Propulsion plant question

[rickusn]

Not a BB question but I know and respect the engineering expertise that frequents this forum so please forgive me for intruding.

When it comes to engineering Im about as smart as a box of rocks. LOL

What are the reasons the Brits used two shaft geared turbines paired with two boilers for their "C"/Battle/Daring class destroyers but the USN used two geared turbines paired with four boilers for the Fletcher/Sumner/Gearing classes?

Does it have to do with shaft horsepower?

The USN ships had 60000 SHP the RN ships had 40000/50000/54000 respectively.

My next question will probably get me slammed but...

Would the Knox class frigates been able to have easilly/economically/space wise incorporated another shaft and geared turbine and with the same or different boilers realised increased speed to 29/30 kts or better?

How would it effect endurance?

I really like these ships except for a couple issues but mostly for being saddled with one screw and one geared turbine.

Thanks in advance for any info, thoughts or direction.

Rick

[Dreadnought]

Hey Rick,
I can only speculate on part of your question.
The reason being "specutively" for the extra boilers is that under normal cruising conditions so many boilers are online maintaining the ordered speed from the bridge while the others are going through maintenance or PM's if you would. They can easily be brought online for full power, flank etc. In addition it would also have a great deal to do with what equipment auxilliary they are powering as a secondary power source. Another reason could be that the USN puts an extra "umph" if you would in the power source demand for their ships to be able to reach slightly above what they are spec'd out to be.

Hope this helps with part of it. Im not up to par with the Knox class.

Some very interesting articles you have been posting.
Thanks

[RAL's_pal?]

I was thinking about this question since yesterday when I first saw it. The Knox class originally being a DE is probably why it only had one fireroom and one engine room. I looked at the specs of the Adams class DDG's and their loaded weight is similiar to the Knox class yet the Adams had two firerooms and two engine rooms. I hated working on Adams class ships because everything was tight and jammed in place where the Knox class had a lot of room throughout the ship. An oddity of the Knox class was that it's forced draft blowers were horizontal and located on the main deck above the fireroom compared to all other DD's and DE's of the same era which had the vertical FDB's on either side of the boilers. You mainly see the horizontal FDB's on auxilliary (LPD, LSD, LHD, LHA, LKA, etc.) classes ship's boilers.

[rickusn]

Thanks guys if yopu ever come across more clarifying info please let me know.

And RAL would there have been enough room to add a better propulsion set-up? I think you implied that but Im not positive.

Yes I know the USNs reasoning behind the the single screw but it was a serious mistake IMHO albeit in hindsight.

However given the discussions(I can expand on this if you like) of the late 50's and early sixties and with the known life expectancy of the Sumner/Gearing/Fletcher classes that the Knox class was really built to replace and as I have in other postings shown actually did irregardless of USN proclamations to the contrary.

The USN really only paid lip service to convoy escort their real intention as always was to fill out their Battle groups first and foremost again I have documentation to prove this. And this couldnt be done w/o inclusion of the Garcia/Brooke/ Knox classes.

But money wise they had to skimp on the Knox class plus it wasnt the ship they really wanted which was a high-end multi-purpose ship with an empasis on AAW. Again I have documentation to support this.

And notice too how the Spruance program got blasted.

Even though the MFE study of 1967 dictated that the USN needed just such a ship.

[RAL's_pal?]

The propulsion plant layouts in the Adams class DDG's, Leahy class DLG's (CG) and Belknap DLG's (CG) are virtually the same as on the Fletcher/Sumner/Gearing class DD's. With the larger ships, there's a bit more room. I haven't set foot on a Gearing since 1981, an Adams since 1986, Leahy/Belknap since late 80's and a Knox class since 1994 so my memory isn't that great. To put in what's necessary to have 2 screws you'd have to create 2 more machinery spaces and you'd have to cram everything else together (berthing, auxiliary spaces etc). A boiler expert would be nice to have around to discuss the volume, efficiency and boiler size difference between an Adams and Knox class on this string.

In hindsight, I don't understand the need for the Knox class when there were so many Adams class ships built.

I think the Garcia/Brooke class was an experiment gone wrong with their pressure fired boilers that always seemed to be in need of repair.

And, I never thought much of the OHP class of ships with their design and armament (just a personal opinion). I can remember standing in the chow line on the Jersey which extended down the passageway and up a deck and around the fantail, with my cup of coffee in my hand and watching the OHP class ship off the starboard quarter, roll heavily.

[rickusn]

"In hindsight, I don't understand the need for the Knox class when there were so many Adams class ships built. "

And provided only one escort for each conventional attack carrier and ASW carrier.

