Flaps and Washout ?

[geoff.sim]

Is there any need for washout in a wing with flaps?

I am modifying an F-14 design to accomodate full length flaps. Problem is that when the flaps are deployed, the two degree washout is showing as a separation from the wing.

I did not want protruding pin hinges on the underside of the wing so was looking at just pinning the flaps on the lower leading edge.

1. Is washout required?
2. Should I drop the idea of hinging the lower edge and use robart hinges to simulate flower flaps (?)

Geoff.

[Sparky Paul]

Is washout required?
Depends.
Wings with lots of taper can benefit from washout.
Full-span flaps though bring up another problem;
tip stalls due to the change in camber, regardless of the washout.
And serious adverse yaw if the flaps are also used for lateral control.
There's no amount of washout that can help, so you can leave it out, but be prepared for the tip stall, and unusual handling when the flaps are down.

[geoff.sim]

Originally posted by Sparky Paul

...Wings with lots of taper can benefit from washout.
...Full-span flaps though bring up another problem;
tip stalls due to the change in camber, regardless of the washout.


Ok, well no quite full length but probably 80%.

Geoff.

[geoff.sim]

Oh, and a picture of the current setup.

Should I consider reducing the flap to the inner 50% of the wing and keep the 2 degree washout the non-flap wing is using ? There are no ailerons on this wing as the plane uses tailerons.

Geoff.

[Ollie]

The washout will be needed on this wing because of the combination of taper and sweep even with the wing in the forward position. This is the only wing position with which flaps should be deployed. Adverse yaw shouldn't be a wing design consideration with tailerons for roll control. However, rudder application together with the minimum sweepback wing position will tend to increase roll response at high angles of attack.