Warship hull lives & building standards

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MKSheppard
Post subject: Warship Hull Service Lives and Building StandardsPostPosted: Fri Oct 22, 2010 2:09 am
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From the other board by Stuart:

Fingolfin_Noldor wrote:
How did any of the newer RN ships turn out to be a wreck? Poor maintenance? Construction? Rusting at the dockside?

All of the above. RN ships were designed for a short operational life. For example, the Type 23 frigates were designed for a hull life of 18 years, half that of their American equivalents. The reason behind that was that in the 1980s, the then MoD decided that half-life refits of major warships was an uneconomic proposition and that it was better to build a new ship than rebuild an old one. Actually, that isn't worng in itself. The majority of the cost of a ship these days resides in its electronics fit and the hull is only a small component of the total cost (in fact, on a Type 23, the hull is 8 percent of the total cost of the ship). Therefore, since the majority of the cost of a refit is replacing the electronics and this pretty much equates to the cost of a new ship, replacing the hull completely by buying a new ship to carry the new electronics makes sense. Therefore, the ships were designed to be replaced rather than refitted and that dictated a short operational life. What this analysis neglected to consider is that the government would simply refuse to authorize the construction of new ships so the older ones had to soldier on.

This was exacerbated by shortage of money for maintenance. The support funding of the fleet was slashed back and no money was made available for ongoing hull repairs so the work simply wasn't done. This is where another impact of the short hull life designs comes in. because the refusal to make timely orders for new ships has forced the Navy to run ships on beyond their operational life, the maintenance costs of those ships has soared. Plot out maintenance costs against hull life and it's an exponentional curve with the break in the curve being at the hull life of the ship in question. To give some idea of the impact this has on the Royal Navy, look at these averages.

Type 42B2 destroyers. Designed hull life, 22 years. Actual hull service life 28 years
Type 42B3 destroyers. Designed hull life, 22 years. Actual hull service life 30 years
Type 23 frigates. Designed hull life, 18 years. Actual hull service life 34 years
Invincible class. Designed hull life, 25 years. Actual hull service life 35 years

So, with money for maintenance short and the demands for maintenance rising exponentially, something had to give and that was that ships spent time alongside when they needn't. This threw a much greater burden on the ships that were operational and extended deployment times which pushed up the rate of deterioration. Remember, hull life is predicated on a certain level of usage. If that level of usage is exceeded, then hull life drops accordingly. Put simply if a ship is designed for a hull life of 18 years with four months at sea per year, pushing her up to eight months at sea per year will reduce her hull life to nine years. This is what the comment one reads after WW1 and WW2 about the ships used then "worn out after war service" means. So, maintenance and its costs for older ships go up, deployability goes down. This throws a greater burden on the newer ships and wears them out faster. Add in the fact that the RN tends to drive its ships harder than the USN and we have a perfect storm brewing.

If the previous Labour government had set out with a deliberate policy to destroy the Royal Navy, they couldn't have done a better job of it.

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MKSheppard
Post subject: Re: Warship Hull Service Lives and Building StandardsPostPosted: Fri Oct 22, 2010 3:27 pm
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Again by Stuart:

Pelranius wrote:
Speaking of military ships built to civilian specs, that doesn't make me very confident about the service lifetimes of a lot of JSDFM ships.


There's a lot of misunderstanding about this "civilian standards" bit. Basically, what it means is that the ships are built in compliance with Lloyds Register or De Norske Veritas standards, mostly for insurance purposes. OK, now why does one want to insure one's warships? Will Lloyds of London pay up if a ship in a firefight does the big firework? Actually, it's for pollution and accidental damage reasons.

Now, in the '60s and '70s warships were built with very thin plating indeed (3/16 steel wasn't unknown) but with the frames and ribs closely spaced. The result was a light, flexible hull that would yield with shockwaves and ride out their impact when a more rigid hull would rupture and sink. This caused something called a "hungry horse" effect where the plating actually bowed inwards between the frames and ribs. Unfortunately, this steel made the ships vulnerable to collision damage and corrosion. In the Cod War, the British paid badly for that light structure.

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This picture shows hungry horse very clearly

Commercial standards are much more concerned with collision and maintenance issues so they specify hulls that use much thicker steel (13/16 or 15/16ths isn't unknown) combined with much more spaced out ribs and frames. The result is actually a stronger hull but one that is much less flexible. So, if a ship gets nuked, it won't ride out the blast and shock waves so well.

Commerical standards also affects things like access to compartments, damage control facilities and so on. It's not necessarily worse, its different. For example, firefighting ability is predicated around a disastrous accident, not a direct hit. So, if a ship just catches fire, she's better off, if somebody clobbers her with something, not so good.

Building to commercial standards isn't necessarily a bad thing but it does mean one has to think about maintenance and refit issues more carefully.

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Man in the Mountains
Post subject: Re: Warship Hull Service Lives and Building StandardsPostPosted: Fri Oct 22, 2010 9:11 pm
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Ryan, can I put up your posts about hydroponics and genetically modified saltwater tolerant crops from the Indian farmer thread at SDN onto here?

It actually made me feel better for the reminder of the week.


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MKSheppard
Post subject: Re: Warship Hull Service Lives and Building StandardsPostPosted: Sat Oct 23, 2010 4:56 pm
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Sure.

