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The weights I quoted are from the USN SAC data = 7556lb and 7975lb. I don't doubt that an F4F-3 without armour, SS tanks, and maybe a partial fuel and ammo load could be pared down considerably but this is hardly a fair comparison.
Even the Aug 1941 spec for the F4F-3 states 7432lb (but these weights increased) for the overload fighter while the March 1942 production inspection of F4F-4 #4058 states 7921lb for the overload fighter and by Oct 1942 these weights had increased to 7975lb.
The Aug 1941 spec for the F4F-3 at 7432lb states 336mph (which, in fact seems like a typo and should probably read 326) while the March 1942 production inspection of the F4F-4 #4508 at 7370lb states 319mph based on flight testing.
I have noticed the same thing on the wwiiaircraft performance website. I hadn't noticed the climb rate but I noticed the top speed difference. Would the folding wing have an aerodynamic drag issue with it? Seems like I read somewhere that in a dive the seam in the folding wing would spread out some. I'm really grasping at straws here. We have both provided evidence proving our own theories. I think we might want to start a thread on F4F-3 vs F4F-4 performance differences at XYZ weights. Maybe some other members have some theoriesWhile the Vmax speeds show the F4F-4 as 17mph slower at a lighter weight than the F4F-3, the difference in climb rates is far more dramatic:
Time to 20K ft:
F4F-3 at 7432lb = 8.4min
F4F-4 at 7370lb = 11min
I understand and I agree with you on hitting power. I've always been a fan of the 50 IF the aircraft has the performance to carry them. Limiting ammo to only 200 rounds per gun would save 1000 rounds total which is 250 pounds. (Load out for the F4F-3 was 450 per gun)Look at the data reference I provided.
I'll do the math for you:
4 x .50cal @ 29Kg each = 116Kg x 2.2Lb/Kg =255Lbs.
8 x .30cal @ 10.4Kg each = 83.2Kg x 2.2Lb/Kg = 183Lbs.
255 - 183 = 72Lbs difference. **My bad for bad math saying it was 57 lbs diff.**
200 rounds of .50cal ammo = 50Lbs ( http://www.wwiiaircraftperformance.org/P-36/P-36_Operation_and_Flight_Instruction.pdf ).
500 rounds of .30cal ammo = 33Lbs. ( Same source as above).
4 x 50Lbs = 200Lbs for 4 .50cal @ 200 rounds/gun, 240Lbs @ 240 rounds/gun.
8 x 33Lbs = 264Lbs for the .30cal @ 500 rounds/gun. Your weight advantage is pretty much gone.
As for firepower:
4 x .50cal x 850 rounds/min x 43g/round = 146,200g = 146Kg/min.
8 x .30cal x 1200 rounds/min x 10g/round = 96,000g = 96Kg/min.
96/146 = 65.7%
Eight .30cals had just under 2/3 the firepower of four .50cals.
In addition, the effective range of the .30cal is 1500 yards; the effective range of the .50cal is 2000 yards.
Use three .50cals: weight is about 191Lbs, firepower is 109Kg/min. You increase firepower by 11% for 8lbs.
Using 8 x .30cals would be in no way an improvement to a WWII fighter.
I have noticed the same thing on the wwiiaircraft performance website. I hadn't noticed the climb rate but I noticed the top speed difference. Would the folding wing have an aerodynamic drag issue with it? Seems like I read somewhere that in a dive the seam in the folding wing would spread out some. I'm really grasping at straws here. We have both provided evidence proving our own theories. I think we might want to start a thread on F4F-3 vs F4F-4 performance differences at XYZ weights. Maybe some other members have some theories
I understand and I agree with you on hitting power. I've always been a fan of the 50 IF the aircraft has the performance to carry them. Limiting ammo to only 200 rounds per gun would save 1000 rounds total which is 250 pounds. (Load out for the F4F-3 was 450 per gun)
200 rounds would give 8-10 seconds of firing time, say 2-3 bursts. Guys that haven't had a lot of air to air gunnery training would probably be better off with 8 303's and a lot of ammo. Well trained pilots would likely do well with either setup.
It's possible that there might be minor drag increases in the F4F-4, but these should have little to no effect on climb because the lower speed in a climb minimizes increases in drag. I suspect that there were instrumentation problems with the F4F-3 performance tests and some transcription errors that have been repeated over time. Consequently, F4F-3 performance has been overestimated and overstated.
