Washin/Washout

[avzq]

I'm fairly new to free flight modeling but have read through many of these forums and built a couple planes. I'm confused about washin and washout and found conflicting answers about this topic. I was wondering: when I create washin and washout for the wing, do I do this on the leading or trailing edge? The TE seems logical and most efficient. Is it better to have both washin and washout? Additionally, if my main wing has dihedral, how do I go about building in this warp?
'
The diagram for washin/washout in this article seemed to show the LE being warped rather than the TE: https://www.soinc.org/sites/default/fil ... iad5.0.pdf

Thanks.

[bernard]

Wash in refers to an angle of incidence that is greater toward the wing tips, and washout refers to an angle of incidence that is greater at the wing roots (closer to the fuselage of the aircraft).

In Wright Stuff, we add wash in because the plane flies in a circle with the points along the wing on the inside of the circle moving slower. Lower speed at these points means they produce less left and the wing would dip inward. To compensate, wash in increases the incidence at these points, allowing them to produce more lift.

For a left turning plane, the left wing should have wash in. This is made by constructing the leading and trailing edges so that they are parallel when looking at the wing from above but skewed when viewing the plane from the front. This is what you see in the document you linked.

Washout is added so that at stall speed the wing root stalls before the wing tip. This adds stability and is preferred to having the wing tips stall before the wing root. I have not seen washout used in Wright Stuff planes.

This is a difficult topic so please let me know if you have any questions.

[avzq]

Wash in refers to an angle of incidence that is greater toward the wing tips, and washout refers to an angle of incidence that is greater at the wing roots (closer to the fuselage of the aircraft).

In Wright Stuff, we add wash in because the plane flies in a circle with the points along the wing on the inside of the circle moving slower. Lower speed at these points means they produce less left and the wing would dip inward. To compensate, wash in increases the incidence at these points, allowing them to produce more lift.

For a left turning plane, the left wing should have wash in. This is made by constructing the leading and trailing edges so that they are parallel when looking at the wing from above but skewed when viewing the plane from the front. This is what you see in the document you linked.

Washout is added so that at stall speed the wing root stalls before the wing tip. This adds stability and is preferred to having the wing tips stall before the wing root. I have not seen washout used in Wright Stuff planes.

This is a difficult topic so please let me know if you have any questions.

Thanks for your reply.

So when constructing the wing with left wing wash in, I would have the leading edge towards the left wingtip slightly twisted upward, correct?

[bernard]

Thanks for your reply.

So when constructing the wing with left wing wash in, I would have the leading edge towards the left wingtip slightly twisted upward, correct?

You would have the leading and trailing edges skewed as shown on page 11 of the article you linked. I'm hesitant to use the word 'twisted' because the leading and trailing edges themselves are not twisted, rather oriented askew.

[jander14indoor]

There are several ways to create washin/out, the key for flight behavior is the result, not the method. A twisting wing with different angles of attack at the root than the tip.
As already mentioned for our left turning indoor planes you want a little wash in in the left wing, right wing can be flat to washed out.
Angling the spars as shown in that document is one way to do it, but only one.
Other ways include:
Cracking the spar (front or back as convenient, lifting left front or lowering left rear for washin) and regluing the spar with a kink to raise or lower the tip as needed.
Twisting the spars from a common plane (as shown in your reference)
Fix the dihedral joint so that it isn't square to the leading and trailing edge. Classic technic with hand launched gliders.
Changing airfoil shape along the length of the wing (not common in our small indoor planes).
Might be others, but those are the ones I can think of.

Jeff Anderson
Livonia, MI

[Crtomir]

Typically, we make the left wing span longer than the right wing span. This is to compensate for the torque imposed on the plane by the propeller. (action-reaction, Newton's 3rd Law) So there is already (hopefully) more lift on the left side of the wing than on the right side. Wouldn't this be enough to keep the plane level during turns as well? How much of a wash-in do you need? Could you increase the length of the left side of the wing compared to the right side of the wing enough so that you wouldn't need a wash-in?