I have an additional question, this time about the sweep of wings. From what I know of this design feature, sweeping wings is an attempt to increase the critical Mach number of an airfoil. Sweeping does this by making the airfoil section "thinner" by decreasing the thickness to chord ratio.
Imagine you have a straight wing with constant chord. For this example, imagine the section thickness is 0.15m, and the chord is 1m, thus making the thickness / chord ratio equal to 0.15.
To increase the critical Mach number, this section is swept at an angle of 45 degrees. The thickness is still 0.15m, but from trigonometry, the "effective" chord has increased to 1.41m. The swept wing now has a thickness / chord ratio of 0.1064, which has increased the critical Mach number.
My question is, wouldn't it be easier to design a straight wing with a constant chord of 1.41m in the first place
. I assume the oncoming air would "see" exactly the same thickness/ chord ratio, so wouldn't this wing have the same critical Mach number as the swept wing
. I imagine a straight wing would be easier to design and manufacture.
The question could be extended to a wing that has a tapering chord length like the 747. This is much harder to picture though. Imagine "slicing" a 747 wing into slices 1cm wide, with the cuts parallel to the effective chord line.
Now imagine arranging these slices such that the trailing edges form a straight, perpendicular line from the side of the fuselage. The oncoming "air" would see exactly the same effective chord lengths as before, thus in theory, shouldn't this new wing have exactly the same critical Mach number as the original 747 wing
. It would have the additional benefit of being easier and simpler to design and construct.
|Swept wing "slicing". Lame, I know!|
Original image; http://www.stanford.edu/~kasidit/images/wing_planform.jpg
[Edited 2006-10-20 09:41:50]