So, basically, we have the same debate Grumman had with the Bureau of Aeronautics. Grumman wanted to build a fighter around the R-2600 and the Bureau thought that would too complicated so they should stick with the test aircraft. Keep in mind that they found the F4F able to compete with the F2A Buffalo, so the navy should give them a contract. Grumman engineers weren't incompetent so they must have thought they could make it work. Granted the alternative would be 15-20% heavier than the OTL F4F-3 but it would have 33% more power to work with. I also don't see where all this additional drag would be coming from. The front and the cowling wouldn't change and that's where most of the parasitic drag would be coming from. Having a longer fuselage and larger tail doesn't necessarily add much drag.
A Wilder Wildcat
- Thread starter Belisarius II
- Start date
Since the Ha-109 is mentioned, just saying that for some reason the americans never quite managed to make their radials with smaller diameters (hence less drag) like the japanese did, the Ha-109 has a diameter of just 126cm while the R-2180 is 137cm (!), which is huge difference comparatively, even if the Ha-109 has a bit more capacity. Even the much larger Kasei has a diameter of "just" 134cm. And the rejected Shinten only 130cm.
So perhaps PW would have been better off working on a redesigned R-2180 of reduced diameter instead of R-2000, let's call this R-2180-B.
I've looked for examples of R-2180 replacing R-1830 on fighters and that seems to only apply to P-43 vs XP-44. From what i read the airframes were pretty much the same except a longer nose on the XP-44. I haven't found any comparative details of weights and dimensions for the two though, as well as XP-44 performance.
Other examples of larger engines replacing smaler ones are Spitfire (Griffon vs Merlin), and Bf-109 ( DB-600 vs Jumo-210), and the aforementioned A6M.
So based on the above, it seems fitting the R-2180 MIGHT work, though of course there will be a weight increase, longer nose etc. If not, then the other option is we go round again to the R-2000, have PW stop work on the R-2180 asap and concentrate on the R-2000 instead, including fitting the 2-stage SC. Seems the R-2000 would be a bit lighter than the R-2180 (though i'm just going by wiki figures), but the most important plus is the more acceptable diameter of 126cm, which means an easier fit in the nose, less drag etc. If the resulting F4F-4/R-2000 ( with the 2-stage SC) has another 10mph in speed and 1000 ft in climb, it still almost restored the F4F-3 performance.
Grumman at the end built a fighter around the R-2600.
I don't think that Grumman's engineers were incompetent, after all they churned out a brand new design per almost each year between 1939 and 1945.
Competent as they were, crucial help to not just compete with F2A, but to make a better performer, came from Pratt & Whitney. P&W's help was the R-1830-76, with it's 2-speed 2-stage supercharger. That engine was making, for example, 1000 HP at 19000 ft, where the R-1830-66 (a.k.a. SCG; installed on the XF4F-2) was good for less than 650 HP - having 50% more power at altitude where air is thin is a major boon. Even at 10000 ft - best altitude of the SCG - the difference was about 200 HP (900 HP vs. 1100 for the -76).
I've mentioned the additional drag only in context of the suggested installation of turbo-supercharger system to help out at high altitudes. Extra drag comes there in requirement that intercoolers are to be installed, and that intakes required for cooling the turbine had to be present. The 'normal' (ie. no turbo) 2-stage supercharged engines also required intercoolers, eg. we can see the two intakes for these at each side of the Hellcat's 'beard (with oil cooler and ram air sharing the central intake). See here, one of the intercoolers is visible.
(engines with just one stage of supercharging, like the Merlin III/XX/45, Allison V-1710 as installed on the P-40, P-39 or P-51, BMW 801, R-2600 in majority of cases, DB 601, most of Japanese and Soviet engines were without the intercooler; radial engines with just 1 stage of supercharging were also very awkward to have the intercooler installed since there was no common manifold leading from the S/C)
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The XP-44 probably never moved upwards fro the back of the envelope sketches. Unfortunately, we will probably never know anything more about it, especially since after Fairchild bought Republic, vast majority of Republic's legacy documents went into landfill.
If USAAC/AAF and Seversky/Republic agreed the terms about the XP-44 to proceed, AAF would've probably have a working 1-engined high-altitude fighter by late 1941, talk 400 mph above 20000 ft? And by mid-1942, the upgraded version with drop tanks etc. Swamping up the Festung Europa all the way to Berlin by early 1943 by many hundreds of fighters at B-17 cruise altitudes, with extra performance due to the upgraded R-2180s, ready to receive water-alcohol injection by late 1943...
