Why no heavier RAF machine gun calibres?

[PAT303]

Mk III prototypes started out as the Mk I airframes, that were taken from the production line in order to be modified into the Mk III. Same fuselage behind the firewall, same tail (bar to cater for the retractable tailwheel), same wing.
A smaller scale of redesign than what the Bf 109 gotten with the F version vs. the E.

Don't look like MkI/II wings to me.

 

[Reluctant Poster]

2. Also, the transport of the war materiel was not always assured. The War of the Atlantic was not really won until the end(?) of 1942.

24 May 1943 to be exact. The day Donitz withdrew the U-Boats from the North Atlantic convoy routes.

 

[Reluctant Poster]

View attachment 811357
Don't look like MkI/II wings to me.

The first MkIII had shortened wings. These were not well received and the second prototype reverted to standard wings. The Me 109 F also went through a similar evolution with prototype's shortened wing being lengthened by adding the round wingtips.

 

[Reluctant Poster]

What awaited the British shipbuilders in 1940.

Like WWII in WWI the US undertook a major merchant ship building program. Like the associated WWI naval program it delivered most of the ships post war. In early 1917 the US had 37 shipyards building steel ships and 24 building wooden ones, by the armistice there were 341 shipyards. A schematic says around 300,000 tons of merchant ships built by the US in 1916, 750,000 in 1917, 1.3 million in 1918, 3.3 million in 1919, nearly 4 million in 1920, 2.25 million in 1921 and under 750,000 in 1922. The Emergency Fleet Corporation built 2,318 vessels. No one should be too surprised the US could do better a generation later and that the overhang from WWI depressed the ship building industry before the trade collapse of the economic depression. In 1922 the US had 11 million GRT of shipping employed on foreign trade, in 1935 around 4.5 million.

"Very few" merchant ships were built in the US between 1922 and 1937, mainly passenger ships and tankers. The depression meant 1930's US merchant seamen were almost back to the conditions of the 1890's in terms of pay and treatment. Strikes in 1936-37 resulted in improvements. In 1936 of the 6 biggest merchant fleets the US was fourth in tonnage, sixth in terms of vessels 10 or more years old and fifth in terms of vessels capable of 12 or more knots. In 1937 about 400 out of 1,500 US merchant ships were engaged in foreign trade.

The Maritime Commission initial objective was 50 new cargo ships a year for 10 years, with defence features, adequate crew quarters and "be the finest, fastest, safest ships on the sea." The law establishing the Commission was signed on 29 June 1936, the first commissioners appointed on 26 September and the law came into effect on 26 October. First orders being placed in 1937, it looks like a lot of the early work was coming up with standard designs. So it was ready to go well before the US entry into WWII, 28 ships delivered in 1939 including 12 C2 and 2 C3-E cargo and 7 T3 tankers, 54 in 1940, including 5 C1 Cargo, 8 C2 Cargo, 12 C3 Cargo, 5 C3-E Cargo, 2 C3 Passenger and Cargo and 5 T3 Tanker.

"A Statistical Summary of Shipbuilding under the U.S. Maritime Commission during World War II" by Gerald J Fischer, all up 164 pages of figures and text, from January 1939 to December 1945. The report covers 5,601 Commission, 111 private (95 tankers) and 65 foreign builds (all freighters) making up a total of 5,777 ships, from large passenger liners to unpowered barges, 56,291,678 DWT, 39,919,523 GRT, 22,218,130 Light Displacement Tons. Apart from the ships the commission helped add another 273 building berths to the yards.

236 Keels laid in 1941 including 121 emergency cargo and 40 tankers
1,133 Keels laid in 1942 including 654 emergency cargo and 79 tankers
1,953 Keels laid in 1943 including 1,194 emergency cargo and 229 tankers
1,661 Keels laid in 1944 including 656 emergency cargo and 214 tankers.

The tankers were very important given the military fuel requirements, 7,499,000 GRT.

EC2-S-C1 Liberty averages 441 feet 6 inches long, 56 feet 10.75 inches beam, 27 feet 8.875 inches draft loaded, 11 knots, single screw, 10,600 DWT, 7,187 GRT, 3,711 light displacement tons. Of the yards that built EC2-S-C1 in bulk, North Carolina was the cheapest at $1,544,000 per ship, St. Johns River the most expensive at $2,099,000 each.