The fact that USN pilots were able to fight the Zero to a draw, in the F4F-3 and -4 is a great credit to them.
When defending a carrier they would always have a max load out of ammo. Over England it wouldn't be as big an issue, they can't sink your airfield if you run out of ammo and don't get that last bomber. Pilots complained about the firing time of the F4F-4 because it only held I think 267 rounds per gun.Well, from http://www.wwiiaircraftperformance.org/f4f/f4f-4-4058.pdf it looks like the "Normal Fighter" compliment was 200 rounds:View attachment 606808
View attachment 606806View attachment 606807
Here is another problem. An FM2 doing 327 mph on 1,000 hp at 19,500 feet. Virtually the same as original F4F-3 specs.
110USG = 92IG. Full fuel on a Hurricane was 97IG or 116USG.
110 was already in imperial, 133 was the load in US gallons of F4F-4
Take 2 identical BoB Hurricanes, Spitfires or ME109's and add 420 pounds of lead directly below the pilot and then let them dogfight each other.
275 pounds isn't a full load of ammo for an F4F-3. It carried 450 rounds per gun which is 1800 rounds total. The P36 site listed 50 ammo at 50 pounds per 200 rounds, that's 450 pounds of ammo. You could of course load less ammo.That's not quite right, we have enough information here to fully compare the 8x .303 vs 4x .50
8x .303 for the Hurricane
guns and accessorizes 201 lbs
ammunition and boxes 204 lbs ( 8 x 330 = 2640 rounds)
pyrotechnics 21 lbs
camera 9 lbs
total 435 lbs
4x .50 F4F
guns and equipment 248.7 lbs ( does this include the ammo boxes?) plus ammo = fixed gun installation (524.5 lbs)
524.5 -248.7= 275.8 lbs of ammo, 275.8 divide by 4 guns = 69 lbs of ammo per gun, @ 50 lbs per 200 rounds =276 rpg approx
Fixed gun installation 524.5 lbs
pyrotechnics 7.9
camera 13.7
total 546.1
The difference is 111 lbs in armament not 420 lbs.
So there you have it, to achieve 330 mph the F4F-3 is loaded to 6,895 lbs which includes less than full fuel ( 110 US gal or 92 Imp) and ammo loads.
Basically a 1941 F4f-3 closely matches a 1940 Hurricane.
I don't know where the 50lbs per hundred for .50 cal ammo comes from. Perhaps a misprint.
Most weight charts come out at about 30lbs per hundred. A substantial difference. But not that big deal in this case.
A problem with the F4F-3 in the Bob is that there weren't very many F4F-3s built in all of 1941 so the time line needs a considerable shift.
The Martlets and F4F-3a's that were built in 1940/41 had engines rated at lower altitudes.
They would have been useful but no real advantage over the Hurricane I.
"Using 8 x .30cals would be in no way an improvement to a WWII fighter"
Besides the fact that they worked? This is 1940, and the 1940 era M2 in a wing mount was next to useless in combat. I am sure the RAF would have preferred 8 firing .303's, over jammed .50's.
Yes I know. I'm very very very pro 50 bmg. But for the BoB and pilots with little gunnery training 8 303's might be better, as well as shedding several hundred poundsAgain, I go back to the fact that after about 1941, no new fighters were designed with that armament; all featured heavier guns.
Great Britain even redesigned the Spitfire's wing for 20mm cannon and .50cal machine guns.
Again, I go back to the fact that after about 1941, no new fighters were designed with that armament; all featured heavier guns.
Great Britain even redesigned the Spitfire's wing for 20mm cannon and .50cal machine guns.
Not sure I understand the point you're making. Aircraft capabilities evolve. Typically, the next generation of aircraft have better performance, to include armament, than the preceding generation. During WW2 the generations came around very quickly, as demanded by the accelerating rate of technological advancement. The RAF had already given up on 303-only armament in 1940, it just took time to make the 20mm cannon installations reliable.
The RAF would have been in dire straits had it tried using wing-mounted 50cals in 1940. Yes, it offered greater throw weight but it didn't become reliable in wing-mounted installations until the tail-end of 1942...that's 2 years too late for the Battle of Britain.