wing attack angle?

[leaded50]

Hey, when making plans/builds, do you set a attack angle of wing at 0 degrees, or adjust what fit/needs?

 

[FDS]

Depends on the airfoil shape and what sort of flight characteristics you want. Most FT designs have neutral angle of attack.

 

[Fluburtur]

Unless you have a fully symetrical wing, it will generate lift at 0 AoA. It is useful to look at the camber line and angle/lift graphs on websites like airfoiltools
http://airfoiltools.com/airfoil/details?airfoil=e205-il
Some planes are built with some angle of attack but it comes at a cost of reduces speed for increased lift.

 

[leaded50]

i just saw a few projects/plans, where it was a very high angle (seems like). 20 degrees are norm as max before stall in aviation it seems though. And wondered if it was something i havent understood yet .

 

[Fluburtur]

Yes if you go past a certain angle of attack relative to the airflow you get flow separation, loss of lift and stall.

 

[FDS]

Remember that air molecules don’t scale down, so what is a workable angle of attack at 1:1 will be stalling at smaller scale.

 

[leaded50]

with close to flat bottom, ill keep on 0 - 2 degrees

 

[FDS]

If the wing is removable like the Simple Cub or trainer, you can alter the angle of attack by using a spacer under the leading edge.

 

[leaded50]

ill check if need eg. after first maiden flight

 

[Sero]

I believe your speaking of angle of incidence. Angle of attack is the the aircraft angle in relation to airflow/flight path where angle of incidence is the cord line of the wing in relation to the fuselage centre line.
Slower planes will generally have a slight angle up, say 3-4 degrees, while faster planes will be generally 1-2. The flight test flat bottom wing will have a few degrees up chord built into it already so you should be fine with mounting it flat. Also, if its off some it can be compensated with trim.

 

[FDS]

Thanks for that correction.

 

[clolsonus]

I'm oversimplifying, but I see the fuselage as simply a mechanism for mounting the wing, tail, and motor relative to each other. The important thing to consider is that to fly at a specific airspeed, the wing and horizontal stabilizer need some relative incidence. We [usually] change the relative tail incidence with elevator movement. (I'm ignoring thrust, drag, airfoil, CG, mass, and lots of other things here ... they exist but assume you are just changing wing/tail incidences.)

It can be nice to design in specific relative angles so that the airplane will cruise at it's "happy" speed with little amount of elevator deflection. Otherwise you may end up with a design that needs a lot of elevator trim for level cruise at the flight speeds you want.

(Again, over simplifying but...) how you set this up also affects how the airplane looks in the air. Does it cruise tail high (looking like it's wanting always dive) or does it cruise tail low (looking like it's always floundering/plowing through the air)?

I think the main goals of building a little bit of incidence into the wing mount is to minimize the amount of elevator trim needed in normal cruise flight and also to make the airplane look right as it's flying through the air.

Factoring in thrust line incidence, the goal of changing your thrust line is to allow a wide variety of throttle settings without affecting the pitch or roll trim too much. This is why you'll often see a motor mounted with a little down and right thrust.

This is where it can be really fun as a designer to go through multiple iterations. You can observe how your first prototype flies, and then design improvements for the next version. How the airplane flies through the air is a combination of all the above factors, and the workmanship of the builder, and the pilot's stick inputs. Trimming the aircraft out is a very important aspect of the overall flight experience.

 

[leaded50]

I believe your speaking of angle of incidence. .

Your right.. sorry.

 

[Sero]

Your right.. sorry.

No need to apologize Getting the term right will help when discussing/researching, that's all.

 

[Sero]

I'm oversimplifying, but I see the fuselage as simply a mechanism for mounting the wing, tail, and motor relative to each other. The important thing to consider is that to fly at a specific airspeed, the wing and horizontal stabilizer need some relative incidence. We [usually] change the relative tail incidence with elevator movement. (I'm ignoring thrust, drag, airfoil, CG, mass, and lots of other things here ... they exist but assume you are just changing wing/tail incidences.)

It can be nice to design in specific relative angles so that the airplane will cruise at it's "happy" speed with little amount of elevator deflection. Otherwise you may end up with a design that needs a lot of elevator trim for level cruise at the flight speeds you want.

(Again, over simplifying but...) how you set this up also affects how the airplane looks in the air. Does it cruise tail high (looking like it's wanting always dive) or does it cruise tail low (looking like it's always floundering/plowing through the air)?

I think the main goals of building a little bit of incidence into the wing mount is to minimize the amount of elevator trim needed in normal cruise flight and also to make the airplane look right as it's flying through the air.

Factoring in thrust line incidence, the goal of changing your thrust line is to allow a wide variety of throttle settings without affecting the pitch or roll trim too much. This is why you'll often see a motor mounted with a little down and right thrust.

This is where it can be really fun as a designer to go through multiple iterations. You can observe how your first prototype flies, and then design improvements for the next version. How the airplane flies through the air is a combination of all the above factors, and the workmanship of the builder, and the pilot's stick inputs. Trimming the aircraft out is a very important aspect of the overall flight experience.

The fuse centre line is just a reference line to line things up. For efficient level flight, having a good angle of incidence is best, but really it's the difference in angle of the chord line of the wing and the chord line of the horizontal stabilizer that matters, this is called decalage angle. A lot of full scale planes trim the whole horizontal stabilizer to adjust this for different speeds and loads. The angle of the fuselage has little effect on flight, with-in reason of coarse as we are only talking about a few degrees.
And honestly, IMO a lot of these things are far less critical when dealing with model aviation, especially FB planes.

 

[FDS]

Fly or fly not there is, there is no try!

 

[stereodreieck86]

Speedmonster fly with 0.5 -1.0, modern motor and sailplanes fly with 1.0 - 2.0 and Retromodels up to 3.0 (maybe even 3.5).

Here is a tutorial on how to measure the AoI:
http://www.rc-network.de/forum/content.php/392-Einstellwinkeldifferenz-(EWD)-messen

 

[Sero]

Fly or fly not there is, there is no try!

This is the way

 

[Sero]

Speedmonster fly with 0.5 -1.0, modern motor and sailplanes fly with 1.0 - 2.0 and Retromodels up to 3.0 (maybe even 3.5).

Here is a tutorial on how to measure the AoI:
http://www.rc-network.de/forum/content.php/392-Einstellwinkeldifferenz-(EWD)-messen

Thanks for sharing the link, that's slick!

For those that have 3D printers there are a fair amount of incidence meters you can print out on the www.