USN 1940's Flightdeck Oiler

[Graham1973]

I was looking through the 1940's Springstyle Catalog and found this design for a ship designed to combine the tasks of fleet refueller and either escort carrier and/or aircraft ferry.


Photo #: S-511-53 - "20 Knot Flightdeck Oiler - Preliminary Study"

 

[Sea Skimmer]

Neat, it'd effectively be a slightly faster, 5000 ton heavier version of the Commencement Bay class which were built on T3 tanker hull and served as oilers. Had the war gone on it would have made some sense to begin building dedicated escort designs, as the British effectively began to do themselves.

 

[shep854]

Actually, the Commencement Bay class was the first CVEs built as such from the keel up; Sangamons were converted tankers. I've never read of CVEs conducting oiling operations, except perhaps for refuelling escorts.

Here's a link to a very interesting, informative article:

http://www.history.navy.mil/download/car-9.pdf

EMERGENCE OF THE ESCORT CARRIERS

 

[Sea Skimmer]

They might have been built from the keel up but the whole project still used an improved Cimarron as the design basis and a Cimarron was just a military version of the T3. A lot of stuff changed in the process in the machinery space to improve survivability but at heart it was a tanker. This was reflected in the ability of a Commencement Bay to carry about 7,350 tons of cargo oil besides 3,380 tons of ship fuel and 150,000 gallons of AVGAS. Figures from Friedman's US Carriers, I didn't type out every last decimal place though. Fueling escorts was common place but the CVEs assigned to aircraft ferry duty, which was a lot of them by the end of the war also carried as much cargo oil across the Pacific as possible. I do believe some of the Morrision's classic USN Histories go into some detail on this and other service force operations but I don't have the relevant volumes at hand. At times the Sangamons were operating as more oiler then carrier due to the critical shortage of oilers that lasted into 1944; which was the only reason why the US didn't build hoards of Sangamons follow-on's in the first place. The advantages of a self escorting submarine killing oiler or cargo tanker are pretty overwhelming; it's surprising really that nobody had adapted the concept for trade protection prior to or in the earliest years of the war.

 

[shep854]

Thanks, Sea Skimmer; this is the first I'd ever read about CVEs having a secondary mission as an oiler. It's definitely a subject to pursue!

 

[Sea Skimmer]

MACs had hangers? I thought they just had a short flight deck and 4-6 aircraft, which was nice but not really the capability you get from even a dozen planes allowing for a mix of fighter and strike-recon types. In any case I don't believe the saw service until late 1941 and most only in 1942 right?

 

[TinWing]

I was looking through the 1940's Springstyle Catalog and found this design for a ship designed to combine the tasks of fleet refueller and either escort carrier and/or aircraft ferry.


http://www.history.navy.mil/photos/images/s-file/s511-53.jpg

There was also a drawing of a dedicated tanker based on the same hull. In any event, this is just a very large CVE in concept. According to Friedman, the RN considered a similar concept.

As far as using a flight deck ship as a fleet replenishment tanker, a flight deck is an impediment to replenishment operations, although it is very clear that carriers have provided refuelling to escorts.

Looking at the date of this study, the navy might have been considering the aborted attempt by the USS Saratoga and Lexington to relieve Wake Island, an operation that was supposedly cancelled for the lack of a fast fleet tanker to replenish the carriers.

In the end, I'm not convinced that a 600", 30,000 ton escort carrier, or the equally large tanker version, would have been any more effective than the standard T2/T3 based ships that were actually built. The ultimate T3 based Commencement Bay ships ended up being 557 feet long, nearly 25,000 tons and capable of just under 20 knots. Granted, a lot of war built tankers were "jumboized" after the war with hull plugs, so there might have been argument for high capacity ships to begin with.

 

[Grey Havoc]

MACs had hangers? I thought they just had a short flight deck and 4-6 aircraft, which was nice but not really the capability you get from even a dozen planes allowing for a mix of fighter and strike-recon types. In any case I don't believe the saw service until late 1941 and most only in 1942 right?

According to one source I've read, the converted grain ships had a 123m/400ft flight deck (413-424ft according to another source, see below), a below-deck hanger and lift, and a normal complement of four Swordfish. The tankers had a 140m/460ft flight deck, but no hanger, which meant that their normal complement of three Swordfish suffered a lot of wear and tear. Apparently Sea Hurricanes were also carried, although I'm not sure of the mix, or whether any all Hurricane compliments were ever deployed.

From the decent but short Wiki article on MACs:

The Merchant Aircraft Carriers were modified bulk grain carriers or tankers built with flight decks and small island structures. Minimal aircraft handling and accommodation facilities were available. The bulk nature of the cargoes did not need deck mounted cargo-handling gear used for general cargoes. The MAC-ships were manned by a Merchant Navy crew, under merchant colours, the Royal Navy provided the air department and the guns were manned by DEMS soldiers. They carried their regular cargo in addition to operating aircraft. Tanker MAC-ships were able to carry about 80 percent of their original cargo, the remaining space being taken for Avgas stowage to Admiralty safety standards. Grain carrier MAC-ships suffered a reduction of about 3,000 tons (or 30 per cent) of the original cargo of grain. Their Fairey Swordfish aircraft carried out anti-submarine patrols around the convoy.[2][3]

The scale of the conversion was small, hence it could be completed in a short time; five months has been quoted as being typical.[1]

The fuel piping arrangements in a tanker made it impossible to build a hangar under the flight deck, so tanker conversions were limited to embarking three Fairey Swordfish which had to be kept on deck. Collapsible deck-edge wind breaks were fitted on the flight deck aft to provide some protection for parked aircraft. The grain carriers had a small hangar aft with a single lift which allowed the carriage of four Swordfish. Flight decks were around 460 feet (140 m) long on the tankers and between 413 and 424 feet for the grain ships, width was 62 feet (19 m) in all cases. All the MAC-ships were fitted with four arrester wires. The permanent deck park of the tanker MAC-ships required a barrier for aircraft recovery. Aircrew accommodation was minimal and ammunition and fuel stores were neither armoured nor partitioned.[3]

Many of the ships were given names with the prefix "Mac-", in a reference to their designation as MACs; the "Empire" prefix was used on ships built by the Ministry of War Transport to distinguish them from pre-war privately owned ships. Since these ships were owned by the Government and only on loan to the shipping companies it was easier to take them out of service for conversion.

*[3]Hobbs, David (1996). Aircraft Carriers of the Royal and Commonwealth Navies: The Complete Illustrated Encyclopedia from World War I to the Present. London: Greenhill Books. pp. 231–248.


http://en.wikipedia.org/wiki/Merchant_aircraft_carrier

 

[Julio Garay Terrazas]

Maybe someone like it: http://drawings.usmaritimecommission.de/drawings_tanker.htm
Is about CV convertions to oilers, after the war.