I come out with different numbers. The engine weight of the R-2800-10 (F6F-3 engine) is 2469 lbs and the engine weight of the P-40C with cooling is 1645 lbs or an 824 lbs difference. This would allow nearly 700 lbs for gear and other strengthening efforts including engine mounts, quite a bit. Remember, I am not recommending modifying the P-40, only using it for parameters in assessing risk in a AAF spec for a 7000 lb empty weight fighter using the new R-2800 engine.
An engine swap is not just the weight of the engine and radiators, the R-2800 needs bigger oil tanks, bigger oil coolers, a heavier exhaust system, a bigger starting system and a bigger propeller. Prop on an a F4U weighed 494lbs compared to the 337lb prop on a P-40C.
This should be no problem. The F6F gear weighs 733 lbs, the P-40C's gear weighs 628 lbs, only 105 lbs more for a much stronger than necessary gear.
Fine, a 16% increase in landing gear weight.
Why is that a problem when it is designed to the requirement? My American engineers are certainly as good as the German's; I guess your American engineers are not.
Was the Fw 190 designed to the same "G" limits as the American planes? The 109 was not. "My" American engineers are just as good, they just can't change the laws of physics.
This actually doesn't appear to be a big problem. The P-51A, at fighter weight, grossed out at 8153, while the P-51D, at fighter weight, grossed out at 9600 lbs with no change in structure. I would accede to some weight increase but not much, especially since it would be designed in.
Actually the P-51D was NOT stressed to 12 Gs at 9600lbs. It was stress for 8 Gs at 8000lbs with a 1.5 safety factor which is were the 12Gs comes from. All flight maneuvers required the actual weight of the plane to divided into 64,000 (8,000lbs X 8 Gs) to get the actual "G" limit. At 9600lbs a P-51D was rated for 6.66Gs plus the 1.5 safety factor or 10 "G"s. By the way, if you can call splicing in a 7in high horizontal section for a good part of the length of the fuselage "no Change in structure" what else are you glossing over? Do you have the weight of the wing of a P-51A?
A Hawk 75a (P-36 had wing that weighed 842lbs, the P-40C had wing that weighed 1002 and the P-40E-N had a wing that weighed about 1120lbs.
Standard load for AAF in 1941 seems to be about 200 rounds per gun.
Standard load in what? the P-39 with CG problems when it fired off the ammo?
Standard load in an early P-40, soon changed to 380rpg. Not the brightest move, the sychro-ed guns fired at under 500rpm. wing guns fired at about 800rpg giving you 15 seconds of firing time. Navy pilots preferred 4 guns with 400rpg to 6 guns with 240 for the longer firing time.
P-40s with 6 guns were often loaded with 200-235rpg in an effort to save weight for performance even though the ammo spaces would hold more. But 6 .50cal P-40s are pretty thin in 1941 aren't they?
If you could find a place for it, you could add 100 gallons of fuel and it would still weigh less than the gross weight of the F8F.
Well that is the trick isn't it? finding space on the center of gravity (or tanks space for and aft 9or side to side) to balance on the center of gravity, plus the weight of the tanks, plus the piping (fuel piping on a F4U-1 was over 100lbs) without making the fuselage or wing any bigger and adding weight that way.
I have no argument with this. I feel the AAF made the correct decision in building large powerful aircraft capable of taking the fight to the enemy even if it did mean there was a lack of capability in 1941-42 time frame. However, I am trying to fill in that shortage by specing an aircraft about the same time as the F4U was speced that would fill in the 1941-42 performance deficiency of US fighter aircraft. The Navy ordered a R2800 test aircraft in June '38. If the Army had done the same thing with a light weight fighter, this is what I would have built.
The Navy ordered the F4U on trust. The R-2800 doesn't make it's first flight until June 12, 1939 in the nose of a Northrop Y-19 test mule. Not that the Army couldn't have gone on trust but only 2 R-2800s were built in 1939 and only 17 more in 1940. Ford was given a contract for $14.3 million to build a factory for the production of R-2800s at a point in time when P&W had completed a total of EIGHT R-2800s. this contract was just for the factory, contracts for engines were separate. This was several months AFTER design work was stared on both the "B" and "C" series engines.
There just aren't many R-2800s of any type available until the fall of 1941, and I as noted in the Post to Tomo the "A" series goes out of production rather quickly, being replace by the "B" series single stage engine.
I think this problem is overstated. The P-51H with a 2200 hp engine seemed to work pretty well with a standard type landing gear.
Yep, but then it had the advantage of a 1944/45 propeller design. Hamilton Standard delivered it's first 2 bladed, two pitch propeller in 1935. Just like engines, propellers made tremendous strides in just a few years but expecting 1944 performance from a 1941 propeller may be asking to much. Try sticking an 11 ft diam 3 bladed 'tooth pick' prop on the P-51H and see how well it does.
I think a simpler F4U design without the hindrance of Navy requirements could have been fielded much faster. There doesn't seem to be too much of a problem for the engine development. Also, a P-66 type should offer far less complexity than the P-47.
A P-66 would be much simpler than a P-47 but then sicking an 1800-2000hp engine in/on a jumped up basic trainer is going to lead to all sorts of problems. I know, you are only using the P-66 as an indicator of size. But with that big R-2800 you are going to need bigger tail surfaces or move them back (longer fuselage). We are back to the landing gear problem, you can't use the same diameter prop as the R-1830 engine. The armament of the P-66 was barely adequate for 1941 and not at all what the customers wanted if given any choice at all. And 220-240 gallon capacity seems rather suspect given the empty and loaded weights quoted for the plane. Maybe the tanks would hold that much but what else had to be left out of the plane in order to fill them? You can find weights for US Navy planes in "ferry" condition. Lots of fuel but they actually pulled the guns out let alone the ammo in order to get to that weight.
I disagree with this. I don't think a bigger prop is a particularly big deal.
It is if you don't want the prop plowing ground. Remember you are designing in 1939-40, what kind of propeller do you KNOW you can get in Jan of 1942, not what kind of propeller do you HOPE to get.