Sort of worried about the cumulative war loss chart, what is the starting position, how are the fleets of France, USSR, Norway etc. counted? Since the axis in Europe seemed to target countries with large merchant fleets the "British" merchant fleet dry cargo only declined from 14.4 million GRT in September 1939 to 11.8 million in December 1942, tankers from 3.2 million to 3 million GRT, despite all the losses. Lloyds thinks the allies lost around 15,000,000 GRT to end 1942, plus 1,140,000 GRT captured, neutrals lost 1,400,000 GRT, the Maritime Commission says it delivered 6,664,000 GRT 1940 to 1942, Britain another 3,200,000 GRT. The tanker losses taken in 1942 meant it was well into the second half of 1943 before the tanker fleet recovered. Not sure how the overall shipping deficit ended up at nearly 12,000,000 GRT in 1942.

With all this there is what is being measured, the US Great Lakes tonnages for example, the minimum size of ship. According to the British for ships of 1,600 GRT or more, ocean going, the world had 56,803,000 GRT as of 1939, with over 12 million owned by axis powers and over 2 million by neutrals as of end 1942 (Mostly Sweden and Spain), that leaves around 42,000,000 GRT total possible allied fleet at the start of the war and it is down to 31,000,000 GRT end 1942?

From the Lloyd's Register of Shipping 1939 that I posted previously the biggest merchant fleets by GRT are:

Grand Total is 68,509,432 GRT
The tricky part is to determine how much of the invaded countries tonnage escaped to join the Allies.
I just discovered this website that may have the answers but I haven't had the chance to really look at it,

Danish Shipping Losses in World War II

The Danish merchant fleet’s history is varied with ships at one time being laid up, in neutral, Allied and Axis hands. Totaling 868,797 tons when the war began on September 1, 1939, by the en…

ww2sunkenships.ca

I should also note that only replacing the pre war fleet losses is a red herring. This assumes that the pre war fleet was adequate to meet the war time demands. This is clearly not the case with the vast number of war materials being shipped all over the world. Also note the convoy system, while necessary, produced inefficiency in utilization of ships. Shiiping was a problem well into 1944.

 

[tomo pauk]

Don't look like MkI/II wings to me.

As noted by the above poster, these wings were with the shorter tips. They reverted that decision for the 2nd prototype, since Dowding was of opinion that the Mk.III would've been mixed up for a Bf 109, and also to make wing loading more favorable.
More can be read about the Mk.III on the pages 127 to 132 of the 'Spitfire - the history' book by Morgan & Shacklady.

 

[PAT303]

The first MkIII had shortened wings. These were not well received and the second prototype reverted to standard wings. The Me 109 F also went through a similar evolution with prototype's shortened wing being lengthened by adding the round wingtips.

The wings were shortened from 36 feet down to 32 feet to improve roll, the Mk III was better than the MkI/II and MkV in every way.

 

[MiTasol]

Yep - so much better that it never went into production.

 

[PAT303]

As noted by the above poster, these wings were with the shorter tips. They reverted that decision for the 2nd prototype, since Dowding was of opinion that the Mk.III would've been mixed up for a Bf 109, and also to make wing loading more favorable.
More can be read about the Mk.III on the pages 127 to 132 of the 'Spitfire - the history' book by Morgan & Shacklady.

It wouldn't have mattered if the Mk III was mistaken for the 109 because the Emil couldn't catch it being a good 30+ MPH slower and unable to turn with it. The first ever kill the Spitfire made was a Hurricane so miss identification was a real thing.

 

[PAT303]

The first MkIII had shortened wings. These were not well received and the second prototype reverted to standard wings. The Me 109 F also went through a similar evolution with prototype's shortened wing being lengthened by adding the round wingtips.

Actually the opposite was true, pilots reported the plane was a major improvement over the Mk I/II in all area's except the landing run was longer, in all four prototypes were made and flown at Boscome Downs leading to an order for 1200 aircraft for front line service. But getting back to the original argument the problem was no HMG's or the Hispano were ready so it would have still been armed with eight .303's.

