A good example of this is the NASA paper on the PRANDTL-D, by Al Bowers. It has been mentioned here on HBA before, and is available on the internet. Although the PRANDTL-D is a flying wing, the paper shows how to control the beginning location of the stall by using wing twist.....If you control the pressure distribution near stall with wing sweep and camber/thickness you should be able to control which part of the wing stalls first. Note that Prandtl's theories on lift distribution assume no wing sweep.
Please understand. Per post #40, I gave the PRANDTL-D as an example of putting the lift at the desired point on a swept tapered wing, by using the wing twist. Not as the ultimate solution.This paper was all about proving a flying wing could have pro-verse yaw. Which was a solution for that particular swept and tailless S&C analysis. Not much use outside that config. Not a real statement of efficiency especially outside tailless. The idea of upwash and over twisted tips tipping the lift vector forward when the AOA is grossly negative is a bit out there and I am not sure was really tested. Gross results seemed to stack up. And it was all a good read.
The formula for change in CLmax with sweep angle (correction factor) is:Andy_RR, Do you have formula for that Wing Sweep effect.
I've calculated effective Wing area loss due to Sweep, it's very small up to 20° at 25% C, after that it rises exponentially.
Aerowerx, looking that up.
In Al Bowers design, the tips do not have negative lift, but they do have negative drag. Because the lift vector is tilted forward slightly...... the tip does not need to have negative lift.....
IIRC, in Nickel's "Tailless Aircraft" book he states that around 20 degrees is "optimum". Of course, he is talking specifically about flying wings but I do not see why that wouldn't apply to a tailed design.Losses are therefore approximately (using Raymer): ~0% @10°, 5% @20°, 15% @30°, 25% @40°, 35% @50°, 50% @60°
Because the sweep is used to substitute the elevator, by shifting lift between inner and outer portion, therefore between rear and front.... around 20 degrees is "optimum". Of course, he is talking specifically about flying wings but I do not see why that wouldn't apply to a tailed design.
As a clarification, the PRANDTL-D is a flying wing developed by Al Bowers of NASA, somewhat based on Prandtl's work. Al Bowers wrote a paper describing his design, including the lift distribution. That paper is what is being referred to here.