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Man in the Mountains
Post subject: Re: Warship Hull Service Lives and Building StandardsPostPosted: Sat Oct 30, 2010 2:25 pm
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Thanks. I'll go root for them sometime this weekend, time permitting.


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Beastro
Post subject: Re: Warship Hull Service Lives and Building StandardsPostPosted: Sun Nov 07, 2010 5:14 am
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Quote:
Now, in the '60s and '70s warships were built with very thin plating indeed (3/16 steel wasn't unknown) but with the frames and ribs closely spaced.


Does this apply to the US CVs built during this era as well?

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p620346
Post subject: Re: Warship Hull Service Lives and Building StandardsPostPosted: Fri Aug 10, 2012 6:37 pm
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Beastro wrote:
Quote:
Now, in the '60s and '70s warships were built with very thin plating indeed (3/16 steel wasn't unknown) but with the frames and ribs closely spaced.

Does this apply to the US CVs built during this era as well?


I have heard that at least one CV Kitty Hawk (AKA **** Kitty) was built with thinner than normal plating and wore out faster as a result.


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M Stockwell
Post subject: Re: Warship Hull Service Lives and Building StandardsPostPosted: Sun Aug 12, 2012 10:22 pm
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p620346 wrote:
Beastro wrote:
Quote:
Now, in the '60s and '70s warships were built with very thin plating indeed (3/16 steel wasn't unknown) but with the frames and ribs closely spaced.

Does this apply to the US CVs built during this era as well?


I have heard that at least one CV Kitty Hawk (AKA *** Kitty) was built with thinner than normal plating and wore out faster as a result.

CVN 66 USS America. Thank you McNamara. By far the shortest career of any carrier from Midway on. 31.5 years. USS Kitty Hawk was retired after 48.0 years, the longest career of her class.

USS America was disposed of by Sinkex. All other Forrestal and later class carriers are still in existence.

USS Enterprise is currently at 50.8 years.

The information is from the NVR website. They should know, it's their business.

Mark

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Scott Brim
Post subject: Re: Warship Hull Service Lives and Building StandardsPostPosted: Mon Aug 13, 2012 11:33 pm
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M Stockwell wrote:
p620346 wrote:
I have heard that at least one CV Kitty Hawk (AKA *** Kitty) was built with thinner than normal plating and wore out faster as a result.

CVN 66 USS America. Thank you McNamara. By far the shortest career of any carrier from Midway on. 31.5 years. USS Kitty Hawk was retired after 48.0 years, the longest career of her class. Mark

One of my former managers, a mechanical engineer and former career naval officer, was assigned to the Kitty Hawk's engineering department for six years in the mid-1970's. Another of my colleagues, a retired USAF officer, had been a B-1 maintenance officer in the 1990's. Both of them seemed to share the same kind of philosophical outlook on life.


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M Stockwell
Post subject: Re: Warship Hull Service Lives and Building StandardsPostPosted: Tue Aug 14, 2012 7:19 pm
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Excuse me for a major brain fart. USS America was built as a CVA, not CVN. Finished her career as a CV. Did not get the final SLEP of her class due to her money saving thinner hull plating.

Mark

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M Stockwell
Post subject: Re: Warship Hull Service Lives and Building StandardsPostPosted: Sat Sep 15, 2012 12:13 am
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There is an aircraft counterpart to CVA-66 USS America.

The Douglas C-133. It was re-designed with a thinner skin due to the failure of the Pratt & Whitney engines to deliver the designed power. (I am a Pratt & Whitney fan).

In this case it was not primarily a political decision, but an engineering decision. The USAF believed they needed the aircraft. Certainly they make good use of the B model as a specialist transport for large rocket bodies.

It was retired after too many accidents. The last such was an inflight airframe failure at altitude while pressurized. The skin failed. The last flying example has finally been retired from occasional civilian use in Alaska as a heavy lifter to remote locations. Heavy earthmoving equipment into and out of gravel airstrips.

USS America's thin skin was a political decision. The end result is obvious. Visit the NVR site and review the length of the careers of all USN carriers from CVA-59 on. You will find 59 listed as CVT 59. Name search also works.

C-133's thin skin was a technical decision based on a partial engineering failure of the designed power plant. In the US, the 1950's were full of partial or full turbojet and turboprop powerplant failures. A number of the turbojet failures were based on foreign designs. The turboprop problems seemed to be largely home grown. After the C-133 problems, all Pratt & Whitney turboprops have been the province of Pratt & Whitney Canada. Currently in hot water with the US government.

The last P&W turboshaft (helicopter) was for the Sikorsky S-64 Skycrane. (US Army CH-54 Tarhe, if anybody actually called it a Tarhe). Today, the S-64E or F Aircrane.

All Pratt & Whitney turboshafts these days are also the province of Pratt & Whitney Canada. It is the turboshafts they are in hot water over. They should have let Turbomecca have the contract. Very short-sighted.

Mark

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constable
Post subject: Re: Warship Hull Service Lives and Building StandardsPostPosted: Sun Oct 07, 2012 8:36 pm
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M Stockwell wrote:
Excuse me for a major brain fart. USS America was built as a CVA, not CVN. Finished her career as a CV. Did not get the final SLEP of her class due to her money saving thinner hull plating.

Mark



I was on America and was told a SLEP was planned for her. We had issues and they were never fixed. Desert Storm and the end of the Cold War cancelled it.

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