6inch Crack appear on the First LCS

colintraveller · Mar 20, 2011

http://www.defensenews.com/story.php?i=5999454&c=AME&s=SEA

If this crack has gone un-noticed the outcome would have been very bad especially the Money that's been spent on that line of vessels

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A 6-inch crack in the hull of the littoral combat ship USS Freedom caused the ship to abort sea-keeping trials on Feb. 12 and return to its homeport of San Diego for repairs, the U.S. Navy confirmed March 18.

The crack, about three and a half feet below the waterline in a weld seam between two steel plates in the hull, allowed water to enter a void space in the ship, according to Naval Sea Systems Command (NAVSEA). Flooding was contained, however, and, at a speed of about 8 knots, the vessel sailed about 600 miles to San Diego to begin repairs.

Laurence · Mar 20, 2011

Perhaps the Navy should not have split the contract between the two designs:

"In October 2005, Austal/General Dynamics was awarded a contract to build the first of their design for a Littoral Combat Ship. The keel of the future USS Independence (LCS-2) was laid on 19 January 2006 at Austal USA's yard in Mobile, Alabama, and the naming ceremony was held on 4 October 2008. It is now operating with the fleet at its current location in Norfolk, Virginia."

Superior built in Alabama.

Grecko · Mar 23, 2011

Lots of "issues" with that ship...

I understand that it's also seriously overweight. As a result she sits lower in the water than it should, and the mission equipment bay that houses the small craft that they launch to perform various missions is very "wet" with several inches of water sloshing around in what was supposed to be a dry work area...

Laurence · Mar 24, 2011

Wet Feet

Would that be with the USS Freedom or the USS Independence?

Grecko · Mar 24, 2011

Wet Feet

Lockheeds finest, the USS Freedom...

Kevin · Mar 24, 2011

Grecko said:

Lots of "issues" with that ship...

I understand that it's also seriously overweight. As a result she sits lower in the water than it should, and the mission equipment bay that houses the small craft that they launch to perform various missions is very "wet" with several inches of water sloshing around in what was supposed to be a dry work area...
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Honestly, given that computer design systems can predict the weight of each and every individual component to the fraction of a pound... how does that happen?

Grecko · Mar 24, 2011

Kevin said:

Honestly, given that computer design systems can predict the weight of each and every individual component to the fraction of a pound... how does that happen?
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From Wiki...

One of the issues with the ship is that it is six percent overweight and therefore more likely to sink if damaged. This seems to have been caused by design changes during construction. The Navy says that the ship will require special operating procedures until this is corrected. The workaround selected will be to install external tanks for additional buoyancy. And the Navy states that LCS 1 now meets the damage stability requirement with the addition of the external tanks and that the design of USS Fort Worth (LCS-3) includes additional stability improvements.

Six percent is 180 tons... That's a bunch. It likely comes from "optimistic engineering" in the planning stages and not keeping some margin in the design, because now we are so smart, since we can keep track of all this stuff on spreadsheets and CAD that we don't need as big a margin.... Or at least they probably didn't think they did Also, the cost versus weight problems that arise when you make something that bit.. Finally, the Military has a bad habit of adding stuff to the progam that adds weight and cost and you have to keep the design frozen when you lock in your dimensions, lest the growth eats you out of house and home...

As Don Gartlits used to say, "It gets hard to add in any more lightness"...

Kevin · Apr 14, 2011

Welding Flaw Led To Crack in LCS-1 Hull

LINK

A manufacturing issue, not a design flaw, led to a six-inch crack along a weld seam on the hull of Littoral Combat Ship, USS Freedom, during heavy weather trials in February, Navy officials said today.

“We’re still reviewing the design for weld improvements, as far as the analysis of [what led to the crack] we’ve completed the analysis and are in the process of working through the release of that information,” said Capt. Jeff Riedel, the Navy’s LCS program manager during a briefing at the Navy League’s annual Sea, Air Space conference held just outside of Washington DC. “Both Lockheed and the Navy are going through their final review that should be available in the next couple of weeks.”

He went on to say that ship’s design wasn’t at fault, but instead, a weak weld-job led to the cracks.

“The design is adequate, how I build it is a different story,” said Riedel. “If I was able to weld it as it was designed to be welded, it wouldn’t have been an issue. The real issue was, getting access to that area to be able to do the weld.”

He added that beginning with LCS-3, welders are able to more easily reach the spot on the ship where the crack occurred, allowing them to lay an extra thick weld.

Other cracks were discovered in known stress points in the ship’s superstructure that computer modeling predicted might be the location of cracks during rough seas, according to Riedel. These cracks have led to design tweaks in subsequent ships of the class.

“We modeled the superstructure and we found that we had areas that were high stress areas, so we would expect, potentially, a crack to occur in that high-stress area,” said Riedel. “So we instrumented the superstructure and we used that instrumentation to validate the model and in fact, we’re now using that to better the design…for LCS-3 and following we’ve gone back and changed the design so we can reduce those stress areas.”

Navy Secretary Ray Mabus said later in the day that all lead ships of a class have “issues” and noted that the crack hasn’t delayed sea trials for the ship.

“Things happen on every lead ship, what you do is learn how to avoid it on the following ships, which we have done,” said Mabus during a press briefing at the conference.
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chuckb · Apr 14, 2011

My understanding is that the Navy changed many requirements after the initial award. So to win the award, the companies optimize the design to the original requirements and specification issued by NAVSEA. Then after the contract is awarded, NAVSEA introduces new requirements... with delays, cost overruns, and basic performance degradation the result. This happened with both builders... Freedom was the first launch and has more sea time. The new requirements may very well be needed, but its not the way to manage a complex build process.

Building ships for the US Navy is not something I'd want to do!

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6inch Crack appear on the First LCS

colintraveller Senior Member

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