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So you could basically say the following
Others would be improvements to the supercharger, a pressurized ignition harness, higher MAP ratings and allowances for higher engine temp (lean mix), water injection, and higher carburetor impact pressure.
- All other things equal: An F6F & F4U of the same period will see the F4U with a speed advantage over the F6F?
- Variables that affected the performance of the F4U would have included
- Quality of paint-job
- Removal of hook & covering over it for land based units
- Smoothing & puttying over the fold-lines for land-based units, and the wing-fold mechanism
- Redesign of the later F4U-1's canopy
- Replacing the 13'4" propeller with the 13'1" propeller when possible.
- Redesign of the tailwheel from short to high
- Addition of a streamlined fairing behind the taller tailwheel on some desigins
- Replacement the 13'4" propeller with the F6F's smaller 13'1" propeller
- Improvement of pylon design
The British didn't have the same problems. They had better spark plugs which were less susceptible. From the Fedden Mission Report that I posted recently:During a test climb to Hellcat service ceiling, Corky Meyer had the engine quit at 32,640 feet "as though someone turned off the ignition switch." Fortunately he got a windmill start after losing about half his altitude. By this time the engine was cold and running poorly so he immediately landed. His next two attempts to reach service ceiling had the same result. Remembering that Grumman's neighbors at Republic were regularly flying the R-2800 at 40,000, Meyer got on the phone. Republic's chief test pilot told him straightaway that they'd never get over 32,000 without a pressurized ignition harness.
"As P-38, P-47, Hellcat and Corsair fighter operating altitudes increased to well above 35,000 feet, the atmospheric pressure 'insulation' of the wires decreased so much from sea level to these altitudes that it allowed the spark electrical energy to easily jump through the normal rubber insulation protection and short out prior to reaching the spark plugs."
"The pressurized harness was developed by sealing each of the wires into flexible tubes from the magnetos to the spark plugs and then pressurizing the wires, magnetos and spark plugs by an air pressure pump driven by the engine."
"We then found out that the Army Air Corps had a very high priority and requisitioned all of the pressurized harnesses that Pratt and Whitney had built for the 40,000 foot ability of the Republic P-47 because it was soon going into high altitude combat in Europe... Needless to say we got the Navy brass in Washington to get us one of the pressurized harnesses for our Hellcat and I made a most anti-climactic climb to 39,455 feet altitude, which was just what we had predicted for the Hellcat's service ceiling."
Incidentally, for flights above 30,000 feet Grumman had their pilots pre-breathe oxygen for 30 minutes while riding a stationary bicycle in order to work the nitrogen out of their blood.
Meyer and Ginter, "Grumman F6F Hellcat," 2012.
The British didn't have the same problems. They had better spark plugs which were less susceptible. From the Fedden Mission Report that I posted recently:
View attachment 582100
According to the book "The Vital Spark" the British used ceramic in lieu of mica for the insulator and platinum for the electrode. The British manufacturers designed spark plugs to fit the American legginess and produced them to allow fitting to American aircraft as they arrived. Roosevelt even mentioned this in a speech to Congress:
" After the United States Eighth Air force began operation from Britain the summer of 1942, the British undertook to double their production so that they could provide all our Eighth Air ice Fortresses with these plugs. Since early in 1943 virtually every United States Flying Fortress has taken o ff from British base with these plugs in each of its four engines
What's of interesting note, in addition to that, is a statement of the F4U-1A reaching 404 mph @ 25300....
I'm not sure why the critical altitude varied by 550', though if I made a guess, it might be a lower manifold pressure (388 mph @ 24350' vs 395 mph @ 23800') seen in the earliest designs.
The reason I came up with that was because there was a picture of the F4U-1A on the top of the page, and the link and summary were the first on the list.BuNo 02334 was the 182nd Birdcage F4U-1, though that doesn't change the importance of the report.
That's a good point, and for all I know, the might have chosen to risk a degree of terminological inexactitude, as Winston Churchill would say.Part of the issue is that 404 mph was an estimate and not accomplished during actual testing.
Do you have any graphics that depict proposed mods?
Looking at what I've see, one proposal was to minimize the gaps in the cowl-flaps (+3 mph); another was to seal over the gaps at the wing-fold joint and gun-access & ammunition doors (+4 mph); add a full-length fairing for the main-landing gear doors (+5 mph); internally seal the bulkhead and/or add external fairings from the openings at the tail-wheel and arrester hook (+3 mph), and; remove radio antenna.If you look at figures 7c, 23, 29a, 30b, 31, and 39b for airplane 10 (F6F-3) you will see drawings of the proposed changes and their effect on speed.
The removal of the radio antenna is ridiculous: Radio is needed; fairing over the wing-fold joints would be unsuitable for carrier-ops, and fairing over the gun access/ammo doors would render the plane unusable (unless the doors could be covered when not in use).
That sounds reasonable, as far as I can see. Would that have affected production seriously?I believe they were concerned about the mast and it's drag invoking qualities. If you look at figure 39b there are examples of radio antenna installations that basically have zero effect on speed. Applying these to the Hellcat and other aircraft would improve speed by 1.5 - 2 mph.
Would that have been hard to implement, and how would the speed reduction compare to removing the panels altogether?NACA found that reducing panel gaps in the wings (possibly with special seals) would allow for smoother air flow without actually removing the panels all together.
So, you suspect that attempts to keep the cowl-flaps sealed right would either be impossible to keep in the right condition, and might be difficult to implement on a wartime footing?According to Dietmar Hermann's "FW190 Long Nose" as a part of the performance enhancing experiments conducted on FW 190 V53 (a D-11 prototype), all gaps on the engine cowling were sealed with rubber. This resulted in a 17 km/h increase in maximum speed. these mods never made it into production. A lot of these types of enhancements never made it into production because it would slow production down. Those that did would often not survive in the field. an example would be the retractable tailwheel of the 109 which tended to be locked in place. In a lifetime of tinkering with cars I have developed an intense dislike of gaskets which tend to fall apart when disassemble or refuse to realest. Remember that materials back in 40s were not as durable as today
I think once you take it apart its is difficult to re-seat. Years ago I took out the dash board of one of my VW Corrados. Getting it back together was not a trivial task. I had the luxury of time, I can imagine that under wartime conditions a lot of the parts would left out. A Corrado in some ways is a good example as only 97,000 were produced and although it was based on a mass produced car it was largely hand assembled by Karmman. Similarly while working on my friends BMW CSi 3.0 (also assembled by Karmann) I found myself cajoling things into place. The engines in both cars are different story, the parts do fit readily if you can get at them.So, you suspect that attempts to keep the cowl-flaps sealed right would either be impossible to keep in the right condition, and might be difficult to implement on a wartime footing?
That sounds reasonable, as far as I can see. Would that have affected production seriously?
Would that have been hard to implement, and how would the speed reduction compare to removing the panels altogether?
How many land-based F6F's were used?
No biggie, we do this all the timeApologies for reheating this thread, but I found discussion very interesting