I can't really see the P-44 going 400 mph just by having anther 200 HP from the R-2180 over the P-43, though later variants with ADI injection and more power might approach that. Still, probably the americans would be better of with P-44s or even P-43s (with a better fuel system) than say P-39s, since aiui the P-43 had very good altitude performance and P-44 would have topped that. I've read they wanted to put a R-2600 on P-44 as well.
In general, seems the later Seversky fighters be it P-41,43 or 44 would have been good to have in numbers until the P-47. (the P-35 though was subpar, i don't know what were they thinking putting that grotesque trousered landing gear on it, surely they could have found a way to retract the wheels flush, either like on P-36 or inward retracting like later etc.)
Last R-2180s mooted before the wartime 'pause' were supposed to make 1500 HP (now turning 2600 rpm vs. 2500 rpm as on the engines sold to Japan), so perhaps that would've been actually done by 2nd half of 1941? Sharing the bore and stroke with R-2800 might've possibly helped with evolution of the 2180 (fingers crossed), as it was possibly the case with the post war 2180E (that one did 2800 rpm and made better power, especially with water-alc injection).
Oh yeah, i've been superficial enough on american engines not to realize till now that the R-2180, R-2800 and R-4360 share the same bore and stroke. So it definitely makes sense to focus on developing the R-2180 instead of the odd-one-out R-2000. They could then get 2600 rpm and 1500 HP from the R-2180 as you say in 1941, and then 2700 rpm and 1600 plus HP later on, then ADI etc, before morphing into the R-2180E.
So indeed the Wildercat F4F-4/FM-1 would have 1400-1500 HP available for 1941-42 and 1600 HP plus for the later FM-2.
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How much did/could the war accelerate the development of the R-2800? If the war had started earlier, could we have seen an R-2800 developed in a correspondingly short (or long) timeframe, just moved forward a year or two?
I'm not sure that we can pinpoint to a right answer there.
We know a few things - like the 1st flight of XF4U-1 (May 1940), or the 1st flight of the B-26 (November 1940) - ironically, the B-26 was flown with a lesser version of the R-2800 (even though these R-2800s were with great power for that time). Joe Baugher's web site says:
On February 22, 1941, the first four B-26s were accepted by the USAAF.
(there was no specific prototype of the B-26 that early, Martin company gotten the contract 'from the drawing board')
It took Vought a lot more time to redesign the XF4U-1 into the combat-worthy Corsair we know and love, the 1st two being delivered in June 1942, and next 9 in August etc. 1st combat was at St. Valentine's day of 1943 (Zeros managing to do better that day than Americans).
P-47B was running even more late, and was plagued with engine fires, and tails detaching from the fuselage under high G maneuvers, leaving the P-47B without the service overseas.
My take on early US fighter with R-2800 in the nose: have a company (or two, or three) make a no-nonsense fighter around a big radial in the nose, perhaps instead of the B-26 for the needs of USAAC/AAF. May the better design win - something looking sorta big P-36? Perhaps have the 1st prototype flying in summer of 1940, and have the 1st examples delivered by late 1941, so the new fighter can be used in combat by mid 1942?
Another take: Lockheed makes a fighter around the R-2600 instead around the two V-1710 (USAAC preference was the V-1710, though), that looks like a big P-43. Re-engine it with R-2800 by 1941?
FWIW, the early R-2800s (making 1850 HP down low) were produced, before 1942, in 1480 pcs at P&W (mostly in second half of 1941) and at 262 ocs at Ford (Oct to Dec 1941). Most of these ended up in the B-26s.
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I might have asked this elsewhere in the past but i don't quite recall the answer/figures, but in general how much extra HP would 100 extra rpm give, all else being equal? I guesstimated earlier on 1600HP for a 2700 rpm R-2180 and wanted to have a better estimate. And would be good to know to apply the percentage for other engines.
The above figures seem to suggest around 7%, or that's too high?
For the engine of such cubic capacity, perhaps 100 HP extra down low, petering down with altitude, to, say, extra 50 HP at 20000 ft? So a gain of 7% is probably a realistic expectance.
Refinements of supercharger, greater area of cooing fins can add perhaps extra 50 HP each? Substantial jump in power should be provided by water-alcohol injection, talk another +-150 HP, as it was the case with post-war 2180s. The 2180s in the SAAB airliner were good for 1650 HP dry and 1800 'wet', as noted upthread.
Fuel better than 100 oct, like the 100/150 grade, or the post-war 115/145 grade should also allow for greater boost = more power. Talk another 100-150 HP.
Granted, the technology transfer from the development of the R-2800 and R-4360 will be needed to put all of these options into the workable engine, like it was certainly the case with the post-war 2180s.
So, are suggesting the lighter R-2180 would make a better engine for the Wildercat? A Wildcat with a 1,400 HP engine with a 2-speed 2-stage supercharger would be big improvement over the OTL Wildcat. Was this engine available in 1939-41?