23 ADAMS class ships wasnt really alot compared to the 250 Fletcher/Gearing/Sumner classes that were slowly being replaced even though FRAM was being undertaken for many of those ships.

FRAMI/II provided for only 8 years and 5 years life-extension although many ships exceeded this they were for all intents and purposes ineffectice combatants.

That is why in the late 50s the new frigate classes were already seen as destroyer replacements but the USN never had the funding to replace those 250 ships with the high-end ships they wanted in the #s neccessary.

So even with the five Mitscher/Norfolk DL/ 18 Forrest Sherman DD/23 Adams DDG/10 Coontz DLG/10 Belknap DLG/N/10 Leahy DLG/N. 76 ships total. And even including the 20 austere but mostly expensive Dealey/Jones/Bronstein escorts. And the 14 cruisers afloat.

Another miniimum of approximately 140 plus !!!!!!!!!!!!!!! surface combatants escorts was required.

The 30 Coontz/Belknap/Leahy provided two for each of 15 active attack carriers.

The Long Beach provided the third escort for the Enterprise along with the two Belknap/Leahy class nuclear powered variants.

The speed and logististical freedom provided by nuclear power was seen as precluding the use of any conventionally powered escorts.

The converted WWII cruisers provided additional resources including a plan(not realized) of one TALOS AAW cruiser for each two carrier grouping again with Long Beach providing TALOS support for the Enterprise.

And it was hoped that always having conventionally powered carrier battlegroups roam the oceans at speed would also preclude the use of FRAM modernized WWII era destroyers.

But experimentation and "real" world operations soon showed the fallacies in the concept.

This three ship escort concept was a radical departure from the USN historical concept first seen in 1941 of one to four cruisers and 4 to 9 destroyers assigned to CVBGs.

Two cruisers and eight destroyers(ie a destroyer squadron) was found to be optimum.

This approximate number has remained unofficially at least to the present as the CSG/ESG/SSG paradigm is to be reconstituted as an NEF in the event of war with all nine escorts(2 cruisers/7 destroyers) primary job would be to support the carrier centerpiece.

And yes the Garcia/Brooke propulsion system was a huge USN failure. However these ships like the Knox class performed admirably despite the inherent limitations imposed on them due to cost and the poor(lack of?) testing of the new propulsion sytem before placing it in a new combatant.

The Adams class was optomised for AAW/ASuW with a fair ASW capablity.

STop for a moment.

Even though the Tartar system was seen as ineffective which along with cost and the MFE study conclusions halted the conversion of all the former DL/DD ships to DDGs.

Which in effect would have provided another DDG similar to the Adams class for each carrier.

So the preferred unofficial carrier battle group would have comprised one TALOS CG, two Terrier CGs, two Tartar DDGs and four-eight FRAM coversions or their replacements which were in fact the new FF/FFG classes.

This paradigm consumed the minimum # of ships estimated to be needed by the MFE (242) and in fact the ADDITION of ships for shipping protection drove the minimum requirement for BOTH CVBG and shipping escort to 340.

But you will have to be an astute student to find the latter contention in the MFE although the number(340) is easilly found but that is my take.

It is remarkable that the MFE has really been the foundation of USN programming for four decades!!!!!!!!!

I have always used the 10 escorts per carrier(24 16 attack/8 ASW of the 1960s) in conjunction with the 250 Fletcher/Sumner/Gearing destroyers in-commission at the end of the Korean war to come up with approximate 240+ escort # to explain USN requirements w/o all the convoluted and tortuous calculations of the MFE, studies and USN conceptual justifications to Congress.

Which aprox. # is repeatedly seen until of course the end of the cold war changed many things. But the approx 10 escorts per carrier wont go away at least in my view.

In spite of or maybe because of its flaws the MFE study was able to please both Congress and the naval purists such as myself w/o meeting either audiences expectations.

Back to warship discussion. Sorry for the longgggggg aside.:

Wheras the Knox was optomised for ASW with a fair AAW/ASuW capability.

But the USN was in a cash crunch because of reliability problmes with the "3-T" AAW system and the new SQS-26 along with the fact that the Typhon AAW system was an expensive failure plus the expensive SSBN/SSN programs, new carriers, new aircraft and Vietnam.

So these ships couldnt be built as they should have been along with the USNs preference for AAW ships and this bias continued even after the MFE study that concluded that escort #s were driven by ASW considerations.

See all the Spruance program criticisms.

The same two old questions still continue:

Multi-purpose vice Single-purpose?