 

[PAT303]

Yep - so much better that it never went into production.

There was a little drama called the Battle of Britain that got in the way. The Mk III did go into production as the Mk VIII and later the Mk XIV.

 

[Alan Stevens]

3. By the end of 1944, the Allies were already pretty sure that the endo of the war was going to occur in 1945. They were so sure of this that they began training and selection of the occupation forces leadership (both civil and military) to the point where they were holding classes for the selected personnel.

" True, but even the US supply chain was not infinite. "
" Only with hindsight can we say (to a degree) concerns and decisions made based on fuel supply/usage did not matter. "
False dichotomy(s).

" By the end of 1944, the Allies were already pretty sure that the end of the war was going to occur in 1945."

Operation Downfall was the proposed Allied plan for the invasion of Japan near the end of World War II. It was planned to be executed in two parts: Operation Olympic and Operation Coronet.
Operation Olympic: Scheduled for November 1945, aimed to capture the southern third of the southernmost main Japanese island, Kyushu.
Operation Coronet: Planned for early 1946, intended to invade the Kantō Plain near Tokyo on the main Japanese island of Honshu.

That could conceivably mean that the war would last into 1947. At the end of 1944 the atom bomb was a top secret project and there was no definite timetable.

The B-29 conventional uses didn't really start having an impact until March 1945.

By mid-1945 more advanced U.S. fighter aircraft such as the F8F and F-80 were about to enter service.

" The fighter aircraft kept in service after the war is telling. The P-38 disappeared almost immediately. The P-47 was kept on in small numbers, mostly in the National Guard. The F4U and P-51 soldiered on through Korea. "

Given the vast drawdown of military forces, only a few would logically be kept, like one or two.

F-80 and F-86 became the state of the art fighters in Korea.

Some research reveals these numbers for WW II kills.
F6F Hellcat: Approximately 5,200 kills.
P-51 Mustang: Around 4,950 kills.
P-38 Lightning: Approximately 3,785 enemy aircraft kills.
P-47 Thunderbolt: Around 3,752 enemy aircraft kills.
The F4U Corsair: F4U and FG pilots claimed 2,140 aerial victories

So of the five, F6F wins and F4U is last. So the decisions weren't based on just kills, but likely more upon what one or two were the best to keep.

F6F was a navy fighter and the F4U was adaptable to both land and sea uses. Probably why a much smaller military and navy would choose the F4U to remain in service.

 

[ThomasP]

re

False dichotomy(s).

??

and

Given the vast drawdown of military forces, only a few would logically be kept.

Well, duh

and

So of the five, F6F wins and F4U is last. So the decisions weren't based on just kills, but likely more upon what one or two were the best to keep.

Well, duh . . . again. And it is telling that the F4U and P-51 were the ones kept.

and

F6F was a navy fighter and the F4U was adaptable to both land and sea uses. Probably why a much smaller military and navy would choose the F4U to remain in service.

??

The F6F could easily have been operated from land, with no more difficulty than the F4U - as all they did for the F4U was remove the tail hook and either lock the wings in the spread position, or remove the hydraulic wing fold mechanism and lock the wings in the spread position. At the time of the Conference the F4U had been developed significantly beyond what the F6F had - eg the F4U had significant advantages in Vmax and Radius of Action over the F6F - to the tune of 30-40 mph TAS Vmax and almost 100 miles greater ROA. The F4U also had 100 ft/min ROC, 1,200 ft Service Ceiling, and VNE advantages, as well as having a wing structure and pylon arrangements more amenable to carrying ordnance. And all of the above was before it received the R-2800-C series engine in the F4U-4 variant.

Again, if you can find a copy of the Report it is worth reading - and it explains the criteria fo the conclusions reached.

 

[Frog]

The F6F could easily have been operated from land...

Agree : that's exactly what the French did in Indochina as the F6F was used concurrently by the Armée de l'Air and Aéronavale. Furthermore, the F8F was exclusively used by the Armée de l'Air, while the French Corsairs served exclusively as French Navy's mounts.

 

[MiTasol]

There was a little drama called the Battle of Britain that got in the way. The Mk III did go into production as the Mk VIII and later the Mk XIV.

