A much different F4U Corsair

[Shortround6]

Basically, to get any worthwhile number of R-2800 powered fighters in 1942 ( hundreds not dozens), you have to kill the B-26 program. You need both the engines and props and there is nothing else to take them from. Now if you do this you reduce the numbero f twin engine medium bombers available to the USAAC by about 1/2 in 1942. Now maybe you can get Martin to build B-25s and squeeze another 1500-2000 R-2600s out of Wright.

And look again at what you get. Everybody seems to be mesmerized by the take-off power of the early R-2800 and R-2600.

The Allison -39 offered 1150hp at 12,000ft for hundreds of pounds less weight (even including radiator and coolant) and less drag and the Merlin V-1650-1 offered 1250hp at 15,600ft in March of 1941 ( before any were actually delivered) also at less weight and drag.

at 12,000ft the R-2600B is offering 1450hp, the R-2800s are offering 1500hp at 14,000ft and 1600hp at 13,500ft. at 15,500 they are offering about 1425hp and 1500hp. at 18500ft where the V-1650-1 delivered 1120hp the R-2600B offered (if you extend the lines) about 1150hp and the two R-2800s delivered around 1250-1275hp and 1325hp? The "B" series R-2800 is delivering about 18% more power at 18,500ft to make up for it's weight and drag compared to the 53% advantage it had at sea level or for take-off. The "A" series R-2800 engine offers even less of an advantage at 18,500ft.

Once Allison straightened out the gear problem the later Allisons were good for 1125hp at 15,500ft and that may be what Allison promised on the earlier failed engine when the "planners" were making decisions. "A" series R-2800 offering 26% more power at 15,500ft than a high geared Allison but at about 900-100lbs more weight (not including radiator and coolant) and the bigger propeller, bigger oil system, etc. Plus a LOT more drag.

 

[tomo pauk]

Basically, to get any worthwhile number of R-2800 powered fighters in 1942 ( hundreds not dozens), you have to kill the B-26 program. You need both the engines and props and there is nothing else to take them from. Now if you do this you reduce the numbero f twin engine medium bombers available to the USAAC by about 1/2 in 1942. Now maybe you can get Martin to build B-25s and squeeze another 1500-2000 R-2600s out of Wrigh

A-20 stays with the R-1830s, so Martin can use the R-2600s?

As for the rest of the post:
The key things are timing and availability. In 1941 USA can install in it's fighters:
- V-1710 'C' series engines, either turbo (1150 HP up to 25000 ft), or non-turbo (1040 HP at 13800 ft). Neither -39, nor the engines with 9.6:1 supercharger drive ratio are available (not counting prototypes) before early and late 1942 respectively
-R-1830, single stage or turbo
-R-2800 'A' series, single stage
-Wright engines (R-1820 and R-2600)

The V-1650-1 is a fine engine, but it's early 1942 when it's available (again, in more than token numbers). Once available, there is no point to compare it with R-2800 'A' series, since now the 'B' series is in production; I do agree that above ~18000 ft the disadvantages might overweight the advantages. Of course, if the intended costumer is the USN, they might decide that, as an overall package, the R-2800 is a better choice.

The V-1710 'C' and early 'F' offer 850 HP at 20000 ft, the R-2800 'A' offers 1200 HP (40% more), R-2800 'B' offers 1270-1280 HP (50% more).

Once Allison straightened out the gear problem the later Allisons were good for 1125hp at 15,500ft and that may be what Allison promised on the earlier failed engine when the "planners" were making decisions. "A" series R-2800 offering 26% more power at 15,500ft than a high geared Allison but at about 900-100lbs more weight (not including radiator and coolant) and the bigger propeller, bigger oil system, etc. Plus a LOT more drag.

Comparing a R-2800 from Jan 1941 with V-1710 from late 1942 (full throttle at 15500 ft) is funny, to say at least.
Anyway, the R-2800 B makes almost 45% more power above 15500 ft (890-900 vs ~1275 HP at 20kft) vs. the improved 1710 (like F-20, as found in P-40Ms and P-51As for example - FTH at 14500 ft). Against the engines with FTH at 15500, it's 35% more power.
The 'B' also beats the BMW-801C and restricted 801D by some 12%, above 15000 ft. At altitudes under 15000 ft the R-2800 does not need out-of-book operation to produce huge power, easily beating all of the mentioned engines.

Chart is from the Mustang I manual (F3R engine), red are V-1710s with 9.6:1 sup. drive ratio, blue are the 'A' and 'B' R-2800s:

 

[ccheese]

Why did the Corsair have gull wings? didn't this have something to do with prop length?

That was the main reason for the inverted gull wings, to allow deck clearance for the larger prop.

Charles

 

[wuzak]

The Spitfire XIV, XVIII and XIX went for a 5 blade prop for ground clearance.

The Griffon was angled down slightly to improve the view over the nose, which reduced the ground clearance for the prop. So they used a smaller diameter prop with more blades and spun it faster. The Spitfire XII used the same diameter (I think) 4 blade prop as the VIII and IX.

From Stona's diagram it would seem that the Tempest II's prop diameter was restricted by the lowered thrust centreline. It seems to indicate that the bottom of teh arcs of both props was in the same place.

 

[model299]

That was the main reason for the inverted gull wings, to allow deck clearance for the larger prop.

Charles

Besides, they look pretty cool.