Highly capable/Less capable?

The OHPs were even worse ships as originally concieved.

In fact until 1/2 of them got two LAMPS III helos and 1/2 of those got CORT they werent very good.

And basically they were used as DDGs surrogates for a time in the middle 90s until enough Burkes entered service even with CORT/2 LAMPS helos this was really stretching credibility.

However like the previous frigate classes they too have performed admirally despite their inherent limitations again because of cost.

Sorry to be so long. I am in the process of putting together an essay for the contentions I have posted here and other similar posts I have made in other threads recently and over the years.

But RAL asked a very good question about the Adams/Knox classes that I didnt have a really good short answer for.

Although I suppose I could just have said that Adams class was only a small part(1/10th approx) of the effort to replace the 250 WWII era destroyers of the Fletcher/Sumner/Gearing classes in-commission at the end of the Korean War.

But that wouldnt have told much about the rest of the story and so would not have been as much fun.

LOL

[dilawar]

hi, Just trying and getting to understand your point, been long since i've been on steam propulsion units. But this seems likely. (My opinions, don't mind if i'm off a bit)

What are the reasons the Brits used two shaft geared turbines paired with two boilers for their "C"/Battle/Daring class destroyers but the USN used two geared turbines paired with four boilers for the Fletcher/Sumner/Gearing classes?

Does it have to do with shaft horsepower?

It would depend on the PSI of the boilers in use. The capacity of the geared turbines to generate power dependent on boiler production. Also it might be dependent on the length of the shafting that could result in power losses. Too many variables here. But it could keep a design person busy configuring the right combo of steam production, usage and utilization ultimately post geared conversion for adequate power/ thrust requirement.

Would the Knox class frigates been able to have easilly/economically/space wise incorporated another shaft and geared turbine and with the same or different boilers realised increased speed to 29/30 kts or better?

I think there's a misconception here. I've been away from steam driven ships awhile, yet i know one can get better speeds theoretically on single screw, single turbine and single boiler with right specs that twin screw ones with inadequate ones. Speed will ultimately depend on delivered HP right at the screw end minus shaft losses and yes also the production capability of oil, (coal), whatever fired boilers, or maybe steam generated through fission. Idea is to get a certain PSI, that drives the main propulsion unit/s. Get certain required BHP which translates to a certain speed at nominal slip, ultimately through the propellers.

Having 2 boilers or more is immaterial to horse power requirements. It matters as stated before on maintenance, possibly extra power requirements if turbine capbailities are adequate. Nothing more. Rest are design issues. These include space, reliability, functionality host of other issues.

How would it effect endurance?

I really like these ships except for a couple issues but mostly for being saddled with one screw and one geared turbine.

Sir, maneouverability is an issue here. IMO twin screws are better in some ways than single with equivalent power o/ps. But i don't see why with bow/ stern thrusters and like, one can't get better maneoverability. Easily controllable, less dependent on boiler turbine functions.

[rickusn]

Thanks for the input Dilawar it was ALL quite helpful.

I was just wondering why or what reasoning the Brits thought two boilers were sufficient and the US decided on four in comparably sized and mission oriented ships. I was abit surprised when I noticed the difference.

I was assuming redundancy as one issue along with the issue I vaguely recall reading about of puttiing more boilers on line as greater speed was required.

As for two screws you are correct "maneouverability" is a factor I failed to mention. Thanks for pointing that out. As this was a criticism of the Knox class also.

I was focusing on cost constraints and redundancy but I surely should have mentioned the "maneouverability" issue.

Any other thoughts/info/sources/documents/articles/books etc on this topic would be greatly appreciated.

[rickusn]

On my USN destroyer replacement post above.

The USN classes included:

16 Garcia/Brooke class
46 Knox class w/ 10 canceled
31 Spruance class
16 Strike cruisers never built
6 California/Virginia class others planned but not realized
51 OH Perry class 24 others planned not built
4 Kidd class
27 Ticonderoga class

So with nominally 250 destroyers and 18 cruisers to replace the USN had plenty of programs planned and/or realized.

Albeit these ships werent built in a timely enough manner due to cost constraints, or in the case of the Strike Cruisers built at all, along with the fact that some of the 1950s built ships were also decommissioned before some of these programs even started and the other 1950 era programs were decommissioned before their replacements, the Burkes, were constructed.

I discount DE replacements as post-WWII saw this category reduced from 361 to 10(all school ships) by 1950.

And relatively few were reactivated during Korea and many of those were converted to radar-pickets(DER) on the DEW line rather than normal/regular USN fleet duties.