What a load of cobblers.

If you had said that the Mk III inspired the Mk VIII and XIV I would totally agree but the absence of Mk III parts in the Mk VIII and XIV blueprints I have says you are massively over reaching.

I have a SMALL collection of Spitfire blueprints and the Vickers part number system is very easy to follow.

Each version has a model number. The Mark 1 was the Model 300. All Mk 1 parts, other than standard parts or parts used on earlier Supermarine aircraft has a part number that consists of the model number followed by a two digit area code followed by a dash followed by an item number.

Taking the fuselage (area 27) as an example Frame 5 is shown on multiple sheets and on sheet 26 the upper port engine mount fitting is item 130. This makes the part number of that fitting 30027-130.

Each part on every later mark that is carried forward from the previous Mark/model keeps the same part number so every mark that uses the same engine mount fitting as on the Mk I has the same part number.

When the part is replaced on a later mark it gets a new part number starting with the new model number, followed by 27 indicating main fuselage and a new dash number.

The Mk VIII is the model 359 so the fuselage is part number 35927. The Mark XIV was model 379. I do not know what model the Mk III was

This is a typical drawing section for the late Mk VIII fuselage which is also used on the Mk XIV. Note all the part numbers start 300 or 379 (meaning a part changed for the Mk XIV but now also used on the Mk VIII) Note also the main frame pressing has only 515 shown as the number. That means it was a new part first used on the Mk VIII and its part number is 35927-515 regardless of which mark that part is used on.

The interesting thing is that I can not find in any Mk VIII and Mk XIV drawings any part numbers that do not start with model numbers for the Mk I, Mk II, Mk V, Ml VIII and Mk XIV. Admittedly I only have 28 sheets of Mk VIII and 181 sheets for the Mk XIV but obviously there should be multiple Mk III parts showing in at least some of the drawings. Even the fuselage stern has all new model 379 parts in the area where the tail gear is attached so even that was redesigned from scratch. See the second drawing below.

 

[EwenS]

The F6F could easily have been operated from land, with no more difficulty than the F4U

The USN did operate the F6F from shore bases in WW2.

VF-33 entered combat with the F6F on 28 August 1943 while based on Guadalcanal, later moving to Munda. That was 3 days before F6Fs from Essex, Yorktown & Independence hit Marcus Island in the first offensive carrier strike involving the new fighter. VF-38 & VF-40 joined VF-33 in the Solomons flying F6F in Oct that year.

In early Aug 1945 there were still 3 USMC squadrons on Okinawa, another split between Pelelieu and Ulithi and another split between Guam & Eniwetok all flying F6F-3N/5N night fighter versions from these vital shore bases.

 

[Reluctant Poster]

Actually the opposite was true, pilots reported the plane was a major improvement over the Mk I/II in all area's except the landing run was longer, in all four prototypes were made and flown at Boscome Downs leading to an order for 1200 aircraft for front line service. But getting back to the original argument the problem was no HMG's or the Hispano were ready so it would have still been armed with eight .303's.

The service trials of the Mk III prototype stated (from Morgan and Shacklady):
"There appear to be two serious disadvantages in an otherwise excellent aircraft.
(a) The landing run is dangerously long, and probably prohibitive for night flying and (b) the square ends to the wings will make the Spitfire still more difficult to differentiate from the Bf109, a matter in which mistakes have been made. May a pair of ordinary wings please be fitted to the Spitfire III so that it may be ascertained what reduction in the landing run is thereby obtained. I feel that the present Spitfire is already wing-loaded to the maximum extent compatible with efficiency and, if extra weight is to be added the wing surface ought to be increased rather than reduced."

 

[Reluctant Poster]

The Spit had to climb fast because it was so short ranged. It could not afford to to be at 30,000 ft when the radar vectors came in.

Even without drop tanks Merlin Mustangs, with either V-1650-1 or V-1650-3, would have met the Luftwaffe over the coast of FRANCE. And so the interceptors would not have been at the continual disadvantage of having the 109's always above them, but rather the opposite.

