Flat Turn With Rudder

[baronbernie]

For many years I flew a Pluma and enjoyed it very much. One thing that made this plane so fantastic was the ability to fly straight and still be able to turn with the rudder with no diving. In other words it would still be flying on a flat line but the yaw was amazing. After some time of surching and realy finding no understandable help I new I could find help here.

Baron

 

[colorex]

Flat turns are very common on indoor 3D planes.

 

[Ak Flyer]

The Pluma is one of my favorite planes. My friend has one and it's awesome!!!! It's great on 2S indoors and outside throw a 3S at it and it's great even in some wind.

 

[quorneng]

baronbernie
It all to do with having sufficient fuselage side area.
You have to bank a normal plane to generate the side force to make it turn.
In a Pluma or similar the side area of the fuselage is so large that it provides all the side force you need without banking the wing at all, indeed you could take the wings completely off a Pluma and fly it on its side with just the fuselage providing all the lift to support it.
Doing a flat turn does need more power than a coordinated banked turn.

I hope this helps.

So

 

[Ak Flyer]

I disagree. The flat fuselage definitely helps you in knife edge and the bigger the better but it adds resistance to turning. What really helps in flat turns is a symmetrical airfoil on the wing (flat is symmetrical) a large rudder, wing placed at or near the center of the fuselage and no dihedral in the wing is crucial. Dihedral in the wing is what makes 3 channel planes fly by causing the wing to roll as if it had ailerons when the rudder is used. If you look at most 3D planes like the Extra Edge and Yak and none of them have big fuselage side areas. They do all have mid mounted symmetrical wings with no dihedral and huge rudders.

If you took your pluma and added dihedral to the wing, it would try to bank when you applied the rudder.

 

[quorneng]

Ak Flyer
A knife edge is in aerodynamic terms exactly the same as pulling a 1g flat turn and you agree you need side area to do that.

 

[Ak Flyer]

I suppose. However by your first statement is it true that all shapes and size planes will turn flat with only rudder input as long as they have a large flat fuselage without regard to wing design?

Let me also point out that that's only one way to fly knife edge that typically only works for flat 3D indoor planes. Typically you fly knife edge by using rudder and thrust. Fighter planes don't have all that much side fuselage. Neither do most of your full scale aerobatic planes. They fly knife edge by pointing upwards using the rudder and thrust to keep them there.