factory option and in fact were installed by the maintenance operation.

Share this post


Link to post
Share on other sites

As everyone's said it's designed to do that. What someone explained to me is that it's called "elastic deformation" - the HY steel is designed for a certain amount of stress in all axes. It will "deform" so much and then it goes back to it's original shape... Then when you exceed the material's ability to deform then it's called inelastic deformation like when a missile explodes and causes a big hole in the side of a ship - the metal will deform inwards away from the blast then fail - resulting in a hole with the jagged edges of metal pointing inwards.

Share this post


Link to post
Share on other sites