Spitfiremk1x

Would someone please define "wing washout" as if talking to a 12 year old? i have seen articles on it,but still don't understand it. Also what is the correction with alerons? Are they adjusted up or down to minimize the situation? I am in my mid sixties, but know very little of aeronautics and its terms. Thanks, John.

jdetray

Hi John,

Washout is a twist in the shape of a wing. Imagine that you are constructing a flat wing on a flat table, except that at the trailing edge near each wing tip, you place a shim under the wing to raise the trailing edge near the tips only. This imparts a slight twist to the wing -- the trailing edges are "flipped up" slightly at the tips. This is washout.

For more info, check these links:
http://www.fly-imaa.org/imaa/hfartic...t/v1-4-10.html
http://www.allstar.fiu.edu/aero/Wing32.htm
http://www.masportaviator.com/ah.asp?ID=27&Index=1

- Jeff

Flypaper 2

As the plane slows down, for instance for landing, there is a point where the wing comes up to a certain point and looses all lift,the stall, and the nose drops. If a tip stalls before the centre, it dumps over towards that tip. The idea of washout is to put a twist in the wing, as explained above, in order to cause the centre of the wing to stall first, as the tips should be still flying. A ready built plane with a tipstall tendency can be helped by raising the ailerons a bit. this acts like washout. Hope this helps. If more explaination is needed, just holler.
Gord

jdetray

Good point about raising the ailerons, Gord. [link=http://www.rcgroups.com/forums/showthread.php?threadid=55713]My BlueCor And_Now[/link] was a handful to fly until I reflexed both ailerons a bit. Instead of making the neutral position of the ailerons follow the curve of the airfoil, I raise both ailerons so their neutral position was parallel with the centerline of the fuse stick. This made the plane a much better flyer.

- Jeff

Spitfiremk1x

Thanks guys for the understandable explanation. I think everyone will know how to make an aleron correction on cranky models. Will test out mine after this alaskian cold front passes. Good flying to you, John.

jdetray

Someone asked for additional explanation of my previous post (#4) in this thread.

The plane I referred to is an And_Now, a plane with a stick-type fuselage, rather than a full fuselage. My And_Now is pictured below. Note that the "fuselage" is simply a 3/8-inch square basswood stick.



When setting up the ailerons for this plane, I had a couple of choices for where the neutral position of the ailerons would be. In most cases, the ailerons follow the slope of the top surface of the wing, so that the ailerons are more or less a continuation of the top surface of the wing, as shown here:



Another option is to set up the ailerons so their neutral position is parallel to the centerline of the fuselage, or in the case of the And_Now, the fuse stick. These are known as reflexed ailerons.



With my And_Now, I started out with normal non-reflexed ailerons, but the plane was a handful to fly. Then I tried reflexed ailerons, and the plane behaved much better -- much easier to fly. Reflexed ailerons are a type of washout, which is the original topic of this thread.

For more about the And_Now, check out my [link=http://www.rcgroups.com/forums/showthread.php?threadid=55713]build thread[/link].

- Jeff

feihu

John:

There needs to be some clarafication here.

Washout is an aeronautical term for a TWIST in the structure of the wing to control the stall characteristics of the wing so that the center section of the wing quits flying before the wing tips. This helps maintain a wings level condition when the whole wing stops flying.

Washout can be achieved by aileron deflection but only in certain cases.
If the ailerons are about half span such as on full size airplanes, then an slight upward deflection of the aileron for a neutral position will allow the outer portion of the wing (the part containing the aileron) to continue flying after the center section of the wing quits flying.

Full span ailerons are a model airplane thing. On an untwisted wing, such as shown in idetray's post #6, setting the aileron neutral position parallel to the centerline of the fuselage is actually resetting the wing incidence to a lower level, and NOT an example of washout.

feihu

Red Scholefield

My Feedback: (9)

Right, the way I have always under stood, and used in practice, is that the wing is slightly twisted so that the leading edge at the tip is just a few degrees negative in respect to the leading edge at the root of the wing. That's the washout that I know. Please don't tell me I have been wrong for the past 60 years.