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Was aware of the plexiglass issue but never put it all together in ref to the Zero canopyKeep in mind that pilots in the late 1930s the technology to make Plexiglas with complex compound curves wasn't there. In other words bubble canopies. Look how the Zero compensated for that!
I think it depends on the circumstances, and the speed operated.
THe argument Bill and soren got into was with the P-51, it turned out a study had shown pressure distribution and the teardrop bubble canopy resulted in less drag than the razorback/turtleback configuration, though the fact that the bubble canopy had a more sloped windscreen threw in a problem as well.
In the case of the P-47 the performance change is much more significant going from 435 down to 426 mph, the changes being the canopy and a gain in 500 lbs gross weight. (fuel capacity the same) The weight alone shouldn't have that much of an effect. (D-22 vs D-23)
KK - the wing pylons of the 51 were smaller than the ones added to the late Model P-47D's and it made about a 10kt difference in the 51.
Added Weight would also decrease speed. That made the 51D slower than the B/C despite a slightly more powerful engine and what Lednicer proved for the bubble canopy, that it had a more efficient canopy (less drag). There was no such comparison for the P-47D so no conclusions could be drawn.
However it isn't clear if the figures were also due to addition of wing pylons, but since it lists fuel levels and ranges with 3x drop tanks for all models, this would be implied that wing racks were fitted. (plus racks were standard on the D-22 iirc)
I suspect the Pylons were a major factor as well as weight in reducing speed for similar fuel loads, requiring more Hp to achieve same or better speed.
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hard to make a case that 'bird cage' canopies are better design as far as drag is concerned.. been a long time since a high performance fighter has had anything but a tear drop type.
Those fighters were designed at a time where air-to-air combat was thought to be a thing of the past. The MiG-21 was an interceptor designed to bring down bombers. Look at the MiG-21F, the first version - it was a day interceptor and still had a bubble canopy. It was the later Mig-21 models that had the turtle back and a bunch of avionics shoved into them.Well, while still frameless canopies, as mentioned earlier there were a number of interceptors like the MiG 21 and Mirage III that had the canopy faired into the fusalage.