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.