The stupidity of RJ Mitchell is very apparent. When he was designing the Spitfire in 1935 he should have known that in 5 years time France would fall like a house of cards and that the Luftwaffe would be based directly across the Channel allowing their bombers to be escorted. Shocking!

 

[Geoffrey Sinclair]

The 1940 limit on Fighter Command operations was pilots, this meant minimising flying time and not fighting over the sea or enemy territory, where more pilots would be lost, even with orders enough RAF fighters chased returning Luftwaffe aircraft far enough to justify the Luftwaffe allocating fighters to withdrawal cover. A design with a pressure cabin would have been quite useful in reducing the stress of repeated rapid transitions from sea level to 20 to 25,000 feet. Even better would be accurate information on Luftwaffe intentions, those bombers forming up over France could be a spoof, or at least had the fuel to circle for a while before setting course for Britain, or could turn back mid channel. For most of the battle the Luftwaffe tried multiple raids on multiple targets, the turn to London simplified the defence problems, bigger formations inbound, probably a single target.

As the battle went on the heights tended to go up, getting to 20,000 feet was one thing, getting another 5,000 feet to give a height advantage was another. The RAF command and control was very fast by 1940 standards, it still took minutes between deciding to intercept and orders for the fighters to scramble, become airborne and begin to climb in formation, which reduced overall rate of climb.

Spitfire III ideas dated from early 1939, first prototype N3297, engine promised for end September 1939 but whether the engines would be available for production was another matter. Four different propeller designs considered, first flight 15 March 1940. Order placed for 1,000 on 24 October 1940. The bombing of Supermarine destroyed the first set of strengthened wings and most production drawings. Despite the new radiator a bigger one was needed during cruise. Apart from the extra landing run maneuverability over 20,000 feet suffered despite the extra engine power. The prototype was seconded to Merlin 60 series development. Second prototype W3237 meant to be a mark V, flew in June 1941.

The ETO was phasing out the P-38 in 1945, as of end 1944 the USAAF was anticipating January 1945 to June 1946, another 5,000 P-38, nearly 7,000 more P-47 and around 10,500 P-51, end March 1945 it was 4,000 P-38, 9,000 P-47, 10,500 P-51, end April 1,000 P-38, 7,300 P-47N, under 8,000 P-51, the P-38 to finish in late 1945, the P-47 and P-51 end 1946.

USAAF inventory end 1944 2,759 P-38, 5,100 P-47, 3,914 P-51, end 1945 1,235 P-38, 4,322 P-47, 4,616 P-51, end 1946 113 P-38, 3,001 P-47, 3,303 P-51, end 1947 1 P-38, 1,827 P-47, 2,154 P-51.

In 1945 the F6F was in theory giving way to the F8F, Grumman built 605 F6F in March 1945, down to 314 in July, there were 530 Corsairs built in March 1945, down to 483 in July. When it comes to the navy, operating jets off carriers was a problem given their initial accelerations, the USN received the first of 60 FH-1/FD-1 in December 1946, the first of 30 FJ-1 in October 1947 and the first F9F in December 1948, while the USA(A)F had the P-80 in series production in 1945, the P/F-84B from June 1947 and the P/F-86A from April 1948.

Post war the P-80 unit costs were over $100,000 each, the F-84 over $200,000 and the first few F-86 over $400,000, the B-45 and B-50 over $1,000,000.

The US considered itself short of 100 octane for most of the war, resulting in training operations using lower octane fuels despite the engines being rated for 100 octane. The loss of tankers in 1942 hurt a lot. When it came to bulk fuel stocks it was a steady juggle between tanker allocations and consumption. Tankers could be "black oil" or "white oil" and changing between the cargo types required an extensive tank cleaning. So it was quite possible for an excess of white products like avgas to build up while stocks of naval oil fuel went down. Fuel consumption in the UK was generally below forecasts enabling stocks to be built up even as the average weekly imports fell from around 364,000 tons/week in mid 1943 to 250,000 tons/week in the first two months of 1944. The trouble was tankers being in such short supply once they were allocated to another run it was very hard to get them back, and consumption rose significantly in early 1944. In the period March to May 1944 weekly imports climbed to 402,000 tons but bunker fuel levels were still below the October 1943 level and stocks of "white" products, like avgas and MT80 continued to fall. For the first time in the war avgas consumption exceeded the forecast. The "white" fuel stocks were still below planned levels on D-Day, the result was a major increase in shipments in the middle of the year, putting stocks well above the agreed levels, some tankers were then withdrawn and the feast/famine cycle began again. UK oil imports in 1938 had been an average of 223,000 tons per week.

