Originally posted by Widewing
Remember, guns were situated to the outside of the propeller arc. Thus, the larger the propeller, the further out the guns must be. When we look at the diameter of the P-51D's prop we find that it is 11'2" in diameter. Looking at the F4U, we find a diameter of 13'6". I also have annotated drawings of the P-51D and F4U showing the distance measured from centerline of the fuselage to the centerline of the inside machine gun.
Span from centerline of left inside gun to centerline of right inside gun....
P-51D: 13'2"
F4U: 15'10"
Therefore, the F4U's guns have naturally greater convergence angle than those of the P-51D.
My regards,
Widewing
Agreed Widewing that the angle is greater for the F4U since the guns are wider out, but is the angle of convergence of the 2 bullet streams 300 yards away really that significant a difference?
Here's the math:
Distance in inches - center gun to center gun:
P51: 158 inches
F4U: 190 inches
Distance in inches - aircraft centerline to center gun (1/2 the above):
P51: 79 inches off aircraft centerline
F4U: 95 inches off aircraft centerline
Target Point: 300 Yards Convergence on aircraft centerline:
10,800 inches
Doing a quick SAS (Side, Angle, Side) on this triangle gives you the degree of cant of the guns to give you convergence at 300 yds. 90 Degrees would be the guns firing straight ahead, so to get them to converge they are set inward at the following angles:
P51: 89.580 degrees (.420 degrees inward on each wing)
F4U: 89.496 degrees (.504 degrees inward on each wing)
The makes the angle of bullet impact 300 yards out is less than 1/10 of 1 degree different between the two. Can it really make that much difference?
Not that I actually fly the F4Us (or the P51s much for that matter), but if the anecdotal evidence really says that the F4Us guns are that much more lethal than a P51s, I think I'd do some more testing.
EagleDNY
$.02