IIRC, an increase from 2500 rpm to 2600 rpm would increase the engine's power by 60hp or 4%, all other things remaining equal.
I'm assuming I remember physics correctly and the engine's torque remains the same. An increase of 2500 rpm to 2600 rpm, a 4% increase in rpm, so a 4% increase in rpm should yield 4 % increase of power or 60 hp.
I'm calculating this based on the idea that power equals torque multiplied by rpm or, as in physics:
P = τ·ω
Where:
P is Power, here given in terms of horsepower
τ is torque, which I'm assuming is constant
ω is angular velocity, which here is given by rpm
It would've been an engine choice with the lower weight penalty than the R-2600, even when we compare the heaviest R-2180A with the lightest R-2600.
That's the kicker - the 2-stage 2-speed R-2180 existed only on paper at P&W.
How about making the F4F-4 lighter (with or without an improved engine)?
I understand that while the F4F-4 had improved firepower over the F4F-3 and had the folding wing this all made it heavier and its rate of climb suffered vs the earlier F4F-3
The other downside of having 6 x .50 cal MGs was reduced ammunition per gun and the requirement was after feedback from the British who were having issues with the earlier 'Martlets' shooting down Condors (which were difficult to attack) - so perhaps keep the 4 gun armament of the F4F-3 for USN aircraft ?
That's got to save 50 odd kilos?
Also could the aircraft be made more aerodynamic - that windshield is like an airbrake?
Improved cockpit design and a proper spinner to improve aerodynamics
The extra weight of the folding wing is a necessary evil given the increased capacity in aircraft numbers that this brings to the USNs carriers air groups
Anywhere else weight could realistically be saved?
I understand that while the F4F-4 had improved firepower over the F4F-3 and had the folding wing this all made it heavier and its rate of climb suffered vs the earlier F4F-3
The other downside of having 6 x .50 cal MGs was reduced ammunition per gun and the requirement was after feedback from the British who were having issues with the earlier 'Martlets' shooting down Condors (which were difficult to attack) - so perhaps keep the 4 gun armament of the F4F-3 for USN aircraft ?
That's got to save 50 odd kilos?
Also could the aircraft be made more aerodynamic - that windshield is like an airbrake?
Improved cockpit design and a proper spinner to improve aerodynamics
The extra weight of the folding wing is a necessary evil given the increased capacity in aircraft numbers that this brings to the USNs carriers air groups
Anywhere else weight could realistically be saved?
Wing of the FM-2 was at 1154 lbs (folding, 4 HMG + ammo, drop tanks' facility).
That of the F4F-4 was at 1181 (same as above, but for 6 HMGs).
Non-folding wing of the F4F-3 was at 893 lbs.
tl;dr - keeping at 4 HMGs on a folding wing would've possibly saved another 25-30 lbs for the '-4 lite'.
Fuel system was there to stay, with simple and light self-sealing tank.
140-150 lbs can be saved with having 2 HMGs less (guns' weight + mountings). Another 100-ish due to need to carry less ammo + ammo boxes.
The best 1-stage superchraged R-1830 (possibly the equivalent of the -33 - a.k.a. S3C4G - as installed on the P-66 and indeed on some Martlets) can still save some 200 lbs vs. the -76, with a bit lower power at high altitudes; the 1-stage supercharged engines are without intercoolers, so there is more free volume in the fuselage, that can be now populated with oil coolers for lower weight and drag of these.
American radials, for the reasons unknown to me, were not very fond of the (big) spinners.
Main help would've come from the installation featuring the individual exhaust stacks instead of the collector exhausts. NACA measured an up to 18 mph gain with that simple expedient on the XF-41. Granted, this is not a save of weight, but the device to improve propulsive power - but this is no time to be picky
FWIW, Wright delivered their 1st and only R-1820-48 with a 2-speed 2-stage S/C in April 1941, to be fitted on a the XFLA-4 (?? Brewster lightweight fighter?). That was some 150-200 lbs lighter than the 2-speed 2-stage R-1830-76 as installed on the F4F-3 and -4, while providing the comparable power at altitudes.
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USN pilots were VERY unhappy about the six gun armament for the very reasons you state. Keeping the four gun armament of the F4F-3 is going to placate a lot of people.
Yeah I never understood that
Even the F4U and F6F and later war T-Bolt didn't have them (later XP-47J and XP-72 - which would have been a superb aircraft - did)!
Although the Brewster Buffalo did!
Oh I wonder if it was due to cooling?
I know the B29s struggled with cooling so much that during take off magneto drop checks were conducted while taxing to the runway and on take off they did not climb until they achieved a certain speed to ensure adequate cooling.