From the Lloyd's Register of Shipping 1939 that I posted previously the biggest merchant fleets by GRT are:

Grand Total is 68,509,432 GRT
The tricky part is to determine how much of the invaded countries tonnage escaped to join the Allies.
I should also note that only replacing the pre war fleet losses is a red herring. This assumes that the pre war fleet was adequate to meet the war time demands. This is clearly not the case with the vast number of war materials being shipped all over the world. Also note the convoy system, while necessary, produced inefficiency in utilization of ships. Shiiping was a problem well into 1944.

As far as I know Lloyds includes the fishing fleets and coasters, which pushes the overall tonnages up, when you go to ships of 1,600 GRT or more Norway drops 600,000, Holland 300,000, Britain 3,500,000 GRT compared to Lloyds. Overall 56,803,000 GRT of ocean going ships versus Lloyds 68,500,000 GRT of shipping. When it comes to what happened in 1940 most of the fleets of the countries attacked by Germany joined the allied cause, more than offsetting allied ships now captured or trapped in Sweden, an exception was Denmark where German threats to the families of the crews resulted in many ships returning or being laid up in neutral ports, the latter a fate a lot of Italian ships suffered, most of these succumbed to US pressure later and joined the allied fleet, on the other hand a number of ships chartered by Japan failed to be returned before December 1941, while the French fleet largely stayed loyal to Vichy. Panama had 700,000 GRT of ocean going ships but generally the minor neutrals tried to stay out of the conflict zones. Apart from the inefficiencies of convoys a lot more "trade" was one way, further reducing shipping efficiency. Add the closure of the Suez canal and, for example, lots of pre war British trade was to Europe, for items that now had to come from much further away or do without.

While there were some wobbles by end 1944 the allies assumed by end 1945 Germany would have been totally defeated and Japan, if still fighting, would have lost most possessions outside Japan and North Asia.

 

[Juha3]

The Spit had to climb fast because it was so short ranged. It could not afford to to be at 30,000 ft when the radar vectors came in.

Even without drop tanks Merlin Mustangs, with either V-1650-1 or V-1650-3, would have met the Luftwaffe over the coast of FRANCE. And so the interceptors would not have been at the continual disadvantage of having the 109's always above them, but rather the opposite.

It was not so simple. Firstly, continuous patrolling is logistically challenging, as it consumes lot of POL products, wear engines and strains the pilots, especially flying at 30,000 feet was tiring in the long run. Secondly, the British would have been fighting on the wrong side of the Channel, the downed aircraft and pilots would have been lost, either as prisoners of war or drowned in the Channel. The British maritime rescue operations in 1940, which were much less developed than those of the Germans, were based mainly on coastal vessels and RNLI lifeboats. The RAF itself had only a few fast boats for maritime rescue missions. As the BoB was fought means that most of the shot down pilots could return Service immediately or after a period at a hospital and many of the crashlanded fighters could be repaired.

 

[Reluctant Poster]

It was not so simple. Firstly, continuous patrolling is logistically challenging, as it consumes lot of POL products, wear engines and strains the pilots, especially flying at 30,000 feet was tiring in the long run. Secondly, the British would have been fighting on the wrong side of the Channel, the downed aircraft and pilots would have been lost, either as prisoners of war or drowned in the Channel. The British maritime rescue operations in 1940, which were much less developed than those of the Germans, were based mainly on coastal vessels and RNLI lifeboats. The RAF itself had only a few fast boats for maritime rescue missions. As the BoB was fought means that most of the shot down pilots could return Service immediately or after a period at a hospital and many of the crashlanded fighters could be repaired.

I would also add that the claim the RAF could not reach Dunkirk is false. They could have done so if they had wanted but they chose wisely to fight over their own territory. In fact the very next year Leigh Mallory did send the Spitfires over France with disastrous results.