And by 1960 all but a few school ships and the DEW ships remained active with all of those planned to be retired by 1965.

However some former DERs were spared as they were seen as useful for duty in the Vietnam coastal Operation MarketTime.

Shades of LCS?

In addition the Dealey class were what started the USN to consider DEs as destroyer replacements rather than WWII DE replacements. Relatively fast but costly while being a bit underarmed. But could and did escort the Essex class ASW carriers. In particular the 1958 of the USS Wasp MED deployment in which her screen was entirely made up of this class. But with the demise of the DASH program their continued usefulness came to an abrupt halt although with the FRAM program IMHO they were already redundant.

The four Jones class was an aborted effort to develope a mobilization escort design to eventually replace supplant the WWII DE types in reserve alos this type of slow, underarmed ship was overtook by events ie they could not possibly cope with the future submarine threat much less the envisioned future war at sea.

Although it is true that WWII DEs served in the NRF through the 1960s.

The Bronsteins too were experimental but had long lives.

The Garcia/Brooke/Knox/OH Perry classes were all concieved as destroyer replacements albeit with severe limitations due to mostly cost issues.

However I reiterate the USN tried to hide this fact by a variety of means as best as possible lest Congress limit the USN to building only these types of ships vice the more capable, multi-purpose ships the USN sought.

And even though as the USN 1967 MFE study acknowledged ASW drove escort requirements the USN remained institutionally fixated on AAW and ASuW capabiliies.

Even though this should have been quite obvious to begin with after all the ASW efforts like the recent FRAM/DASH/SQS 23/SQS 26/ dedicated ASW carriers and aircraft both carrier and land based efforts but also going back to WWII and late 1940s destroyer conversions that emphasised ASW IMHO.

But in reality FRAM was the only real alternative to a massive decommissioning of the Fletcher/Sumner/Gearing class destroyers due to block obsolescence so while the USN surface force institutionally refused to embrace an emphasis on ASW they were more or less forced to by expedience, practicalities, pragmatism and reality.

And this fixation on AAW/AsuW also accounts for much of the slowness of the USN surface force to adopt the passive sonar means of submarine detection.

Well at least this is the conclusions Ive come to although they certainly arent original or unique but a synthesis based on what I have read.

[dilawar]

What are the reasons the Brits used two shaft geared turbines paired with two boilers for their "C"/Battle/Daring class destroyers but the USN used two geared turbines paired with four boilers for the Fletcher/Sumner/Gearing classes?

Sir, one simple reason i can think of is operational doctrine put into design. This is irrespective of power developed by individual or ssociater turbine capacity to utilize it. The US doctrine could be using these ships much further away from base or dockyards for longer periods of times. The Brit thinking in dfesigning the ships that way could be a more modest doctrine in terms of usage and operational time. So for the Americans it made sense to have more boilers that could power the turbines and also be standby for maintenance. Just thinking out aloud though. Will appreciate any correction to it.

[RustyBattleship]

Originally Posted by dilawar

Sir, one simple reason i can think of is operational doctrine put into design. This is irrespective of power developed by individual or ssociater turbine capacity to utilize it. The US doctrine could be using these ships much further away from base or dockyards for longer periods of times. The Brit thinking in dfesigning the ships that way could be a more modest doctrine in terms of usage and operational time. So for the Americans it made sense to have more boilers that could power the turbines and also be standby for maintenance. Just thinking out aloud though. Will appreciate any correction to it.

As a retired Naval Architect, I can say that you are just about smack dab on the money. US warships have always been designed with almost extreme redundancy to increase chances of survival when damaged.

However, lately some modern boiler fired ships are not considered to be front line fighting ships (such as LHA's and LHD's) and can get by with one large boiler per shaft.

Modern Destroyers and Cruisers are now gas turbine powered. They use two gas turbines per shaft simply to get as much horsepower as possible out of them rather than for survival redundancy.

[Dreadnought]

And..The can be underway within minutes instead of hours on the burners as such in boilers.

[RustyBattleship]

Originally Posted by Dreadnought

And..The can be underway within minutes instead of hours on the burners as such in boilers.

And can use anything for fuel from Methane (the most efficient) through Navy Distillate (actually used) on to Banana Oil (fuel selection valve has to be all the way open and you can only hope the on-board pumps can handle it).

[Dreadnought]

I bet that banana oil smells alot better then the distilliate. Hmm a ship that smells like bananas? I think I could get used to that. That was a new one for me. Mr. L. is it used much in service or just an experimental option?