What Is Dihedral? How Does It Work? When To Use It?

in geometry dihedral is the inclination or angling of any two planes not airplanes but flat surfaces planes to one another and in an aircraft dihedral is referred to when each wing is inclined to the other and typically in an upward sense there is a concept of anhedral in certain high wing mostly jet aircraft which accomplish something different which I won't go into in this video polyhedral incorporates the exact same concept which I'm about to describe but goes about this by angling the wing tips in one or more segments in some angle relative to the actual main airfoil and this can occur and to places like this example here or it can be particularly in many places or it can actually be curved smoothly and accomplish the exact same outcome there's a couple of main reasons why builder might want to use dihedral the first is to economize on complexity weight and expense now the expense one is increasingly less valid because servos are so cheap these days for less than five dollars you could easily put in a couple of aileron servos with a straight wing and get by with that weight considerations mostly for gliders particularly discus launch gliders that is a valid concern and the complexity of ailerons is moderate I happen to think that a lot of newb fliers are unnecessarily scared of ailerons but I will admit that does add some additional complexity and build an operation and maybe that's not something you're ready to tackle the overwhelming reason to consider building and dihedral polyhedral is role stability or self-righting ability now at this plane will operate with just a rudder with pilot inputs to accomplish roles but what we're really speaking of is the self writing ability either from pilot poor inputs or by turbulence or air movements poor launches and that sort of thing in which the plane may end up in an unusual attitude and with dihedral that have some ability not complete to write itself wings level attitude so that self writing behavior is very helpful in long wingspan planes sail planes which fly in a bit of turbulence but have such a large wingspan but also two new fliers who may just be a couple of seconds behind cognitively as to what the plane is doing and it allows them a little bit of leeway to think about what the plane is doing and put in the correct control inputs to make the plane do what they want it to do so let's talk a little bit about how all works first to get this out of the way the way it doesn't work is by asymmetrically applying lift to each of the wings some may intuitively think when this plane is rolled in this direction that because this is parallel to the earth perpendicular to gravity that it generates more lift than the opposite wing which is inclined up but remember the lift vector is perpendicular to the the cord of the wing and the span of the wing so that it points up so playing in a bank the lift is simply directed towards the inside of the turn that has no writing effect at all this wing has just as much lift as this wing and no more no less and so the plane would simply be lifted in this direction rather than lifted up into its upright position instead dihedral in principle works by the concept of side slip now this is much more apparent with a pilot input of yaw but it also accounts for the role stability that dihedral tends to impart even in a plane flying in a neutral wings level attitude and how this works is if there's any yaw perturbation either input by the pilot by wind Britany any other factor the upwind wing that's the one facing the relative wind that's facing you incurs a greater angle of attack and the downwind wing facing the rear of the relative wind sees a lower angle of attack so this greater angle of attack rolls the plane this way so in the case of a pilot input we may put the airplane end yaw by inputting rudder this wing sees more a higher angle of attack thus more lift rolls the plane to the right if the pilot puts in left rudder this wing is brought forward sees a greater angle of attack rolls the plane to the left now how this works in let's say slightly turbulent err where you want to play in like a sail plane to maintain wings level in a somewhat automated fashion this is not a perfect thing but it is a stability factor that helps a little bit is when the plane is put into a row let's say by some turbulence it slips in this direction and therefore this wing sees a greater angle of attack and it writes the plane like that if the plane is rolled slightly in this direction by the wind because remember this doesn't have a Lorenz it could only be turbulence or air movements that roll the plane not the pilot its side slips in this wing sees a greater angle of attack so it writes the plane like that so to visually exaggerate that a little bit out inclined the plane at a greater angle of attack than it would ordinarily fly but you should see that the wings look about symmetrical right there I'll put in a left rudder and point the right wing towards you and you'll see a greater proportion the lower surface of the wing you're looking from the relative winds view and you can imagine that higher angle of attack will lift that way oh ah the plane to the right and you'll see that there's a greater lower surface area on this wing visible than this wing and this is what causes this wing to increase lift and roll off to the right now for normal everyday flying I'm personally not a big fan of dihedral just being very accustomed to ailerons and scale aircraft and model aircraft I just like the the actual axial roll component that ailerons in part and then coordinating that with rudder if you're brand new pilot you probably won't miss that until you get into three axes flying but in a dihedral plane when pilot inputs rudder the plane was sort of Yas you'd expect kind of in this walky way and then start its turn and this is in a way you can illustrate the concept of side slip if you put in a very aggressive let's say right rudder the plane will first y'all aggressively and the up one wing will see that increase a relative win and it will sort of back over like that some pilots like me find that a little bit awkward and weird to fly but if you're just getting started some of the benefits of the dihedral may actually work out better for you where you are in your flying experience we're thick grace wait nice nice gentle

Channel: Experimental Airlines

Views: 84,211

Keywords: foamboard, scratchbuilt, airplane, rc, dihedral, wing, armin

Id: u_pyNpvUejo

Length: 7min 32sec (452 seconds)

Published: Thu Mar 24 2016